U.S. patent application number 11/483845 was filed with the patent office on 2007-01-11 for method for producing fine circuit lines and conductive board.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Yoon-Ah Baik, Myung-Joon Jang, Hyun-Chul Jung, Young-Gun Ko, Jae-Chan Park, Shang-Hoon Seo.
Application Number | 20070006983 11/483845 |
Document ID | / |
Family ID | 37617241 |
Filed Date | 2007-01-11 |
United States Patent
Application |
20070006983 |
Kind Code |
A1 |
Ko; Young-Gun ; et
al. |
January 11, 2007 |
Method for producing fine circuit lines and conductive board
Abstract
The present invention provides a method for forming a circuit
line which may be formed simply and economically by alleviating
spread of an ink and exhibit excellent electric conductivity by
having even height of the formed ink. The present invention further
provides a conductive board with excellent high-dense electric
conductivity including fine circuit lines. According to one
embodiment of the present invention, a method for forming fine
circuit lines comprises (a) treating at least one side of a circuit
line pattern to be formed on a base substrate with an alkali metal
hydroxide solution and (b) treating a hydrophobic ink in accordance
to a circuit line pattern to be formed.
Inventors: |
Ko; Young-Gun; (Seoul,
KR) ; Jung; Hyun-Chul; (Yongin-si, KR) ; Park;
Jae-Chan; (Suwon-si, KR) ; Seo; Shang-Hoon;
(Seoul, KR) ; Jang; Myung-Joon; (Seoul, KR)
; Baik; Yoon-Ah; (Suwon-si, KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
37617241 |
Appl. No.: |
11/483845 |
Filed: |
July 11, 2006 |
Current U.S.
Class: |
162/5 |
Current CPC
Class: |
H05K 2203/1173 20130101;
H05K 3/1208 20130101; H05K 2203/0793 20130101; H05K 3/1241
20130101 |
Class at
Publication: |
162/005 |
International
Class: |
D21C 5/02 20060101
D21C005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 11, 2005 |
KR |
10-2005-0062373 |
Claims
1. A method for forming fine circuit lines comprising: (a) treating
at least one side of a circuit line pattern to be formed on a base
substrate with an alkali metal hydroxide solution; and (b) treating
with an hydrophobic ink along with the circuit line pattern to be
formed.
2. The method for forming fine circuit lines of claim 1, wherein
both sides of the circuit line pattern to be formed are
simultaneously treated in the step (a).
3. The method for forming fine circuit lines of claim 2, wherein a
step for treating the portion treated with the alkali metal
hydroxide solution further with a weak acid solution prior to the
step (b).
4. The method for forming fine circuit lines of claim 3, wherein
the weak acid is at least one selected from the group consisting of
formic acid and C1-C20 alkanoic acids.
5. The method for forming fine circuit lines of claim 1, wherein
the alkali metal hydroxide solution is at least one selected from
the group consisting of KOH, NaOH, and LiOH.
6. The method for forming fine circuit lines of claim 5, wherein a
concentration of the alkali metal hydroxide solution is in the
range of from 0.1 to 10M.
7. The method for forming fine circuit lines of claim 1, wherein
the hydrophobic ink is an ink including tetradecane.
8. The method for forming fine circuit lines of claim 1, wherein
the base substrate is a polyimide film.
9. The method for forming fine circuit lines of claim 1, wherein
the alkali metal hydroxide solution or the hydrophobic ink is
treated by an ink-jet method.
10. A conductive board including circuit lines formed by a method
for forming fine circuit lines comprising: (a) treating at least
one side of a circuit line pattern to be formed on a base substrate
with an alkali metal hydroxide solution; and (b) treating with an
hydrophobic ink along with the circuit line pattern to be
formed.
11. The conductive board of claim 10, wherein the circuit lines
have a width of 1 to 80 .mu.m.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 2005-0062373 filed with the Korea Industrial
Property Office on Jul. 11, 2005, the disclosure of which is
incorporated herein by reference.
