TW202222563A - Electromagnetic wave shielding film and shielded printed wiring board having a shielding layer with a high adhesion strength and excellent bending resistance - Google Patents

Abstract

Provided is an electromagnetic wave shielding film that has a shielding layer with a high adhesion strength and excellent bending resistance. The electromagnetic wave shielding film according to the present invention has an isotropic electrically conductive adhesive layer, an insulating layer, and a metal layer laminated in that order, and has the feature that the total thickness of the insulating layer and the metal layer is 0.5 [mu]m or more and less than 20 [mu]m.

Description

Electromagnetic wave shielding film and shielding printed wiring board

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

Background technique In smartphones, tablet computers, etc., which are mobile devices, in order to shield electromagnetic waves generated from the inside or electromagnetic waves intruded from the outside, a shielded flexible printed wiring board with an electromagnetic wave shielding film (hereinafter also referred to as "" Shielded Printed Wiring Board”). The shielding layer used for the electromagnetic wave shielding film is formed of a thin-film metal layer formed by vapor deposition, sputtering, plating, or the like, and a conductive paste that is highly filled with a conductive filler and the like. If 5G is really popular in the future, in order to communicate large-capacity data, high-frequency and high-speed transmission will be developed, and noise control measures of electronic equipment will be required.

Regarding the above-mentioned electromagnetic wave shielding film, Patent Document 1 discloses an electromagnetic wave shielding material (electromagnetic wave shielding film) which is formed on the surface of a polymer film by any one of sputtering, vapor deposition and plating. With one or more shielding layers, the shielding layer is 1-8 μm thick, and is selected from the group consisting of Ni, Fe, Co, Ti, Zn, Cr, Sn, Cu and at least one of these At least one of the group consisting of metal alloys; between the surface of the polymer film and the shielding layer, a substrate with one or more layers is formed by either sputtering or vapor deposition. layer, the base layer has a thickness of 1 μm or less, and is composed of Ni, Co, Zn, Fe, Cu, Ti, Cr, oxides, nitrides of these metals, and alloys containing at least one of these metals At least one of the constituted groups is constituted.

In addition, Patent Document 2 discloses an electromagnetic wave shielding film (electromagnetic wave shielding film) characterized in that it is applied to a molded article formed of any one of ABS resin, PC, and ABS/PC-based polymer blend, and It consists of the first layer of Cu and the second layer of the Sn-Cr coating. prior art literature Patent Literature

[Patent Document 1] Japanese Patent Laid-Open No. 2004-128158 [Patent Document 2] Japanese Patent No. 3826756

Summary of Invention The problem to be solved by the invention Since the electromagnetic wave shielding film described above is laminated in a state where a plurality of metal layers are in contact with each other, there is a problem that the adhesion between the shielding layers is insufficient and cracks are easily generated when repeatedly folded.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an electromagnetic wave shielding film having high adhesion strength of the shielding layer and excellent bending resistance. means of solving problems

That is, the electromagnetic wave shielding film of the present invention is characterized in that an isotropic conductive adhesive layer, an insulating layer and a metal layer are laminated in this order, and the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm. .

In the electromagnetic wave shielding film of the present invention, both the isotropic conductive adhesive layer and the metal layer have the effect of shielding electromagnetic waves. In the electromagnetic wave shielding film of the present invention, an insulating layer is formed between the isotropic conductive adhesive layer and the metal layer. Therefore, the metal layer is not easily peeled off. Furthermore, even if the electromagnetic wave shielding film of the present invention is repeatedly folded, the metal layer is less likely to be cracked.

In the electromagnetic wave shielding film of this invention, the total thickness of the said insulating layer and the said metal layer is 0.5 micrometer or more and less than 20 micrometers. When the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm, the metal layer is not easily peeled off, and even if the electromagnetic wave shielding film is repeatedly folded, the metal layer is not easily cracked.

In the electromagnetic wave shielding film of the present invention, the thickness of the metal layer is preferably 0.1 to 8 μm. When the thickness of the said metal layer is less than 0.1 micrometer, the intensity|strength of a metal layer becomes weak, and it becomes easy to break. If the thickness of the above-mentioned metal layer exceeds 8 μm, since the flexibility of the metal layer is reduced, cracks are likely to occur in the metal layer during repeated bending.

In the electromagnetic wave shielding film of the present invention, the thickness of the insulating layer is preferably 0.5 to 10 μm. If the thickness of the insulating layer is less than 0.5 μm, since the amount of the insulating layer is reduced, the metal layer is easily peeled off. If the thickness of the insulating layer exceeds 10 μm, since the insulating layer is thick, stress is easily applied to the metal layer when the electromagnetic wave shielding film is bent. Therefore, cracks are easily generated in the metal layer during repeated bending.

