Indian Patents
Title of Invention

SHIELDING FILM, SHIELDED PRINTED CIRCUIT BOARD, SHIELDED FLEXIBLE PRINTED CIRCUIT BOARD, METHOD OF MANUFACTURING SHIELDING FILM AND METHOD OF MANUFACTURING SHIELDED PRINTED CIRCUIT BOARD
Abstract The invention includes a shielding film, which does not have breakage of a metal layer, and has excellent abrasion resistance and blocking resistance, and does not crack. The cover film 7 is provided on one surface of a separation film 6a, and an adhesive layer 8a is formed on the surface of the cover film 7 opposite to the separation film 6a via the metal layer. The cover film 7 has at least one hard layer 7a and at least one soft layer 7b, and the surface of the cover film 7 facing the separation film 6a is composed of the hard layer 7a.
Full Text WO 2006/121194 PCT/JP2006/309870
DESCRIPTION
SHIELDING FILM, SHIELDED PRINTED CIRCUIT BOARD, SHIELDED
FLEXIBLE PRINTED CIRCUIT BOARD, METHOD OF MANUFACTURING
SHIELDING FILM, AND METHOD OF MANUFACTURING SHIELDED
PRINTED CIRCUIT BOARD
Technical Field
The present invention relates to a shielding film
shielding a printed circuit board etc. which is used in a
device such as a computer, a communication device, a
printer, a mobile phone, a video camera, or the like, a
method of manufacturing the shielding film, a shielded
printed circuit board and a shielded flexible printed
circuit board that are manufactured by using the shielding
film, and a method of manufacturing a shielded printed
circuit board.
Background Art
A flexible printed circuit board (hereinafter,
referred to as 'FPC') has a printed circuit, which is
provided on at least one surface of a flexible insulating
film such as a polyimide film or a polyester film with or
without an adhesive between the printed circuit and the
flexible film. According to need, a flexible insulating
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film having openings is adhered on the surface of the
printed circuit by an adhesive, or a protective layer is
formed on the surface of the printed circuit. The
openings are formed on the flexible insulating film so as
to correspond to portions on which terminals used to mount
circuit components or terminals used to be connected with
an external board are formed. The protective layer is
formed on the surface of the printed circuit by methods of
coating, drying, exposing, developing, and heat-treating a
photosensitive insulating resin. The FPC is widely used
to build a circuit into a complex mechanism of an
electronic device such as a mobile phone, video camera,
personal lap top computer or the like which have been
rapidly miniaturized and multi-functionalized. in
addition, the FPC is also used to connect a moving unit
such as a printer head with a control unit due to its
excellent flexibility. A shielding countermeasure against
electromagnetic wave has been required for the electronic
device in which the FPC is widely used. Accordingly, a
shielded flexible printed circuit board (hereinafter,
referred to as a 'shielded FPC) having the shielding
countermeasure against electromagnetic wave has been, used
as the FPC to be built in the device.
In addition, similar to a flex rigid board or a
flexboard (registered trade mark), the following FPC has
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been used recently. In the FPC, the printed circuit board
is partially laminated to form multilayered portions used
to mount components, and cable portions extend outside
from the multilayered portions. Specifically, Similar to
the electronic device, shielding countermeasures against
electromagnetic wave have been required for the cable
portions of the boards.
The shielded FPC uses a flexible insulating film as
a cover film. Furthermore, a shielding layer is provided
on one surface of the cover film, and a releasable
adhesive film having adhesion is adhered on the other
surface of the cover film in order to form a
reinforcement-shielding film. Then, the shielding film is
adhered on at least one surface of the FPC by using a
conductive adhesive and by heating and pressing the
shielding film and the FPC. Further, after the shielding
layer is electrically connected to the grounding circuit
formed on the FPC by the conductive adhesive, the adhesive
film is released. Here, when an electric connection
between the shielding layer and the grounding circuit is
not particularly required, a normal adhesive not having
conductivity may be used instead of the conductive
adhesive to adhere the shielding layer to the grounding
circuit. The FPC is directly connected to a rigid circuit
board, or the multilayered portions -used to mount
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components are formed to be connected to the cable
portions like the flex rigid board or the flexboard. In
this case, according to need, a shielding layer is also
provided on a rigid circuit board or the multilayered
portions used to mount components similar to the above-
mentioned structure. Therefore, it is possible to
adequately manage electromagnetic wave.
However, there are many cases where the cover film
used in the shielding film is made of engineering plastic
such as polyphenylenesulfide (PPS), polyester, aromatic
aramid, and the thickness of the cover film is thick (for
example, 9 pin) or the stiffness thereof is strong. For
this reason, the flexibility of the cover film
deteriorates. Moreover, when the adhesive film is
released from the shielded FPC and then a glass epoxy
board or the like is adhered on the cover film to
reinforce the shielded FPC, PPS barely adheres to the
glass epoxy board or the like due to the fact that PPS has
difficulty in adhesion.
In order to solve the above-mentioned problem, the
following shielding film and a method of manufacturing the
shielding film has been disclosed in JP-A-2004-95566. In
the shielding film, a resin having excellent thermal
resistance and adhesiveness is coated on one surface of a
separation film via a release agent layer to form the
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shielding film, and an adhesive layer is further provided
on the cover film via a metal layer. Here, since the
cover film has excellent flexibility and is formed by the
coating method, the thickness of the cover film is thin,
that is, about 5 pm. In addition, since the cover film
has adhesion, it is possible to easily adhere a glass
epoxy board after the release of the separation film.
Disclosure of the Invention
However, the following problems are generated. That
is, (1) the cover film, which is formed by coating the
resin having excellent thermal resistance such as a
polyimide resin, an epoxy resin, or the like, is soft.
For example, a shielded FPC used for a moving unit such as
a mobile phone, a printer, or the like, is worn by rubbing
against another part such as a housing or the like, and
does not serve as a protective layer after the release of
the separation film. (2) In addition, when the shielded
FPC is heated and pressed, the cover film serving as a
base is softened. For this reason, dents occur on the
upper side of the insulation removed portions for
connecting the grounding circuit. As a result, breakage
such as a cracking, fracture, or the like occurs in the
metal layer. (3) Furthermore, the cover film has
excellent adhesion. For this reason, when the cover film
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comes in contact with a conveyor jig, conveyor belt, or
the like on which the circuit board is loaded to be
conveyed, in a process requiring heat, such as a reflow
process in the process of mounting circuit components, the
cover film is attached thereto. As a result, the blocking
resistance deteriorates.
Consequently, a method in which a cover film having
high hardness is made of a resin having excellent abrasion
resistance has been considered. However, the cover film
having high hardness is brittle. For this reason, when
the shielding film using the cover film is adhered on a
foundation film including printed circuits, the cover film
having high hardness cracks due to the concavity and
convexity of the insulation removed portions of the
insulating film.
It is an object of the invention to provide a
shielding film, a shielded printed circuit board, a
shielded flexible printed circuit board in which each have
a cover film not having breakage of a metal layer, and
having excellent abrasion resistance and blocking
resistance, and no cracking is generated. In addition, it
is an object of the invention to provide a method of
manufacturing the shielding film and a method of
manufacturing the shielded printed circuit board.
A shielding film according to an aspect of the
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invention includes: a separation film; a cover film
provided on one surface of the separation film; and an
adhesive layer, which is formed on the surface of the
cover film opposite to the separation film via a metal
layer. In this case, the cover film includes at least one
hard layer and at least one soft layer, and the surface of
the cover film facing the separation film is composed of
the hard layer.
