U.S. patent application number 13/735527 was filed with the patent office on 2013-05-16 for method of manufacturing printed circuit board for optical waveguide.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. The applicant listed for this patent is SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Han Seo Cho, Jae Hyun Jung, Joon Sung KIM, Sang Hoon Kim.
Application Number | 20130122430 13/735527 |
Document ID | / |
Family ID | 42231160 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130122430 |
Kind Code |
A1 |
KIM; Joon Sung ; et
al. |
May 16, 2013 |
METHOD OF MANUFACTURING PRINTED CIRCUIT BOARD FOR OPTICAL
WAVEGUIDE
Abstract
A method of manufacturing a printed circuit board for an optical
waveguide includes forming an insulation layer having a through
hole on a substrate; forming a lower clad layer on a bottom of the
through hole; forming a core part on the lower clad layer; and
forming an upper clad layer covering the core part on the lower
clad layer and the core part.
Inventors: |
KIM; Joon Sung; (Suwon,
KR) ; Cho; Han Seo; (Seoul, KR) ; Jung; Jae
Hyun; (Ansan-si, KR) ; Kim; Sang Hoon;
(Gunpo-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG ELECTRO-MECHANICS CO., LTD.; |
Suwon |
|
KR |
|
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
Suwon
KR
|
Family ID: |
42231160 |
Appl. No.: |
13/735527 |
Filed: |
January 7, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12385007 |
Mar 27, 2009 |
8369676 |
|
|
13735527 |
|
|
|
|
Current U.S.
Class: |
430/319 ;
427/555; 427/558; 427/97.3; 427/97.4 |
Current CPC
Class: |
H05K 1/0274 20130101;
H05K 2201/0187 20130101; G02B 2006/12073 20130101; Y10T 29/49165
20150115; G02B 6/138 20130101; H05K 3/00 20130101; H05K 3/28
20130101 |
Class at
Publication: |
430/319 ;
427/97.3; 427/555; 427/558; 427/97.4 |
International
Class: |
H05K 3/00 20060101
H05K003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 2008 |
KR |
10-2008-0124830 |
Claims
1. A method of manufacturing a printed circuit board for an optical
waveguide, comprising: forming an insulation layer having a through
hole on a substrate; forming a lower clad layer on a bottom of the
through hole; forming a core part on the lower clad layer; and
forming an upper clad layer covering the core part on the lower
clad layer and the core part.
2. The method according to claim 1, wherein the forming of the
insulation layer having the through hole comprises: forming an
insulation layer on a substrate; and forming a through hole in the
insulation layer through an exposure/development process or a laser
drilling process.
3. The method according to claim 1, wherein the forming of the
lower clad layer comprises: applying a liquid lower clad material
on a bottom of the through hole; flattening the applied lower clad
material by placing a transparent release film thereon; and curing
the flattened lower clad material by applying ultraviolet rays or
heat thereto to form the lower clad layer on a bottom of the
through hole.
4. The method according to claim 1, wherein the forming of the core
part comprises: applying a liquid core material on the lower clad
layer formed in the through hole; flattening the applied core
material by placing a transparent release film thereon; selectively
exposing the flattened core material using a pattern mask; and
removing the transparent release film and then developing the
exposed core material to form the core part.
5. The method according to claim 1, wherein the forming of the core
part comprises: applying a liquid core material on the lower clad
layer formed in the through hole; curing the applied core material
by applying light or heat thereto; and patterning the cured core
material using a laser to form the core part.
6. The method according to claim 1, wherein the forming of the
upper clad layer is performed through a process of applying an
upper clad material on the lower clad layer and the core part and
then curing the applied upper clad material or a process of placing
an upper clad film on the lower clad layer and the core part.
7. The method according to claim 1, wherein the substrate includes
a polyimide layer and a metal layer formed beneath the polyimide
layer, and wherein the method further comprises: patterning the
metal layer to form circuit patterns after the forming of the upper
clad layer.
8. A method of manufacturing a printed circuit board for an optical
waveguide, comprising: forming a lower insulation layer having a
lower through hole on a substrate; forming a lower clad layer in
the lower through hole; forming an upper insulation layer having an
upper through hole connected with the lower through hole to thus
form a single through hole on the lower insulation layer; forming
core part on the lower clad layer; and forming an upper clad layer
covering the core part on the lower clad layer and the core
part.
