JP6564534B2 - Electromagnetic shielding film, shield printed wiring board, and electronic equipment - Google Patents

Description

The present invention relates to an electromagnetic wave shielding film, a shield printed wiring board, and an electronic device.

Conventionally, for example, an electromagnetic wave shielding film is attached to a printed wiring board such as a flexible printed wiring board (FPC) to shield electromagnetic waves from the outside.

An electromagnetic wave shielding film usually has a configuration in which a conductive adhesive layer, a shielding layer made of a metal thin film, and an insulating layer are sequentially laminated. By heating and pressing the electromagnetic wave shielding film on the printed wiring board, the electromagnetic wave shielding film is adhered to the printed wiring board by the adhesive layer, thereby producing a shield printed wiring board. After this bonding, components are mounted on the printed wiring board by solder reflow. The printed wiring board has a configuration in which a printed pattern on a base film is covered with an insulating film.

When a shield printed wiring board is manufactured, if the shield printed wiring board is heated by a heating press or solder reflow, gas is generated from the conductive adhesive layer of the electromagnetic shielding film, the insulating film of the printed wiring board, or the like. Further, when the base film of the printed wiring board is formed of a highly hygroscopic resin such as polyimide, water vapor may be generated from the base film by heating. Since these volatile components generated from the conductive adhesive layer, the insulating film, and the base film cannot pass through the shield layer, they accumulate between the shield layer and the conductive adhesive layer. Therefore, if rapid heating is performed in the solder reflow process, the volatile component accumulated between the shield layer and the conductive adhesive layer destroys the interlayer adhesion between the shield layer and the conductive adhesive layer, and the shield characteristics are improved. It may decrease.

In order to solve such a problem, Patent Document 1 describes an electromagnetic wave shielding film in which a plurality of openings are provided in a shield layer (metal thin film) to improve air permeability.
When a plurality of openings are provided in the shield layer, even if volatile components are generated, the volatile components can pass through the shield layer through the openings. Therefore, it is possible to prevent volatile components from accumulating between the shield layer and the conductive adhesive layer, and it is possible to prevent a decrease in shield characteristics due to destruction of interlayer adhesion.

International Publication No. 2014/192494

However, since the electromagnetic wave shielding film described in Patent Document 1 has an opening in the shield layer, the strength of the shield layer is weak.
Therefore, when the electromagnetic wave shielding film described in Patent Document 1 is used for a flexible printed wiring board, the following problems occur.
That is, the flexible printed wiring board is repeatedly bent during use. The electromagnetic wave shielding film used for such a flexible printed wiring board and the shielding layer constituting the electromagnetic wave shielding film are also repeatedly bent.
As described above, since the shield layer of the electromagnetic wave shielding film described in Patent Document 1 has low strength, there is a problem that the shield layer is easily broken when it is repeatedly bent.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electromagnetic wave shielding film having sufficient bending resistance, in which the shielding characteristics are hardly deteriorated when a shield printed wiring board is produced. That is.

In order to solve the above-mentioned problems, the present inventor has conducted intensive studies, and as a result, by controlling the opening area of the opening formed in the shield layer of the electromagnetic shielding film and the opening ratio of the opening, the electromagnetic wave The present inventors have found that the shield printed wiring board manufactured using the shield film can be prevented from being deteriorated in shield characteristics and that the bending resistance of the shield printed wiring board is improved, and the present invention has been completed.

That is, the electromagnetic wave shielding film of the present invention is an electromagnetic wave shielding film comprising a conductive adhesive layer, a shield layer laminated on the conductive adhesive layer, and an insulating layer laminated on the shield layer. In the shield layer, a plurality of openings are formed, the opening area of the openings is 70 to 71000 μm ² , and the opening ratio of the openings is 0.05 to 3 It is characterized by 6%.

In the electromagnetic wave shielding film of the present invention, a plurality of openings are formed in the shield layer. Therefore, even when a volatile component is generated between the shield layer and the conductive adhesive layer in the heating press process or the solder reflow process when the shield printed wiring board is manufactured using the electromagnetic wave shielding film of the present invention, Volatile components can pass through the opening of the shield layer.
Therefore, it is difficult for volatile components to accumulate between the shield layer and the conductive adhesive layer. As a result, it is possible to prevent the interlayer adhesion from being broken.

In the electromagnetic wave shielding film of the present invention, the opening area of the opening is 70 to 71000 μm ² , and the opening ratio of the opening is 0.05 to 3.6%.
If the opening area and the opening ratio of the opening formed in the shield layer are within this range, the bending resistance is sufficient, and the accumulation of volatile components between the shield layer and the conductive adhesive layer is prevented. can do.
When the opening area of the opening is less than 70 μm ² , the opening is too narrow and the volatile component is difficult to pass through the shield layer. As a result, volatile components tend to accumulate between the shield layer and the conductive adhesive layer. Therefore, when manufacturing a shield printed wiring board using the electromagnetic wave shielding film, interlayer adhesion between the shield layer and the conductive adhesive layer is easily broken. As a result, the shield characteristics are degraded.
If the opening area of the opening exceeds 71000 μm ² , the opening is too wide, the shield layer becomes weak, and the bending resistance decreases.
When the opening ratio of the opening is less than 0.05%, the ratio of the opening is too small, and the volatile component is difficult to pass through the shield layer. As a result, volatile components tend to accumulate between the shield layer and the conductive adhesive layer.
When the opening ratio of the opening exceeds 3.6%, the ratio of the opening is too large, the shield layer becomes weak, and the bending resistance is lowered.
In this specification, “aperture ratio” means the total opening area of a plurality of openings with respect to the area of the entire main surface of the shield layer.