[0002] BACKGROUND
[0003] 1. Field of the Invention
[0004] The present invention relates to a method for forming fine
circuit lines on a base substrate, particularly to a method for
forming fine circuit lines by an ink-jet method.
[0005] 2. Description of the Related Art
[0006] A conventional method for forming circuit lines on a base
substrate is an etching resist treatment. But it is difficult to
form fine circuit lines and requires a process of removing resist.
Another method for forming fine circuit lines is a laser processing
which after forming a water repellent coating layer all over a base
substrate, a portion of the water repellent coating layer is
removed by a laser light and a conductive ink is sprayed on the
portion where the water repellent coating layer is removed.
However, it requires an additional laser light producing device
which increases a manufacturing cost and is complicated and
inefficient since the water repellent coating layer has to be
formed and then removed.
[0007] Therefore, an ink-jet method has been used these days to
form fine circuit lines on a base substrate which allows several
advantages including selective forming of fine circuit lines.
However, it still needs to improve resolution which is very much
affected by a diameter of an ink ejected from an ink-jet head,
surface tension, and interfacial tension. Since metal nanoparticles
are used to provide conductivity to the circuit lines, there is
limitation to decrease a size of an ink-jet head and a diameter of
droplets ejected. There is another problem of spread of an ink when
the ink is ejected on a base substrate with a viscosity able to be
ejected by an ink-jet method. Therefore, there have been various
efforts to develop a method for forming fine circuit lines by an
ink-jet method.
SUMMARY
[0008] As a solution to the forgoing problems of prior art, one
aspect of the present invention provides a method for forming fine
circuit lines simply and economically by alleviating spread of an
ink with a pretreatment on a base substrate before ejecting an ink.
Further, the present invention provides a high dense conductive
board including such fine circuit lines.
[0009] Additional aspects and advantages of the present invention
will be set forth in part in the description which follows and, in
part, will be obvious from the description, or may be learned by
practice of the invention.
[0010] According to an embodiment of the present invention, a
method for forming fine circuit lines comprises treating at least
one side of a circuit line pattern on a base substrate with an
alkali metal hydroxide solution and (b) treating a hydrophobic ink
along with the circuit line pattern to be formed. Here, both sides
of the circuit line pattern to be formed may be treated
simultaneously in Step (a) and a treatment with a weak acid
solution to the portion treated with the alkali metal hydroxide
solution may be performed before Step (b). According to a preferred
embodiment of the present invention, the weak acid solution is at
least one selected from the group consisting of a formic acid and
C1-C20 alkanoic acids
[0011] According to a preferred embodiment of the present
invention, the alkali metal hydroxide solution is at least one
selected from the group consisting of KOH, NaOH, and LiOH and it is
preferable that its concentration be in the range of from 0.1 to
10M. The hydrophobic ink is tetradecanes.
[0012] The base substrate is a polyimide film and the alkali metal
hydroxide solution and the hydrophobic ink are ejected by an
ink-jet method.
[0013] According to another embodiment of the present invention, a
conductive board including fine circuit lines prepared by the
method for forming fine circuit lines is provided. It is preferable
that the circuit lines have a width of 1 to 80 .mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic drawing illustrating a fine circuit
line according to a preferred embodiment of the present
invention.
DETAILED DESCRIPTION
[0015] Hereinafter, the method for forming fine circuit lines and
the conductive board, according to embodiments of the present
invention will be described in more detail with reference to the
accompanying drawing.
[0016] FIG. 1 is a schematic drawing illustrating a fine circuit
line according to a preferred embodiment of the present invention.
Referring to FIG. 1, a high dense board is prepared by treating at
least one side of a circuit line pattern to be formed with an
alkali metal hydroxide solution in Step (A), reforming surface of a
base substrate by reacting the alkali metal hydroxide solution and
the base substrate in Step (B), treating a weak acid solution to
the portion treated with the alkali metal hydroxide solution in
Step (C) which is optional, ejecting a hydrophobic ink along with
the circuit line pattern to be formed in Step (D), and curing a
board including the formed circuit line in Step (E).
