TWI760431B - Electromagnetic wave shielding film, shielding printed wiring board and electronic equipment - Google Patents

Abstract

An object of the present invention is to provide an electromagnetic wave shielding film which, when manufacturing a shielded printed wiring board, has a sufficient resistance to bending and is not easily degraded in shielding properties. The electromagnetic wave shielding film of the present invention is composed of a conductive adhesive layer, a shielding layer laminated on the conductive adhesive layer, and an insulating layer laminated on the shielding layer, wherein the shielding layer is formed with a plurality of layers. For the opening, the opening area of the opening is 70-71000 μm ² , and the opening ratio of the opening is 0.05-3.6%.

Description

Electromagnetic wave shielding film, shielding printed wiring board and electronic equipment

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

Background Art Attaching an electromagnetic wave shielding film to a printed wiring board such as a flexible printed wiring board (FPC) has hitherto been adopted to shield electromagnetic waves from the outside.

The electromagnetic wave shielding film generally has a structure in which a conductive adhesive layer, a shielding layer composed of a metal thin film or the like, and an insulating layer are laminated in this order. Such an electromagnetic wave shielding film is heated in a state of being laminated on a printed wiring board, whereby the electromagnetic wave shielding film is bonded to the printed wiring board through the adhesive layer, and a shielded printed wiring board is produced. After this connection, components are mounted on the printed wiring board by reflow. In addition, the printed wiring board has a structure in which the printed pattern on the base film is covered by the insulating film.

When manufacturing a shielded printed wiring board, if the shielded printed wiring board is heated by hot pressing or reflow, gas will be generated from the conductive adhesive layer of the electromagnetic wave shielding film or the insulating film of the printed wiring board. In addition, 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, insulating film or base film cannot pass through the shielding layer, they will accumulate between the shielding layer and the conductive adhesive layer. Therefore, if rapid heating is performed in the reflow step, the interlayer adhesion between the shielding layer and the conductive adhesive layer may be destroyed by the volatile components accumulated between the shielding layer and the conductive adhesive layer, and the shielding properties may be deteriorated.

In order to solve such a problem, Patent Document 1 describes an electromagnetic wave shielding film in which a large number of openings are provided in a shielding layer (metal thin film) to improve air permeability. If a plurality of openings are provided in the shielding layer, even if volatile components are generated, the volatile components can pass through the openings and pass through the shielding layer. Therefore, the accumulation of volatile components between the shielding layer and the conductive adhesive layer can be prevented, and the shielding properties can be prevented from being deteriorated due to the destruction of the interlayer adhesion. Prior art documents Patent documents

[Patent Document 1] International Publication No. 2014/192494

SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION However, in the electromagnetic wave shielding film disclosed in Patent Document 1, since the shielding layer has openings formed, the strength of the shielding 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 arise. 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, the electromagnetic wave shielding film disclosed in Patent Document 1 has a problem that the shielding layer is easily damaged when the shielding layer is repeatedly bent because the strength of the shielding layer is weak.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an electromagnetic wave shielding film which does not easily reduce the shielding properties and has sufficient bending resistance when manufacturing a shielded printed wiring board. means of solving problems

In order to solve the above-mentioned problems, the inventors of the present application have repeatedly studied and found that, by controlling the opening area and the opening ratio of the openings formed in the shielding layer of the electromagnetic wave shielding film, it is possible to prevent the electromagnetic wave shielding film from being used The shielding property of the shielding printed wiring board obtained is reduced, and the bending resistance of the shielding printed wiring board can be further improved, and the present invention is completed.

That is, the electromagnetic wave shielding film of the present invention is an electromagnetic wave shielding film composed of a conductive adhesive layer, a shielding layer laminated on the above-mentioned conductive adhesive layer, and an insulating layer laminated on the above-mentioned shielding layer, and is characterized by: : The shielding layer is formed with many openings, the opening area of the openings is 70-71000 μm ² , and the opening ratio of the openings is 0.05-3.6%.

In the electromagnetic wave shielding film of the present invention, a plurality of openings are formed in the shielding layer. Therefore, when using the electromagnetic wave shielding film of the present invention to manufacture a shielded printed wiring board, even if volatile components are generated between the shielding layer and the conductive adhesive layer in the hot pressing step and the reflow step, the volatile components can still pass through the opening of the shielding layer. department. Therefore, it becomes difficult to accumulate volatile components between the shield layer and the conductive adhesive layer. As a result, the interlayer adhesion can be prevented from being damaged.

In the electromagnetic wave shielding film of this invention, the opening area of the said opening part is 70-71000 micrometers< ² >, and the aperture ratio of the said opening part is 0.05-3.6%. When the opening area and the aperture ratio of the openings formed in the shielding layer are within these ranges, the bending resistance is sufficient and the accumulation of volatile components between the shielding layer and the conductive adhesive layer can be prevented. If the opening area of the opening is less than 70 μm ² , the opening is too narrow, and it becomes difficult for the volatile components to pass through the shielding layer. As a result, the volatile components tend to accumulate between the shield layer and the conductive adhesive layer. Therefore, when a shielded printed wiring board is produced using this electromagnetic wave shielding film, the interlayer adhesion between the shielding layer and the conductive adhesive layer is easily broken. As a result, the shielding characteristic is lowered. When the opening area of the opening is larger than 71000 μm ² , the opening is too wide, the shielding layer becomes weak, and the bending resistance is lowered. If the aperture ratio of the openings is less than 0.05%, the ratio of the openings is too low, and it becomes difficult for the volatile components to pass through the shielding layer. As a result, volatile components tend to accumulate between the shield layer and the conductive adhesive layer. If the aperture ratio of the openings exceeds 3.6%, the ratio of the openings is too high, the shielding layer becomes weak, and the bending resistance decreases. In addition, in this specification, the "aperture ratio" means the total opening area of a plurality of openings with respect to the whole area of the main surface of the shielding layer.

