U.S. patent application number 12/711746 was filed with the patent office on 2010-06-17 for surface treatment method, circuit lines formation method, circuit lines formation apparatus, and printed circuit board formed thereby.
This patent application is currently assigned to Samsung Electro-Mechanics Co., Ltd. Invention is credited to Yoon-Ah BAIK, Hyun-Chul JUNG.
Application Number | 20100146777 12/711746 |
Document ID | / |
Family ID | 37071128 |
Filed Date | 2010-06-17 |
United States Patent
Application |
20100146777 |
Kind Code |
A1 |
BAIK; Yoon-Ah ; et
al. |
June 17, 2010 |
SURFACE TREATMENT METHOD, CIRCUIT LINES FORMATION METHOD, CIRCUIT
LINES FORMATION APPARATUS, AND PRINTED CIRCUIT BOARD FORMED
THEREBY
Abstract
The present invention relates to a method of surface treatment,
a method for forming circuit lines, a printed circuit board formed
thereby, and an apparatus for forming circuit lines on a substrate,
wherein fine circuit lines are formed simply, rapidly, and
economically. The method for forming circuit lines of the present
invention comprises: (a) selectively applying a surface treatment
solution which includes an alkali metal compound on a base film in
accordance with circuit patterns by a discharging method; (b)
applying a conductive ink which includes metal nanoparticles in
accordance with the surface-treated circuit pattern; and (c) curing
the base film on which the conductive ink is applied under a
reduction atmosphere lines.
Inventors: |
BAIK; Yoon-Ah; (Suwon-si,
KR) ; JUNG; Hyun-Chul; (Suwon-si, KR) |
Correspondence
Address: |
STANZIONE & KIM, LLP
919 18TH STREET, N.W., SUITE 440
WASHINGTON
DC
20006
US
|
Assignee: |
Samsung Electro-Mechanics Co.,
Ltd
Suwon-si
KR
|
Family ID: |
37071128 |
Appl. No.: |
12/711746 |
Filed: |
February 24, 2010 |
Current U.S.
Class: |
29/829 |
Current CPC
Class: |
H05K 2203/0793 20130101;
H05K 3/125 20130101; H05K 3/381 20130101; Y10T 29/49124 20150115;
H05K 3/1208 20130101; H05K 2203/013 20130101; H05K 2203/1157
20130101 |
Class at
Publication: |
29/829 |
International
Class: |
H05K 3/10 20060101
H05K003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 2005 |
KR |
2005-27508 |
Claims
1. A printed circuit board having fine circuit lines, wherein said
fine circuit lines are manufactured comprising the steps of: (a)
selectively applying a surface treatment solution which includes
alkali metal compound on a base film in accordance with the circuit
pattern by a discharging method; (b) applying the conductive ink
which includes metal nano particle in accordance with the surface
treated circuit pattern by said step (a); and (c) curing the base
film on which the conductive ink is applied under reduction
atmosphere.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of prior application Ser.
No. 11/278,205, filed Mar. 31, 2006, in the U.S. Patent and
Trademark Office, which claims priority from Korean Patent
Application No. 10-2005-27508, filed on Apr. 1, 2005, respectively,
in the Korean Intellectual Property Office, the disclosures of
which are incorporated herein in their entirety by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of surface
treatment, a method for forming circuit lines, an apparatus for
forming circuit lines, and a printed circuit board formed
thereby.
[0004] 2. Description of the Related Art
[0005] There are two kinds of conventional methods for forming
circuit lines on a substrate of which one is a substractive process
forming circuit lines by etching a copper layer and the other is an
additive process forming circuit lines by plating with copper on a
bare dielectric material. Both methods require a photoresist film
for forming a circuit pattern on a substrate, and exposure and
development steps of the photoresist film. Especially, the
substractive process requires a longer etching step of the copper
layer. These methods have some drawbacks: 1) the copper layer in
the substractive process must be introduced to a whole space of the
substrate, whether or not circuit lines are formed, so that it
becomes costly and low efficient, and 2) these processes require
the steps of providing a photoresist film and removing it later, so
that the manufacturing time becomes longer and the manufacturing
process becomes complicate and inefficient. Further, these
processes cannot provide fine circuit lines.