In the electromagnetic wave shielding film of the present invention, the opening pitch of the openings is preferably 10 to 10,000 μm.
When the opening pitch of the openings is less than 10 μm, the ratio of the openings increases in the entire shield layer. As a result, the shield layer becomes weak and the bending resistance is lowered.
When the opening pitch of the openings exceeds 10,000 μm, the ratio of the openings is reduced in the entire shield layer. As a result, it becomes difficult for the volatile component to pass through the shield layer, and the volatile component tends to accumulate between the shield layer and the conductive adhesive layer.
In the present specification, the “opening pitch of openings” refers to the distance between the centers of gravity of the adjacent openings.

In the electromagnetic wave shielding film of the present invention, the thickness of the shield layer is preferably 0.5 μm or more.
When the thickness of the shield layer is less than 0.5 μm, the shield layer is too thin, and the shield characteristics are lowered.

In the electromagnetic wave shielding film of the present invention, the shielding layer preferably includes a copper layer.
Copper is a suitable material for the shield layer from the viewpoint of conductivity and economy.

In the electromagnetic wave shielding film of the present invention, the shield layer further includes a silver layer, the silver layer is disposed on the insulating layer side, and the copper layer is disposed on the conductive adhesive layer side. It is desirable.
The electromagnetic wave shielding film having such a configuration can be easily produced by applying a silver paste to the insulating layer so that an opening is formed to form a silver layer and plating the silver layer with copper.

The electromagnetic wave shielding film of the present invention is preferably for a flexible printed wiring board.
As described above, the electromagnetic wave shielding film of the present invention hardly accumulates volatile components between the shield layer and the conductive adhesive layer when producing a shield printed wiring board. Moreover, the electromagnetic wave shielding film of the present invention has sufficient bending resistance. Therefore, even if the electromagnetic wave shielding film of this invention is used for a flexible printed wiring board and it is repeatedly bent, it is hard to be damaged.
Therefore, the electromagnetic wave shielding film of the present invention can be suitably used as an electromagnetic wave shielding film for flexible printed wiring boards.

The shield printed wiring board of the present invention is provided on a base member on which a printed circuit is formed, a printed wiring board having an insulating film provided on the base member so as to cover the printed circuit, and the printed wiring board. The electromagnetic wave shielding film is the electromagnetic wave shielding film of the present invention.

In the shielded printed wiring board of the present invention, it is desirable that the printed wiring board is a flexible printed wiring board.

The shield printed wiring board of the present invention has the electromagnetic wave shielding film of the present invention having sufficient bending resistance. Therefore, the shield printed wiring board of the present invention also has sufficient bending resistance.

The electronic device of the present invention is characterized in that the shield printed wiring board of the present invention is incorporated in a folded state.

As described above, the shield printed wiring board of the present invention has sufficient bending resistance. Therefore, even if it is incorporated in an electronic device in a bent state, it is not easily damaged. Therefore, the electronic device of the present invention can narrow the space for arranging the shield printed wiring board.
Therefore, the electronic device of the present invention can be thinned.

In the electromagnetic wave shielding film of the present invention, a plurality of openings are formed in the shield layer, the opening area of the opening is 70 to 71000 μm ² , and the opening ratio of the opening is 0.05 to 3.6%.
If the characteristics of the opening formed in the shield layer are within this range, the bending resistance is sufficient, and when the shield printed wiring board is produced using the electromagnetic wave shielding film of the present invention, the shield layer and the conductive layer are electrically conductive. It is possible to prevent accumulation of volatile components between the adhesive layer and the adhesive layer.

FIG. 1 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention. 2A and 2B are schematic views schematically showing a case where a shield printed wiring board is manufactured using an electromagnetic wave shielding film in which no opening is formed in the shield layer. FIGS. 3A to 3C are plan views schematically showing an example of an arrangement pattern of openings in the shield layer constituting the electromagnetic wave shielding film of the present invention. FIG. 4 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention in which the shield layer is composed of a copper layer and a silver layer. 5A to 5C are process diagrams schematically showing an example of the method for producing the electromagnetic wave shielding film of the present invention in order. FIG. 6 is a process diagram schematically showing an example of an insulating layer preparation process in the method for producing an electromagnetic wave shielding film of the present invention. FIG. 7 is a process diagram schematically showing an example of a silver paste printing process in the method for producing an electromagnetic wave shielding film of the present invention. FIG. 8 is a process diagram schematically showing an example of a silver paste printing process in the method for producing an electromagnetic wave shielding film of the present invention. FIG. 9 is a process diagram schematically showing an example of a silver paste printing process in the method for producing an electromagnetic wave shielding film of the present invention. 10A and 10B are process diagrams schematically showing an example of a copper plating process in the method for producing an electromagnetic wave shielding film of the present invention. FIGS. 11A and 11B are process diagrams schematically showing an example of a conductive adhesive layer forming process in the method for producing an electromagnetic wave shielding film of the present invention. FIG. 12 is a schematic diagram schematically showing the configuration of a system used in the KEC method.

Hereinafter, the electromagnetic wave shielding film of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and can be applied with appropriate modifications without departing from the scope of the present invention.

FIG. 1 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention.
As shown in FIG. 1, the electromagnetic wave shielding film 10 includes a conductive adhesive layer 20, a shield layer 30 laminated on the conductive adhesive layer 20, and an insulating layer 40 laminated on the shield layer 30. It consists of.
A plurality of openings 50 are formed in the shield layer 30.