According to the shielding film of the invention,
the surface face is composed of the hard layer, and the
hard layer having excellent abrasion resistance serves as
a protective layer after the release of the separation
film. Accordingly, it is possible to prevent the abrasion
of the cover film. Furthermore, since the hard layer has
excellent blocking resistance, the hard layer is not
attached to another part in a process required to be
heated. The metal layer, which is provided on the hard
layer with the soft layer interposed between the metal
layer and the hard layer, is protected by excellent
hardness of the hard layer. For this reason, even though
the metal layer provided on the hard layer via a soft
layer is heated and pressed, breakage such as a cracking,
fracture, or the like does not occur. Further, when the
shielding film is adhered on the foundation including the
printed circuit, it is possible to prevent the hard layer
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from cracking because of the cushioning effect of the soft
layer.
Further, in the shielding film of the invention, at
least one layer of the hard layer and the soft layer may
be composed of a coating layer. As a result, it is
possible to make the shielding film thin, and to provide a
shielding film having excellent flexibility.
A shielded printed circuit board according to
another aspect of the invention includes: a metal layer,
which is provided on at least one surface of a foundation
including at least one printed circuit via a adhesive
layer; and a cover film, which is provided on the surface
of the metal layer opposite to the adhesive layer. In
this case, the cover film includes at least one hard layer
and at least one soft layer, and the outermost surface of
the cover film is composed of a hard layer.
According to the shielded printed circuit board of
the invention, since the outermost surface of the cover
film is composed of the hard layer having excellent
abrasion resistance and blocking resistance, it is
possible to prevent abrasion of the cover film. In
addition, since the hard layer has excellent blocking
resistance, the hard layer is not attached to a conveyor
jig, conveyor belt, or the like on which the circuit board
is loaded to be conveyed, in a process requiring heat,
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such as a reflow process in the process of mounting
circuit components.
In the above-mentioned shielded flexible printed
circuit board, it is preferable that the foundation
including the printed circuit be composed of a flexible
printed circuit board in the above-mentioned shielded
printed circuit board.
According to the shielded flexible printed circuit
board of the invention, the shielded flexible printed
circuit board can have excellent sliding resistance, which
is a characteristic required for the flexible printed
circuit board.
In the shielded flexible printed circuit board of
the invention, it is preferable that the foundation
including the printed circuit be composed of a TAB tape
for a tape carrier package. As a result, since the
shielding film has excellent flexibility, the rebound
resilience of the shielding film deteriorates, such that
it is possible to improve the efficiency in assembling.
In the shielding film of the invention, the adhesive
layer, which is formed on the surface of the cover film
opposite to the separation film via a metal layer, may be
composed of a conductive adhesive. As a result, the metal
layer and the grounding circuit of the printed circuit
board can be electrically connected to each other.
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Moreover, in the shielding film of the invention,
the above-mentioned conductive adhesive may be an
anisotropic conductive adhesive. As a result, it is
possible to make the conductive adhesive thinner than the
above-mentioned conductive adhesive, and to reduce the
amount of conductive filler. Accordingly, it is possible
to form a shielding film having excellent flexibility.
In a method of manufacturing a shielding film of the
invention, the cover film is formed by stratifying a hard
layer and a soft layer on one surface of the separation
film. The shielding film includes: a separation film; a
cover film provided on one surface of the separation film;
and an adhesive layer that is formed on the surface of the
cover film opposite to the separation film via the metal
layer.
According to the method of manufacturing a shielding
film of the invention, since the hard layer and the soft
layer are stratified, it is possible to manufacture the
shielding film, which has excellent abrasion resistance
and blocking resistance. Furthermore, even though the
shielding film is heated and pressed, breakage such as a
cracking, fracture, or the like does not occur in the
shielding film.
Further, in the method of manufacturing a shielding
film of the invention, at least one layer of the hard
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layer and the soft layer may be composed of a coating
layer. As a result, it is possible to make the cover film
thin, and to manufacture shielding film having excellent
flexibility.
Furthermore, in the method of manufacturing a
shielding film of the invention, the hard layer and the
soft layer may be sequentially coated on one surface of
the separation film. According to this structure, since
the separation film can be used as a carrier film during
the coating, it is possible to easily make the hard layer
and the soft layer thin. In addition, it is possible to
provide the shielding film, which has a thinner cover film,
having excellent flexibility, and to reliably provide the
shielding film at low cost.
It is preferable that a method of manufacturing the
shielded printed circuit board of the invention, include:
placing the above-mentioned shielding film on at least one
surface of a foundation including at least one printed
circuit; heating and pressing the shielding film; and
releasing the separation film.
According to the method of manufacturing the
shielded printed circuit board of the invention, it is
possible to easily manufacture the shielded printed
circuit board having a cover film, which does not have
breakage of a metal layer, having excellent abrasion
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resistance and blocking resistance, and not cracking.
Furthermore, a method of manufacturing a shielded
printed circuit board according to another aspect of the
invention includes: removing a portion of an insulating
material covering a grounding circuit from a printed
circuit, which includes a signal circuit and a grounding
circuit formed on a base film, in order to prepare a
foundation having the exposed grounding circuit; placing
the above-mentioned shielding film in which the above-
mentioned adhesive layer is a conductive adhesive layer or
an anisotropic conductive adhesive layer on the
foundation; and heating and pressing the shielding film so
that the shielding film are adhered to each other and the
grounding circuit is electrically connected to the metal
layer.
According to the above-mentioned method of
manufacturing a shielded printed circuit board, since the
cover film is composed of the hard layer and the soft
layer, the conductive adhesive or the anisotropic
conductive adhesive softened due to heating is easily
embedded into the insulation removed portions. Further,
it is possible to ground the metal layer or the shielding
layer, which is composed of the metal layer and the
adhesive layer, via a grounding circuit. In addition,
when the adhesive layer is non-conductive, the metal layer
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may be connected to a case or the like by another method.
Moreover, in the above-mentioned method of
manufacturing a shielded printed circuit board of the
invention, the foundation including at least one printed
circuit may be composed of a flexible printed circuit
board. As a result, it is possible to obtain a flexible
printed circuit board having excellent flexibility and
sliding resistance.
Furthermore, in the above-mentioned method of
manufacturing a shielded printed circuit board, the
foundation including at least one printed circuit may be
composed of a TAB tape for a tape carrier package. As a
result, it is possible to obtain a flexible TAB tape for a
tape carrier package, which has excellent efficiency in
assembling.
Brief Description of the Drawings
Fig. 1 is a view illustrating a method of
manufacturing a shielded FPC according to an embodiment of
the invention, Fig. l(a) shows a state in which a
shielding film is placed on a foundation film and is then
pressed by a press while heated, Fig. 1 (b) shows a state
in which a separation film is released, and Fig. l(c)
shows a state in which the separation film has been
released.
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Fig. 2 is a cross-sectional view showing the
shielding film used to manufacture the shielded FPC, Fig.
2(a) shows a shielding layer composed of an adhesive layer
and a metal layer, and Fig. 2 (b) shows a shielding layer
composed of only an adhesive layer.
Fig. 3 is a cross-sectional view showing the
shielded FPC, Fig. 3(a) is similar to Fig. 1 (c), and each
of Figs. 2(b) and 2(c) is a cross-sectional view showing a
shielded FPC that is shielded on the both surfaces thereof.
Fig. 4 is a view showing a state in which
rectangular ground members are provided to the end of the
shielded FPC according to the invention, Fig. 4 (a) is a
top view of the shielded FPC, Fig. 4 (b) is a cross-
sectional view thereof in a width direction of the
shielded FPC, and Fig. 4 (c) is a cross-sectional view
thereof in a longitudinal direction.
Fig. 5 is a view showing a (Japan Society for the
Promotion of Science type) rubbing tester defined in JIS L
0849: 2004.
Fig. 6 is view showing a dynamic elastic modulus-
measuring device using a tensile non-resonant oscillation
method, which is defined in JIS K 7244-4.