In the electromagnetic wave shielding film of the present invention, the opening pitch of the openings is preferably 10 to 10000 μm. If the opening pitch of the openings is less than 10 μm, the opening ratio of the entire shielding layer increases. As a result, the shielding layer becomes weak and the bending resistance decreases. If the opening pitch of the openings is larger than 10000 μm, the opening ratio of the entire shielding layer decreases. As a result, it becomes difficult for the volatile component to pass through the shielding layer, and the volatile component becomes easy to accumulate between the shielding layer and the conductive adhesive layer. In addition, in this specification, "the opening pitch of an opening part" means the distance between the center of gravity of the opening parts most adjacent to each other.

In the electromagnetic wave shielding film of the present invention, the thickness of the shielding layer is preferably 0.5 μm or more. If the thickness of the shielding layer is less than 0.5μm, the shielding properties will be reduced because the shielding layer is too thin.

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

In the electromagnetic wave shielding film of the present invention, the shielding layer preferably further includes a silver layer, the silver layer is preferably arranged on the side of the insulating layer, and the copper layer is preferably arranged on the side of the conductive adhesive layer. The electromagnetic wave shielding film of this structure can be easily produced by coating silver paste on the insulating layer to form an opening to form a silver layer, and then plating the silver layer with copper.

The electromagnetic wave shielding film of the present invention is suitable for use in flexible printed wiring boards. In the electromagnetic wave shielding film of the present invention, as described above, when manufacturing a shielded printed wiring board, volatile components are less likely to accumulate between the shielding layer and the conductive adhesive layer. In addition, the electromagnetic wave shielding film of the present invention has sufficient bending resistance. Therefore, even if the electromagnetic wave shielding film of the present invention is used for a flexible printed wiring board and is repeatedly bent, it is not easily damaged. Therefore, the electromagnetic wave shielding film of the present invention can be suitably used as an electromagnetic wave shielding film for a flexible printed wiring board.

The shielding 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 an electromagnetic wave shielding film provided with On the above-mentioned printed wiring board, the shielding printed wiring board is characterized in that: the above-mentioned electromagnetic wave shielding film is the above-mentioned electromagnetic wave shielding film of the present invention.

In addition, in the shielded printed wiring board of the present invention, the printed wiring board is preferably a flexible printed wiring board.

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

The electronic apparatus of the present invention is characterized in that the shielded printed wiring board of the present invention is assembled, and the shielded printed wiring board is assembled in a bent state.

As described above, the shielded printed wiring board of the present invention has sufficient bending resistance. Therefore, even if it is assembled to an electronic device in a folded state, it is not easily damaged. Therefore, the electronic apparatus of the present invention can narrow the space for disposing the shielded printed wiring board. Therefore, the electronic device of the present invention can be made thin. Invention effect

In the electromagnetic wave shielding film of the present invention, a plurality of openings are formed in the shielding layer, the opening area of the openings is 70-71000 μm ² , and the opening ratio of the openings is 0.05-3.6%. If the characteristics of the opening formed in the shielding layer are within this range, the bending resistance is sufficient, and when the electromagnetic wave shielding film of the present invention is used to manufacture a shielded printed wiring board, the accumulation of volatile components in the shielding layer and the conductive adhesive layer can be prevented. between.

Modes for Carrying Out the Invention 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 appropriately modified and applied within the scope of not changing the gist 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 is composed of a conductive adhesive layer 20 , a shielding layer 30 laminated on the conductive adhesive layer 20 , and an insulating layer 40 laminated on the shielding layer 30 . In addition, the shielding layer 30 is formed with a plurality of openings 50 .

(Conductive Adhesive Layer) In the electromagnetic wave shielding film 10 , the conductive adhesive layer 20 only needs to have conductivity and function as an adhesive, and may be made of any material. For example, the conductive adhesive layer 20 may be composed of conductive particles and an adhesive resin composition.

The conductive particles are not particularly limited, and may be metal microparticles, carbon nanotubes, carbon fibers, metal fibers, and the like.

When the conductive particles are metal particles, the metal particles are not particularly limited, and can be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder obtained by applying silver plating to copper powder, and polymer powder. Microparticles, glass beads, etc., which are coated with metal, and the like. From the viewpoint of economy, among them, copper powder or silver-clad copper powder which can be obtained at low cost is preferable.

The average particle diameter of the conductive particles is not particularly limited, but is preferably 0.5 to 15.0 μm. When the average particle diameter of the electroconductive particles is 0.5 μm or more, the electroconductivity of the electroconductive adhesive layer is favorable. When the average particle diameter of the conductive particles is 15.0 μm or less, the conductive adhesive layer can be thinned.

The shape of the electroconductive particles is not particularly limited, and can be appropriately selected from spherical, flat, scaly, dendritic, rod-like, fibrous, and the like.