[0006] To overcome the drawbacks associated with above mentioned
conventional processes, a method for forming fine circuit lines is
suggested by an ink-jet process, which forms circuit lines by
applying a conductive ink on a substrate in accordance with a
circuit pattern. The method for forming fine circuit lines by the
ink-jet process does not require a photoresist film or an etching
step, and can form fine circuit lines. However, it also has a
drawback that a bonding power between the substrate and the circuit
lines is weak, so that it deteriorates an electric reliability.
[0007] To solve the defects associated with the method for forming
fine circuit lines by the ink-jet process, referring to FIG. 1, it
shows cross-sectional views of a substrate for forming circuit
lines on a printed circuit board by using a laser beam. This laser
process for forming conductive circuit lines comprises the steps
for forming a waterproofing layer 150 on a whole surface of a base
film 110, removing the waterproofing layer by the laser beam in
accordance with a circuit pattern, and applying a conductive ink
170 on parts of a substrate where the waterproofing layer is
removed. The laser process requires an extra apparatus of
generating the laser beam which is expensive and the extra steps
for forming and removing the waterproofing layer, so that it
becomes inconvenient and inefficient.
[0008] It would therefore be desirable to have an improved method
for forming fine circuit lines and printed circuit board made
thereby.
SUMMARY OF THE INVENTION
[0009] The present invention was invented to overcome the defects
associated with conventional technologies, and it is an object of
the present invention to provide a method of surface treatment on a
substrate which may treat not a whole surface of the substrate but
a surface of circuit patterns selectively, so that the
manufacturing process may be simplified and the manufacturing cost
may be reduced.
[0010] It is another object of the present invention to provide a
method for forming circuit lines on a substrate which may form fine
circuit lines by a simplified process including the above mentioned
method of surface treatment, which do not require a photoresist
film or an etching process.
[0011] It is still another object of the present invention to
provide a printed circuit board having fine circuit lines formed by
the simplified method.
[0012] It is still another object of the present invention to
provide an apparatus which may form the printed circuit board.
[0013] One aspect of the present invention provides a method of
surface treatment on a substrate, wherein a surface treatment
solution including an alkali metal compound is discharged on a base
film in accordance with circuit patterns by a discharging method.
The alkali metal compound may be selected from the group consisting
of KOH, NaOH, LiOH and a mixture thereof. The discharging method
may be an ink-jet printing method. According to a preferred
embodiment, an ink-jet printer head used in the ink-jet printing
method has a nozzle diameter of 1 to 80 .mu.m and the base film may
be a polyimide film.
[0014] Another aspect of the present invention provides a method
for forming circuit lines on a substrate, wherein the method may
comprise the steps of (a) selectively applying a surface treatment
solution which includes an alkali metal compound on a base film in
accordance with circuit patterns by a discharging method, (b)
applying a conductive ink which includes metal nanoparticles in
accordance with the surface treated circuit patterns, and (c)
curing the base film on which the conductive ink is applied under
reduction atmosphere. The step (b) may be performed simultaneously
while the step (a) is performed. According to a preferred
embodiment, the base film may be a polyimide film, and the
discharging method may use an ink-jet printer. The ink-jet printer
may comprise a plurality of ink-jet printer heads, wherein the
plurality of ink-jet printer heads may comprise an ink-jet printer
head for the surface treatment, which discharges a surface
treatment solution including an alkali metal compound, and an
ink-jet printer head for the conductive ink, which discharges a
conductive ink. The ink-jet printer head for the surface treatment
and the ink-jet printer head for the conductive ink may operate
independently in corresponding to different action control signals
from each other, and discharge the surface treatment solution and
the conductive ink, respectively.
[0015] A nozzle size of the ink-jet printer head for the surface
treatment may be smaller than that of the ink-jet printer head for
the conductive ink or discharging frequencies of the ink-jet
printer head for the surface treatment and the ink-jet printer head
for the conductive ink may be different.
[0016] According to a preferred embodiment, the nozzle diameter of
the ink-jet printer head for the surface treatment is smaller than
the nozzle diameter of the ink-jet printer head for the conductive
ink by from 1 to 20 .mu.m. And the alkali metal compound is
selected from the group consisting of KOH, NaOH, LiOH and a mixture
thereof.
