U.S. patent application number 17/279527 was filed with the patent office on 2021-11-04 for catalyst ink for plating and electroless plating method using same.
The applicant listed for this patent is KOREA ELECTROTECHNOLOGY RESEARCH INSTITUTE. Invention is credited to Won Suk CHANG, Sang Hyeon LEE, Jae Yeon PYO, Seung Kwon SEOL.
Application Number | 20210340397 17/279527 |
Document ID | / |
Family ID | 1000005766677 |
Filed Date | 2021-11-04 |
United States Patent
Application |
20210340397 |
Kind Code |
A1 |
SEOL; Seung Kwon ; et
al. |
November 4, 2021 |
CATALYST INK FOR PLATING AND ELECTROLESS PLATING METHOD USING
SAME
Abstract
A catalyst ink for plating and a method for electrochemically
manufacturing an electronic device by using same are disclosed. The
present invention provides a catalyst ink for plating, comprising:
a polymer binder; a metal ion as a catalyst; a silane coupling
agent for coupling the metal ion and the polymer; and a solvent,
wherein the polymer has a lower critical solution temperature in
the temperature-composition phase diagram for a solvent-polymer
binary system, and the lower critical solution temperature is
30.degree. C. or higher. According to the present invention, a high
resolution plated pattern having a line width and a width between
lines can be manufactured.
Inventors: |
SEOL; Seung Kwon;
(Namyangju, KR) ; LEE; Sang Hyeon; (Gangneung,
KR) ; CHANG; Won Suk; (Seoul, KR) ; PYO; Jae
Yeon; (Changwon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOREA ELECTROTECHNOLOGY RESEARCH INSTITUTE |
Changwon |
|
KR |
|
|
Family ID: |
1000005766677 |
Appl. No.: |
17/279527 |
Filed: |
October 26, 2018 |
PCT Filed: |
October 26, 2018 |
PCT NO: |
PCT/KR2018/012831 |
371 Date: |
March 24, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09D 11/322 20130101;
C09D 11/033 20130101; C23C 18/161 20130101; C09D 11/38 20130101;
C23C 18/1608 20130101; C23C 18/2066 20130101; H05K 3/182 20130101;
C09D 11/037 20130101; C09D 11/14 20130101; C09D 11/52 20130101 |
International
Class: |
C09D 11/52 20060101
C09D011/52; C09D 11/14 20060101 C09D011/14; C09D 11/033 20060101
C09D011/033; C09D 11/037 20060101 C09D011/037; C09D 11/322 20060101
C09D011/322; C09D 11/38 20060101 C09D011/38; H05K 3/18 20060101
H05K003/18; C23C 18/16 20060101 C23C018/16; C23C 18/20 20060101
C23C018/20 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2018 |
KR |
10-2018-0114732 |
Claims
1. A catalyst ink for plating, comprising: a polymer binder; a
metal ion as a catalyst; a coupling agent for coupling the metal
ion and the polymer; and a solvent, wherein the polymer has a lower
critical solution temperature in the temperature-composition phase
diagram for a solvent-polymer binary system.
2. The catalyst ink of claim 1, wherein the lower critical solution
temperature is 30.degree. C. or higher.
3. The catalyst ink of claim 1, wherein the lower critical solution
temperature is 50.degree. C. or higher.
4. The catalyst ink of claim 1, wherein the lower critical solution
temperature is 55.degree. C. or higher.
5. The catalyst ink of claim 1, wherein the lower critical solution
temperature is 60.degree. C. or higher.
6. The catalyst ink of claim 1, wherein the lower critical solution
temperature is 65.degree. C. or higher.
7. The catalyst ink of claim 1, wherein the solvent is water,
alcohol, or acetone.
8. The catalyst ink of claim 3, wherein the polymer comprises an OH
functional group.