(Conductive adhesive layer)
In the electromagnetic wave shielding film 10, the conductive adhesive layer 20 may be made of any material as long as it has conductivity and can function as an adhesive.
For example, the conductive adhesive layer 20 may be composed of conductive particles and an adhesive resin composition.

Although it does not specifically limit as electroconductive particle, A metal microparticle, a carbon nanotube, carbon fiber, a metal fiber, etc. may be sufficient.

When the conductive particles are metal fine particles, the metal fine particles are not particularly limited, but silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder obtained by silver plating on copper powder, polymer fine particles Or fine particles in which glass beads or the like are coated with a metal.
In these, it is desirable that it is the copper powder or silver coat copper powder which can be obtained cheaply from an economical viewpoint.

Although the average particle diameter of electroconductive particle is not specifically limited, It is desirable that it is 0.5-15.0 micrometers. When the average particle diameter of the conductive particles is 0.5 μm or more, the conductivity of the conductive adhesive layer is improved. When the average particle size of the conductive particles is 15.0 μm or less, the conductive adhesive layer can be thinned.

The shape of the conductive particles is not particularly limited, but can be appropriately selected from spherical, flat, flakes, dendrites, rods, fibers, and the like.

The material of the adhesive resin composition is not particularly limited, but a styrene resin composition, a vinyl acetate resin composition, a polyester resin composition, a polyethylene resin composition, a polypropylene resin composition, and an imide resin composition. Products, amide resin compositions, acrylic resin compositions, etc., phenol resin compositions, epoxy resin compositions, urethane resin compositions, melamine resin compositions, alkyd resin compositions A thermosetting resin composition such as a product can be used.
The material of the adhesive resin composition may be one of these alone or a combination of two or more.

For the conductive adhesive layer 20, a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, if necessary. Further, a viscosity modifier or the like may be contained.

Although the compounding quantity of the electroconductive particle in the electroconductive adhesive layer 20 is not specifically limited, It is desirable that it is 15-80 mass%, and it is more desirable that it is 15-60 mass%.
The adhesiveness to the printed wiring board of a conductive adhesive layer improves that it is the said range.

The thickness of the conductive adhesive layer 20 is not particularly limited and can be appropriately set as necessary, but is preferably 0.5 to 20.0 μm.
When the thickness of the conductive adhesive layer is less than 0.5 μm, it is difficult to obtain good conductivity. If the thickness of the conductive adhesive layer exceeds 20.0 μm, the thickness of the entire electromagnetic wave shielding film becomes thick and difficult to handle.

Moreover, it is desirable that the conductive adhesive layer 20 has anisotropic conductivity.
When the conductive adhesive layer 20 has anisotropic conductivity, the transmission characteristics of the high-frequency signal transmitted by the signal circuit of the printed wiring board are improved as compared with the case where the conductive adhesive layer 20 has isotropic conductivity.

(Insulating layer)
In the electromagnetic wave shielding film 10, the insulating layer 40 has sufficient insulating properties, and is not particularly limited as long as the conductive adhesive layer 20 and the shield layer 30 can be protected. For example, a thermoplastic resin composition, a thermosetting resin composition, and the like. It is desirable that the composition is composed of an active energy ray-curable composition or the like.
The thermoplastic resin composition is not particularly limited, but a styrene resin composition, a vinyl acetate resin composition, a polyester resin composition, a polyethylene resin composition, a polypropylene resin composition, and an imide resin composition. And acrylic resin compositions.

Although it does not specifically limit as said thermosetting resin composition, A phenol-type resin composition, an epoxy-type resin composition, a urethane-type resin composition, a melamine-type resin composition, an alkyd-type resin composition etc. are mentioned.

Although it does not specifically limit as said active energy ray curable composition, For example, the polymeric compound etc. which have at least 2 (meth) acryloyloxy group in a molecule | numerator etc. are mentioned.

The insulating layer 40 may be composed of one kind of material or may be composed of two or more kinds of materials.

For the insulating layer 40, a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, and a viscosity adjuster, if necessary. An agent, an antiblocking agent and the like may be contained.

The thickness of the insulating layer 40 is not particularly limited and can be appropriately set as necessary, but is preferably 1 to 15 μm, and more preferably 3 to 10 μm.
If the thickness of the insulating layer 40 is less than 1 μm, the conductive adhesive layer 20 and the shield layer 30 are not easily protected sufficiently because they are too thin.
When the thickness of the insulating layer 40 exceeds 15 μm, the electromagnetic wave shielding film 10 is difficult to bend because it is too thick, and the insulating layer 40 itself is easily damaged. Therefore, it becomes difficult to apply to members that require bending resistance.

(Shield layer)
Before explaining the shield layer of the electromagnetic wave shielding film of the present invention, the case of producing a shield printed wiring board using an electromagnetic wave shielding film in which no opening is formed in the shield layer will be explained with reference to the drawings.
2A and 2B are schematic views schematically showing a case where a shield printed wiring board is manufactured using an electromagnetic wave shielding film in which no opening is formed in the shield layer.

As shown in FIG. 2A, when the shield printed wiring board is manufactured, the shield printed wiring board on which the electromagnetic wave shielding film 510 is arranged is heated by a heating press or solder reflow.
By this heating, a volatile component 560 is generated from the conductive adhesive layer 520 of the electromagnetic wave shielding film 510, the insulating film of the printed wiring board, the base film, and the like.

When rapid heating is performed in such a state, as shown in FIG. 2B, the volatile component 560 accumulated between the shield layer 530 and the conductive adhesive layer 520 causes conductivity between the shield layer 530 and the conductive layer. Interlayer adhesion with the adhesive layer 520 may be destroyed.