[0017] In Step (A), an alkali metal hydroxide solution 20 is
treated to at least one side of a circuit line pattern on a base
substrate 10. If surface of the base substrate 10 can be chemically
reformed by reacting with the alkali metal hydroxide solution, it
is not limited to any particular one, preferably a polymer
substrate, more preferably a polyimide substrate. The polyimide
substrate has been used as a base substrate of various flexible
boards including PCB circuits and semiconductor integrated
circuits. The base substrate may be a film type having a thickness
of several .mu.m or a sheet type having a thicker thickness of
several mm. However, the polyimide substrate is not limited to such
types or thicknesses in the present invention.
[0018] The treatment on at least one side of a circuit line
pattern, preferably both sides, is to control the spread of an ink
when the ink is ejected at a later process. A treatment part of the
alkali metal hydroxide solution may eject the alkali metal
hydroxide solution on the base substrate in constant intervals in
accordance to the width of the circuit line. A degree of spread of
the ink should be considered at this time. When the alkali metal
hydroxide solution is ejected, a size of droplets ejected on the
surface of the base substrate is 1.2 to 2 times of a size of
droplets from an ink-jet head 30 and it is preferable as it is
smaller within the range not to deteriorate a yield of a reaction
for chemically reforming the surface. It is also preferable that
portions treated with the alkali metal hydroxide solution be even
and have constant intervals to achieve a continuous border. The
narrower interval is required for the smaller size of droplets.
This thus practically allows forming desired even circuit
lines.
[0019] Both sides of the circuit line pattern may be treated with
same alkali metal hydroxide solution or different from each
other.
[0020] Here, the alkali metal hydroxide solution is prepared by
dissolving at least one chosen from KOH, NaOH, and LiOH in water
and adding ethylene glycol thereto. The ethylene glycol is added to
control volatility, viscosity, surface tension, and degree of
spread on the polyimide substrate.
[0021] It is preferable that the ethylene glycol use 0.1 to 1
volume ratio based to 1 of water, more preferable 0.3 volume ratio,
since viscosity of the alkali metal hydroxide solution and degree
of spread on the polyimide substrate become better. When the
ethylene glycol is used more than 1 volume ratio, it deteriorates a
reaction yield on the substrate surface. On the other hand, when it
is used less than 0.1, the degree of spread of the alkali metal
hydroxide solution on the substrate increases and thus it is not
desirable.
[0022] It is preferable that a concentration of at least one
hydroxide chosen from KOH, NaOH and LiOH be 0.1 to 10M in which it
reforms the surface of the base substrate. When the concentration
is less than 0.1 M, it is not proper to form an evenly continuous
board. On the other hand, when it is higher than 10M, the
solubility of the alkali metal hydroxide solution becomes
lowered.
[0023] In the treatment process with the alkali metal hydroxide
solution, temperature and humidity may be varied with reaction
time, preferably 18 to 99.degree. C. for 1 minute to 24 hours. When
the temperature is lower than 18.degree. C., the reaction takes too
long while when it is higher than 100.degree. C., it is difficult
to control the reaction because water used as a solvent boils. It
is more preferable to treat with 1 M of the alkali metal hydroxide
solution at 50.degree. C. for 5 minutes. Since an exothermic
reaction is generally occurred on the surface of the polyimide
substrate, it does not require to heat additionally. Such
concentration of the alkali metal hydroxide solution and treating
time also vary with a thickness of the polyimide substrate. It is
preferable to treat for a short time at a mile temperature for a
polyimide film having a thickness of several .mu.m and it should
not damage the polyimide film due to the matter of surface
modification.
[0024] The alkali metal hydroxide solution may be treated by a mask
method or ink-jet method but the ink-jet method is preferable to
form fine circuit lines.