9. The catalyst ink of claim 3, wherein the polymer comprises at
least one selected from the group consisting of hydroxypropyl
cellulose, methyl cellulose, hydroxypropylmethyl cellulose,
ethyl(hydroxyethyl)cellulose, poly(N-isopropylacrylamide-co-acrylic
acid) and poly(propylene glycol).
10. The catalyst ink of claim 1, wherein the metal of the metal ion
is at least one selected from the group consisting of Ag, Fe, Co,
Ni, Cu, Pd, Pt, Sn, and Au.
11. The catalyst ink of claim 1, wherein the ink has a viscosity of
5 mPas to 1,500 mPas.
12. The catalyst ink of claim 1, wherein the ink has a loss modulus
higher than a storage modulus.
13. A plating method comprising: providing a base material in which
a precursor pattern is formed by ejecting a catalyst ink for
plating, comprising a polymer binder, a metal ion as a catalyst,
and a solvent; and forming a plated pattern by immersing the base
material in which the precursor pattern is formed in a plating
solution which is maintained at a temperature equal to or higher
than a lower critical solution temperature in the
temperature-composition phase diagram for a solvent-polymer binary
system for electroless plating.
14. The plating method of claim 13, wherein the solvent is water,
and the polymer comprises at least one selected from the group
consisting of hydroxypropyl cellulose, methyl cellulose,
hydroxypropylmethyl cellulose, ethyl(hydroxyethyl)cellulose,
poly(N-isopropylacrylamide-co-acrylic acid) and poly(propylene
glycol).
15. The plating method of claim 13, wherein the lower critical
solution temperature is 30.degree. C. or higher.
16. The plating method of claim 13, wherein the lower critical
solution temperature is 50.degree. C. or higher.
17. The plating method of claim 13, wherein in the providing of the
base material, the catalyst ink for plating is ejected without
pressure through a nozzle.
18. The plating method of claim 17, wherein the catalyst ink for
plating has a loss modulus higher than a storage modulus.
Description
TECHNICAL FIELD
[0001] The present invention relates to a catalyst ink for plating
and a method for electrochemically manufacturing an electronic
device by using same, and more particularly, to a method for
manufacturing an electronic device by using a catalyst ink for
plating.
BACKGROUND ART
[0002] Printed electronics have advantages in that a process can be
simplified and a rapid and inexpensive circuit device can be
manufactured on various substrates by directly printing a desired
shape, compared to a complicated and expensive photolithography
technique in the related art.
[0003] Typically, printed electronics manufacture a wiring pattern
in the form of directly printing a two-dimensional wiring pattern
with a pattern-forming material, for example, a paste including a
conductive metal such as Cu However, the wiring pattern
manufactured by these printed electronics has a problem in that the
wiring pattern shows a high resistance value.
[0004] Due to such a problem, there has been an attempt to apply an
electrochemical plating method capable of obtaining a high-quality
conductive film for forming a pattern of an electronic device or
wiring. The plating method has an advantage in that it is possible
to obtain a high-quality conductive film, but the formation of a
precursor pattern such as a seed for electroplating or a catalyst
for electroless plating on a base material needs to be preceded.
These precursor patterns need to be able to implement high adhesion
to a base material and a high resolution line width. However, there
remains a problem in that it is difficult to implement a high
resolution wiring pattern having a line width and a width between
lines while having high adhesion with an ink for plating and
printed electronics in the related art.
DISCLOSURE
Technical Problem
[0005] As a result of studies on printed electronics and
electrochemical plating technique, the present inventors have found
that obtaining a metal plated film having high adhesion to a base
material and a fine pattern having a uniform line width is closely
related to thermodynamic and/or dynamic characteristics of a
catalyst ink for plating.
[0006] Thus, an object of the present invention is to provide a
catalyst ink for plating capable of forming a high resolution
precursor pattern having a line width and a width between lines
while having high adhesion to a base material.