9. The method according to claim 8, wherein the forming of the
lower clad layer comprises: applying a liquid lower clad material
in the lower through hole; flattening the applied lower clad
material by placing a transparent release film thereon; and curing
the flattened lower clad material by applying ultraviolet rays or
heat thereto to form the lower clad layer in the lower through
hole.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. Ser. No.
12/385,007, filed Mar. 27, 2009, which claims the benefit of Korean
Patent Application No. 10-2008-0124830, filed Dec. 9, 2008 in the
Korean Intellectual Property Office, the disclosures of which are
hereby incorporated by reference in their entirety.
BACKGROUND
[0002] 1. Field
[0003] The present invention relates to a printed circuit board for
an optical waveguide and a method of manufacturing the same, and,
more particularly, to a printed circuit board which can be
efficiently used to fabricate an optical waveguide using a
relatively small amount of a clad material and a core material by
forming a lower clad layer only in a through-hole of an insulation
layer and by applying a core material only on the inner surface of
the through-hole and then conducting a patterning process to form a
core part, and a method of manufacturing the same.
[0004] 2. Description of the Related Art
[0005] Recently, the demand for an optical substrate including
optical wire enabling electrical signals and optical signals to be
transmitted to mobile or network equipment has increased.
[0006] Generally, an optical wire is made of a polymer having low
optical transmittance, and includes a square core part having a
x-width of about 50 .mu.m and a y-width of about 50 .mu.m through
which signals are propagated, and a clad part covering the square
core part. The square core part is generally fabricated through a
photo-etching process.
[0007] In relation to this, a conventional method of manufacturing
a printed circuit board for an optical waveguide will be described
as follows with reference to FIGS. 1A to 1C.
[0008] First, a lower clad layer 13 and a core layer 14 are
sequentially formed on a polyimide layer 12 of a flexible substrate
including copper foil 11 and the polyimide layer 12 (see FIG.
1A).
[0009] Next, the core layer 14 is patterned through a general
photo-etching process to form core parts 14a (see FIG. 1B).
[0010] Finally, an upper clad layer 15 is formed on the lower clad
layer 13 including the core parts 14a formed thereon, thus
producing a printed circuit board for an optical waveguide (see
FIG. 1C).
[0011] However, the conventional method of manufacturing a printed
circuit board for an optical waveguide is problematic in that,
since the core layer 14 is formed by applying a core material on
the entire work area of the substrate and then the core layer 14 is
patterned through an exposure/development process to form the core
parts 14a, a very large amount of the core material is
unnecessarily removed compared to the amount of actually required
core parts 14a, and thus the loss of material cost is
increased.
[0012] Further, the conventional method is problematic in that,
since the lower and upper clad layers 13 and 15 are formed
throughout the substrate although it is sufficient that they cover
the core parts 14a to such a degree that the core parts 14a can
easily transmit optical signals, a clad material is excessively
used unnecessarily.
[0013] Therefore, considering that an optical wire is expensive, it
is keenly required to manufacture an optical substrate through an
economical and efficient method.
SUMMARY
[0014] Accordingly, the present invention has been made keeping in
mind the above problems occurring in the prior art, and the present
invention provides a printed circuit board for an optical
waveguide, which can decrease its production cost by reducing the
used amount of core and clad materials, and a method of
manufacturing the same.
[0015] An aspect of the present invention provides a printed
circuit board for an optical waveguide, including: a substrate; an
insulation layer having a through hole and formed on the substrate;
a lower clad layer formed on a bottom of the through hole; core
part formed on the lower clad layer; and an upper clad layer formed
on the lower clad layer and the core part and thus covering an
exposed surface of the core part.
[0016] In the printed circuit board, the substrate may be any one
selected from among a metal layer for forming a circuit, a flexible
printed circuit board, a rigid printed circuit board and a
rigid-flexible printed circuit board.
[0017] Further, the substrate may include a light transmission part
beneath the through hole.
[0018] Further, the insulation layer may be made of any one
selected from among a thermosetting resin, a thermoplastic resin, a
thermosetting resin impregnated with a reinforcing material, a
thermoplastic resin impregnated with a reinforcing material, and
combinations thereof.
[0019] Further, the insulation layer may include a lower insulation
layer and an upper insulation layer, which have through holes
corresponding to each other.
[0020] Further, the core part may be formed of a plurality of core
patterns.
[0021] Further, the substrate may include a polyimide layer, and
circuit patterns formed on and/or beneath the polyimide layer and
transmitting electric signals.