In the electromagnetic wave shielding film of the present invention, the metal layer preferably contains at least one selected from the group consisting of copper, silver, and aluminum. These metals are inexpensive, and if the metal layer is composed of these metals, they exhibit excellent electromagnetic wave shielding properties.

In the electromagnetic wave shielding film of the present invention, through holes are preferably formed in the metal layer. The electromagnetic wave shielding film will be arranged on the printed wiring board. At this time, the electromagnetic wave shielding film is subjected to thermocompression bonding. At this time, volatile components may be generated between the insulating layer and the metal layer. When the metal layer does not have a through hole, the volatile component may expand due to heat, so that the metal layer and the insulating layer may be peeled off. However, if a through hole is formed in the metal layer, since the volatile component can pass through the through hole, the metal layer and the insulating layer can be prevented from being peeled off.

In the electromagnetic wave shielding film of the present invention, the opening area of each of the through holes is preferably 10 to 80000 μm ² . If the opening area of the through hole formed in the metal layer is within the above-mentioned range, the bending resistance is sufficient, and volatile components can be prevented from staying between the metal layer and the insulating layer.

In the electromagnetic wave shielding film of the present invention, the aperture ratio of the through holes is preferably 0.05 to 30%. When the aperture ratio of the through-hole formed in the metal layer is in the above-mentioned range, the bending resistance is sufficient, and volatile components can be prevented from staying between the metal layer and the insulating layer.

The shielded printed wiring board of the present invention is characterized by comprising: a printed wiring board composed of a base film, a printed circuit including a ground circuit disposed on the base film, and a cover film covering the printed circuit; and an electromagnetic wave The shielding film is sequentially laminated with an isotropic conductive adhesive layer, an insulating layer and a metal layer, and the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm; and the electromagnetic wave shielding film is made of The said isotropic conductive adhesive layer is arrange|positioned on the said printed wiring board so that the said coverlay film may contact.

The electromagnetic wave shielding film provided in the shielding printed wiring board of the present invention has an isotropic conductive adhesive layer, an insulating layer and a metal layer laminated in this order, and the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm. That is, the shield printed wiring board of this invention is equipped with the electromagnetic wave shielding film of this invention mentioned above. Therefore, in the shielded printed wiring board of the present invention, the metal layer is not easily peeled off, and even if the shielded printed wiring board is repeatedly bent, the metal layer is not easily cracked.

In the shielded printed wiring board of the present invention, it is preferable that the cover film is formed with an opening for exposing the ground circuit, the opening is filled with the isotropic conductive adhesive layer, and the isotropic conductive adhesive layer is preferably formed. The adhesive layer is in contact with the above ground circuit. In the above-mentioned shielded printed wiring board, the isotropic conductive adhesive layer and the ground circuit are sufficiently contacted and electrically connected. In the shielded printed wiring board of the present invention, since the isotropic conductive adhesive layer has the function of shielding electromagnetic waves, the electromagnetic wave shielding effect becomes high.

In the shielded printed wiring board of the present invention, the metal layer is electrically connected to the external ground. In the shielded printed wiring board of the present invention, since the metal layer has the function of shielding electromagnetic waves, if the metal layer is electrically connected to the external ground, the electromagnetic wave shielding effect will be enhanced. Invention effect

In the electromagnetic wave shielding film of the present invention, an insulating layer is formed between the isotropic conductive adhesive layer and the metal layer. Therefore, the metal layer is not easily peeled off. Furthermore, even if the electromagnetic wave shielding film of the present invention is repeatedly folded, the metal layer is less likely to be cracked. Moreover, in the electromagnetic wave shielding film of this invention, the total thickness of the said insulating layer and the said metal layer is 0.5 micrometer or more and less than 20 micrometers. When the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm, the metal layer is not easily peeled off, and even if the electromagnetic wave shielding film is repeatedly folded, the metal layer is not easily cracked.

Form for carrying out the invention Hereinafter, the electromagnetic wave shielding film of this invention is demonstrated concretely. However, the present invention is not limited to the following embodiments, and can be appropriately changed 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. In the electromagnetic wave shielding film 10 shown in FIG. 1 , an isotropic conductive adhesive layer 20 , an insulating layer 30 and a metal layer 40 are laminated in this order. Moreover, in the electromagnetic wave shielding film 10, the total thickness of the insulating layer 30 and the metal layer 40 is 0.5 micrometer or more and less than 20 micrometers.

The electromagnetic wave shielding film 10 is to be arranged on a printed wiring board. In the electromagnetic wave shielding film 10, since both the isotropic conductive adhesive layer 20 and the metal layer 40 have the effect of shielding electromagnetic waves, in the shielding printed wiring board equipped with the electromagnetic wave shielding film 10, the isotropic conductive The adhesive layer 20 and the metal layer 40 shield electromagnetic waves.