[0007] Another object of the present invention is to provide a
precursor pattern having thermodynamic stability in a plating tank
environment and furthermore to finally provide a catalyst ink for
plating capable of forming a plated pattern having a uniform line
width.
[0008] Still another object of the present invention is to provide
a method for manufacturing a high resolution wiring pattern having
a line width and a width between lines, which is uniform and fine
by using the above-described catalyst ink for plating.
Technical Solution
[0009] To achieve the technical objects, the present invention
provides a catalyst ink for plating, comprising: a polymer binder;
a metal ion as a catalyst; a coupling agent for coupling the metal
ion and the polymer; and a solvent, wherein the polymer has a lower
critical solution temperature in the temperature-composition phase
diagram for a solvent-polymer binary system, and the lower critical
solution temperature is 30.degree. C. or higher.
[0010] In the present invention, the lower critical solution
temperature may be about 50.degree. C. or more, about 55.degree. C.
or more, about 60.degree. C. or more, and about 65.degree. C. or
more.
[0011] Further, in the present invention, the solvent may be water,
alcohol, or acetone.
[0012] In addition, in the present invention, it is preferred that
the polymer includes an OH functional group. In this case, the
polymer may include at least one selected from the group consisting
of hydroxypropyl cellulose, methyl cellulose, hydroxypropylmethyl
cellulose, ethyl(hydroxyethyl)cellulose,
poly(N-isopropylacrylamide-co-acrylic acid) and poly(propylene
glycol).
[0013] In the present invention, the metal of the metal ion may be
at least one selected from the group consisting of Ag, Fe, Co, Ni,
Cu, Pd, Pt, Sn, and Au.
[0014] In the present invention, it is preferred that the ink has a
viscosity of 5 mPas to 1,500 mPas.
[0015] Furthermore, it is preferred that the ink has a loss modulus
higher than a storage modulus, and it is more preferred that the
ink has a loss modulus/storage modulus ratio of 10.sup.1 or
more.
[0016] Further, the present invention provides a plating method,
comprising: providing a base material in which a precursor pattern
is formed by ejecting a catalyst ink for plating, comprising a
polymer binder, a metal ion as a catalyst, and a solvent; and
immersing the base material in which the precursor pattern is
formed in a plating solution which is maintained at a temperature
equal to or higher than a lower critical solution temperature in
the temperature-composition phase diagram for a solvent-polymer
binary system and forming a plated pattern through electroless
plating.
[0017] In the present invention, the precursor pattern may be
formed by a method of ejecting the catalyst ink for plating without
pressure through a nozzle.
Advantageous Effects
[0018] According to the present invention, it is possible to form a
high resolution precursor pattern having a line width and a width
between lines while having high adhesion, and to provide a
precursor pattern having thermodynamic stability in a plating tank
environment. Further, the present invention can finally provide a
metal plated pattern having a uniform line width, and this pattern
can be used for manufacturing wiring or an electronic device.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 is a view schematically illustrating the pattern
forming mechanisms of a catalyst ink for plating of the present
invention.
[0020] FIG. 2 is a schematic phase diagram for an exemplary
polymer-solvent system as the catalyst ink for plating of the
present invention.
[0021] FIG. 3 is a set of views for schematically explaining a
meniscus-guided printing technique of the present invention.
[0022] FIG. 4 is a set of views for schematically explaining a
method of forming a wiring pattern according to an example of the
present invention.
[0023] FIG. 5 is graphs illustrating the flow characteristics of a
catalyst ink for plating prepared according to an example of the
present invention.
[0024] FIG. 6 is a plan photograph of a sample in which the
precursor pattern manufactured according to an experimental example
of the present invention is immersed in a plating solution and
plated.
[0025] FIG. 7 is a set of electron microscope photographs
illustrating the morphology of the plated film of a pattern
manufactured according to the examples of the present invention
over the plating time.
[0026] FIG. 8 is a graph showing the results of measuring the
resistance value of the plated pattern of the pattern manufactured
according to the examples of the present invention over the plating
time.