[0022] Another aspect of the present invention provides a method of
manufacturing a printed circuit board for an optical waveguide,
including: forming an insulation layer having a through hole on a
substrate; forming a lower clad layer on a bottom of the through
hole; forming core part on the lower clad layer; and forming an
upper clad layer covering the core part on the lower clad layer and
the core part.
[0023] In the method, the forming of the insulation layer having
the through hole may include: forming an insulation layer on a
substrate; and forming a through hole in the insulation layer
through an exposure/development process or a laser drilling
process.
[0024] Further, the forming of the lower clad layer may include:
applying a liquid lower clad material on a bottom of the through
hole; flattening the applied lower clad material by placing a
transparent release film thereon; and curing the flattened lower
clad material by applying ultraviolet rays or heat thereto to form
the lower clad layer on a bottom of the through hole.
[0025] Further, the forming of the core part may include: applying
a liquid core material on the lower clad layer formed in the
through hole; flattening the applied core material by placing a
transparent release film thereon; selectively exposing the
flattened core material using a pattern mask; and removing the
transparent release film and then developing the exposed core
material to form the core part.
[0026] Further, the forming of the upper clad layer may be
performed through a process of applying an upper clad material on
the lower clad layer and the core part and then curing the applied
upper clad material or a process of placing an upper clad film on
the lower clad layer and the core part.
[0027] Further, the substrate may include a polyimide layer and a
metal layer formed beneath the polyimide layer, and the method may
further include: patterning the metal layer to form circuit
patterns after the forming of the upper clad layer.
[0028] Still another aspect of the present invention provides a
method of manufacturing a printed circuit board for an optical
waveguide, including: forming a lower insulation layer having a
lower through hole on a substrate; forming a lower clad layer in
the lower through hole; forming an upper insulation layer having an
upper through hole connected with the lower through hole to thus
form a single through hole on the lower insulation layer; forming
core part on the lower clad layer; and forming an upper clad layer
covering the core part on the lower clad layer and the core
part.
[0029] In the method, the forming of the lower clad layer may
include: applying a liquid lower clad material in the lower through
hole; flattening the applied lower clad material by placing a
transparent release film thereon; and curing the flattened lower
clad material by applying ultraviolet rays or heat thereto to form
the lower clad layer in the lower through hole.
[0030] Various objects, advantages and features of the invention
will become apparent from the following description of embodiments
with reference to the accompanying drawings.
[0031] The terms and words used in the present specification and
claims should not be interpreted as being limited to typical
meanings or dictionary definitions, but should be interpreted as
having meanings and concepts relevant to the technical scope of the
present invention based on the rule according to which an inventor
can appropriately define the concept of the term to describe the
best method he or she knows for carrying out the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The above and other objects, features and advantages of the
present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0033] FIGS. 1A to 1C are sectional views showing a conventional
method of manufacturing a printed circuit board for an optical
waveguide;
[0034] FIG. 2A is a sectional view showing a printed circuit board
for an optical waveguide according to an embodiment of the present
invention;
[0035] FIG. 2B is a sectional view showing a printed circuit board
for an optical waveguide according to another embodiment of the
present invention;
[0036] FIG. 3A is a sectional view showing a printed circuit board
for an optical waveguide according to another embodiment of the
present invention;
[0037] FIG. 3B is a sectional view showing a printed circuit board
for an optical waveguide according to another embodiment of the
present invention;
[0038] FIGS. 4 to 11, 12A to 12B, 13 and 14 are sectional views
showing a process of manufacturing a printed circuit board for an
optical waveguide according to an embodiment of the present
invention; and
[0039] FIGS. 15 to 23, 24A to 24B, 25 and 26 are sectional views
showing a process of manufacturing a printed circuit board for an
optical waveguide according to another embodiment of the present
invention.
DESCRIPTION OF EMBODIMENTS
[0040] Hereinafter, preferred embodiments of the present invention
will be described in detail with reference to the attached
drawings.
[0041] Throughout the accompanying drawings, the same reference
numerals are used to designate the same or similar components, and
redundant descriptions thereof are omitted. In the following
description, the terms "upper", "lower" and the like are used to
differentiate a certain component from other components, but the
configuration of such components should not be construed to be
limited by the terms.
[0042] FIG. 2A is a sectional view showing a printed circuit board
for an optical waveguide according to an embodiment of the present
invention, and FIG. 2B is a sectional view showing a printed
circuit board for an optical waveguide according to another
embodiment of the present invention.