[0025] When the substrate is treated with the alkali metal
hydroxide solution as in Step (B), the surface of the substrate is
chemically reformed 23. For example, when the substrate is a
polyimide, --N--CO-- group of the surface is reformed to --NH and
--COO.sup.-- groups by the alkali metal hydroxide solution and
alkali metals of the hydroxide are adsorbed on the surface of the
polyimide having carboxylic acids as positive ions of K.sup.+,
Na.sup.+, or Li.sup.+. The surface of polyimide having carboxylic
acids or carboxylic ions is reformed to be hydrophilic, so that it
repulses against a hydrophobic solution.
[0026] In Step (C), a weak acid solution is treated to the portion
treated with the alkali metal hydroxide solution which may be
optionally performed to stabilize the carboxylic groups formed on
the surface of polyimide in Step (B). When the portion treated with
the alkali metal hydroxide solution is treated with the weak acid,
positive ions of the alkali metal react with the weak acid, so that
unnecessary metal ions are removed.
[0027] Examples of the weak acid include acetic acid, formic acid,
phosphoric acid, carbonic acid and the like, more preferably at
least one weak acid chosen from C1-C20 alkanoic acids such as
formic acid and acetic acid having carboxylic groups. A
concentration of this weak acid is in the range of form 0.01 to 5N.
It is preferable that a polyimide substrate be treated with the
weak acid at 18 to 50.degree. C. for 1 minute to 24 hours. If it is
treated at a temperature of less than 18.degree. C., the reaction
takes too slow and since the reaction is generally performed at a
room temperature, it is not necessary to perform at a temperature
of higher than 50.degree. C. A reaction temperature and reaction
time may be determined within an appropriate range which is enough
to complete the reaction described above for the surface of the
polyimide substrate. It is more preferable to perform with 1N of an
alkanoic acid at 20.degree. C. for 10 minutes.
[0028] A hydrophobic ink 50 is ejected in accordance to a circuit
line pattern to be formed in Step (D). The surface of the polyimide
substrate may be reformed to be hydrophilic by treating at least
one side of the circuit line pattern to be formed before ejecting
the ink. Use of weak hydrophilic ink is therefore more preferable
in the present invention. Any kind of such weak hydrophilic inks,
which are hydrophobic inks, may be used but inks should include
metal nanoparticles since they are for forming conductive circuit
lines. The hydrophobic ink may be a conductive ink using a solvent
such as tetradecane, hexane, octane, toluene, 2-butoxyethyl
acetate, acryl monomer, and epoxy monomer.
[0029] Since an ink containing a tetradecane solvent has a high
boiling temperature, it dose not cause blocking of a head during
ejection and thus allows to be used for a long period of time. Even
if it has advantages, it has high spread on the surface of the
substrate, so that it becomes to the difficult in practical use.
However, a method for forming circuit lines according to the
present invention allows forming fine circuit lines by controlling
such spread of the ink. Further, when side of a circuit line
pattern to be formed is modified by the above method, the spread of
the ink is improved to have an even height of the ejected ink.
Since the even height of the ink highly influences the conductivity
of the conductive circuit line, the conductivity of the circuit
line can be guaranteed with a particular even height of the ink.
The method for forming circuit lines according to the present
invention not only allows forming fine circuit lines but also
improves the conductivity of the circuit lines. A size of droplets
of the ink printed on the base substrate is generally 1.2 to 2
times to a size of a nozzle used. In the present invention, a size
of droplets of the ink printed on the base substrate is not higher
than 1.2 times which is smaller than that of conventional ones
since a contact angle where the droplet of the ink contacts with
the surface of the base substrate is reduced.
[0030] The board including such formed circuit lines is then cured
in Step (E) to produce a desired high dense board. A reaction
solution or any organic compound within the ink are removed and the
remained metal which has the conductivity is by curing in this
step. The curing may be performed at 80 to 350.degree. C. for 1
minute to 5 hours and it is preferable that since a polyimide is
not stable at a high temperature, it is cured for a short time.