[0027] FIG. 9 is a set of photographs taken before and after the
evaluation of the adhesive strength of the pattern manufactured
according to the examples of the present invention.
BEST MODE
[0028] Hereinafter, the present invention will be described in
detail by explaining preferred exemplary embodiments of the present
invention.
[0029] In the present invention, a catalyst ink for plating
includes a metal as a catalyst, a polymer as a binder, a coupling
agent for coupling the metal and the polymer, and a solvent.
[0030] In the present invention, the metal includes at least one
metal selected from the group consisting of Ag, Fe, Co, Ni, Cu, Pd,
Pt, Sn, and Au. Since the catalyst is preferably present in the
form of ions in an ink composition of the present invention, it is
preferred that the metal in the ink is provided as a metal
salt.
[0031] Further, in the present invention, the polymer provides
adhesion to the base material. It is preferred that the polymer
required in the present invention includes an OH group at the end.
In addition, in the present invention, the polymer is required to
have predetermined thermodynamic characteristics, which will be
separately described below.
[0032] Furthermore, in the present invention, the coupling agent
couples a polymer with a metal salt. For example, a silane coupling
agent may be used as the coupling agent, and examples thereof
include 3-aminopropyl trimethoxysilane (APTMS), 3-aminopropyl
triethoxysilane (APTES), 3-aminopropyldimethylethoxysilane
(APDMES), and the like.
FIG. 1 is a view schematically illustrating the pattern forming
mechanisms of a catalyst ink for plating of the present
invention.
[0033] As illustrated, for example, a silanization reaction in
which a silane coupling agent is bound to a terminal OH group on a
polymer such as hydroxypropyl cellulose (HPC) is performed, and a
metal salt is bound to an amino group on a surface formed, so that
a metal ion complex is formed.
[0034] FIG. 2 is a phase diagram of a polymer-solvent system for
explaining the thermodynamic characteristics required for the
catalyst ink for plating of the present invention.
[0035] In the present invention, a mixture of the polymer and the
solvent constituting the catalyst ink for plating shows a change in
phase depending on the composition-temperature. Preferably, it is
stable that the mixture forms a completely solid solution state of
a liquid phase at a temperature which is equal to and less than a
predetermined temperature, and the temperature is referred to as a
lower critical solution temperature (LCST). In contrast, when the
composition-temperature coordinates of the mixture on the phase
diagram are located inside the spinodal curve passing the lower
critical solution temperature, the mixture is separated into two
phases, that is, the polymer or a phase derived therefrom is
precipitated from the solvent. When the composition-temperature
coordinates of the mixture are located between the spinodal curve
and the coexistence curve on the phase diagram, a partial
separation of the phase occurs, and the partial separation of the
phase can be called a metastable state.
[0036] The characteristics of such a polymer-solvent mixture may
provide the following preferred advantages in the present
invention. At the temperature of the preparation and storage
conditions of ink (for example, room temperature), the mixture is
stable as a solid solution state of the liquid phase, so that the
polymer may be uniformly dispersed in the solvent.
[0037] In contrast, when the plating conditions are maintained at a
higher temperature, for example, a relatively high temperature
equal to and higher than the LCST temperature, a printed precursor
pattern immersed in a plating tank does not deteriorate even when
exposed to the plating solution (for example, a solvent such as
water). In this case, this is because it is thermodynamically
stable for the polymer forming the precursor pattern to be
separated from the solvent.
[0038] Since such ink characteristics do not dissolve or decompose
the precursor pattern in the plating solution, the precursor
pattern makes the plated film firmly bound to the base material.
Further, the line width of the precursor pattern formed by the ink
for plating may be maintained as it is even in the plating
solution, and the uniformly printed line width may be maintained
throughout the plating process.
[0039] The polymer and the solvent which constitute the ink for
plating of the present invention have a relationship on the phase
diagram exhibited by the above-described polymer-solvent.