However, in the electromagnetic wave shielding film 10, a plurality of openings 50 are formed in the shield layer 30.
Therefore, even when a volatile component is generated between the shield layer 30 and the conductive adhesive layer 20 due to heating when a shield printed wiring board is manufactured using the electromagnetic wave shield film 10, the volatile component is It can pass through the opening 50.
Therefore, it is difficult for volatile components to accumulate between the shield layer 30 and the conductive adhesive layer 20. As a result, it is possible to prevent the interlayer adhesion from being broken.

In the electromagnetic wave shielding film 10, the opening area of the opening 50 is 70 to 71000 μm ² , and the opening ratio of the opening 50 is 0.05 to 3.6%.
Area of the opening 50 is preferably a 70～32000Myuemu ^2, and more desirably 70～10000Myuemu ^2, it is further desirable that 80~8000μm ^2.
Moreover, it is desirable that the opening ratio of the opening 50 is 0.1 to 3.6%.
If the opening area and the opening ratio of the opening 50 formed in the shield layer 30 are within this range, the bending resistance is sufficient, and a volatile component is present between the shield layer 30 and the conductive adhesive layer 20. Accumulation can be prevented.

When the opening area of the opening of the shield layer is less than 70 μm ² , the opening is too narrow and volatile components are difficult to pass through the shield layer. As a result, volatile components tend to accumulate between the shield layer and the conductive adhesive layer.
If the opening area of the opening of the shield layer exceeds 71000 μm ² , the opening is too wide, the shield layer becomes weak, and the bending resistance decreases.

When the opening ratio of the opening of the shield layer is less than 0.05%, the ratio of the opening is too small, and the volatile component hardly passes through the shield layer. As a result, volatile components tend to accumulate between the shield layer and the conductive adhesive layer.
When the aperture ratio of the opening part of a shield layer exceeds 3.6%, there are too many ratios of an opening part, a shield layer will become weak and bending resistance will fall.

In the electromagnetic wave shielding film 10, the shape of the opening 50 is not particularly limited, and may be a circle, an ellipse, a racetrack, a triangle, a quadrangle, a pentagon, a hexagon, an octagon, a star, or the like.
Among these, a circular shape is desirable for ease of formation of the opening 50.
Moreover, the shape of the plurality of openings 50 may be one type alone, or a plurality of types may be combined.

In the electromagnetic wave shielding film 10, the opening pitch of the openings 50 is preferably 10 to 10,000 μm, more preferably 25 to 2000 μm, and further preferably 250 to 2000 μm.
When the opening pitch of the openings is less than 10 μm, the ratio of the openings increases in the entire shield layer. As a result, the shield layer becomes weak and the bending resistance is lowered.
When the opening pitch of the openings exceeds 10,000 μm, the ratio of the openings is reduced in the entire shield layer. As a result, it becomes difficult for the volatile component to pass through the shield layer, and the volatile component tends to accumulate between the shield layer and the conductive adhesive layer.

In the electromagnetic wave shielding film 10, the arrangement pattern of the openings 50 is not particularly limited. For example, the arrangement pattern shown below may be used.

FIGS. 3A to 3C are plan views schematically showing an example of an arrangement pattern of openings in the shield layer constituting the electromagnetic wave shielding film of the present invention.

As shown in FIG. 3A, the arrangement pattern of the openings 50 is an arrangement pattern in which the center of each opening 50 is located at the apex of the equilateral triangle on a plane in which equilateral triangles are continuously arranged vertically and horizontally. There may be.

In addition, as shown in FIG. 3B, the array pattern of the openings 50 is an array pattern in which the center of the openings 50 is located at the apex of the square in a plane in which squares are continuously arranged vertically and horizontally. May be.

Further, as shown in FIG. 3C, the arrangement pattern of the openings 50 is an arrangement pattern in which the center of the openings 50 is located at the apex of the regular hexagons in a plane in which regular hexagons are continuously arranged vertically and horizontally. It may be.

In the electromagnetic wave shielding film 10, the thickness of the shielding layer 30 is desirably 0.5 μm or more, and more desirably 1.0 μm or more. The thickness of the shield layer 30 is desirably 10 μm or less.
When the thickness of the shield layer is less than 0.5 μm, the shield layer is too thin, and the shield characteristics are lowered.

Moreover, when the thickness of the shield layer 30 is 1.0 μm or more, the transmission characteristics are improved in a signal transmission system that transmits a high-frequency signal having a frequency of 0.01 to 10 GHz.
In addition, when the opening is not formed in the shield layer, when the shield layer becomes thick, when the shield printed wiring board is manufactured, the interlayer adhesion between the shield layer and the conductive adhesive layer is easily broken. . In particular, when the thickness of the shield layer 30 exceeds 1.0 μm, the interlaminar adhesion is significantly broken. However, in the electromagnetic wave shielding film 10, since the opening 50 is formed in the shield layer 30, it is possible to prevent the interlayer adhesion between the shield layer 30 and the conductive adhesive layer 20 from being broken. .

The electromagnetic wave shielding film of the present invention is preferably used in a signal transmission system that transmits a signal having a frequency of 0.01 to 10 GHz.

In the electromagnetic wave shielding film of the present invention, the shielding layer may be made of any material as long as it has electromagnetic wave shielding properties, for example, a metallic layer.

The shield layer may include a layer made of a material such as gold, silver, copper, aluminum, nickel, tin, palladium, chromium, titanium, or zinc, and preferably includes a copper layer.
Copper is a suitable material for the shield layer from the viewpoint of conductivity and economy.

The shield layer may include a layer made of the metal alloy.

The shield layer may be formed by laminating a plurality of metal layers.
In particular, the shield layer preferably includes a copper layer and a silver layer.