The material of the adhesive resin composition is not particularly limited, and styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, polyethylene-based resin compositions, and polypropylene-based resin compositions can be used , Imide resin composition, amide resin composition and acrylic resin composition and other thermoplastic resin compositions, or phenolic resin composition, epoxy resin composition, urethane resin composition , Thermosetting resin compositions such as melamine-based resin compositions and alkyd-based resin compositions. The material of the adhesive resin composition may be a single type, or a combination of two or more types.

The conductive adhesive layer 20 may optionally contain a hardening accelerator, an adhesion imparting agent, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, a defoaming agent, a leveling agent, a filler, a flame retardant and a viscosity regulators, etc.

The blending amount of the conductive particles in the conductive adhesive layer 20 is not particularly limited, but is preferably 15 to 80% by mass, more preferably 15 to 60% by mass. Within the above-mentioned range, the adhesiveness of the conductive adhesive layer to the printed wiring board will be improved.

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

In addition, the conductive adhesive layer 20 preferably has anisotropic conductivity. If 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 will be improved more than when the conductive adhesive layer 20 has the isotropic conductivity.

(Insulating Layer) In the electromagnetic wave shielding film 10, the insulating layer 40 only needs to have sufficient insulating properties and can protect the conductive adhesive layer 20 and the shielding layer 30, and is not particularly limited. It consists of a plastic resin composition, a thermosetting resin composition, an active energy ray curable composition, and the like. The thermoplastic resin composition described above is not particularly limited, but examples include styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, polyethylene-based resin compositions, and polypropylene-based resin compositions. products, imide resin compositions, acrylic resin compositions, etc.

The above-mentioned thermosetting resin composition is not particularly limited, but examples include phenol-based resin compositions, epoxy-based resin compositions, urethane-based resin compositions, melamine-based resin compositions, and alkyd-based resin compositions things etc.

The said active energy ray curable composition is not specifically limited, For example, the polymerizable compound etc. which have at least 2 (meth)acryloyloxy groups in a molecule|numerator are mentioned.

The insulating layer 40 may be formed of a single type of material, or may be formed of two or more types of materials.

The insulating layer 40 may optionally contain hardening accelerators, adhesion imparting agents, antioxidants, pigments, dyes, plasticizers, ultraviolet absorbers, defoaming agents, leveling agents, fillers, flame retardants, viscosity modifiers and Anti-adhesive, etc.

The thickness of the insulating layer 40 is not particularly limited, and can be appropriately set as needed, but is preferably 1-15 μm, more preferably 3-10 μm. If the thickness of the insulating layer 40 is less than 1 μm, the conductive adhesive layer 20 and the shielding layer 30 cannot be sufficiently protected due to being too thin. When the thickness of the insulating layer 40 is larger than 15 μm, the electromagnetic wave shielding film 10 is not easily bent due to the excessive thickness, and the insulating layer 40 itself is easily damaged. Therefore, it becomes difficult to apply to a member that requires bending resistance.

(Shielding Layer) Before describing the shielding layer of the electromagnetic wave shielding film of the present invention, a case where a shielded printed wiring board is manufactured using the electromagnetic wave shielding film without forming an opening in the shielding layer will be described with reference to the drawings. FIGS. 2( a ) and ( b ) are schematic views schematically showing a case where a shielded printed wiring board is manufactured using an electromagnetic wave shielding film in which an opening is not formed in a shielding layer.

As shown in FIG. 2( a ), when manufacturing a shielded printed wiring board, the shielded printed wiring board provided with the electromagnetic wave shielding film 510 is heated by hot pressing or reflow. Due to this heating, volatile components 560 are generated from the conductive adhesive layer 520 of the electromagnetic wave shielding film 510 , the insulating film and the base film of the printed wiring board, and the like.

Once rapidly heated in this state, as shown in FIG. 2( b ), due to the volatile components 560 accumulated between the shielding layer 530 and the conductive adhesive layer 520 , the distance between the shielding layer 530 and the conductive adhesive layer 520 is reduced. The interlayer adhesion is sometimes broken.

However, the electromagnetic wave shielding film 10 has many openings 50 formed in the shielding layer 30 . Therefore, when a shielded printed wiring board is manufactured using the electromagnetic wave shielding film 10 , even if volatile components are generated between the shielding layer 30 and the conductive adhesive layer 20 due to heating, the volatile components can pass through the openings 50 of the shielding layer 30 . Therefore, it becomes difficult for volatile components to accumulate between the shield layer 30 and the conductive adhesive layer 20 . As a result, the interlayer adhesion can be prevented from being damaged.

In the electromagnetic wave shielding film 10, the opening area of the opening portion 50 is 70 to 71000 μm ² , and the aperture ratio of the opening portion 50 is 0.05 to 3.6%. The opening area of the opening portion 50 is preferably 70 to 32000 μm ² , more preferably 70 to 10000 μm ² , and more preferably 80 to 8000 μm ² . In addition, the aperture ratio of the opening portion 50 is preferably 0.1 to 3.6%. If the opening area and aperture ratio of the openings 50 formed in the shielding layer 30 are within these ranges, the bending resistance is sufficient and the accumulation of volatile components between the shielding layer 30 and the conductive adhesive layer 20 can be prevented.

If the opening area of the opening of the shielding layer is less than 70 μm ² , the opening is too narrow, and it becomes difficult for volatile components to pass through the shielding 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 shielding layer is larger than 71000 μm ² , the opening will be too wide, the shielding layer will become weak, and the bending resistance will decrease.