Preferably, the polymer and the solvent, which are used in the ink
for plating, have a lower critical solution temperature (LCST) in
the temperature-composition phase diagram of the polymer-solvent
system, and the lower critical solution temperature is about
30.degree. C. or higher, 35.degree. C. or higher, 40.degree. C. or
higher, 45.degree. C. or higher, 50.degree. C. or higher,
55.degree. C. or higher, 60.degree. C. or higher, and 65.degree. C.
or higher.
[0040] In the present invention, the preferred polymer-solvent
system and LCST values are shown in Table 1.
TABLE-US-00001 TABLE 1 Classification Polymer Solvent LCST 1
Hydroxypropyl cellulose Water 45.degree. C. 2 Methyl cellulose
Water 50.degree. C. 3 Hydroxypropylmethyle cellulose Water
70.degree. C. 4 Ethyl(hydroxyethyl)cellulose Water 65.degree. C. 5
Poly(N-isopropylacrylamide-co- Water 32 to acrylic acid) 36.degree.
C. 6 Poly(propylene glycol) Water 50.degree. C.
[0041] In the present invention, the plating working conditions
regarding the polymer, solvent content and composition of the ink
for plating may be designed by reflecting the following items.
[0042] For example, when hydroxypropyl cellulose (HPC) in Table 1
is used as a polymer, the LCST is approximately 45.degree. C. By
the way, the spinodal curve corresponding to the polymer-solvent
composition has a downwardly convex shape, the LCST is set as a
base point, and the corresponding temperature value is increased as
the composition is changed based on the LCST. Therefore, in the
actual polymer-solvent composition in the ink, the polymer may
remain co-dissolved in the solvent even at a temperature higher
than the LCST. Therefore, in order to suppress the dissolution of
the printed precursor pattern, it is preferred to perform plating
at a temperature equal to or higher than the temperature of the
spinodal curve corresponding to the composition, for example,
60.degree. C. or higher.
[0043] Meanwhile, in the present invention, the ink for plating may
be designed to have the required flow characteristics.
[0044] Examples of printed electronics using ink include various
methods such as the use of a high-viscosity ink paste, such as
screen printing, gravure, and offset printing, the use of a
pressure injection method such as inkjet with a slightly
low-viscosity ink paste, and a so-called meniscus guided printing
method that does not use any other external force other than the
self-weight and surface tension to eject ink.
[0045] When an external force acts on the ejection of ink, the ink
discharged from the nozzle collides with the base material, so that
the bleeding of the ink is inevitable, and due to the bleeding of
the ink, a pattern having a line width larger than an intended line
width is formed. In contrast, the meniscus guided printing method
is a method in which the ink inside the nozzle is discharged by the
surface tension of the ink ejected outside the nozzle, so that it
is possible to form a pattern equal to or smaller than the nozzle
diameter by changing the moving speed of the nozzle. Hereinafter, a
method for forming a pattern in the meniscus guided printing method
will be described with reference to FIG. 3.
[0046] FIG. 3 is a set of views for schematically explaining a
meniscus-guided printing technique of the present invention.
[0047] Referring to FIG. 3, an ink for plating for a precursor
pattern having a high surface tension is maintained in a printing
pen 110 provided with a nozzle. The ink can include dispersed
particles 22 including a metal ion, a polymer and the like, and a
solvent 24.