The case where a shield layer contains a copper layer and a silver layer is demonstrated using drawing.
FIG. 4 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention in which the shield layer is composed of a copper layer and a silver layer.

The electromagnetic wave shielding film 110 shown in FIG. 4 includes a conductive adhesive layer 120, a shield layer 130 laminated on the conductive adhesive layer 120, and an insulating layer 140 laminated on the shield layer 130. .
The shield layer 130 includes a copper layer 132 and a silver layer 131. The silver layer 131 is disposed on the insulating layer 140 side, and the copper layer 132 is disposed on the conductive adhesive layer 120 side.

The electromagnetic wave shielding film 110 having such a configuration can be easily produced by applying a silver paste to the insulating layer 140 so that an opening is formed, forming a silver layer, and plating the silver layer with copper.

(Other configurations)
In the electromagnetic wave shielding film of the present invention, an anchor coat layer may be formed between the insulating layer and the shield layer.
Anchor coat layer materials include urethane resin, acrylic resin, core-shell type composite resin with urethane resin as shell and acrylic resin as core, epoxy resin, imide resin, amide resin, melamine resin, phenol resin, urea formaldehyde resin And blocked isocyanates obtained by reacting a polyisocyanate with a blocking agent such as phenol, polyvinyl alcohol, polyvinylpyrrolidone and the like.

In the electromagnetic wave shielding film of the present invention, a support film may be provided on the insulating layer side, and a peelable film may be provided on the conductive adhesive layer side. When the electromagnetic wave shielding film has a support film or a peelable film, in the operation of transporting the electromagnetic wave shielding film of the present invention or manufacturing a shield printed wiring board using the electromagnetic wave shielding film of the present invention. The electromagnetic wave shielding film of the present invention is easy to handle.
Moreover, when arrange | positioning the electromagnetic wave shielding film of this invention on a shield printed wiring board etc., such a support body film and a peelable film will be peeled off.

The electromagnetic wave shielding film of the present invention may be used for any application as long as it aims to block electromagnetic waves.
In particular, the electromagnetic wave shielding film of the present invention is desirably used for a printed wiring board, particularly a flexible printed wiring board.
As described above, the electromagnetic wave shielding film of the present invention hardly accumulates volatile components between the shield layer and the conductive adhesive layer when producing a shield printed wiring board. Moreover, the electromagnetic wave shielding film of the present invention has sufficient bending resistance. Therefore, even if the electromagnetic wave shielding film of this invention is used for a flexible printed wiring board and it is repeatedly bent, it is hard to be damaged.
Therefore, the electromagnetic wave shielding film of the present invention can be suitably used as an electromagnetic wave shielding film for flexible printed wiring boards.

Thus, the shield printed wiring board having the electromagnetic wave shielding film of the present invention is the shield printed wiring board of the present invention.
That is, the shield printed wiring board of the present invention includes a base member on which a printed circuit is formed, a printed wiring board having an insulating film provided on the base member so as to cover the printed circuit, and the printed wiring board. A shield printed wiring board having an electromagnetic wave shielding film provided on the electromagnetic wave shielding film, wherein the electromagnetic wave shielding film is the electromagnetic wave shielding film of the present invention.
The printed wiring board is preferably a flexible printed wiring board.
The shield printed wiring board of the present invention has the electromagnetic wave shielding film of the present invention having sufficient bending resistance. Therefore, the shield printed wiring board of the present invention also has sufficient bending resistance.

The shield printed wiring board of the present invention is used by being incorporated in an electronic device.
In particular, the electronic device in which the shield printed wiring board of the present invention is incorporated in a folded state is the electronic device of the present invention.
As described above, the shield printed wiring board of the present invention has sufficient bending resistance. Therefore, even if it is incorporated in an electronic device in a bent state, it is not easily damaged. Therefore, the electronic device of the present invention can narrow the space for arranging the shield printed wiring board.
Therefore, the electronic device of the present invention can be thinned.

(Method for producing electromagnetic shielding film)
Next, the manufacturing method of the electromagnetic wave shielding film of this invention is demonstrated. In addition, the electromagnetic wave shielding film of this invention is not limited to what was manufactured by the method shown below.

First, an example of the manufacturing method of the electromagnetic wave shielding film 10 which is an example of the electromagnetic wave shielding film of this invention is demonstrated.
The method for producing the electromagnetic wave shielding film 10 includes (1) a shield layer forming step, (2) an insulating layer forming step, and (3) a conductive adhesive layer forming step.

These steps will be described in detail below with reference to the drawings.
5A to 5C are process diagrams schematically showing an example of the method for producing the electromagnetic wave shielding film of the present invention in order.

(1) Shield layer forming step First, as shown in FIG. 5 (a), a sheet 35 having electromagnetic wave shielding properties is prepared. The sheet 35 has an opening area of 70 to 71000 μm ² and an opening ratio of 0.05 to The opening 50 is formed so as to be 3.6%, and the shield layer 30 is manufactured.
The opening 50 can be formed by punching, laser irradiation, or the like.
When the sheet 35 is made of an etchable material such as copper, a resist having a pattern that forms the opening 50 may be disposed on the surface of the sheet 35 and the opening 50 may be formed by etching.
Further, a conductive paste or a paste that functions as a plating catalyst may be printed on the surface of the sheet 35.
In this printing, the opening 50 may be formed by printing with a predetermined pattern.
When printing the paste that functions as the plating catalyst, it is desirable to form the shield layer by printing the paste to form the opening 50 and then forming a metal film by an electroless plating method or an electrolytic plating method.
As the paste functioning as the plating catalyst, a fluid containing a metal composed of nickel, copper, chromium, zinc, gold, silver, aluminum, tin, cobalt, palladium, lead, platinum, cadmium, rhodium, or the like is used. it can.