If the aperture ratio of the openings of the shielding layer is less than 0.05%, the ratio of the openings is too low, and it becomes difficult for the volatile components to pass through the shielding layer. As a result, the volatile components tend to accumulate between the shield layer and the conductive adhesive layer. If the aperture ratio of the opening portion of the shielding layer is greater than 3.6%, the ratio of the opening portion is too large, and the shielding layer becomes weak and the bending resistance decreases.

In the electromagnetic wave shielding film 10, the shape of the opening 50 is not particularly limited, and may be a circle, an ellipse, an orbit, a triangle, a quadrangle, a pentagon, a hexagon, an octagon, a star, or the like. From the viewpoint of the ease of forming the opening portion 50, a circular shape is preferable among these. In addition, the shape of the plurality of openings 50 may be a single type or a combination of a plurality of types.

In the electromagnetic wave shielding film 10, the opening pitch of the opening portion 50 is preferably 10-10000 μm, more preferably 25-2000 μm, and more preferably 250-2000 μm. If the opening pitch of the openings is less than 10 μm, the opening ratio of the entire shielding layer increases. As a result, the shielding layer becomes weak and the bending resistance decreases. If the opening pitch of the openings is larger than 10000 μm, the opening ratio of the entire shielding layer decreases. As a result, it becomes difficult for the volatile component to pass through the shielding layer, and the volatile component becomes easy to accumulate between the shielding 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 can be used.

FIGS. 3( a ) to ( c ) are plan views schematically showing an example of an arrangement pattern of openings in the shielding layer constituting the electromagnetic wave shielding film of the present invention.

As shown in FIG. 3( a ), the arrangement pattern of the openings 50 may be an arrangement pattern as follows: in a plane formed by arranging equilateral triangles vertically and horizontally, the center of each opening 50 is located on the apex of the equilateral triangle .

In addition, as shown in FIG. 3( b ), the arrangement pattern of the openings 50 may also be an arrangement pattern as follows: In a plane formed by continuously arranging squares vertically and horizontally, the center of the openings 50 is located on the apex of the squares .

In addition, as shown in FIG. 3( c ), the arrangement pattern of the openings 50 may also be an arrangement pattern as follows: In a plane formed by arranging regular hexagons vertically and horizontally, the center of the openings 50 is located on the regular hexagons on the apex of the shape.

In the electromagnetic wave shielding film 10, the thickness of the shielding layer 30 is preferably 0.5 μm or more, and more preferably 1.0 μm or more. In addition, the thickness of the shielding layer 30 is preferably 10 μm or less. If the thickness of the shielding layer is less than 0.5 μm, the shielding properties will be degraded because the shielding layer is too thin.

In addition, when the thickness of the shielding layer 30 is 1.0 μm or more, in a signal transmission system that transmits a high-frequency signal having a frequency of 0.01 to 10 GHz, the transmission characteristics become favorable. In addition, when the shield layer is not formed with an opening, if the shield layer is thickened, the interlayer adhesion between the shield layer and the conductive adhesive layer is likely to be broken when manufacturing a shield printed wiring board. In particular, if the thickness of the shielding layer 30 is greater than 1.0 μm, the failure of the interlayer adhesion will remarkably occur. However, in the electromagnetic wave shielding film 10 , since the shielding layer 30 is formed with the openings 50 , the interlayer adhesion between the shielding layer 30 and the conductive adhesive layer 20 can be prevented from being damaged.

The electromagnetic wave shielding film of the present invention is suitable for a signal transmission system that transmits signals with a frequency of 0.01 to 10 GHz.

In the electromagnetic wave shielding film of the present invention, as long as the shielding layer has electromagnetic wave shielding properties, any material may be used, and for example, a metal layer may be used.

The shielding layer may include a layer composed of materials such as gold, silver, copper, aluminum, nickel, tin, palladium, chromium, titanium, zinc, etc., and preferably includes a copper layer. Copper is an ideal material for shielding layers from the viewpoint of conductivity and economy.

Moreover, the said shield layer may contain the layer which consists of the alloy of the said metal.

In addition, the shielding layer may be laminated with a plurality of metal layers. In particular, the shielding layer preferably includes a copper layer and a silver layer.

The diagrams are used to illustrate the case where the shielding layer includes a copper layer and a silver layer. 4 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention in which the shielding layer is composed of a copper layer and a silver layer.

The electromagnetic wave shielding film 110 shown in FIG. 4 is composed of a conductive adhesive layer 120 , a shielding layer 130 laminated on the conductive adhesive layer 120 , and an insulating layer 140 laminated on the shielding layer 130 . In addition, the shielding layer 130 is composed of a copper layer 132 and a silver layer 131 , the silver layer 131 is arranged on the insulating layer 140 side, and the copper layer 132 is arranged on the conductive adhesive layer 120 side.

The electromagnetic wave shielding film 110 of this structure can be easily produced by coating silver paste on the insulating layer 140 to form an opening to form a silver layer, and then plating copper on the silver layer.

(Other Structures) The electromagnetic wave shielding film of the present invention may have an anchor coating layer formed between the insulating layer and the shielding layer. The materials of the anchor coating include urethane resin, acrylic resin, core-shell composite resin with urethane resin as shell and acrylic resin as core, epoxy resin, imide resin, amide Resins, melamine resins, phenol resins, urea formaldehyde resins, blocked isocyanates obtained by reacting blocking agents such as phenol with polyisocyanates, polyvinyl alcohol and polyvinylpyrrolidone, etc.