[0017] Further another aspect of the present invention provides a
printed circuit board having fine circuit lines formed by the steps
of (a) selectively applying the surface treatment solution which
includes an alkali metal compound on a base film in accordance with
circuit patterns by a discharging method, (b) applying a conductive
ink which includes metal nanoparticles in accordance with the
surface treated circuit patterns, and (c) curing the base film on
which the conductive ink is applied under a reduction
atmosphere.
[0018] Further another aspect of the present invention provides an
apparatus for forming circuit lines on a substrate. The apparatus
comprises an ink-jet printer head for the surface treatment which
discharges a surface treatment solution and an ink-jet printer head
for the conductive ink which discharges a conductive ink including
metal nanoparticles, wherein the ink-jet printer head for the
surface treatment and the ink-jet printer head for the conductive
ink simultaneously discharge the surface treatment solution and the
conductive ink, respectively.
[0019] The ink-jet printer head for the surface treatment and the
ink-jet printer head for the conductive ink operate independently
in corresponding to different action control signals from each
other, and discharge the surface treatment solution and the
conductive ink, respectively. The nozzle size of the ink-jet
printer head for the surface treatment is smaller than that of the
ink-jet printer head for the conductive ink or discharging
frequencies of the ink-jet printer head for the surface treatment
and the ink-jet printer head for the conductive ink may be
different.
[0020] According to a preferred embodiment, the nozzle diameter of
the ink-jet printer head for the surface treatment is smaller than
that of the ink-jet printer head for the conductive ink by from 1
to 20 .mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows cross-sectional views of a substrate for
forming circuit lines on a printed circuit board in accordance with
a conventional process.
[0022] FIG. 2 is a perspective view illustrating a method of the
surface treatment on a substrate in accordance with a preferred
embodiment of the present invention.
[0023] FIG. 3 is a perspective view illustrating a method for
forming circuit lines in accordance with a preferred embodiment of
the present invention.
[0024] FIG. 4 shows a cross-sectional view of the circuit lines
before curing in accordance with a preferred embodiment of the
present invention.
[0025] FIG. 5 shows a cross-sectional view of the circuit lines
before curing in accordance with another preferred embodiment of
the present invention.
[0026] FIG. 6 is a flow diagram illustrating a process of
manufacturing a printed circuit board in accordance with a
preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Prior to describe embodiments of the present invention,
firstly, examples of a surface treatment on a substrate and
reactions which can occur during the surface treatment are
described.
[0028] The method of the surface treatment for forming conductive
circuit lines can be divided broadly by a dry method and a wetting
method. The wetting method is generally used compared to the dry
method because of ease reaction and low cost. Due to rapid surface
treatment of the wetting method, there has been a great deal of
development research on alkali treatments using an alkali
solution.
[0029] In accordance with a preferred embodiment, in case that the
base film is a polyimide film and the surface treatment solution is
a KOH solution, it will describe reactions which can occur on the
surface of the substrate.
[0030] Referring to Chemical Equation 1, when a polyimid film is
treated with a KOH alkali solution, the polyimid ring is opened by
hydrolysis.
##STR00001##
[0031] The opened-polyimid ring is then unstable, so that it reacts
again with KOH. Referring to Chemical Equation 2, the
opened-polyimide in Chemical Equation 1 becomes polyamate by an
acid-base reaction.
##STR00002##
[0032] When the surface of the polyimide is polyamate, a conductive
ink is applied thereon. This is because if the conductive ink is
applied when polar groups are introduced on the surface of the
polyimide film, it can improve a bonding power between the
conductive ink and the film.
[0033] After applying the ink, the substrate is cured under a
reduction atmosphere. In case that hydrochloric acid is used as a
reduction condition, the reaction as Chemical Equation 3 may occur
on the surface of the film. Referring to Chemical Equation 3, the
polyamate of the film surface becomes stable polyamic acid by a
protonation.
##STR00003##
[0034] Hereinafter, preferred embodiments of the surface treatment
method, circuit lines formation method, and circuit lines formation
apparatus of a substrate and the printed circuit board according to
the invention will be described in more detail with reference to
the accompanying drawings. In the description with reference to the
accompanying drawings, those components are rendered the same
reference number that are the same or are in correspondence
regardless of the figure number, and redundant explanations are
omitted. lines.
[0035] The "simultaneously," "perform simultaneously" or "discharge
simultaneously" mean that it is possible to discharge the surface
treatment solution and the conductive ink not only at the same time
but also by using a plurality of ink-jet heads in accordance with a
preset program.