[0043] As shown in FIG. 2A, a printed circuit board for an optical
waveguide according to an embodiment of the present invention
includes a substrate 100, an insulation layer 300 having a thorough
hole 305 (see FIG. 5) and formed on the substrate 100, and an
optical waveguide.
[0044] The substrate 100 includes an insulating material layer 110
and circuit patterns 135 for electrical signal transmission formed
on the insulating material layer 110. In this embodiment, a
substrate 100 in which circuit patterns 135 are formed beneath an
insulating material layer 110 is exemplified. However, the present
invention is not limited thereto, and, as shown in FIG. 2B, a
substrate in which circuit patterns 135 are formed on an insulating
material layer 110 may be used, or a substrate (not shown) in which
circuit patterns 135 are formed on and beneath an insulating
material layer 110 may be used.
[0045] Here, the insulating material layer 110 used in the
substrate 100 may be made of polyimide. However, the present
invention is not limited thereto, and the insulating material layer
may be formed of prepreg including an epoxy resin, which is a
general insulating material. That is, the substrate may be a
flexible printed circuit board, a rigid printed circuit board or a
rigid-flexible printed circuit board, as is generally used for
printed circuit boards.
[0046] In this case, the substrate 100 may include a light
transmission part (not shown) for transmitting optical signals
to/from an optical waveguide to be described later. The light
transmission part has a light transmission rate of 50% or more at a
wavelength of 850 nm. The light transmission part may be configured
by forming the insulating material layer 110 using a transparent
material, or may be intentionally formed by forming holes in the
opaque insulating material layer 110.
[0047] The insulation layer 300 is formed on the substrate 100, and
has a through hole 305. The through hole 305 may have a diameter of
0.5.about.10 mm such that an optical waveguide can be housed in the
through hole 305. The insulation layer 300 may be made of any one
selected from among a thermosetting resin, a thermoplastic resin, a
thermosetting resin impregnated with a reinforcing material, a
thermoplastic resin impregnated with a reinforcing material, and
combinations thereof. For example, the insulation layer 300 may be
formed of prepreg, polyimide film or a photosensitive insulating
material.
[0048] The optical waveguide includes a lower clad layer 530 formed
on the bottom of the thorough hole 305, core parts 730 formed on
the lower clad layer 530, and an upper clad layer 930 formed on the
lower clad layer 530 and the core parts 730 to cover the exposed
surfaces of the core parts 730.
[0049] The lower clad layer 530 may be formed to have a thickness
of 10.about.100 .mu.m. The lower clad layer 530 is made of a
polymer material such as an acrylic resin, an epoxy resin, a
polyimide resin, a fluorinated acrylic resin, a fluorinated
polyimide resin or the like.
[0050] The core parts 730 are formed on the lower clad layer 530 in
the through hole 305. The height of each of the core parts 730
based on the substrate 100 may be equal to, lower than or higher
than that of the insulation layer 300. The core parts 730 are
interposed between the lower clad layer 530 and the upper clad
layer 930, and function as channels for transmitting optical
signals. The core parts 730 are also made of a polymer material
similar to that of the upper clad layer 930 or the lower clad layer
530, and have a refractive index higher than that of the upper clad
layer 930 or the lower clad layer 530 in order to efficiently
transmit optical signals. As shown in drawings, the core parts 730
may be formed of a plurality of core patterns.
[0051] The upper clad layer 930 is formed on the lower clad layer
530 and the core parts 730 to cover the exposed surfaces of the
core parts 730, and is made of a material the same as or similar to
that of the lower clad layer 530. As shown in FIG. 2A, the upper
clad layer 930 is configured such that it is charged in the through
hole 305 and covers the insulation layer 300. However, the present
invention is not limited thereto, and, as shown in FIG. 3A, the
upper clad layer 930 may be configured such that it is only charged
in the through hole 305, similar to the lower clad layer 530.
[0052] The above-mentioned printed circuit board can transmit
electrical signals through the circuit patterns 135 formed in the
substrate 100, and can transmit optical signals through the optical
waveguide. In this case, optical signals are incident on the core
parts 730 through the light transmission part formed in the
substrate 100, and are then totally reflected by the lower clad
layer 530 and the upper clad layer 930 and simultaneously
transmitted along the core parts 730. The optical signals are
reflected by a mirror (not shown) and then go outside.