Moreover, the electromagnetic wave shielding film of this invention may have a support film on the insulating layer side, and may have a peelable film on the conductive adhesive layer side. If the electromagnetic wave shielding film has a support film and a peelable film, the electromagnetic wave shielding film of the present invention will be removed during the operation of transporting the electromagnetic wave shielding film of the present invention and manufacturing a shielded printed wiring board using the electromagnetic wave shielding film of the present invention. become easier to handle. Moreover, when the electromagnetic wave shielding film of this invention is arrange|positioned on a shielding printed wiring board etc., these support body films and peelable films are peeled off.

The electromagnetic wave shielding film of the present invention can be used in any application as long as the purpose is to block electromagnetic waves. The electromagnetic wave shielding film of the present invention is particularly suitable for printed wiring boards, especially flexible printed wiring boards. In the electromagnetic wave shielding film of the present invention, as described above, when manufacturing a shielded printed wiring board, volatile components are less likely to accumulate between the shielding layer and the conductive adhesive layer. Moreover, the electromagnetic wave shielding film of this invention has sufficient bending resistance. Therefore, even if the electromagnetic wave shielding film of the present invention is used for a flexible printed wiring board and is repeatedly bent, it is not easily damaged. Therefore, the electromagnetic wave shielding film of the present invention can be suitably used as an electromagnetic wave shielding film for a flexible printed wiring board.

As described above, the shielded printed wiring board having the electromagnetic wave shielding film of the present invention is the shielded printed wiring board of the present invention. That is, the shielding printed wiring board of the present invention has: 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 an electromagnetic wave shielding film , which is provided on the above-mentioned printed wiring board; and, the shielding printed wiring board is characterized in that: the above-mentioned electromagnetic wave shielding film is the above-mentioned electromagnetic wave shielding film of the present invention. In addition, it is preferable that the above-mentioned printed wiring board is a flexible printed wiring board. The shielding printed wiring board of the present invention has the electromagnetic wave shielding film of the present invention having sufficient bending resistance. Therefore, the shielded printed wiring board of the present invention also has sufficient bending resistance.

The shielded printed wiring board of the present invention is assembled in electronic equipment for use. In particular, an electronic device in which the above-mentioned shielded printed wiring board of the present invention is assembled in a bent state is an electronic device of the present invention. As described above, the shielded printed wiring board of the present invention has sufficient bending resistance. Therefore, even if it is assembled to an electronic device in a folded state, it is not easily damaged. Therefore, the electronic apparatus of the present invention can narrow the space for disposing the shielded printed wiring board. Therefore, the electronic apparatus of the present invention can be made thin.

(Manufacturing method of electromagnetic wave 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 the thing produced by the following method.

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 of manufacturing the electromagnetic wave shielding film 10 includes (1) a shielding layer forming step, (2) an insulating layer forming step, and (3) a conductive adhesive layer forming step.

These steps are detailed below using diagrams. FIGS. 5( a ) to ( c ) are step diagrams schematically showing an example of the manufacturing method of the electromagnetic wave shielding film of the present invention in sequence.

(1) Shielding layer forming step First, as shown in FIG. 5( a ), a sheet 35 with electromagnetic wave shielding properties is prepared, and the sheet 35 has an opening area of 70-71000 μm ² and an opening ratio of 0.05-3.6%. The openings 50 are formed in such a manner as to form the shielding layer 30 . The opening portion 50 can be formed by punching, laser irradiation, or the like. In addition, when the sheet 35 is made of an etchable material such as copper, a photoresist forming a pattern of the openings 50 may be arranged on the surface of the sheet 35, and the openings 50 may be formed by etching. In addition, 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, it is also possible to perform printing in a predetermined pattern, thereby forming the openings 50 . When printing the above-described paste that functions as a plating catalyst, it is preferable to form a shield layer by forming a metal film by electroless plating or electroplating after the paste is printed and the openings 50 are formed. As the paste that functions as a plating catalyst, a fluid containing metals such as nickel, copper, chromium, zinc, gold, silver, aluminum, tin, cobalt, palladium, lead, platinum, cadmium, and rhodium can be used.

(2) Insulating layer forming step Next, as shown in FIG. 5( b ), the insulating layer 40 is formed by coating the insulating layer resin composition 45 on one side surface of the shielding layer 30 and curing it. The method of coating the resin composition for the insulating layer may include conventionally known coating methods, such as gravure coating, kiss coating, die coating, lip coating, and comma coating. coating, blade coating, roll coating, knife coating, spray coating, bar coating, spin coating and dip coating, etc. As the method for curing the resin composition for the 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 on the surface opposite to the surface on which the insulating layer 40 of the shield layer 30 is formed to form The conductive adhesive layer 20 . The method of coating the composition 25 for the conductive adhesive layer can be, for example, a conventionally known coating method, such as a gravure coating type, a fitting coating type, a die coating type, a lip coating type, a corner wheel coating type, a blade coating type, and a knife coating type. Coating, roll coating, blade coating, spray coating, bar coating, spin coating and dip coating, etc.

Through the above steps, the electromagnetic wave shielding film 10 which is an example of the electromagnetic wave shielding film of the present invention can be manufactured.

Next, an example of a method of manufacturing the electromagnetic wave shielding film 110 whose shielding layer is composed of a copper layer and a silver layer, which is an example of the electromagnetic wave shielding film of the present invention, 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 are described in detail below using FIGS. 6 to 11 .