[0036] FIG. 2 is a perspective view illustrating a method of the
surface treatment of a substrate in accordance with a preferred
embodiment of the present invention. Referring to FIG. 2, a surface
treatment solution is discharged on base film 210 in accordance
with a preset circuit pattern 261 by an ink-jet printer including
an ink-jet printer head 230 for the surface treatment solution.
Surface treated circuit lines 263 on the base film 210 are
formed.
[0037] Unlike a conventional method which treats a whole surface of
a base film, the surface treatment of the present invention allows
selective surface treatment of the base film since circuit patterns
can be formed by using an ink-jet printer. Also, it does not
require photo-resistor or elimination of water repellent film, so
that it allows simple and low-cost surface treatment. It further
allows selective surface treatment in accordance with fine circuit
lines by controlling nozzle size of an ink-jet printer or
discharging frequency of an ink-jet printer head.
[0038] FIG. 3 is a perspective view illustrating a method for
forming circuit lines of a substrate in accordance with a preferred
embodiment of the present invention. Referring FIG. 3, the surface
treatment solution is discharged on the base film 210 in accordance
with the preset circuit pattern 261 by the ink-jet printer
including the ink-jet printer head for the surface treatment 230.
The surface treated circuit lines 263 was then formed on the base
film 210. A conductive ink 270 which includes metal nanoparticles
is discharged on the surface treated circuit lines 263 by an
ink-jet printer including an ink-jet printer head for the
conductive ink 250. The circuit lines 265 applied with the
conductive ink is then formed on the base film 210.
[0039] FIG. 4 shows a cross-sectional view of circuit lines, before
curing, formed in accordance with a preferred embodiment of the
invention and FIG. 5 shows a cross-sectional view of circuit lines,
before curing, formed in accordance with another preferred
embodiment of the present invention. Referring to FIG. 4 and FIG.
5, a surface treatment solution 280 layer is formed on the base
film 210 and a conductive ink 270 layer is then formed on the
surface treatment solution 280 layer. The surface treatment
solution 280 layer forms the surface treated circuit lines 263, by
the ink-jet printer head for the surface treatment 230. The
conductive ink 270 layer forms the conductive circuit lines 265, by
the ink-jet printer head for the conductive ink 250. FIG. 4 shows
that a drop size of the surface treatment solution 280 on the
surface of the base film is bigger than that of the conductive ink
270. FIG. 5 shows that a drop size of the surface treatment
solution 280 on the surface of the base film is smaller than that
of the conductive ink 270.
[0040] After the surface treatment as described above, the base
film 210 having the conductive ink-discharged circuit lines 265 is
cured under reduction atmosphere to produce conductive circuit
lines. The step of curing can be performed by the general method in
the field of the manufacturing printed circuit board, but is not
limited to a particular method.
[0041] According to a preferred embodiment of the invention, the
surface treatment and discharging the conductive ink may be
performed simultaneously by arrange the ink-jet printer head for
the surface treatment 230 and the ink-jet printer head for the
conductive ink 250 in series. Here, the term of "performed
simultaneously" means that not only the surface treatment solution
280 and the conductive ink 270 can be discharged at the same time,
but also the surface treatment solution 280 and the conductive ink
270 can be discharged in accordance with a preset program by
employing a plurality of ink-jet printer heads. Referring to FIG.
3, the ink-jet printer head for the surface treatment 230 and the
ink-jet printer head for the conductive ink 250 move by facing the
base film 210 and simultaneously discharge the surface treatment
solution and the conductive ink, respectively, Herein, there may be
an interval of time in discharging the ink-jet printer head for the
surface treatment 230 and the discharging of the ink-jet printer
head for the conductive ink 250, to provide time for forming
polyamates on the surface treated circuit lines by a reaction
between alkali solution and polyimide.
[0042] The surface treatment solution and the conductive ink may
simultaneously be discharged, respectively, through the ink-jet
printer head for the surface treatment 230 and the ink-jet printer
head for the conductive ink 250 arranged by having a certain
distance to provide time for forming polyamates on the surface
treated circuit lines by a reaction between alkali solution and
polyimide.