Fig. 7 (a) is a cross-sectional view of a specimen
used for a rubbing test, and Fig. 7 (b) is a cross-
sectional view of a specimen used for a blocking
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resistance test.
Fig. 8 is a view illustrating a test method of a
sliding resistance test.
Fig. 9 is a graph representing the result of the
sliding resistance test.
Fig. 10 is a cross-sectional view of a shielded
flexible printed circuit board during an embedding
resistance test.
Best Mode for Carrying Out the Invention
Hereinafter, a shielded FPC according to an
embodiment of the invention will be described with
reference to the drawings. Fig. 1 is a view illustrating
a method of manufacturing a shielded FPC according to the
present embodiment, and Fig. 2 is a cross-sectional view
showing a shielding film used to manufacture the shielded
FPC. Fig. l(a) shows a state in which a shielding film 1
is placed on a foundation film 5 and is then pressed P by
a press P (PA and PB) while being heated h. The
foundation film 5 is formed by covering a printed circuit
3, which is formed on a base film 2 and includes a signal
circuit 3a and a grounding circuit 3b, with an insulating
film 4 except for at least a portion (non-insulated
portions} 3c of the grounding circuit 3b.
Here, the base film 2 and the printed circuit 3 may
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be adhered to each other by an adhesive, and may be
adhered to each other without using an adhesive similarly
to a so-called non-adhesive type copper-clad laminated
plate. In addition, the insulating film 4 may be formed
by adhering flexible insulating films to each other by an
adhesive, and may be formed by serial methods of coating,
drying, exposing developing, and heat-treating a
photosensitive insulating resin.
In addition, single-sided FPC having a printed
circuit on only one side of a base film, a double-sided
FPC having a printed circuit on both sides of a base film,
a multilayered FPC in which several FPCs are laminated, a
flexboard (registered trade mark) having a multilayered
part mounting portion and a cable portion, a flexible
rigid board having a multilayered portion made of a hard
material, a TAB tape for a tape carrier package, and the
like can be properly used as the foundation film 5.
Here, a film shown in Fig. 2 (a) is used as the
shielding film 1. As shown in Fig. 2 (a), the shielding
film 1 includes a separation film 6a, a mold-releasing
layer 6b formed on one side of the separation film 6a, and
a shielding film body 9. The shielding film body 9
includes a cover film 7 and an adhesive layer 8a. The
cover film 7 is formed by sequentially coating a hard
layer 7a, which is made of a resin having excellent
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abrasion resistance and blocking resistance, and a soft
layer 7b, which is made of a resin having excellent
cushioning characteristics, on the mold-releasing layer 6b.
The adhesive layer 8a is formed on the surface of the
cover film 7 opposite to a mold-releasing layer 6b via a
metal layer Sb. Here, a shielding layer 8 is composed of
the adhesive layer 8a made of a conductive adhesive, and
the metal layer 8b. In the shielding layer 8, an adhesive
8a1 softened due to heating h flows in a direction
indicated by arrows to insulation removed portions 4a (see
Fig. 1 (a) ) . Furthermore, if the mold-releasing layer 6b
formed on the separation film 6a has release
characteristic with respect to the cover film 7, the mold-
releasing layer 6b is not limited to a specific one. For
example, it is possible to use a PET film coated by
silicon as the mold-releasing layer. Moreover, coating is
preferably used as a method of forming the hard layer 7a
and the soft layer 7b on one side of the separation film
6a. However, lamination, extrusion, dipping, or the like
in addition to coating may be employed as the method of
forming the hard layer and the soft layer.
In this way, the adhesive 8a' is sufficiently
applied to the non-insulated portions 3c of the grounding
circuit 3b, and the insulating film 4. After that, as
shown in Fig. 1(b), a shielded-flexible printed circuit
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board 10 formed as mentioned above is separated from the
press P, and the separation film 6a of the shielding film
1 is released together with the mold-releasing layer 6b,
thereby obtaining a shielded FPC 10' shown in Fig. l(c).
As shown in Fig. 2 (a), the shielding film 1 has a
larger thickness than that of the shielding film body 9 as
much as the thickness of the separation film 6a.
Accordingly, the shielding film is easily blanked with a
predetermined size, can be cleanly cut, and is easily
positioned on the foundation film 5. In addition,
cushioning effect caused by the separation film 6 is
increased during the heating and pressing, and thus,
pressure is slowly applied. As a result, since the
adhesive 8a' easily flows into the insulation removed
portions 4a and the adhesive 8a1 is sufficiently applied
to the non-insulated portions 3c of the grounding circuit
3b, connecting conductivity is improved. Furthermore,
when the separation film 6a is released together with the
mold-releasing layer 6b, a thin and flexible shielded FPC
10 is easily obtained. Further, the shielding film 1 may
be used in a rigid circuit board.
All of the base film 2 and the insulating film 4 are
made of engineering plastic. For example, a resin such as
polypropylene, cross-linked polyethylene, polyester,
polybenzimidazole, polyimide, polyimidoamide,
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polyetherimide, polyphenylenesulfide (PPS), or the like is
used as the engineering plastic. When thermal resistance
is not particularly required, an inexpensive polyester
film is preferably used. When fire retardancy is required,
a polyphenylenesulfide film is preferably used. Further,
when the thermal resistance is required, a polyirtide film
is preferably used.
The hard layer 7a comprising the cover film 7 is
made of a resin having abrasion resistance. Abrasion does
not occur on the resin composing the hard layer under the
following conditions of a rubbing test, which is performed
by a (Japan Society for the Promotion of Science type)
rubbing tester defined in JIS L 0849. For the conditions,
a rubbing element has a mass of 500 g, and a specimen
table is horizontally reciprocated in a distance of 120 mm
at a speed of 30 reciprocations per minute and is
reciprocated 1000 times. The soft layer 7b is made of a
resin having an elastic modulus of 3 Gpa (giga pascal) or
less. The elastic modulus is measured under the following
conditions by a method of testing dynamic mechanical
properties, which is defined in JIS K 7244-4. For the
conditions, a frequency is 1 Hz, a measurement temperature
is in the range of -50 to 150 °C, and a temperature rise
rate is 5 °C/min. Since the separation film 6a needs to
be released from the cover film 7 during the post
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processes, the hard layer 7a is coated on the mold-
releasing layer 6b formed on one side of the separation
film 6a. Further, after the separation film 6a is
released, the hard layer 7a having excellent abrasion
resistance serves as a protective layer and prevents the
abrasion of the cover film 7. Furthermore, since the hard
layer 7a has excellent blocking resistance, the hard layer
is not attached to a conveyor jig, conveyor belt, or the
like on which the circuit board is loaded to be conveyed,
in a process requiring heat, such as a reflow process in
the process of mounting circuit components. Since the
cover film 7 serving as a base has excellent hardness of
the hard layer 7a and cushioning characteristics of the
soft layer 7b, breaking such as a crack, fracture, or the
like does not occur even when the shielding film is heated
and pressed. Moreover, when the shielding film 1 is
placed on the foundation film 5 including the printed
circuit 3 and is then pressed P by the press P (PA and PB)
while heated h, the pressure is slowly applied to the hard
layer 7a because of the cushioning effect of the soft
layer 7b. Accordingly, it is possible to prevent the hard
layer 7a having high hardness from cracking. A
thermosetting resin, a thermoplastic resin, an electron
beam curable resin, or the like can be used as a resin for
the hard layer or the soft layer.
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The separation film 6a is also made of engineering
plastic similar to the base film 2, the insulating film 4,
and the cover film 7. However, since the separation film
6a is removed in the processes of manufacturing the
printed circuit board, it is preferable that the
inexpensive polyester film be used as the separation film.