(2) Insulating Layer Forming Step Next, as shown in FIG. 5B, the insulating layer 40 is formed by coating and curing the insulating layer resin composition 45 on one surface of the shield layer 30.
As a method for coating the resin composition for the insulating layer, conventionally known coating methods such as gravure coating method, kiss coating method, die coating method, lip coating method, comma coating method, blade coating method, roll coating method, knife coating method , Spray coating method, bar coating method, spin coating method, dip coating method and the like.
As a method for curing the resin composition for an insulating layer, various conventionally known methods can be employed depending on the type of the resin composition for the insulating layer.

(3) Conductive adhesive layer forming step Next, as shown in FIG. 5 (c), the conductive adhesive layer composition 25 is applied to the surface of the shield layer 30 opposite to the surface on which the insulating layer 40 is formed. The conductive adhesive layer 20 is formed by coating.
As a method for coating the conductive adhesive layer composition 25, a conventionally known coating method such as a gravure coating method, a kiss coating method, a die coating method, a lip coating method, a comma coating method, a blade coating method, a roll coating method, Examples include knife coating, spray coating, bar coating, spin coating, and dip coating.

The electromagnetic wave shielding film 10 which is an example of the electromagnetic wave shielding film of this invention can be manufactured through the above process.

Next, an example of a method for producing the electromagnetic wave shielding film 110, which is an example of the electromagnetic wave shielding film of the present invention and in which the shield layer is composed of a copper layer and a silver layer, will be described.
The method of manufacturing the electromagnetic wave shielding film 110 includes (1) an insulating layer preparation step, (2) a silver paste printing step, (3) a copper plating step, and (4) a conductive adhesive layer forming step.

These steps will be described in detail below with reference to FIGS.

(1) Insulating layer preparatory process FIG. 6: is process drawing which shows typically an example of the insulating layer preparatory process in the manufacturing method of the electromagnetic wave shield film of this invention.
First, as shown in FIG. 6, an insulating layer 140 is prepared.
The insulating layer 140 can be prepared by a conventional method.

(2) Printing process of fluid containing metal as plating catalyst (silver paste printing process)
Next, the silver paste 133 is printed on one main surface of the insulating layer 140 as a plating catalyst. At this time, a plurality of openings 150 having an opening area of 70 to 71000 μm ² and an opening ratio of 0.05 to 3.6% are formed in the silver paste.
As a method for printing the silver paste 133, intaglio printing such as gravure printing, relief printing such as flexographic printing, screen printing, offset printing performed by transferring a pattern formed on the intaglio, relief printing, or screen. And a method using inkjet printing that does not require a plate.
A method for printing the silver paste 133 by gravure printing will be described below.

7-9 is process drawing which shows typically an example of the silver paste printing process in the manufacturing method of the electromagnetic wave shield film of this invention.
First, as shown in FIG. 7, a roll-shaped plate cylinder 70 having a plurality of columnar protrusions 72 formed on the surface is prepared. At this time, the area of the upper surface 73 of each protrusion 72 is set to 70 to 71000 μm ² . Further, the plurality of protrusions 72 are provided such that the ratio of the total area of the upper surfaces 73 of the plurality of protrusions 72 to the surface area of the plate cylinder 70 is 0.05 to 3.6%.
The surface of the plate cylinder on which the protrusions 72 are not formed is a protrusion non-formation region 71.
The area of the surface of the plate cylinder 70 means the sum of the areas of the protrusion non-formation regions 71 of the plate cylinder 70 where the protrusions 72 are not formed and the total area of the upper surfaces 73 of the plurality of protrusions 72. To do.

Next, as shown in FIG. 8, the silver paste 133 is taken into the protrusion non-formation region 71. At this time, the silver paste 133 is prevented from being applied to the upper surface 73 of the protrusion 72.

Then, as shown in FIG. 9, the silver paste 133 is printed on one main surface of the insulating layer 140 by passing the insulating layer 140 between the impression cylinder 75 and the plate cylinder 70 into which the silver paste 133 is taken. .
In this printing, the silver paste 133 is not printed on the portion of the insulating layer 140 where the protrusion 72 hits, and the opening 150 can be formed.
The silver paste 133 printed on the insulating layer 140 becomes the silver layer 131.

As long as the silver paste 133 contains silver particles, the silver paste 133 may contain various additives such as a dispersant, a thickener, a leveling agent, and an antifoaming agent.
The shape of the silver particles is not particularly limited, and a material having an arbitrary shape such as a spherical shape, a flake shape, a dendritic shape, a needle shape, or a fibrous shape can be used.
When the silver particles are in the form of particles, nano-sized particles are desirable. Specifically, silver particles having an average particle diameter in the range of 1 to 100 nm are desirable, and silver particles in the range of 1 to 50 nm are more desirable.
In the present specification, the “average particle diameter” means a volume average value obtained by diluting silver particles with a dispersion solvent and measuring by a dynamic light scattering method.
For this measurement, “Nanotrack UPA-150” manufactured by Microtrack Co. can be used.

The thickness of the silver layer formed by the silver paste to be printed is preferably 5 to 200 nm.

(3) Copper Plating Process FIGS. 10A and 10B are process diagrams schematically showing an example of a copper plating process in the method for producing an electromagnetic wave shielding film of the present invention.
Next, as shown in FIGS. 10A and 10B, the copper layer 132 is formed on the silver layer 131 by plating copper on the silver layer 131.
The copper plating method is not particularly limited, and conventional electroless plating and electrolytic plating can be used.