[0043] Such ink-jet printer head for the surface treatment 230 and
ink-jet printer head for the conductive ink 250 may be a head of an
ink-jet printer apparatus for lines discharging. For example, the
ink-jet printer apparatus lines may comprise a support which
supports the apparatus; an ink-jet printer head which discharges
the surface treatment solution and the conductive ink,
respectively, along with a pre-set circuit pattern 261 on the base
film; a moving part which moves the ink-jet printer head on the
base film 210; a circuit part which performs a program to control
discharging of inks along with the preset circuit pattern; and the
like.
[0044] In accordance with a preferred embodiment of the present
invention, the ink-jet printer head for the surface treatment 230
and the ink-jet printer head for the conductive ink 250 moves
together and simultaneously discharge the surface treatment
solution and the conductive ink, respectively. Therefore, these
ink-jet printer heads can discharge the surface treatment solution
and the conductive ink, respectively, by moving together over the
same path of the base film in accordance with the preset circuit
pattern. When the ink-jet printer heads move, it is possible to
control discharging position or discharging amount of the surface
treatment solution and the conductive ink from each head, so that
the surface treatment solution and the conductive ink may be
discharged in accordance with the preset program.
[0045] In accordance with another preferred embodiment of the
present invention, the ink-jet printer head for the surface
treatment 230 and the ink-jet printer head for the conductive ink
250 move individually in corresponding to a different moving
control signal and may discharge the surface treatment solution and
the conductive ink, respectively, That is, each ink-jet printer
head may be equipped in one apparatus or separate apparatuses, and
may be moved independently in corresponding to its own different
moving control signal by different programs.
[0046] It is also possible to use simultaneously a plurality of the
ink-jet printer heads of the surface treatment 230 and a plurality
of the ink-jet printer heads for the conductive ink 250.
[0047] Nozzle sizes of the ink-jet printer head of the surface
treatment 230 and the ink-jet printer head for the conductive ink
250 should be suitable to form fine circuit lines. Recently, there
is a demand to be a diameter of the nozzle of the ink-jet printer
head under several tens .mu.m to form fine circuit lines which have
the width under several tens .mu.m. The nozzle diameter of the
ink-jet printer head used in the present invention is from 1 to 80
.mu.m, preferably about 20 .mu.m. In case that the nozzle size is
80 .mu.m or above, it is not suitable for forming the fine circuit
lines. In case that the nozzle size is under 1 .mu.m, it is
difficult to discharge the surface treatment solution or the
conductive ink.
[0048] Referring to FIG. 4, a drop size of the surface treatment
solution is different from that of the conductive ink. Having same
drop sizes of the surface treatment solution and the conductive ink
is ideal. But, the drop size of the surface treatment solution is
generally bigger than the drop size of the conductive ink due to
different viscosities between the surface treatment solution and
the conductive ink. If the drop size of the surface treatment
solution is excessively bigger than the drop size of the conductive
ink, it cannot form desired circuit lines because the conductive
ink cannot be gathered lines. Referring to FIG. 5, if the drop size
of the surface treatment solution is excessively smaller than the
drop size of the conductive ink, the conductive ink cannot bond
stably to the substrate. Therefore, a diameter of the drop size of
the surface treatment solution may preferably be from 0.6 to 1.5
times a diameter of the drop size of the conductive ink.
[0049] In accordance with a preferred embodiment of the present
invention, the nozzle size of the ink-jet printer head for the
surface treatment may be smaller than the nozzle size of the
ink-jet printer head for the conductive ink to allow a difference
of the drop size between the surface treatment solution and the
conductive ink to be in the above range. That is, the nozzle size
of the ink-jet printer head for the surface treatment 230 providing
a bigger drop size can be reduced, so that the drop size of the
surface treatment solution becomes smaller. According to a
preferred embodiment, when the nozzle diameter of the ink-jet
printer head for the surface treatment is smaller than the nozzle
diameter of the ink-jet printer head for the conductive ink by from
1 to 20 .mu.m, the drop size of the surface treatment solution can
be in the range from 0.6 to 1.5 times to the drop size of the
conductive ink.
[0050] In accordance with another preferred embodiment of the
present invention, the drop sizes of the surface treatment solution
and the conductive ink may be controlled by employing different
discharging frequencies to allow a difference of the drop size
between the surface treatment solution and the conductive ink to be
within the preferred range even if the nozzle sizes of diameter of
the ink-jet printer head for the surface treatment and the ink-jet
printer head for the conductive ink are identical.