As described above, since the mold-releasing layer 6b is
formed on the surface of the separate film 6a so as to
have release characteristic with respect to the hard layer
7a. The mold-releasing layer 6b may be formed to cover
the overall surface of the separate film 6a, or may be
formed only on the surface, on which the hard layer 7a is
coated, of the separate film. In addition, a silicon film
formed by known method can be used as the mold-releasing
layer 6b.
The adhesive layer 8a is made of an adhesive resin,
that is, a thermoplastic resin or a thermosetting resin.
The thermoplastic resin includes polystyrenes, vinyl
acetates, polyesters, polyethylenes, polypropylenes,
polyamides, rubbers, acryls, and the like. The
thermosetting resin includes phenols, epoxys, urethanes,
melamines, alkyds, and the like. In addition, the
adhesive layer can be also made of a conductive adhesive,
which has conductivity by mixing a conductive filler such
as a metal, carbon, or the like into the-adhesive resin.
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Furthermore, it is possible to form an anisotropic
conductive layer by reducing the amount of the conductive
filler. When thermal resistance is not particularly
required, a polyester-based thermoplastic resin not having
limitation in storage conditions is preferably used. When
thermal resistance or better flexibility is required, an
epoxy-based thermosetting resin having high reliability
after the shielding layer 8 is formed is preferably used.
Further, for all of them, it is preferable that the resin
hardly flow out of the shielding film during the heating
and pressing.
Carbon, silver, copper, nickel, solder, a copper
filler coated with silver that is formed by coating
aluminum and copper powder with silver, a filler that is
formed coating resinous balls or glass pieces with a metal,
and the mixture thereof are used as the conductive filler.
Silver is expensive, copper lacks reliability in thermal
resistance, aluminum lacks reliability in humidity
resistance, and solder does not have sufficient
conductivity. Therefore, the relatively inexpensive
copper filler coated with silver or nickel filler, which
has conductivity and high reliability, may be preferably
used as the conductive filler.
The mixing ratio of the conductive filler such as
the metal filler into the adhesive resin depends on the
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shape of the filler. However, it is preferable that 10 to
400 parts by weight of the copper filler coated with
silver be contained relative to 100 parts by weight of the
adhesive resin, and is more preferable that 20 to 150
parts by weight of the copper filler coated with silver be
contained relative thereto. When the copper filler coated
with silver is more than 400 parts by weight, the adhesion
of the copper filler coated with silver to the grounding
circuit (copper foil) 3b deteriorates and thus the
flexibility of the shielded FPC 10' deteriorates. In
addition, when the copper filler coated with silver is
less than 10 parts by weight, the conductivity thereof
deteriorates. It is preferable that 40 to 400 parts by
weight of the nickel filler be contained relative to 100
parts by weight of the adhesive resin, and is more
preferable that 100 to 350 parts by weight of the nickel
filler be contained relative thereto. When the nickel
filler is more than 400 parts by weight, the adhesion to
the grounding circuit (copper foil) 3b of the nickel
filler deteriorates and thus the flexibility of the
shielded FPC 10' deteriorates. In addition, when the
nickel filler is less than 40 parts by weight, the
conductivity thereof deteriorates. The conductive filler
such as a metal filler may be formed in the shape of a
sphere, needle, fiber, flake, or resin.
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If the conductive filler such as a metal filler is
mixed into the adhesive resin as described above, the
thickness of the adhesive layer 8a becomes as large as
much as that of the filler and thus is about 20 ± 5 m.
In addition, if the conductive filler is not mixed into
the adhesive resin, the thickness of the adhesive layer is
about 1 + 10 m. For this reason, since the shielding
layer 8 can be made thin, it is possible to obtain a thin
shielded FPC 10' .
Aluminum, copper, silver, gold, or the like can be
used as a metal material of the metal layer 8b. The metal
material may be selected in consideration of the shielding
characteristic thereof. However, taking into
consideration, copper is likely to be oxidized when coming
in contact with the atmosphere, and gold is expensive.
Accordingly, inexpensive aluminum or silver having high
reliability may be preferably used as the metal material.
The thickness of the metal layer is properly set in
consideration of the shielding characteristic and
flexibility thereof. However, in general, the thickness
of the metal layer is preferably set in the range of 0.01
to 1.0 m. When the thickness of the metal layer is less
than 0.01 m, the shielding effect thereof is not
sufficient. In contrast, when the thickness of the metal
layer is more than 1.0 m, the flexibility thereof
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deteriorates. Vacuum deposition, sputtering, a CVD method,
MO (metal organic), plating, and the like can be used as a
method of forming the metal layer 8b. However, vacuum
deposition is preferable considering mass productivity,
and can allow a stable and thin metal film to be obtained
at low cost. Moreover, the metal layer is not limited to
the thin metal film, and a metal foil may be used as the
metal layer.
A shielding film 1 shown in Fig. 2 (b) is different
from the shielding film 1 shown in Fig. 2 (a) in that a
shielding layer 8 is formed on one side of the cover film
7. The shielding layer 8' is composed of only an adhesive
layer 8a, and the adhesive layer 8a is made of a
conductive adhesive into which the conductive filler is
mixed. The metal layer 8b has higher conductivity than
the adhesive layer 8a. Accordingly, when the metal layer
8b is provided as shown in Fig. 2 (a), the conductive
adhesive does not need to be used. As a result, it is
possible to make the shielding layer 8 thin. In addition,
the structure of the shielding layer 8 is not limited
thereto, and it is preferable that shielding layer have
high conductivity and flexibility.
Fig. 3 is a cross-sectional view showing the
shielded FPC obtained as described above, and Fig. 3(a) is
similar to Fig. l(c). It is natural that the shielded FPC
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WO 2006/121194 PCT/JP2006/309870
of the invention includes a shielding film body 9' instead
of the shielding film body 9 shown in Fig. 3 (a). In the
shielding film body 9', the shielding layer 8' is composed
of only an adhesive layer 8a made of a conductive adhesive
as shown in Fig. 2 (b). In addition, various members
constituting the shielding film body 9 and a method of
forming the shielding film body also include various ones
as described above.
Furthermore, the FPC is not limited to the one-sided
shielded FPC, and includes both-sided shielded FPC as
shown in Figs. 3 (b) and 3 (a). In the both-sided shielded
FPC 10A of Fig. 3 (b) ,- insulation removed portions 4a and
2a' are formed in an insulating film 4 and a base film 2',
respectively, in order to connect an adhesive layer 8a
with a grounding circuit 3b. The insulating film 4 is
disposed on the grounding circuit 3b, and the base film 2'
is disposed beneath the grounding circuit. Non-insulated
portions 3c, which are upper and lower surfaces of the
grounding circuit 3b, are connected to adhesive layers 8a.
Here, the base film 2', the printed circuit 3 (a signal
circuit 3a and a grounding circuit 3b), and the insulating
film 4 constitute a foundation film 5'.
In the both-sided shielded FPC 10B of Fig. 3(c),
insulation removed portions 4a and 2a' are formed in an
insulating film 4 and a base film 2' respectively.
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Similar to the both-sided shielded FPC of Fig. 3 (b) , the
insulating film 4 is disposed on the grounding circuit 3b,
and the base film 2' is disposed beneath the grounding
circuit. However, through holes 3d1 are further provided
in the grounding circuit 3b to form a grounding circuit
3b'. Accordingly, the adhesive layers 8a permeate into
the through holes 3d' from the both sides, and are joined
to each other at interfaces S. The upper surface of the
non-insulated portion 3c and the inner surface 3c' of the
through holes are connected to the adhesive layer 8a.
Here, the base film 2', the printed circuit 3' (a signal
circuit 3a' and a grounding circuit 3b'), and the
insulating film 4 constitute a foundation film 5".
Furthermore, as shown in Fig. 4, in the shielded FPC
according to the invention, one surface of the foundation
film 5 is covered with the shielding film body 9, and a
rectangular ground member 13 can also be provided at the
end of the foundation film.