[0048] As the printing pen 110 is brought into contact with a
substrate 10 (FIG. 3(A)) and the pen 110 moves from the contact
point in a specific direction, for example, in a direction
perpendicular to the substrate by a predetermined distance, the ink
is released to the nozzle at the tip of the pen at a predetermined
flow rate (W) (FIG. 3(B)). A meniscus (B) is formed by the surface
tension of the ink released from the vicinity of the nozzle at the
tip of the pen. Subsequently, when the pen moves in a direction
parallel to the substrate at a predetermined speed, the solvent of
the ink is instantaneously evaporated from the surface of the
meniscus, and as a result, a precursor pattern (A) is formed on the
substrate. When the printing pen 110 is moved, the surface tension
of the meniscus (B) formed at the tip of the nozzle acts in a
direction of minimizing the surface area of the ink, and the ink in
the nozzle is pulled to release the ink to the outside of the
nozzle without interruption. As a result, a precursor pattern
corresponding to the movement locus of the nozzle may be printed on
the substrate. In order to eject the ink during this process, no
other external energy is applied other than the self-weight of the
ink.
[0049] In this method, the width of the meniscus depends on the
diameter of the nozzle and the moving speed of the nozzle. In
addition, since the particles in the ink are guided and flow in the
meniscus that acts like a pipeline, the line width of the resulting
print pattern may have a value equal to or smaller than the width
(d) of the meniscus.
[0050] In the meniscus guided printing method, the flow
characteristics of the ink need to be controlled to eject ink
without interruption. A considerable amount of binder and coupling
agent may be used to provide sufficient bonding force between the
printed precursor pattern and the base material (substrate), and
the ink exhibits viscoelastic behavior in which the viscosity of
the ink is changed depending on an external force. In this case, in
the present invention, it is preferred that the ink for plating
exhibits a liquid-like behavior within an appropriate stress range.
For example, it is preferred that the ink for plating has a storage
modulus value lower than the loss modulus under a shear stress of
10.sup.1 to 10.sup.3 Pa. More preferably, it is preferred that the
ratio of storage modulus/loss modulus in the above-described shear
stress range is 10.sup.1 or more.
[0051] In the present invention, it is preferred that the catalyst
ink for plating has a viscosity of 5 to 1,500 mPas. An ink having a
low viscosity exhibit good flow characteristics, but a low catalyst
concentration makes efficient plating difficult. Further, an
increase in the viscosity of the ink may increase the catalyst
concentration, but may cause a change in the flow characteristics
of the ink.
[0052] In the present invention, the flow characteristics of the
ink for plating may be controlled by the concentration of a metal
ion, the concentration of a binder, and the concentration of a
coupling agent. Preferably, in the present invention, it is
preferred that the concentration of the metal ion, the
concentration of the binder, and the concentration of the coupling
agent are 1 to 15 g/L, 10 to 200 g/L, and 5 to 15 g/L,
respectively.
Mode for Invention
[0053] Hereinafter, a method for forming a wiring pattern with the
above-described ink for plating will be described.
[0054] FIG. 4 is a set of views for schematically explaining a
method of forming a wiring pattern according to an example of the
present invention.
[0055] Referring to FIG. 4(A), a predetermined precursor pattern is
formed on a base material (substrate) with the above-described
catalyst ink for plating. In the present invention, the precursor
pattern may be formed to be brought into contact with the base
material, but may be formed on another pattern on the base material
unlike the above formation of the precursor pattern.
[0056] In the illustrated drawing, the character pattern `PRINTING`
is illustrated. In this case, a meniscus guided printing technique
may be used as the printing technique, but the present invention is
not limited thereto, and a printing technique of a pressure
ejection method such as an inkjet may be applied. In the printing
method of the present invention, the implementable minimum line
width of the precursor pattern is 1.mu.m. An implementable maximum
line width is not particularly limited, and a line width of up to
300 .mu.m can be implemented. FIG. 4 illustrates a pattern with a
line width of 10 .mu.m.
[0057] In the pattern printed on the surface of the substrate as
illustrated in FIG. 4(A), an HPC binder provides adhesive strength
to a base material, a metal ion is exposed on the surface of the
pattern, and the metal ion acts as a catalyst for electroless
plating.
[0058] Next, as illustrated in FIG. 4(B), a base material on which
a precursor pattern is printed is immersed in a plating solution to
electrolessly plate a metal. The plated metal is selectively plated
on the surface of the pattern. The drawing on the right side of
FIG. 4 is a photograph of the surface state of the plated film, and
it can be confirmed that the plated film has a domain with a size
of several tens of nm and the metal is plated.