(1) Insulating layer preparation step Fig. 6 is a step diagram schematically showing an example of an insulating layer preparation step in the method of manufacturing the electromagnetic wave shielding film of the present invention. First, as shown in FIG. 6 , the insulating layer 140 is prepared. The insulating layer 140 can be prepared using conventional methods.

(2) Printing Step of Fluid Containing Metal as Plating Catalyst (Silver Paste Printing Step) Next, silver paste 133 as a plating catalyst is printed on one main surface of insulating layer 140 . In this case, it is necessary to form many openings 150 with an opening area of 70 to 71000 μm ² and an opening ratio of 0.05 to 3.6% in the silver paste. Methods of printing the silver paste 133 include: methods of gravure printing such as gravure printing and letterpress printing such as flexo printing, methods of using screen printing, and lithographic printing (that is, objects that are patterned by gravure, letterpress, screen, etc.). transfer method), a method of using inkjet printing without a printing plate, etc. Hereinafter, a method of printing the silver paste 133 by gravure printing will be described.

7 to 9 are step diagrams, which schematically show an example of the silver paste printing step in the manufacturing method of the electromagnetic wave shielding film of the present invention. First, as shown in FIG. 7, a cylinder-shaped printing plate cylinder 70 having a plurality of columnar protrusions 72 formed on its surface is prepared. At this time, the area of the upper surface 73 of each protruding portion 72 is set to be 70 to 71000 μm ² . In addition, the protruding portions 72 are provided so that the total area ratio of the upper surface 73 of the protruding portions 72 relative to the surface area of the plate cylinder 70 is 0.05-3.6%. In addition, the surface of the plate cylinder on which the protrusions 72 are not formed is the protrusion non-formation region 71 . In addition, the area of the surface of the plate cylinder 70 means the total area of the protrusion non-formation region 71 where the protrusions 72 are not formed and the total area of the upper surface 73 of the protrusions 72 of the plate cylinder 70 .

Next, as shown in FIG. 8 , the protrusion non-formation region 71 is covered with the silver paste 133 . At this time, it is performed so that the silver paste 133 is not applied to the upper surface 73 of the protrusion 72 .

Next, as shown in FIG. 9 , the insulating layer 140 is passed between the impression cylinder 75 and the printing plate cylinder 70 covered with the silver paste 133 , thereby printing the silver paste 133 on one main surface of the insulating layer 140 . In this printing, the portion of the insulating layer 140 that is in contact with the protruding portion 72 is not printed on the silver paste 133, and the opening portion 150 can be formed. The silver paste 133 printed on the insulating layer 140 will become the silver layer 131 .

The silver paste 133 only needs to contain silver particles, and may also contain various additives such as other dispersants, thickeners, leveling agents, and antifoaming agents. The shape of the silver particles is not particularly limited, and materials of any shape such as spherical, flake-like, dendritic, needle-like, and fibrous can be used. When the above-mentioned silver particles are particles, they are preferably nano-sized. Specifically, silver particles with an average particle size in the range of 1 to 100 nm are suitable, and silver particles in the range of 1 to 50 nm are more suitable. In addition, in this specification, "average particle diameter" means the volume average value measured by the dynamic light scattering method by diluting silver particles with a dispersion solvent. For this measurement, "Nanotrac UPA-150" manufactured by MicrotracBEL Corp. can be used.

In addition, the thickness of the silver layer formed by printing the silver paste is preferably 5-200 nm.

(3) Copper plating step Figures 10(a) and (b) are step diagrams schematically showing an example of the copper plating step in the method for producing the electromagnetic wave shielding film of the present invention. Next, as shown in FIGS. 10( a ) and ( b ), 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 electroplating can be used.

When copper plating is performed by electroless plating, the plating solution preferably contains copper sulfate, a reducing agent, an aqueous medium, an organic solvent, and other solvents. When copper is plated by electroplating, the plating solution should be made of copper sulfate, sulfuric acid and aqueous medium, and should be adjusted by controlling the plating treatment time, current density and the amount of plating additives used to form the desired material. Copper thickness.

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

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

(4) Conductive adhesive layer forming step Figures 11(a) and (b) are step diagrams schematically showing an example of the conductive adhesive layer forming step in the method for producing the electromagnetic wave shielding film of the present invention. In addition, Fig. 11(a) and (b) reverse Fig. 10(b) up and down to illustrate the subsequent steps. Next, as shown in FIGS. 11( a ) and ( b ), the conductive adhesive layer composition 125 is applied on the copper layer 132 to form the conductive adhesive layer 120 . The method of coating the composition 125 for the conductive adhesive layer can be, for example, a conventionally known coating method, such as a gravure coating type, a fitting coating type, a die coating type, a lip coating type, a notch coating type, a doctor blade coating Coating, roll coating, blade coating, spray coating, bar coating, spin coating and dip coating, etc.

After the above steps, the electromagnetic wave shielding film 110 can be manufactured, and the electromagnetic wave shielding film 110 is an example of the electromagnetic wave shielding film of the present invention.

Hereinafter, although the Example which demonstrates this invention more concretely is shown, this invention is not limited to these Examples.

(Preparation Example 1: Preparation Example of Silver Paste) 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, silver particles having an average particle diameter of 30 nm were dispersed to thereby disperse silver particles having an average particle diameter of 30 nm. A silver paste having a silver concentration of 15% by mass was obtained.

(Example 1) (1) Step of preparing insulating layer An insulating layer made of epoxy resin having a thickness of 5 µm was prepared.