The ground member 13 is a member in which an
adhesive resin layer 12 is disposed on one surface of a
rectangular metal foil 11 having a width W. As the width
W of the ground member 13 is increased, the ground
impedance of the ground member 13 is decreased, which is
preferable. However, the width W of the ground member is
set in consideration of handling and economical efficiency
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WO 2006/121194 PCT/JP2006/309870
thereof. Furthermore, in the present embodiment, a
portion of the ground member corresponding to the width Wl
of the width W is exposed, and a portion of the ground
member corresponding to the width W2 is adhered to the
adhesive layer 8a. If the exposed portion thereof
corresponding to the width Wl is connected to the ground
portion around it by using a proper conductive member, it
is possible to reliably ground the ground member.
Moreover, if the ground member is reliably grounded, the
width W2 may be further reduced. In the present
embodiment, the length of the ground member 13 is set
equal to the width of the shielding film body 9 or the
foundation film 5 in order to facilitate machining of the
ground member. However, the length of the ground member
may be set shorter or longer than the width of the
shielding film body or the foundation film, and may be set
to be connected to the portion of the ground member, which
is connected to the conductive-adhesive layer 12, and the
portion of the ground member, which is exposed and
connected to the ground portion around it.
Similarly, the shape of the ground member 13 is also
not limited to the rectangular shape, and may be set so
that one portion of the ground member is connected to the
adhesive layer 8a and the other portion thereof is
connected to the ground portion around it.-
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In addition, a position of the ground member is not
limited to the end portion of the shielded FPC 10', and
the ground member may be positioned at the position 13a
other than the end portion indicated by an imaginary line
in Fig. 4 (a) . However, in this case, the ground member
13a protrude and is exposed to the side portion from the
shielding film body 9 so as to be connected to the ground
portion around it. The lengths LI and L2 of the both
portions of the ground member, which protrude from the
both sides of the shielding film body, may be set to be
grounded to the ground portion around it such as the case
of the device, and only one side of the protruding
portions may protrude from the shielding film body. The
surface of the metal layer 8b comes in contact with the
ground portion so as to connected to each other by screws
or solder.
Although a copper foil is preferably used as the
metal foil 11 of the ground member 13 in consideration of
conductivity, flexibility, economical efficiency, and the
like, the metal foil is not limited thereto. In addition,
although conductive resin can be used instead of the metal
foil, it is preferable to use the metal foil in
consideration of conductivity.
Furthermore, the adhesive resin layer 12 is made of
a thermoplastic resin or a thermosetting resin. The
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thermoplastic resin includes polystyrenes, vinyl acetates,
polyesters, polyethylenes, polypropylenes, polyamides,
rubbers, acryls, and the like. The thermosetting resin
includes phenols, epoxys, urethanes, melamines, polyimides,
alkyds, and the like. It is preferable that the adhesive
resin layer is made of a material having excellent
adhesion with respect to the metal foil and the adhesive
resin layer constituting the ground member 13, or the
insulating film 4 of the foundation film 5. Moreover,
when being positioned at the position other than the end
portion to be covered with the shielding layer 8, the
ground member 13 may be made of a metal foil or a metal
wire.
As described above, since the shielding layer 8 of
the shielding film body 9 is grounded by the ground member
13, it is not necessary to provide a wide ground wire as a
part of the printed circuit. For this reason, it is
possible to increase wiring density. In addition, the
ground impedance of the ground member 13 is easily
decreased to be smaller than that of the ground wire of
the conventional shielded FPC. Therefore, the
electromagnetic wave shielding effect of the shielding
layer is also improved.
Further, the invention naturally includes a
conventional shielded FPC in which a wide ground wire is
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provided to ground the shielding layer 8. In this case,
since the board ground effect caused by the wide ground
wire and the frame ground effect caused by the ground
member are added to each other, the electromagnetic wave
shielding effect is further improved and stabilized.
The end portion of the foundation film 5
corresponding to the width tl is exposed, and the printed
circuit 3 is exposed. In addition, in the present
embodiment, the ground member 13 is adhered to the
insulating film 4 such that one end of the ground member
in the width direction thereof is kept separate from the
end of insulating film by a width t2. Accordingly,
insulating resistance between signal lines 4 is ensured by
the width t2.
Moreover, the ground member can have various
structures other than the structure shown in Fig. 4. For
example, the ground member may have the following
structure. In the structure, the ground member is a metal
foil made of copper, silver, aluminum, or the like.
Further, a plurality of conductive bumps protruding from
one surface of the metal foil is connected to the
shielding layer through the cover film, and the exposed
metal foil is connected to the ground portion around it.
In addition, the ground member may have the
following structure. In another structure, the ground
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member is a metal plate, which is made of copper, silver,
aluminum, or the like, and has a plurality of protrusions
on one surface thereof. The protrusions are connected to
the shielding layer through the cover film, and the
exposed metal plate is connected to the ground portion
around it.
Furthermore, the following ground member may have
another structure. In another structure, the ground
member is a metal foil made of copper, silver, aluminum,
or the like. Further, a plurality of metal fillers
protruding from one surface of the metal foil is connected
to the adhesive layer and metal layer of the shielding
layer through the cover film, and the exposed metal foil
is connected to the ground portion around it.
In addition, the following structure may be employed.
In the structure, the cover film is removed by excimer
laser to form a window at a predetermined position on the
shielding film, and one end of the ground member
(conductor) is connected to the window through the
conductive adhesive into which a conductive filler is
mixed. The other end of the ground member is connected to
the ground portion around it. Alternatively, the ground
portion around it may be directly connected to the window
without using the ground member.
•(Examples)
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Next, the results of the evaluation tests, which are
performed with the examples of the invention, and
comparative examples will be described.
(1) Rubbing test
Specimens: Each of the shielding films, which have
cover films 7 according to first to third examples and
first to third comparative examples shown in Table 1, is
adhered to a CCL 20 as shown in Fig. 7 (a) , and the
shielding film and the CCL are then heated and pressed to
prepare each sheet having a width of 50 mm and a length of
140 mm. The sheets have been used as the specimens. Here,
the CCL 20 is obtained by adhering a polyimide film 23 to
a copper foil 21 by an adhesive 22. The thickness of each
layer is as follows: the thickness of the hard layer 7a is
2 urn, the thickness of the soft layer 7b is 3 m, the
thickness of the metal layer 8b is 0.15 jam, the thickness
of the adhesive layer 8a having conductivity is 20 m, the
thickness of the copper foil 21 is 18 m, the thickness of
the adhesive 22 is 17 m, and the thickness of the
polyimide film 23 is 25 m.
Test method: As shown in Fig. 5, the rubbing test
has been performed by a (Japan Society for the Promotion
of Science type) rubbing tester 50 defined in JIS L 0849:
2004. Whether abrasion occurs on the surface 52a of the
specimen (abrasion resistance) has been tested under the
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following conditions. Under the conditions, a rubbing
element 51 has a mass of 500 g. Furthermore, a specimen
table 53, on which the specimen 52 is placed, is
horizontally reciprocated in a distance of 120 mm at a
speed of 30 reciprocations per minute. In Table 1, the
result is represented as 'O' when abrasion does not occur,
and the result is represented as 'x' when abrasion occurs.
(2) Blocking resistance test
Specimens: Each of the shielding films, which have
cover films 7 according to the first to the third examples
and the first to the third comparative examples shown in
Table 1, and a polyimide film 31 (Kapton 100H manufactured
by Du Pont-Toray Co. Ltd.) (Kapton is a registered trade
mark) are adhered to the specimen 54 of the rubbing test
disclosed in (1) as shown in Fig. 7 (b) , and then are
heated at 265°C for 30 seconds to prepare the sheets. The
sheets have been used as the specimens.