[0059] In the present invention, the plating solution may be a
solution containing various metals and metal alloys such as Cu, Ni,
Ni--P, Ni--W--P, and Ni--W--Cu--P.
[0060] In the present invention, a polymer binder of the catalyst
ink for plating exhibits the LCST behavior in the plating solution.
Therefore, the temperature of the plating solution is maintained at
the LCST or higher. Preferably, the temperature of the plating
solution is adjusted to be located above the spinodal curve on the
composition-temperature phase diagram of the polymer-solvent
system. Accordingly, the polymer binder is not dissolved in the
plating solution, and the plated film may be firmly bound to the
base material. Further, a uniform line width implemented on a
precursor pattern may be directly transferred to a wiring pattern
after plating.
[0061] A plating rate in electroless plating depends on the
temperature of a plating solution. Specifically, the plating rate
may be increased exponentially in proportion to the plating
temperature. Therefore, the plating method using the catalyst ink
for plating of the present invention enables plating at a high
temperature, so that the growth rate of the plated film may be
significantly improved.
Experimental Example 1: Preparation of Ink for Plating
[0062] Ink was prepared by sequentially dissolving 10 g/L of silver
nitrate (Daejung Chemicals & Metals Co., Ltd.), 10 g/L of
3-aminopropyltriethoxysilane (Sigma-Aldrich), and 180 g/L of
hydroxypropyl cellulose (Sigma-Aldrich) in water at room
temperature. For comparison with the present invention, an ink to
which HPC was not added (hereinafter, referred to as `Excluding
HPC`) was also prepared.
[0063] The viscosity of the catalyst ink for plating was measured
with a cone-and-plate rheometer (MCR102, Anton Paar) in a shear
rate range of 10.sup.1 to 10.sup.4 s.sup.-1. In order to obtain a
storage elastic modulus and a loss elastic modulus by the function
of stress, the stress was continuously changed at a constant
frequency of 1 Hz.
[0064] FIG. 5 is a graph illustrating the flow characteristics of a
prepared catalyst ink for plating. As can be seen in FIG. 5(A), an
ink to which the HPC is not added shows a Newtonian fluid behavior
in which the viscosity is not changed depending on the shear rate,
but an HPC-added ink shows a shear thinning phenomenon in which the
viscosity is decreased depending on the shear rate.
[0065] Meanwhile, as illustrated in FIG. 5(B), the modulus value of
the ink to which the HPC is not added is kept constant in the shear
stress interval. In contrast, in the case of the HPC-added ink, the
ink shows a behavior in which the storage modulus value is
decreased while the shear stress is increased, and a relationship
of loss modulus>storage modulus in all shear stress intervals is
maintained. This is called a liquid-like behavior. Meanwhile, in
the case of the ink to which the HPC is not added, the loss
modulus/storage modulus ratio is >10.sup.4 or more, but in the
case of the HPC-added ink, this ratio is decreased, but shows
10.sup.2 or more in the illustrated stress interval, and it can be
seen that the difference is reduced in a region where the shear
stress is high.
Experimental Example 2: Manufacture of Precursor Pattern
[0066] From the ink prepared in Experimental Example 1, a
two-dimensional line pattern having a line width of 10 .mu.m and
repeatedly continuous in the horizontal and vertical directions was
formed on a polyimide (PI) base material using a glass micronozzle
with a nozzle tip opening diameter of 10 .mu.m and a P-97 nozzle
puller manufactured by Sutter Instrument Company. In this case, the
ink was released from the tip of the nozzle through a meniscus
produced by the surface tension. The manufactured precursor pattern
was annealed by air at a temperature of 70.degree. C. The
manufactured precursor pattern was observed with S-4800 FE-SEM
manufactured by Hitachi High-Technologies Corporation.