[0053] FIG. 3A is a sectional view showing a printed circuit board
for an optical waveguide according to another embodiment of the
present invention, and FIG. 3B is a sectional view showing a
printed circuit board for an optical waveguide according to another
embodiment of the present invention. Here, the description
overlapping with the above embodiment will be omitted.
[0054] As shown in FIG. 3A, a printed circuit board for an optical
waveguide according to another embodiment of the present invention
includes a substrate 100, an insulation layer 310 and 330 having a
thorough hole 315 or 335 (see FIGS. 16 and 20) and formed on the
substrate 100, and an optical waveguide.
[0055] In this embodiment, the insulation layer includes a lower
insulation layer 310 and an upper insulation layer 330, which have
through holes corresponding to each other. The lower insulation
layer 310 may have a thickness of 10.about.100 .mu.m, and the upper
insulation layer 330 may have a thickness of 10.about.200
.mu.m.
[0056] The substrate of this embodiment may also include circuit
patterns 135 thereon, as shown in FIG. 3B. In this case, the lower
clad layer 530 functions as a general insulation layer 300 with
respect to the circuit patterns 135.
[0057] Meanwhile, in this embodiment, the upper clad layer 930 is
charged in only the through hole 315 or 335, but the present
invention is not limited thereto. A part of the upper clad layer
930 covering the core parts 730 may be extended onto the insulation
layer 300 (see FIG. 2A).
[0058] In the above-mentioned printed circuit board, since at least
one of the lower clad layer 530 and the upper clad layer 930 is
formed in the through hole, the amount of a clad material used can
be reduced, thus decreasing the production cost thereof.
[0059] FIGS. 4 to 14 are sectional views showing a process of
manufacturing a printed circuit board for an optical waveguide
according to an embodiment of the present invention. Hereinafter,
the process of manufacturing a printed circuit board for an optical
waveguide according to an embodiment of the present invention will
be described with reference to FIGS. 4 to 14.
[0060] First, a process of forming an insulation layer 300 having a
through hole 305 on a substrate 100 will be described.
[0061] As shown in FIG. 4, when a substrate 100 is provided, an
insulation layer 300 is formed on the substrate 100. The substrate
100 is composed of an insulating material layer 110 and a metal
layer 130 formed on one side of the insulating material layer 110.
In this embodiment, a flexible copper clad laminate in which copper
foil is applied on one side of the insulating material layer 110
made of polyimide is used as the substrate 100, but the present
invention is not limited thereto. The metal layer 130 for forming
circuits, such as copper foil, may be directly used as the
substrate 100. Further, if necessary, other flexible copper clad
laminates, rigid copper clad laminates and rigid-flexible copper
clad laminates, which are generally used in printed circuit boards,
may be selectively used as the substrate 100. Furthermore, other
flexible copper clad laminates, rigid copper clad laminates and
rigid-flexible copper clad laminates, in which one or more circuit
layers are previously formed, may be selectively used as the
substrate 100.
[0062] The insulation layer 300 may be made of any one selected
from among a thermosetting resin, a thermoplastic resin, a
thermosetting resin impregnated with a reinforcing material, a
thermoplastic resin impregnated with a reinforcing material, and
combinations thereof. Examples of the insulation layer 300 may
include, but may be not limited to, prepreg, polyimide film and a
photosensitive insulating material.
[0063] Subsequently, as shown in FIG. 5, a through hole 305 is
formed in the insulation layer 300. Methods of forming the through
hole 305 in the insulation layer 300 are not particularly limited,
and may be suitably selected depending on the kind of an insulating
material constituting the insulation layer 300. For example, the
through hole 305 may be formed through a photo-etching process
using exposure/development, a laser machining process, or the
like.
[0064] Next, a process of forming a lower clad layer 530 on the
bottom of the through hole 305 will be described.
[0065] As shown in FIG. 6, a liquid lower clad material 510 is
applied on the bottom of the through hole 305. The liquid lower
clad material 510 is charged in the through hole 305 through a
method well known to those skilled in the art, such as a dispensing
method, an ink jetting method, a printing method or the like.
[0066] Subsequently, as shown in FIG. 7, the liquid lower clad
material 510 is flattened by placing a transparent release film 800
thereon, and is then cured by applying ultraviolet rays or heat to
the flattened liquid lower clad material 510 to form a lower clad
layer 530 on the bottom of the through hole 305.