Test method: The polyimide film 31 is released from
the hard layer 7a, and whether transformation occurs on
the releasing surface of the hard layer 7a has been tested.
In Table 1, the result is represented as 'O' when abrasion
does not occur, and the result is represented as 'x' when
abrasion occurs.
(3) Elastic modulus test
• Specimens: Each of sheets, which has a width of 50
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WO 2006/121194 PCT/JP2006/309870
mm, a length of 100 mm, and a thickness of 15 pm, and is
made of modified epoxy, and a sheet, which has a width of
50 mm, a length of 100 mm, and a thickness of 9 p,m, and is
made of PPS according to a third comparative example, are
prepared to be used as soft layers 7b of the first to the
third examples and the second comparative example shown in
Table 1. The sheets have been used as specimens.
Test method: As shown in Fig. 6, a specimen S is
clamped by clamps Cl and C2. Then, while the specimen is
oscillated by an oscillator V at a frequency of 1 Hz and
is heated at a rising temperature rate of 5 °C/ min, an
elastic modulus has been measured by a dynamic elastic
modulus measuring device (EXSTAR 6100 DMS by manufactured
by SII Nano Technology Inc.: old SEIKO Instruments Inc.)
60 using a tensile non-resonant oscillation method, which
is defined in JIS K 7244-4, in the measurement temperature
range of -50 to 150 °C.
(4) Sliding resistance test
Specimens: The respective cover films of the second
example and the third comparative example are used to be
laminated as shown in Fig. 1 (c) in order to form shielded
FPCs 10' having a width of 12 mm and a length of 150 mm.
•The shielded FPCs 10' have been used as the specimens.
Test method: As shown in Fig. 8, a shielded FPC 10'
is bent in the shape of a letter 'U', -and is provided
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WO 2006/121194 PCT/JP2006/309870
between a stationary plate 56 and a sliding plate 57.
Then, the sliding plate 57 slides in a vertical direction
on the basis of IPC standards. Under the conditions, a
measurement temperature is 23°C, a stroke of the sliding
plate 57 is 30 mm, and a sliding speed is 1000 times/min.
In this case, a flexible duration when the curvature
changes (the number of sliding times until breakage) has
been measured. A printed circuit, which has six lines, a
line width of 0.12 mm, and a space width of 0.1 mm, has
been used as the printed circuit 3 of the shielded FPC 10".
The result is shown by a log-log graph in Fig. 9 in which
a reciprocal number of the radius of curvature R at the U-
shaped portion is represented on a vertical axis, and the
flexible duration is represented on a horizontal axis.
(5) Embedding resistance test
Specimens: The respective cover films of the first
to the third examples and the first to the fourth
comparative examples are used to be laminated, heated, and
pressed as shown in Fig. l(c) in order to form shielded-
flexible printed circuit boards 10 having a width of 12 mm
and a length of 150 mm. The shielded-flexible printed
circuit boards 10 have been used as specimens.
Test method: As shown in a cross-sectional view of
Fig. 10, whether a crack / fracture of the metal layer or
breakage of the cover film occurs due to dents C occurring
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WO 2006/121194 PCT/JP2006/309870
when the shielded-flexible printed circuit boards 10 are
heated and pressed has been observed with the naked eye.
[First example]
The following shielding film is used as a first
example. The shielding film includes a hard layer, a soft
layer, and a shielding layer. The hard layer has a
thickness of 2 μM and is formed by mixing 100 parts by
weight of ultraviolet curing polyfunctional acrylate and
50 parts by weight of ultraviolet curing bifunctional
acrylate to each other. The soft layer has a thickness of
3 μm, and is made of a modified epoxy resin. Furthermore,
the shielding layer is formed on the soft layer. Then,
abrasion resistance, blocking resistance, and embedding
resistance has been evaluated for the first example. In
this case, the thickness of an evaporated silver layer,
which is the metal layer 8b of the shielding layer 8, has
been set to 0.15 μm, the thickness of the adhesive layer
8a having conductivity has been set to 20 μm, the
thickness of the insulating layer has been set to 40 μm,
and the diameter of the insulation removed portion has
been set to 1.4 mm (hereinafter, the structures of the
shielding layer and the insulating film will be the same
as those in the second and third examples, and the first
to the fourth comparative examples). The results of the
rubbing test, the blocking resistance test, and the
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WO 2006/121194 PCT/JP2006/309870
embedding resistance test are shown in Table 1.
[Second example]
The following shielding film is used as a second
example. The shielding film includes a hard layer, a soft
layer, and a shielding layer. The hard layer has a
thickness of 2 μm and is formed by mixing 100 parts by
weight of ultraviolet curing polyfunctional acrylate and
150 parts by weight of ultraviolet curing bifunctional
acrylate to each other. The soft layer has a thickness of
3 μm, and is made of a modified epoxy resin. Furthermore,
the shielding layer is formed on the soft layer. Then,
abrasion resistance, blocking resistance, and embedding
resistance has been evaluated for the second example. The
results thereof are shown in Table 1. In addition, a
flexible duration has been evaluated through the sliding
resistance test. The result thereof is shown in Fig. 9.
[Third example]
The following shielding film is used as a third
example. The shielding film includes a hard layer, a soft
layer, and a shielding layer. The hard layer has a
thickness of 2 μm and is formed by mixing 100 parts by
weight of ultraviolet curing polyfunctional acrylate and
250 parts by weight of ultraviolet curing bifunctional
acrylate to each other. The soft layer has a thickness of
3 μm, • and is made of a modified epoxy resin. Furthermore,
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the shielding layer is formed on the soft layer. Then,
abrasion resistance, blocking resistance, and embedding
resistance has been evaluated for the third example. The
results thereof are shown in Table 1.
[First comparative example]
The following shielding film is used as a first
comparative example. The shielding film includes a hard
layer and a shielding layer, and does not include a soft
layer. The hard layer has a thickness of 2 μm and is made
of ultraviolet curing bifunctional acrylate. Furthermore,
the shielding layer is formed on one surface of the hard
layer. Then, abrasion resistance, blocking resistance,
and embedding resistance has been evaluated for the first
comparative example. The results thereof are shown in
Table 1.
[Second comparative example]
The following shielding film is used as a second
comparative example. The shielding film includes a hard
layer and a shielding layer, and does not include a soft
layer. The hard layer has a thickness of 2 μm and is made
of ultraviolet curing polyfunctional acrylate.
Furthermore, the shielding layer is formed on one surface
of the hard layer. Then, abrasion resistance, blocking
resistance, and embedding resistance has been evaluated
for the second comparative example. The -results thereof
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are shown in Table 1.
[Third comparative example]
The following shielding film is used as a third
comparative example. The shielding film includes a soft
layer and a shielding layer, and does not include a hard
layer. The soft layer has a thickness of 3 μm and is made
of a modified epoxy resin. Furthermore, the shielding
layer is formed on one surface of the soft layer. Then,
abrasion resistance, blocking resistance, and an embedding
resistance have been evaluated for the third comparative
example. The results thereof are shown in Table 1.
[Fourth comparative example]
The following shielding film is used as a fourth
comparative example. The shielding film includes a cover
film and a shielding layer. The cover film has a
thickness of 9 μm and is made of PPS. Furthermore, the
shielding layer is formed on one surface of the cover film.
Then, abrasion resistance, blocking resistance, and
embedding resistance has been evaluated for the fourth
comparative example. The results thereof are shown in
Table 1. In addition, a flexible duration has been
evaluated through the sliding resistance test. The result
thereof is shown in Fig. 9.