Experimental Example 3: Electroless Plating
[0067] The precursor pattern manufactured in Experimental Example 1
was immersed in a Cu electroless plating solution (6.78 g/L copper
(II) sulfate pentahydrate (Daejung Chemicals & Metals Co.,
Ltd.), 20.04 g/L potassium hydrogen tartrate (Daejung Chemicals
& Metals Co., Ltd.), and 8 g/L sodium hydroxide (Daejung
Chemicals & Metals Co., Ltd.)) maintained at a temperature of
about 60.degree. C. for 1 to 50 minutes and plated. The
manufactured plated pattern was observed with S-4800 FE-SEM
manufactured by Hitachi High-Technologies Corporation. In addition,
the electrical conductivity was measured by a two-point probe
method using a Keithley 2612A device at room temperature.
[0068] FIG. 6 is a plan photograph of a sample in which the
precursor pattern manufactured according to the experimental
example is immersed in a plating solution for 20 minutes and
plated.
[0069] FIGS. 6(A) and 6(B) are a plan photograph of a pattern
(Including HPC) manufactured with the ink of the example of the
present invention and a pattern (Excluding HPC) manufactured with
the ink in the comparative example, respectively, and FIGS. 6(C)
and 6(D) are plan photographs of the pattern after being plated. In
the photographs FIGS. 6(A) to 6(D), the inside of the small box on
the right side shows the overall pattern at low magnification.
[0070] First, as illustrated in FIGS. 6(A) and 6(C), it can be seen
that a uniform line width can be implemented in the precursor
pattern manufactured with the HPC-added ink, and the uniformity of
the line width and the line width is almost maintained even after
plating.
[0071] However, as illustrated in FIGS. 6(B) and (D), it can be
confirmed that the precursor pattern manufactured with the ink to
which the HPC is not added has a non-uniform line width, and an
untidy plated film is formed after plating. This is a result of
pattern decomposition at 60.degree. C. during the electroless
plating process when the HPC is not added.
[0072] FIGS. 7(A) to 7(D) are electron microscope photographs
illustrating the morphology of the plated film formed over the
plating time of the pattern (Including HPC) manufactured with the
ink of the example of the present invention.
[0073] From FIG. 7, it can be seen that as the plating time is
increased, the particle size is increased and the thickness of the
plated film is also increased.
[0074] FIG. 8 is a graph showing the results of measuring the
resistance value of the plated pattern over the plating time
(reaction time).
[0075] Referring to FIG. 8, it can be seen that when the plating
time is 20 minutes or more, the electrical characteristics are kept
almost constant. Meanwhile, it can be seen that when the plated
pattern is plated for 50 minutes, the resistance of the plated film
is only about 1.53 times the resistivity of bulk Cu, and a plated
film with high conductivity can be obtained.
Experimental Example 4: Evaluation of Adhesive Strength
[0076] As in Experimental Example 3, Cu plating was performed
between two terminals of a plastic board for 20 minutes to form a
plated pattern, thereby electrically connecting the two terminals.
After an adhesive tape was attached to a plated pattern forming
portion, it was confirmed whether or not the plated pattern was
peeled off when the adhesive tape was removed.
[0077] FIG. 9 is a set of photographs taken after the adhesive tape
was attached and after the adhesive tape was removed. As
illustrated, it can be seen that there was no disconnection before
and after the adhesive tape was attached.
[0078] Although the present invention has been described in detail
through the examples of the present invention, the above
description exemplifies the present invention, and the present
invention is not limited thereto. It should be considered to belong
to the scope of the present invention to the extent that various
modifications can be made by any person having ordinary skill in
the art to which the invention pertains without departing from the
appended claims and the gist of the invention.
INDUSTRIAL APPLICABILITY
[0079] The present invention can be used in printed electronics
which implement electronic devices, electronic components, printed
circuit boards, and the like.
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