According to a preferred embodiment, when tetradecane is used as a
solvent, it is preferable to cure at 70.degree. C. for 20 minutes.
The curing may be also performed under nitrogen or argon at a
lowered temperature. Further, formic acid may be added at this
step.
[0031] A board including such formed conductive circuit lines 53
may be laminated if necessary, surface is treated by solder resist,
symbol mark printing or HASL method, and terminal coating and holes
or exterior fabrication is additionally performed to produce a
desired conductive board.
[0032] The conductive board of the present invention may be used as
single layer or multi-layer PCBs, LTCCs, MLCs, and the like but the
board having circuit lines formed by the method described above may
not be limited to its use. The circuit lines of the present
invention has 1 to 80 .mu.m of a width, so that a high dense
circuit line board may be produced.
[0033] Embodiments relating methods of forming fine circuit lines
were set forth above, and hereinafter, explanations will be given
in greater detail with reference to specific examples.
EXAMPLE 1
[0034] After dissolving solid KOH 57 g to water 730 Ml, ethylene
glycol 230 Ml was added to obtain a KOH solution. Both sides of a
circuit line to be formed on a polyimide film was treated with the
prepared KOH solution by an ink-jet method. A gap between heads was
controlled to be 80 .mu.m by using an ink-jet head having a nozzle
size of 30 .mu.m. After 5 minutes since the surface of the
polyimide substrate had been treated with a KOH solution, 5N acetic
acid was treated on the portion where the KOH solution was treated
and left for 10 minutes. Tetradecane ink was ejected between
reformed portions on the polyimide film by using an ink-jet head
having a nozzle size of 30 .mu.m. Such a formed board was then
cured at 70.degree. C. for 20 minutes to provide a board having an
average circuit line width of 30 .mu.m of which low electric
resistivity was 3.1 .mu..OMEGA.cm.
EXAMPLE 2
[0035] After dissolving solid KOH 41 g to water 730 Ml, ethylene
glycol 230 Ml was added to obtain a KOH solution. Both sides of a
circuit line to be formed on a polyimide film was treated with the
prepared KOH solution by an ink-jet method. A gap between heads was
controlled to be 80 .mu.m by using an ink-jet head having a nozzle
size of 30 .mu.m. After 5 minutes since the surface of the
polyimide substrate had been treated with a KOH solution, 5N acetic
acid was treated on the portion where the KOH solution was treated
and left for 10 minutes. Tetradecane ink was ejected between
reformed portions on the polyimide film by using an ink-jet head
having a nozzle size of 30 .mu.m. Such a formed board was then
cured at 70.degree. C. for 20 minutes to provide a board having an
average circuit line width of 30 .mu.m of which low electric
resistivity was 2.9 .mu..OMEGA.cm.
[0036] Thetradecane ink was ejected by an ink-jet head having a
nozzle size of 30 .mu.m as in Example 1 and the formed board was
then cured at 70.degree. C. for 20 minutes to provide a board
having an average circuit line width of higher than 40 .mu.m. It
was noted that when circuit lines was formed according to the
present invention, fine circuit lines may be formed.
[0037] The present invention provides a method for forming fine
circuit lines at a low cost and by a simple process by alleviating
the spread of an ink with performing a pretreatment on the base
substrate before ejecting the ink. The fine circuit lines produced
by this method have even height and thus provide excellent
electrical conductivity. Further it has an advantage of using an
ink containing tetradecanes which have had limitation in their uses
to the conventional methods.
[0038] Further, the present invention provides a conductive board
having such fine circuit lines which exhibits high density and
excellent electrical conductivity.
[0039] Although a few embodiments of the present invention have
been shown and described, it will be appreciated by those skilled
in the art that changes may be made in these embodiments without
departing from the principles and spirit of the present invention,
the scope of which is defined in the appended claims and their
equivalents.
* * * * *