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As clarified from the results of the rubbing test,
the blocking resistance test, and the embedding resistance
test as shown in Table 1, all of the first to the third
examples have excellent abrasion resistance, blocking
resistance, and embedding resistance. However, there has
been no comparative example that satisfies all of the
excellent abrasion resistance, blocking resistance, and
embedding resistance. That is, although each of the first
and the third comparative examples has a relatively small
thickness, the first and the third comparative examples
have poor abrasion resistance, blocking resistance, and
embedding resistance. The second comparative example has
s small thickness, excellent abrasion resistance, and
excellent blocking resistance. However, the second
comparative example has poor embedding resistance. In
addition, although the fourth comparative example has
excellent blocking resistance and excellent embedding
resistance, there is a problem in that the fourth
comparative example has a large thickness and poor
abrasion resistance.
Furthermore, the following fact has been understood
through the elastic modulus test. The elastic modulus of
a sheet, which is composed of each soft layer 7b made of
modified epoxy according to the first to the third
examples and the third comparative example, is 0.1 Gpa,
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and the elastic modulus of a sheet, which is composed of
the soft layer 7b made of PPS according to the fourth
comparative example, is 6 Gpa. As a result, it has been
understood that the soft layer 7b made of modified epoxy
is very flexible, and has excellent cushioning effect.
In addition, as clarified from the result of the
sliding resistance test, it has been understood that the
second example has longer flexible duration than the
fourth comparative example, and is hardly broken.
As disclosed above, the shielding film 1 according
to the present embodiment includes the separation film 6a,
the cover film 7 provided on one surface of the separation
film 6a, and the adhesive layer 8a, which is formed on the
surface of the cover film 7 opposite to the separation
film 6a via the metal layer 8b. In this case, the cover
film 7 includes at least one hard layer 7a and at least
one soft layer 7b. Further, the surface of the cover film
7 facing the separation film 6a is composed of the hard
layer 7a. As a result, the surface facing the separation
film 6a is composed of the hard layer 7a, and the hard
layer 7a having excellent abrasion resistance serves as a
protective layer after the release of the separation film
6a. Accordingly, it is possible to prevent the abrasion
of the cover film 7. Furthermore, since the hard layer 7a
has excellent blocking resistance, the hard layer is not
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attached to a conveyor jig, conveyor belt, or the like on
which the circuit board is loaded to be conveyed, in a
process requiring heat, such as a reflow process in the
process of mounting circuit components. In addition, the
hard layer 7a has excellent hardness. For this reason,
even though the metal layer 8b provided on the hard layer
7a via the soft layer 7b is heated and pressed, breakage
such as a cracking, fracture, or the like does not occur.
Further, when the shielding film 1 is adhered to the
foundation 5 including the printed circuit 3, it is
possible to prevent the hard layer 7a from cracking
because of the cushioning effect of the soft layer 7b.
Moreover, in the shielding film 1 according to the
present embodiment, at least one layer of the above-
mentioned hard layer 7a and the soft layer 7b is composed
of a coating layer. As a result, it is possible to reduce
the thickness of the shielding film 1.
Further, the shielded printed circuit board
according to the present embodiment includes the metal
layer 8b, which is provided on at least one surface of the
foundation 5 including at least one printed circuit 3 via
the adhesive layer 8a, and the cover film 7, which is
provided on the surface of the metal layer 8b opposite to
the adhesive layer 8a. In this case, the cover film 7
includes at least one hard layer 7a and at least one soft
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layer 7b. Further, the outermost surface of the cover
film 7 is composed of the hard layer 7a. As a result, the
outermost surface layer of the cover film 7 is composed of
the hard layer 7a having excellent abrasion resistance and
blocking resistance. Accordingly, it is possible to
prevent the abrasion of the cover film 7. Furthermore,
since the hard layer 7a has excellent blocking resistance,
the hard layer is not attached to a conveyor jig, conveyor
belt, or the like on which the circuit board is loaded to
be conveyed, in a process requiring heat, such as a reflow
process in the process of mounting circuit components.
Moreover, in the shielded flexible printed circuit
board (shield FPC 10') according to the present embodiment,
the foundation 5 including the printed circuit 3 is
composed of a flexible printed circuit board. As a result,
the shielded flexible printed circuit board can have
excellent sliding resistance, which is a characteristic
required for the flexible printed circuit board.
Further, in the shielded flexible printed circuit
board (shield FPC 10') according to the present embodiment,
when the foundation 5 including the printed circuit 3 is
composed of a TAB tape for a tape carrier package, the
shielding film 1 has excellent flexibility. As a result,
since the rebound resilience of the shielding film
deteriorates, it is possible to improve the assembly
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efficiency.
In the shielding film 1 according to the present
embodiment, the adhesive layer 8a, which is formed on the
surface of the cover film 7 opposite to the separation
film 6a via the metal layer 8b, is composed of a
conductive adhesive. Accordingly, the metal layer 8b and
the grounding circuit 3b of the printed circuit board can
be electrically connected to each other.
In the shielding film 1 according to the present
embodiment, the above-mentioned conductive adhesive is
composed of an anisotropic conductive adhesive. If the
anisotropic conductive adhesive is used, it is possible to
reduce the thickness of the shielding film and thereof
used to form the shielding film as compared to when the
conductive adhesive is used. Therefore, since an amount
of the conductive fillers is little, it is possible to
improve flexibility of the shielding film.
Furthermore, in a method of manufacturing the
shielding film according to the present embodiment, the
cover film 7 is formed by laminating a hard layer 7a and a
soft layer 7b on one surface of the separation film 6a.
The shielding film according to the invention includes the
separation film 6a, the cover film 7 provided on one
surface of the separation film 6a, and the adhesive layer
8a, which is formed on the surface of the cover film 7
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opposite to the separation film 6a via the metal layer 8b.
As a result, it is possible to manufacture the shielding
film 1, which has excellent abrasion resistance and
blocking resistance. Furthermore, even though the
shielding film is heated and pressed, breakage such as
cracking, fracture, or the like does not occur in the
shielding film 1.
Moreover, in the method of manufacturing the
shielding film according to the present embodiment, at
least one layer of the above-mentioned hard layer 7a and
the soft layer 7b is composed of a coating layer.
According to this structure, since it is possible to
reduce the thickness of the cover film 7, it is possible
to manufacture the shielding film 1 having excellent
flexibility.
In the method of manufacturing the shielding film
according to the present embodiment, the above-mentioned
hard layer 7a and the soft layer 7b are sequentially
coated on one surface of the separation film 6a.
According to this structure, since the separation film 6a
can be used as a carrier film, it is possible to also
reduce the thickness of the hard layer 7a and the soft
layer 7b. In addition, it is possible to provide the
shielding film 1, which has a thinner cover film 7, having
excellent flexibility, and to reliably provide the
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shielding film at low cost.
Further, as for a method of manufacturing the
shielded printed circuit board according to the present
embodiment, in the above-mentioned shielded printed
circuit board, the above-mentioned shielding film 1 is
placed on at least one surface of the foundation 5
including at least one printed circuit 3, and is heated
and pressed. After that, the separation film 6a is
released. According to this method, it is possible to
very easily manufacture the following shielded printed
circuit board in which breakage does not occur in the
metal layer 8b and a cover film 7. The cover film 7 has
excellent abrasion resistance and blocking resistance, and
does not crack.
Furthermore, in a method of manufacturing the
shielded printed circuit board according to the present
embodiment, a portion of an insulating material covering
the grounding circuit 3b is removed from the printed
circuit 3, which includes the signal circuit 3a and the
grounding circuit 3b formed on the base film 2, in order
to prepare the foundation 5 having the exposed grounding
circuit 3b. Then, the shielding film 1 having the above-
mentioned adhesive layer, which is composed of the
conductive adhesive or the anisotropic conductive adhesive,
is placed on the foundation 5, and the shielding film and
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WO 2006/121194 PCT/JP2006/309870
the foundation are heated and pressed so that the
shielding film and the foundation are adhered to each
other and the grounding circuit 3b is electrically
connected with the metal layer 8b. According to this
method, since the conductive adhesive or the anisotropic
conductive adhesive softened due to heating is easily
embedded into the insulation removed portions 4a, it is
possible to ground the metal layer 8a or the shielding
layer 8, which is composed of the metal layer 8b and the
adhesive layer 8a through the ground circuit 3b. In
addition, when the adhesive layer 8a is non-conductive,
the metal layer 8b may be connected to a case or the like
by another method.