(2) Silver paste printing step Next, using the method shown in FIG. 7 to FIG. 9 , a roller-shaped printing plate cylinder is used to form an opening area of 79 μm ² , an opening ratio of 0.15% and a main surface of one side of the insulating layer. A silver layer was formed by printing a silver paste so as to have many openings with an opening pitch of 250 μm. In addition, the thickness of the silver layer was 50 nm. 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 located on the apex of the equilateral triangle in a plane formed by continuously arranging equilateral triangles vertically and horizontally.

(3) Copper plating step Next, the insulating layer after printing the silver paste was immersed in an electroless copper plating solution (“ARG Copper” manufactured by Okuno Pharmaceutical Co., Ltd., pH 12.5) at 55° C. for 20 minutes, and the silver An electroless copper plating film (thickness 0.5 μm) was formed on the layer. Next, the surface of the electroless copper plated film obtained above was set as a cathode, and phosphorous-containing copper was set as an anode, and electroplating was performed for 30 minutes using a copper sulfate-containing electroplating solution at a current density of 2.5 A/dm ² , and the silver layer was laminated with a total of Copper plating with a thickness of 1 μm. The above-mentioned plating solution used a solution of 70 g/liter of copper sulfate, 200 g/liter of sulfuric acid, 50 mg/liter of chloride ion, and 5 g/liter of Top Lucina SF (manufactured by Okuno Pharmaceutical Co., Ltd., gloss agent).

(4) Conductive adhesive layer forming step A conductive adhesive layer obtained by adding 20% by mass of Cu powder coated with Ag to phosphorus-containing epoxy resin was applied on the copper layer to a thickness of 15 µm. The coating method uses a lip coating type.

Through the above steps, the electromagnetic wave shielding film of Example 1 was obtained.

(Example 2) to (Example 36) and (Comparative Example 1) to (Comparative Example 30) Except that the opening area, opening ratio, opening pitch and copper layer thickness of the opening were changed as shown in Table 1 and Table 2 Other than that, the electromagnetic wave shielding films of Examples 2 to 36 and Comparative Examples 1 to 30 were produced in the same manner as in Example 1.

[Table 1]

[Table 2]

(Evaluation of electromagnetic wave shielding properties) The electromagnetic wave shielding properties of the electromagnetic wave shielding films of the respective Examples and Comparative Examples were evaluated by the KEC method using the electromagnetic wave shielding effect measuring device 80 developed by the KEC Kansai Electronics Industry Promotion Center. Fig. 12 is a schematic diagram schematically showing the structure of a system used in the KEC method. The system used in the KEC method is composed of an electromagnetic wave shielding effect measuring device 80 , a spectrometer 91 , an attenuator 92 for 10 dB attenuation, an attenuator 93 for 3 dB attenuation, and a preamplifier 94 .

As shown in FIG. 12 , in the electromagnetic wave shielding effect measuring device 80 , two measuring jigs 83 are provided so as to face each other. Furthermore, the electromagnetic wave shielding films (indicated by the reference numeral 110 in FIG. 12 ) of the respective Examples and Comparative Examples were installed so as to be sandwiched between the measurement jigs 83 . The measuring jig 83 has been taken into account in the dimension of the TEM cell (Transverse Electro Magnetic Cell), and has a structure that is divided into left-right symmetry in a plane perpendicular to the direction of the transmission axis. However, in order to prevent short-circuiting due to insertion of the electromagnetic wave shielding film 110 , the flat-shaped central conductor 84 and each measurement jig 83 are arranged with a gap therebetween.

In the KEC method, the signal output from the spectrometer 91 is first input to the measurement jig 83 on the transmission side through the attenuator 92 . Next, after being received by the measuring jig 83 on the receiving side, the signal from the attenuator 93 is amplified by the preamplifier 94 , and then the signal level is measured by the spectrometer 91 . The analyzer 91 outputs the attenuation when the electromagnetic wave shielding film 110 is installed in the electromagnetic wave shielding effect measuring device 80 based on the state in which the electromagnetic wave shielding film 110 is not installed in the electromagnetic wave shielding effect measuring device 80 .

Using this device, under the conditions of a temperature of 25°C and a relative humidity of 30 to 50%, the electromagnetic wave shielding films of each example and each comparative example were cut into a square with a side length of 15cm, and the electromagnetic wave shielding characteristics of 200MHz were measured and measured. Evaluation. The evaluation criteria are as follows. The results are shown in Tables 1 and 2. ○: 85dB or more. ×: Less than 85dB.

(Evaluation of interlayer peeling) The electromagnetic wave shielding films of each Example and each Comparative Example were evaluated by the following method. First, each electromagnetic wave shielding film is attached to a printed wiring board by hot pressing. Next, the shielded printed wiring board was placed in a clean room at 23° C. and 63% RH for 7 days, and then exposed to the temperature conditions during reflow to evaluate the presence or absence of interlayer peeling. In addition, in terms of temperature conditions during reflow, lead-free soldering is preset, and the maximum temperature profile is set to 265°C. In addition, the presence or absence of interlayer peeling was evaluated by visually observing the presence or absence of swelling after passing the shielded printed wiring board through atmospheric reflow for 5 times. The evaluation criteria are as follows. The results are shown in Tables 1 and 2. ○: The shielding film did not swell at all. ×: The shielding film swelled.