[0067] In this case, the process of flattening the liquid lower
clad material 510 is not an essential process but an optional
process performed only when the surface of the lower clad material
510 is curved. In particular, the lower clad layer 530 may be
formed by laminating a clad material film, and, in this case, the
process of flattening the liquid lower clad material 510 may not be
performed.
[0068] Next, a process of forming core parts 730 on the lower clad
layer 530 will be described.
[0069] As shown in FIG. 8, a liquid core material 710 is applied on
the lower clad layer 530 formed in the through hole 305. The liquid
core material 710 is charged in the through hole 305 through a
method well known to those skilled in the art, such as a dispensing
method, an ink jetting method, a printing method or the like, and
is then pre-baked. In this case, the liquid core material 710 can
be fully charged in the through hole 305, but may not be fully
charged in the through hole 305. Further, a large amount of the
liquid core material greater than the volume of the through hole
305 may be charged in the through hole 305 because of the surface
tension of the liquid core material 710, thus determining the
height of the core parts 730 (core patterns) to be formed
later.
[0070] Subsequently, in order to apply a general exposure process,
the liquid core material 710 is flattened by placing a transparent
release film 800 thereon. That is, the liquid core material 710 is
flattened by placing the transparent release film 800 thereon under
vacuum conditions. All types of transparent release film 80 may be
used without limitation as long as it enables the liquid core
material 710 to be flattened while preventing the liquid core
material 710 from being polluted by impurities, it enables the
permeation of light in a subsequent exposure process, and it can be
easily removed after the exposure process. Even in this case, the
process of flattening the liquid core material 710 is not an
essential process but an optional process performed only when the
surface of the liquid core material 710 is curved. Further, in this
case, in addition to the liquid core material 710, a core material
film 710 can be laminated.
[0071] Subsequently, as shown in FIG. 9, the core material 710 is
selectively exposed using a pattern mask (M). In this case, if
necessary, post exposure baking (PEB) may be performed before or
after the exposure of the core material 710.
[0072] Subsequently, as shown in FIG. 10, the transparent release
film 800 is removed, and then the exposed core material 710 is
developed to form core parts 730.
[0073] Meanwhile, in this embodiment, a process of forming the core
parts 730 through exposure and development is described, but the
core parts 730 may be formed through laser etching. That is, core
parts can be formed by applying a liquid core material on the lower
clad layer formed in the through hole and then applying ultraviolet
(UV) rays or heat to the applied liquid core material to cure the
core material and then patterning the cured core material using a
laser. At the time of pattering the cured core material, the cured
core material may be selectively etched using an eximer laser, a
YAG laser or a CO.sub.2 laser while controlling the number of laser
pulses and shots.
[0074] Further, the core parts 730 may be formed using a process of
changing the refractive index of the core material using
ultraviolet (UV) rays and a mask or a process of changing the
refractive index of the core material using a laser.
[0075] Next, a process of forming an upper clad layer 930 covering
the core parts 730 on the lower clad layer 530 and the core parts
730 will be described.
[0076] As shown in FIG. 11, the upper clad layer 930 may be formed
by applying an upper clad material 910 on the lower clad layer 530
and the core parts 730 and then curing the applied upper clad
material 910 or by placing an upper clad film on the lower clad
layer 530 and the core parts 730. In this case, as shown in FIG.
12A, the upper clad layer 930 may be formed such that it covers
both the core parts 730 and the insulation layer 300, and, as shown
in FIG. 12B, the upper clad layer 930 may be formed only in the
through hole 305 such that it covers only the core parts 730.
[0077] Subsequently, as shown in FIG. 13, circuit patterns 135 are
formed by patterning the metal layer 130. This process is performed
only when a substrate 100 in which a metal layer 130 is formed
beneath an insulating material layer 110 is used, but this process
may be omitted when a substrate 100 in which circuit patterns 135
are formed on an insulating material layer 110 is used as shown in
FIG. 14.
[0078] FIGS. 15 to 26 are sectional views showing a process of
manufacturing a printed circuit board for an optical waveguide
according to another embodiment of the present invention.
Hereinafter, the process of manufacturing a printed circuit board
for an optical waveguide according to another embodiment of the
present invention will be described with reference to FIGS. 15 to
16. Here, the description overlapping with the above embodiment
will be omitted.
[0079] First, a process of forming a lower insulation layer 310
having a lower through hole 315 on a substrate 100 will be
described.