Moreover, in the method of manufacturing the
shielded printed circuit board according to the present
embodiment, the foundation 5 including at least one
printed circuit 3 is composed of a flexible printed
circuit board. According to this method, it is possible
to obtain the flexible printed circuit board having
excellent flexibility and sliding resistance.
In addition, in the method of manufacturing the
shielded printed circuit board according to the present
embodiment, the foundation 5 including at least one
printed circuit 3 is composed of a TAB tape for a tape
carrier package. According to this method, it is possible
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WO 2006/121194 PCT/JP2006/309870
to obtain a TAB tape for a tape carrier package, which is
soft and has excellent assembly efficiency.
Although the invention has been described with
reference to a preferred embodiment, the invention can be
modified within the scope thereof. That is, the cover
film may have a three-layer structure in which another
hard layer is coated on a soft layer coated on a hard
layer. Even in this case, the metal layer provided on the
cover film is hardly broken because of the hardness of the
hard layer, and it is possible to prevent the hard layer
from cracking because of the cushioning characteristics of
the soft layer.
Industrial Applicability
The invention can be applied to shield a printed
circuit board, which is used in a device such as a
computer, communication device, printer, mobile phone,
video camera, or the like, from electromagnetic wave.
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CLAIMS
1. A shielding film comprising:
a separation film;
a cover film provided on one surface of the
separation film; and
an adhesive layer, which is formed on the surface of
the cover film opposite to the separation film via the
metal layer,
wherein the cover film includes at least one hard
layer and at least one soft layer, and
the surface of the cover film facing the separation
film is composed of the hard layer.
2. The shielding film according to claim 1,
wherein at least one of the hard layer and the soft
layer is composed of a coating layer.
3. A shielded printed circuit board comprising:
a metal layer, which is provided on at least one
surface of a foundation including at least one printed
circuit via the adhesive layer; and
a cover film, which is provided on the surface of
the metal layer opposite to the adhesive layer,
wherein the cover film includes at least one hard
layer and at least one soft layer, and
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WO 2006/121194 PCT/JP2006/309870
the outermost surface layer of the cover film is
composed of a hard layer.
4. The shielded flexible printed circuit board
according to claim 3,
wherein the foundation including the printed circuit
is composed of a flexible printed circuit board.
5. The shielded flexible printed circuit board
according to claim 4,
wherein the foundation including the printed circuit
is composed of a TAB tape for a tape carrier package.
6. The shielding film according to claim 1 or 2,
wherein the adhesive layer, which is formed on the
surface of the cover film opposite to the separation film
via the metal layer, is composed of a conductive adhesive.
7. The shielding film according to claim 6,
wherein the conductive adhesive is an anisotropic
conductive adhesive.
8. A method of manufacturing a shielding film,
which comprises a separation film, a cover film provided
on one surface of the separation film, and an adhesive
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WO 2006/121194 PCT/JP2006/309870
layer that is formed on the surface of the cover film
opposite to the separation film via the metal layer,
wherein the cover film is formed by laminating a
hard layer and a soft layer on one surface of the
separation film.
9. The method of manufacturing a shielding film
according to claim 8,
wherein at least one layer of the hard layer and the
soft layer is composed of a coating layer.
10. The method of manufacturing a shielding film
according to claim 8,
wherein the hard layer and the soft layer are
sequentially coated on one surface of the separation film.
11. A method of manufacturing the shielded printed
circuit board according to claim 3, comprising:
placing the shielding film according to claim 1 or 2
on at least one surface of a foundation including at least
one printed circuit;
heating and pressing the shielding film; and
releasing the separation film.
• 12. A method of manufacturing a shielded printed
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WO 2006/121194 PCT/JP2006/309870
circuit board, comprising:
removing a portion of an insulating material
covering a grounding circuit from a printed circuit, which
includes a signal circuit and a grounding circuit formed
on a base film, in order to prepare a foundation having
the exposed grounding circuit;
placing the shielding film according to claim 6 or 7
on the foundation; and
heating and pressing the shielding film and the
foundation so that the shielding film and the foundation
are adhered to each other and the grounding circuit is
electrically connected with the metal layer.
13. The method of manufacturing a shielded printed
circuit board according to claim 11,
wherein the foundation including at least one
printed circuit is composed of a flexible printed circuit
board.
14. The method of manufacturing a shielded printed
circuit board according to claim 12,
wherein the foundation including at least one
printed circuit is composed of a flexible printed circuit
board.
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WO 2006/121194 PCT/JP2006/309870
15. The method of manufacturing a shielded printed
circuit board according to claim 11,
wherein the foundation including at least one
printed circuit is composed of a TAB tape for a tape
carrier package.
16. The method of manufacturing a shielded printed
circuit board according to claim 12,
wherein the foundation including at least one
printed circuit is composed of a TAB tape for a tape
carrier package.
55

The invention includes a shielding film,
which does not have breakage of a metal layer, and has
excellent abrasion resistance and blocking resistance, and
does not crack. The cover film 7 is provided on one surface
of a separation film 6a, and an adhesive layer 8a is formed
on the surface of the cover film 7 opposite to the separation
film 6a via the metal layer. The cover film 7 has at least one
hard layer 7a and at least one soft layer 7b, and the surface
of the cover film 7 facing the separation film 6a is composed
of the hard layer 7a.

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Patent Number 270667
Indian Patent Application Number 4476/KOLNP/2007
PG Journal Number 02/2016
Publication Date 08-Jan-2016
Grant Date 07-Jan-2016
Date of Filing 20-Nov-2007
Name of Patentee NIPPON MEKTRON, LTD.
Applicant Address 12-15, SHIBADAIMON 1 CHOME, MINATO-KU, TOKYO 105-8585
Inventors:
# Inventor's Name Inventor's Address
1 MORIMOTO SYOHEI C/O TATSUTA SYSTEM ELECTRONICS CO., LTD. 3-1, IWATA-CHO 2-CHOME,, HIGASHIOSAKA-SHI, OSAKA 578-8585
2 HASHIMOTO KAZUHIRO C/O TATSUTA SYSTEM ELECTRONICS CO., LTD. 3-1, IWATA-CHO 2-CHOME,, HIGASHIOSAKA-SHI, OSAKA 578-8585
3 KAWAKAMI YOSHINORI C/O TATSUTA SYSTEM ELECTRONICS CO., LTD. 3-1, IWATA-CHO 2-CHOME,, HIGASHIOSAKA-SHI, OSAKA 578-8585
4 KAMINO KENJI C/O TATSUTA SYSTEM ELECTRONICS CO., LTD. 3-1, IWATA-CHO 2-CHOME,, HIGASHIOSAKA-SHI, OSAKA 578-8585
5 EBIHARA SATOSHI C/O NIPPON MEKTRON, LTD. 757, AMABOKI,, TSUKUBA-SHI, IBARAKI 300-1253
6 TANAKA HIDEAKI C/O NIPPON MEKTRON, LTD. 757, AMABOKI,, TSUKUBA-SHI, IBARAKI 300-1253
7 AKATSUKA TAKAHISA C/O NIPPON MEKTRON, LTD. 757, AMABOKI,, TSUKUBA-SHI, IBARAKI 300-1253
PCT International Classification Number H05K 1/02, H05K 9/00
PCT International Application Number PCT/JP2006/309870
PCT International Filing date 2006-05-10
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2005-141872 2005-05-13 Japan