[0051] In accordance with the other preferred embodiment of the
present invention, the difference of the drop size can be
controlled by changing waveform shapes or waveform steps of
discharging pressure or absorption pressure to allow a difference
of the drop size between the surface treatment solution and the
conductive ink to be within the preferred range.
[0052] In accordance with another preferred embodiment of the
present invention, a dot number of the surface treatment solution
and the conductive ink which is discharged respectively per 1 inch
of the circuit pattern may be controlled to make a difference of
the drop size between the surface treatment solution and the
conductive ink.
[0053] FIG. 6 is a flow diagram illustrating a process of
manufacturing a printed circuit board in accordance with a
preferred embodiment of the present invention. Referring to FIG. 6,
surface of the base film 210 is cleaned for following steps in
S205, and a circuit pattern is preset for next steps of surface
treatment by means of a general method in this technical field. In
S215, the surface treatment solution is selectively applied in
accordance with the circuit pattern on the base film by a
discharging method. This step is described in detail in the
following embodiment. In S220, a conductive ink including
nanoparticles is applied, so that the ink-applied circuit lines 265
is formed on the surface-treated one. This step is also described
in detail in the following embodiment. In S225, the base film
having circuit lines formed in S215 and S220 is cured under a
reduction atmosphere.
[0054] A desired number of the substrate is laminated for forming
multilayer printed circuit board, which includes copper layer or
dielectric layer in S230. A soldering process forms a solder resist
layer to prevent any undesired contact with external parts on the
formed conductive circuit lines in S235. Symbol marks, for example
part name and part position, are printed on the substrate in S240,
and a final surface treatment such as a HASL process is performed
in S245. A terminal is plated in S250, and hole and appearance
treatment are performed to produce a printed circuit board in
S255.
[0055] Use of the printed circuit board (PCB) manufactured in
accordance with the method of the present invention is not limited,
and it may be used in manufacturing printed circuit boards which
include a polyimide film such as a flexible printed circuit board
(FPCB).
EMBODIMENTS
[0056] Hereinafter, an embodiment of the method of surface
treatment, the method for forming circuit lines, the printed
circuit board formed thereby, and the apparatus for forming circuit
lines on a substrate according to the present invention will be
described in more detail with accordance to each condition of the
steps.
[0057] 1) Base Film
[0058] A base film 210 is generally an organic dielectric material.
The organic dielectric material requires relatively high
elasticity, lower hygroscopic swelling coefficient, and lower
linesar expansion coefficient. When the hygroscopic swelling
coefficient of the organic dielectric material is high, a PCB
manufactured by using such an organic dielectric material easily
bends or produces curls with changes of external circumstances,
such as temperature or humidity. FPCBs for PDP which have a wider
area compared to other uses specially require a high dimensional
stability of the base film. In order to use an organic dielectric
material as the base film, it is preferred to have heat resistance,
appropriate elasticity, flexibility, appropriate hygroscopic
swelling coefficient, and appropriate linesar expansion
coefficient. The preferred organic dielectric material having such
properties is polyimide, but not limited to it.
[0059] The method of the surface treatment of a substrate of the
present invention is exampled for the base film used in FPCBs for
PDP, but is not limited thereto. The base film may be used in
circuit lines or method for forming circuit lines of substrates
below to be described.
[0060] 2) Surface Treatment Condition
[0061] (1) Surface Treatment Solution and Additives
[0062] Studies using alkali solutions as a surface treatment
solution have been extensively increased. The alkali solution
includes an alkali metal (that is elements of 1A row of the
periodic table) compound, preferably KOH, NaOH, LiOH and a mixture
of thereby. In accordance with a preferred embodiment, the surface
treatment solution may also include additives by 40 volume % in the
total surface treatment solution. Example of the additives include
ethylene glycol, di(ethylene glycol) butyl ether, 1-butanol,
terpinol, .alpha.-terpinol, propylene glycol, methanol, ethanol,
propanol, butanol, isobutanol, 2-(isopropylamino) ethanol, ethylene
diamene, glycerol, hexyl alcohol, 2-methyl-2,4-pentandiol,
acetonitrile, ethylene glycol butyl ether, 1-methyl-2-pyrrolidione,
diethylene glycol diethyl ether, diethylene glycol, proethylene
glycol, xylene, toluene, tetradecane, dodecane, propylene glycol,
triethylene glycol, dipropylene glycol, hexylene glycol, butylene
glycol, methyl ethyl ether and so on. These additives can be added
depending on a desired condition since they control viscosity,
adhesion to the surface of the base film, spread rate of the
surface treatment solution, evaporation rate, and the like.