(Evaluation of bending resistance) The electromagnetic wave shielding film of each Example and each comparative example was evaluated by the following method. Each electromagnetic wave shielding film was attached to both sides of a 50 μm thick polyimide film by hot pressing, and the length × width = 130 mm × 15 mm was cut to make a test piece, and then the MIT folding endurance tester (Yasta Seiki Manufacturing Co., Ltd. was used) was used. The company's product, No. 307 MIT type folding endurance tester), the bending resistance of each test piece was measured according to the method specified in JIS P8115:2001. The test conditions are as follows. Front R of the bending clamp: 0.38mm Bending angle: ±135° Bending speed: 175cpm Load: 500gf Detection method: Built-in power-on device to sense the disconnection of the shielding film

In addition, the evaluation criteria of bending resistance are as follows. The results are shown in Tables 1 and 2. ◎: Wire breakage occurs only when the number of bending times is 2,000 or more. ○: Breakage occurs when the number of bending times is 600 or more and less than 2000 times. ×: Disconnection occurred when the number of bending times was less than 600 times.

As shown in Tables 1 and 2, if 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% as in the electromagnetic wave shielding films of the respective examples, the evaluation of electromagnetic wave shielding properties, the interlayer Both the evaluation of peeling and the evaluation of bending resistance were favorable.

10. 110‧‧‧Electromagnetic wave shielding film 20, 120‧‧‧Conductive adhesive layer 25, 125‧‧‧Conductive adhesive layer composition 30, 130‧‧‧Shielding layer 40, 140‧‧‧Insulating layer 45‧‧‧Resin composition for insulating layer 50, 150‧‧‧Opening part 70‧‧‧Printing plate cylinder 71‧‧‧Protrusion non-formation area 72‧‧‧Protrusion part 73‧‧‧Protrusion part upper surface 75 ‧‧‧Impression cylinder 80‧‧‧Electromagnetic wave shielding effect measuring device 83‧‧‧Measuring fixture 84‧‧‧Central conductor 91‧‧‧Spectrometer 92, 93‧‧‧Attenuator 94‧‧‧Preamplifier 131 ‧‧‧Silver layer 132‧‧‧Copper layer 133‧‧‧Silver paste

FIG. 1 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention. FIGS. 2( a ) and ( b ) are schematic views schematically showing a case where a shielded printed wiring board is manufactured using an electromagnetic wave shielding film in which an opening is not formed in the shielding layer. FIGS. 3( a ) to ( c ) are plan views schematically showing an example of an arrangement pattern of openings in the shielding layer constituting the electromagnetic wave shielding film of the present invention. 4 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention in which the shielding layer is composed of a copper layer and a silver layer. FIGS. 5( a ) to ( c ) are step diagrams schematically showing an example of the manufacturing method of the electromagnetic wave shielding film of the present invention in sequence. 6 is a step diagram schematically showing an example of an insulating layer preparation step in the method of manufacturing the electromagnetic wave shielding film of the present invention. FIG. 7 is a step diagram schematically showing an example of a silver paste printing step in the method of manufacturing the electromagnetic wave shielding film of the present invention. FIG. 8 is a step diagram schematically showing an example of a silver paste printing step in the manufacturing method of the electromagnetic wave shielding film of the present invention. FIG. 9 is a step diagram schematically showing an example of a silver paste printing step in the manufacturing method of the electromagnetic wave shielding film of the present invention. FIGS. 10( a ) and ( b ) are step diagrams schematically showing an example of the copper plating step in the manufacturing method of the electromagnetic wave shielding film of the present invention. FIGS. 11( a ) and ( b ) are step diagrams schematically showing an example of the steps of forming the conductive adhesive layer in the method for producing the electromagnetic wave shielding film of the present invention. FIG. 12 is a schematic diagram schematically showing the structure of the system used in the KEC method.

10‧‧‧Electromagnetic wave shielding film

20‧‧‧Conductive adhesive layer

30‧‧‧Shielding

40‧‧‧Insulating layer

50‧‧‧Opening

Claims (8)

An electromagnetic wave shielding film is composed of a conductive adhesive layer, a shielding layer laminated on the conductive adhesive layer, and an insulating layer laminated on the shielding layer, characterized in that the shielding layer is formed with a plurality of openings The opening area of the openings is 70-71000μm ² ; the opening ratio of the openings is 0.05-3.6%; the opening pitch of the openings is 10-10000μm; and the openings are regularly arranged at certain intervals. The electromagnetic wave shielding film of claim 1, wherein the thickness of the shielding layer is 0.5 μm or more. The electromagnetic wave shielding film of claim 1 or 2, wherein the shielding layer comprises a copper layer. The electromagnetic wave shielding film of claim 3, wherein the shielding layer further comprises a silver layer, the silver layer is disposed on the side of the insulating layer, and the copper layer is disposed on the side of the conductive adhesive layer. The electromagnetic wave shielding film of claim 1 or 2 is used for flexible printed wiring boards. A shielded printed wiring board comprising: a base member having a printed circuit formed thereon; a printed wiring board having an insulating film provided on the base member so as to cover the printed circuit; and an electromagnetic wave shielding film provided on the aforementioned A printed wiring board; the shielded printed wiring board is characterized by: The aforementioned electromagnetic wave shielding film is the electromagnetic wave shielding film according to any one of claims 1 to 5. The shielded printed wiring board of claim 6, wherein the aforementioned printed wiring board is a flexible printed wiring board. An electronic machine, characterized in that the shielded printed wiring board according to claim 6 or 7 is assembled, and the shielded printed wiring board is assembled in a bent state.

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