When plating copper by electroless plating, it is desirable to use a plating solution containing copper sulfate, a reducing agent, and a solvent such as an aqueous medium or an organic solvent.
When copper is plated by the electrolytic plating method, a plating solution containing copper sulfate, sulfuric acid, and an aqueous medium is used, and the plating processing time, current density, and plating are adjusted so that the desired copper thickness is obtained. It is desirable to adjust by controlling the amount of additives used.

The thickness of the copper to be plated is preferably 0.1 to 10 μm.

Through the above steps, the shield layer 130 composed of the silver layer 131 and the copper layer 132 can be formed.

(4) Conductive adhesive layer forming process FIGS. 11A and 11B are process diagrams schematically showing an example of the conductive adhesive layer forming process in the method for producing an electromagnetic wave shielding film of the present invention.
In FIGS. 11A and 11B, FIG. 10B is turned upside down and the subsequent steps are illustrated.
Next, as shown in FIGS. 11A and 11B, a conductive adhesive layer 120 is formed by coating a conductive adhesive layer composition 125 on the copper layer 132.
As a method for coating the conductive adhesive layer composition 125, a conventionally known coating method such as gravure coating method, kiss coating method, die coating method, lip coating method, comma coating method, blade coating method, roll coating method, Examples include knife coating, spray coating, bar coating, spin coating, and dip coating.

The electromagnetic wave shielding film 110 which is an example of the electromagnetic wave shielding film of this invention can be manufactured through the above process.

Examples for more specifically explaining the present invention are shown below, but the present invention is not limited to these examples.

(Preparation Example 1: Silver paste preparation example)
By dispersing silver particles having an average particle diameter of 30 nm in a mixed solvent of 35 parts by mass of ethanol and 65 parts by mass of ion-exchanged water using a polyethyleneimine compound as a dispersant, a silver paste having a silver concentration of 15% by mass is obtained. Obtained.

Example 1
(1) Insulating layer preparation step An insulating layer made of an epoxy resin having a thickness of 5 μm was prepared.

(2) Silver Paste Printing Step Next, using a roll-shaped plate cylinder by the method as shown in FIGS. 7 to 9, an opening area is 79 μm ² and an opening ratio is 0. 0 on one main surface of the insulating layer. A silver layer was formed by printing a silver paste so that a plurality of openings with an opening pitch of 15% and an opening pitch of 250 μm were formed.
The thickness of the silver layer was 50 nm.
As the silver paste, the silver paste obtained in Preparation Example 1 was used.
In addition, the shape of the openings is circular, and the arrangement pattern of the openings is an arrangement pattern in which the center of each opening is positioned at the apex of the equilateral triangle on a plane in which equilateral triangles are continuously arranged vertically and horizontally. .

(3) Copper plating step Next, the insulating layer after silver paste printing is immersed in an electroless copper plating solution ("ARG Copper" manufactured by Okuno Pharmaceutical Co., Ltd., pH 12.5) at 55 ° C for 20 minutes to form a silver layer. An electroless copper plating film (thickness 0.5 μm) was formed on the substrate.
Next, the surface of the electroless copper plating film obtained above was placed on the cathode, phosphorous copper was placed on the anode, and an electroplating solution containing copper sulfate was used at a current density of 2.5 A / dm ² for 30 minutes. By performing electroplating, a copper plating layer having a total thickness of 1 μm was laminated on the silver layer. As the electroplating solution, a solution of copper sulfate 70 g / liter, sulfuric acid 200 g / liter, chloride ion 50 mg / liter, Top Lucina SF (brightener manufactured by Okuno Pharmaceutical Co., Ltd.) 5 g / liter was used.

(4) Conductive adhesive layer formation process The conductive adhesive layer which added 20 mass% of Ag coat Cu powder to phosphorus containing epoxy resin was coated on the copper layer so that thickness might be set to 15 micrometers.
A lip coat method was used as a coating method.

The electromagnetic wave shielding film according to Example 1 was manufactured through the above steps.

(Example 2) to (Example 36) and (Comparative Example 1) to (Comparative Example 30)
Example 2 to Example 36 and Comparative Example are the same as Example 1 except that the opening area of the opening, the opening ratio and the opening pitch, and the thickness of the copper layer are changed as shown in Tables 1 and 2. 1 to Electromagnetic wave shielding film according to Comparative Example 30 were produced.

(Evaluation of electromagnetic shielding properties)
The electromagnetic wave shielding characteristics of the electromagnetic wave shielding films according to the examples and the comparative examples were evaluated by the KEC method using the electromagnetic wave shielding effect measuring device 80 developed at the KEC Kansai Electronics Industry Promotion Center.
FIG. 12 is a schematic diagram schematically showing the configuration of a system used in the KEC method.
The system used in the KEC method includes an electromagnetic wave shielding effect measuring device 80, a spectrum analyzer 91, an attenuator 92 that attenuates 10 dB, an attenuator 93 that attenuates 3 dB, and a preamplifier 94.

As shown in FIG. 12, the electromagnetic wave shielding effect measuring device 80 is provided with two measuring jigs 83 facing each other. Between the measurement jigs 83, the electromagnetic wave shielding films (indicated by reference numeral 110 in FIG. 12) according to the examples and the comparative examples are installed so as to be sandwiched. The measurement jig 83 has a structure in which a TEM cell (Transverse Electro Magnetic Cell) size distribution is incorporated and is symmetrically divided in a plane perpendicular to the transmission axis direction. However, in order to prevent a short circuit from being formed due to the insertion of the electromagnetic wave shielding film 110, the flat plate-shaped center conductor 84 is disposed with a gap between each measurement jig 83.