[0080] As shown in FIG. 15, when a substrate 100 is provided, a
lower insulation layer 310 having a thickness of 10.about.100 .mu.m
is formed on the substrate 100.
[0081] Subsequently, as shown in FIG. 16, a lower through hole 315
is formed in the lower insulation layer 310.
[0082] Subsequently, a lower clad layer 530 is formed on the lower
through hole 315.
[0083] As shown in FIG. 17, a liquid lower clad material 510 is
applied in the lower through hole 315. Subsequently, as shown in
FIG. 18, the applied liquid lower clad material 510 is flattened by
placing a transparent release film 200 thereon. Subsequently, as
shown in FIG. 19, the flattened liquid lower clad material 510 is
cured by applying ultraviolet rays or heat thereto to form a lower
clad layer 530 in the lower through hole 315. In this case, the
process of flattening the applied liquid lower clad material 510
using the transparent release film 200 is not an essential process
but an optional process.
[0084] Subsequently, as shown in FIG. 20, an upper insulation layer
330 having an upper through hole 335 connected with the lower
through hole 315 and thus formed into a single through hole is
formed on the lower insulation layer 310. The upper through hole
335 and the lower through hole 315 may be exactly matched with each
other, but they may also be connected with each other within an
allowable error.
[0085] The upper insulation layer 330 may be made of any one
selected from among a thermosetting resin, a thermoplastic resin, a
thermosetting resin impregnated with a reinforcing material, a
thermoplastic resin impregnated with a reinforcing material, and
combinations thereof. Examples of the upper insulation layer 330
may include prepreg, polyimide film, a photosensitive insulating
material, and the like. Methods of forming the upper through hole
335 in the upper insulation layer 330 are not particularly limited,
and may be suitably selected depending on the kind of upper
insulating material constituting the insulation layer 330. For
example, the upper through hole 335 may be formed through a
photo-etching process using exposure/development, a laser machining
process, or the like.
[0086] Next, a process of forming core parts 730 on the lower clad
layer 530 will be described.
[0087] As shown in FIGS. 21 and 22, the core parts 730 are formed
by charging a core material 710 in the upper through hole 335,
flattening the charged core material 710 and then selectively
exposing and developing the flattened core material 710. Since the
process of forming the core parts 730 in this embodiment is the
same as or very similar to that in the above embodiment, it is not
described in detail.
[0088] Next, a process of forming an upper clad layer 930 covering
the core parts 730 on the lower clad layer 530 and the core parts
730 will be described.
[0089] As shown in FIG. 23, the upper clad layer 930 may be formed
by applying an upper clad material 910 on the lower clad layer 530
and the core parts 730 and then curing the applied upper clad
material 910 or by disposing an upper clad film on the lower clad
layer 530 and the core parts 730. In this case, as shown in FIG.
24A, the upper clad layer 930 may be formed such that it covers
both the core parts 730 and the upper insulation layer 330, and, as
shown in FIG. 24B, the upper clad layer 930 may be formed only in
the upper through hole 335 such that it covers only the core parts
730.
[0090] Subsequently, as shown in FIG. 25, circuit patterns 135 are
formed by patterning the metal layer 130. This process is performed
only when a substrate 100 in which a metal layer 130 is formed
beneath an insulating material layer 110 is used, but this process
may be omitted when a substrate 100 in which circuit patterns 135
are formed on an insulating material layer 110 is used as shown in
FIG. 26.
[0091] As described above, according to the present invention, when
an optical waveguide is formed on a substrate 100, first, an
insulation layer 300 having a through hole 305 is formed, and then
a core material 710 is charged only in the through hole 305 and
then patterned to form core parts 730, so that the used amount of
the core material 710 in the present invention is reduced to about
1/10.about. 1/50 of the used amount of the core material 710 in a
conventional technology, thereby increasing economic
efficiency.
[0092] Further, according to the present invention, since a lower
clad layer 530 is formed only in a through hole 305 of an
insulation layer 300, the amount of a clad material used to form
the lower clad layer 530 can be reduced.
[0093] Moreover, according to the present invention, since a member
having a through hole for forming cores and a transparent release
film 800 are selectively used, more precise and fine core parts 730
can be formed, the core parts 730 can be flattened, and the
deterioration of optical properties attributable to the pollution
caused by impurities can be prevented, so that a highly-reliable
printed circuit board for an optical waveguide can be efficiently
manufactured.
[0094] Although the preferred embodiments of the present invention
have been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
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