[0063] (2) Concentration of the Surface Treatment Solution
[0064] In case that KOH is selected as the surface treatment
solution, the concentration of KOH is preferred from 0.1 to 10M,
more preferred 1M. It is scarcely any effect of the surface
treatment on a polyimide film when the concentration of the KOH is
under 0.1M. It is not preferred because the property of the
polyimide film may be changed when the concentration of the KOH is
over 10M. According to a preferred embodiment, in case that the
thickness of the polyimide film is 25 .mu.m, over 10 .mu.m of the
polyimide film surface is reformed when the concentration of the
surface treatment solution is over 10M. As a result, it becomes
difficult to control the polyimide film.
[0065] (3) Surface Treatment Time
[0066] It is preferable that the surface treatment time be a time
to form polyamates by reacting polyimides with KOH solution on the
surface of the polyimide film. The conductive ink is discharged
after the polyamates are formed from polyimides, so that the
corresponding conductive circuit lines may be obtained. In
accordance with the preferred embodiment of the present invention,
the surface treatment time is preferred from to 1 to 20 minutes,
more preferred from 3 to 10 minutes. Enough ployamates are not
formed when it is under 1 minute. On the other hand when it is more
than 20 minutes, further polyamates are not formed due to
stabilized reaction state on the surface of the polyimide.
[0067] (4) Surface Treatment Temperature
[0068] The temperature of the surface treatment is preferred in the
range from 3 to 80.degree. C. It may be difficult to discharge the
surface treatment solution or the conductive ink from the nozzle of
the ink-jet printer because the viscosity thereof becomes low when
the temperature is under 3. The chemical property of the KOH
solution may be changed and especially, compounds of the conductive
ink may react each other when the temperature is over 80.degree.
C.
[0069] (5) Surface Treatment Pressure
[0070] It is preferred that the discharging of the surface
treatment solution is performed under 0.8 to 1.5 atm pressure. In
case that the pressure is out of the range, it is difficult to
maintain the straightness of the surface treatment solution and
control the drop size. Also, the surface treatment may be performed
under air or nitrogen atmosphere. In the case of the surface
treatment under nitrogen atmosphere, it is required a flow control
of the surface treatment solution
[0071] Herein, the alkali solution is not limited to KOH, it is
apparent that NaOH or LiOH solution may be used.
[0072] 3) Conductive Ink
[0073] It is not limited especially the kind of metal nanoparticles
included the conductive ink to form the fine circuit lines.
Examples of the metal of the metal nanoparticles include gold,
silver, copper, platinum, chromium, nickel, aluminum, titanium,
palladium, tin, vanadium, zinc, manganese, cobalt, zirconium, and
the like. These metals can be used also as a mixture of 2 or more.
It is preferred gold, silver, copper and nickel among examples. The
conductive ink is a colloid which the metal nanoparticles are
dispersed by a dispersing agent. The preferred viscosity of the
conductive ink for fine circuit printing is from 1 to 50 cps.
[0074] 4) Reduction Atmosphere
[0075] An acid such as acetic acid, formic acid, and hydrochloric
acid may be used for forming the reduction atmosphere. Under the
reduction atmosphere, polyamates become their stable state of the
corresponding polyamic acid.
[0076] 5) Discharging Method
[0077] `Discharging method` is a printing method which jets or
discharges a desired low viscosity solution or colloid on an object
by using nozzle or needle. A preferred method is an ink-jet
printing method which uses the ink-jet printer. Herein, the ink-jet
printing method is divided broadly by Piezo method and Thermal
method in accordance with driving mechanism of the ink-jet printer
head, but it is not limited to these methods. If a concentration of
the surface treatment solution is controlled, an ink-jet printer
for OA may also be possible.
[0078] Here, number or kind of ink-jet printer heads, nozzle size
of ink-jet printer heads and the like are described in detail in
the above-mentioned embodiment, so that descriptions relating
thereto will be omitted.
[0079] The foregoing detailed description is intended to be
illustrative rather than limiting, and the scope of the invention
is to be measured by the following claims, including any
equivalents thereto.
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