In the KEC method, first, a signal output from the spectrum analyzer 91 is input to the transmission side measurement jig 83 via the attenuator 92. Then, the signal is received by the measuring jig 83 on the receiving side and the signal via the attenuator 93 is amplified by the preamplifier 94, and then the signal level is measured by the spectrum analyzer 91. The spectrum analyzer 91 outputs the amount of attenuation when the electromagnetic wave shielding film 110 is installed in the electromagnetic wave shielding effect measuring device 80 with reference to the state where the electromagnetic wave shielding film 110 is not installed in the electromagnetic wave shielding effect measuring device 80. .

Using such an apparatus, the electromagnetic wave shielding film according to each example and each comparative example was cut into 15 cm squares at a temperature of 25 ° C. and a relative humidity of 30 to 50%, and the electromagnetic wave shielding characteristics at 200 MHz were measured and evaluated. did.
The evaluation criteria are as follows. The results are shown in Tables 1 and 2.
○: 85 dB or more.
X: Less than 85 dB.

(Evaluation of delamination)
The electromagnetic wave shielding film according to each example and each comparative example was evaluated by the following method.
First, each electromagnetic wave shielding film was affixed on the printed wiring board by hot press.
Next, the shield printed wiring board was left in a clean room at 23 ° C. and 63% RH for 7 days, and then exposed to temperature conditions during reflow to evaluate the presence or absence of delamination. As the temperature condition at the time of reflow, a temperature profile of 265 ° C. at maximum was set assuming lead-free solder. Also, the presence or absence of delamination was evaluated by passing the shield printed wiring board through atmospheric reflow five times and visually observing the presence or absence of swelling.
The evaluation criteria are as follows. The results are shown in Tables 1 and 2.
○: No swelling occurred in the shield film.
X: Swelling occurred in the shield film.

(Evaluation of bending resistance)
The electromagnetic wave shielding film according to each example and each comparative example was evaluated by the following method.
Each electromagnetic shielding film is attached to both sides of a 50 μm-thick polyimide film by hot pressing and cut into a size of length × width = 130 mm × 15 mm to obtain a test piece. The bending resistance of each test piece is determined by MIT folding fatigue resistance. Using a testing machine (No.307 MIT fold resistance tester manufactured by Yasuda Seiki Seisakusho Co., Ltd.), the bending resistance was measured based on the method defined in JIS P8115: 2001.
The test conditions are as follows.
Bending clamp tip R: 0.38mm
Bending angle: ± 135 °
Bending speed: 175 cpm
Load: 500gf
Detection method: Detects disconnection of shield film with built-in Dentsu device

Moreover, the evaluation criteria for bending resistance are as follows. The results are shown in Tables 1 and 2.
A: Disconnection occurred when the number of bendings was 2000 times or more.
○: Disconnection occurred when the number of bendings was 600 times or more and less than 2000 times.
X: Disconnection occurred when the number of bendings was less than 600.

As shown in Tables 1 and 2, like the electromagnetic wave shielding film according to each example, the opening area of the opening is 70 to 71000 μm ² and the opening ratio of the opening is 0.05 to 3.6%. It was shown that the evaluation of the electromagnetic wave shielding characteristics, the evaluation of delamination, and the evaluation of bending resistance were all good.

10, 110 Electromagnetic wave shielding film 20, 120 Conductive adhesive layer 25, 125 Conductive adhesive layer composition 30, 130 Shield layer 40, 140 Insulating layer 45 Insulating layer resin composition 50, 150 Opening 70 Plate cylinder 71 Protruding part non-formation region 72 Protruding part 73 Upper surface 75 of the projecting part Pressure drum 80 Electromagnetic wave shielding effect measuring device 83 Measuring jig 84 Center conductor 91 Spectrum analyzer 92, 93 Attenuator 94 Preamplifier 131 Silver layer 132 Copper layer 133 Silver paste

Claims (9)

An electromagnetic wave shielding film comprising a conductive adhesive layer, a shield layer laminated on the conductive adhesive layer, and an insulating layer laminated on the shield layer,
A plurality of openings are formed in the shield layer,
The openings are regularly arranged at regular intervals,
The opening area of the opening is 70 to 71000 μm ² , and
The electromagnetic wave shielding film, wherein the opening ratio of the opening is 0.05 to 3.6%. The electromagnetic wave shielding film according to claim 1, wherein an opening pitch of the openings is 10 to 10,000 μm. The electromagnetic wave shielding film according to claim 1 or 2, wherein the shield layer has a thickness of 0.5 µm or more. The electromagnetic shielding film according to claim 1, wherein the shield layer includes a copper layer. The shield layer further includes a silver layer,
The silver layer is disposed on the insulating layer side,
The electromagnetic wave shielding film according to claim 4, wherein the copper layer is disposed on the conductive adhesive layer side. It is an object for flexible printed wiring boards, The electromagnetic wave shielding film in any one of Claims 1-5. A base member on which a printed circuit is formed;
A printed wiring board having an insulating film provided on the base member so as to cover the printed circuit;
A shielded printed wiring board having an electromagnetic wave shielding film provided on the printed wiring board,
The said electromagnetic wave shielding film is an electromagnetic wave shielding film in any one of Claims 1-6, The shield printed wiring board characterized by the above-mentioned. The shielded printed wiring board according to claim 7, wherein the printed wiring board is a flexible printed wiring board. 9. An electronic apparatus, wherein the shield printed wiring board according to claim 7 or 8 is incorporated in a bent state.

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