In the electromagnetic wave shielding film 10 , the insulating layer 30 is formed between the isotropic conductive adhesive layer 20 and the metal layer 40 . Therefore, the metal layer 40 is not easily peeled off. In addition, even if the electromagnetic wave shielding film 10 is repeatedly folded, the metal layer 40 is less likely to be cracked.

In the electromagnetic wave shielding film 10 , the total thickness of the insulating layer 30 and the metal layer 40 is 0.5 μm or more and less than 20 μm. The thickness is preferably 1 to 12 μm. When the total thickness of the insulating layer 30 and the metal layer 40 is 0.5 μm or more and less than 20 μm, the metal layer 40 is not easily peeled off, and even if the electromagnetic wave shielding film 10 is repeatedly bent, the metal layer 40 is not easily cracked.

Hereinafter, each configuration of the electromagnetic wave shielding film 10 will be described.

(metal layer) The material constituting the metal layer 40 is not particularly limited as long as it can shield electromagnetic waves, and preferably includes at least one selected from the group consisting of copper, silver, and aluminum. These metals are inexpensive, and if the metal layer 40 is formed of these metals, they exhibit excellent electromagnetic wave shielding properties.

As described above, in the electromagnetic wave shielding film 10, the thickness of the metal layer 40 is preferably 0.1-8 μm, preferably 0.1-4 μm. When the thickness of the said metal layer is less than 0.1 micrometer, the intensity|strength of a metal layer becomes weak, and it becomes easy to break. If the thickness of the above-mentioned metal layer exceeds 8 μm, since the flexibility of the metal layer is reduced, cracks are likely to occur in the metal layer during repeated bending.

The metal layer 40 may be a vapor-deposited metal layer, a plated metal layer, or a rolled or electrolytic metal foil.

Through holes are preferably formed in the metal layer 40 . The electromagnetic wave shielding film 10 is to be arranged on a printed wiring board. At this time, the electromagnetic wave shielding film 10 is subjected to thermocompression bonding. At this time, volatile components may be generated between the insulating layer 30 and the metal layer 40 . When the metal layer 40 does not have a through hole, the volatile component may expand due to heat, so that the metal layer 40 and the insulating layer 30 may be peeled off. However, if through holes are formed in the metal layer 40 , since the volatile components can pass through the through holes, the metal layer 40 and the insulating layer 30 can be prevented from being peeled off.

The shape of the through hole is not particularly limited, and may be a polygonal shape such as a triangle or a quadrangle, a circle, or an ellipse.

In the metal layer 40 , the opening area of each of the through holes is preferably 10-80000 μm ² , preferably 10-8000 μm ² . If the opening area of the through hole formed in the metal layer 40 is within the above range, the bending resistance is sufficient, and volatile components can be prevented from staying between the metal layer 40 and the insulating layer 30 .

In the metal layer 40, the aperture ratio of the through holes is preferably 0.05-30%, preferably 0.1-10%. If the aperture ratio of the through hole formed in the metal layer 40 is within the above range, the bending resistance is sufficient, and volatile components can be prevented from staying between the metal layer 40 and the insulating layer 30 .

The through holes may be arranged in the metal layer 40 at equal intervals. When the through holes are arranged at equal intervals, the through holes should preferably be arranged continuously in a fixed pattern. The arrangement pattern of the through holes may be an arrangement pattern in which the center of the through holes is located at the apex of the equilateral triangle in the plane in which the equilateral triangles are continuously arranged vertically and horizontally when the metal layer 40 is viewed in plan. In addition, when the metal layer 40 is viewed from above, in a plane in which squares are continuously arranged vertically and horizontally, the center of the through-holes may be located at the apexes of the squares. In addition, when the metal layer 40 is viewed from above, the center of the through hole may be located at the apex of a regular hexagon.

(Insulation) The material of the insulating layer 30 is not particularly limited as long as it can sufficiently adhere to the metal layer 40, and may be a thermosetting resin composition or a thermoplastic resin composition. In addition, when the electromagnetic wave shielding film 10 is arrange|positioned on a printed wiring board, thermocompression bonding is performed. Whether to use a thermosetting resin composition or a thermoplastic resin composition for the insulating layer 30 should be determined according to the conditions at the time of thermocompression bonding. In addition, from the viewpoint of heat resistance, the insulating layer 30 is preferably made of a thermosetting resin composition.

The thermoplastic resin contained in the thermoplastic resin composition includes urethane resin, polystyrene-based resin, vinyl acetate-based resin, polyester-based resin, and polyolefin-based resin (for example, polyethylene-based resin, polystyrene acrylic resin composition, etc.), acrylic resin, etc. The insulating layer 30 may be composed of only one of these resins, or may be composed of two or more kinds.

The thermosetting resins contained in the thermosetting resin composition include phenol-based resins, epoxy-based resins, urethane-based resins, melamine-based resins, alkyd-based resins, and the like, polyimide-based resins, and the like. resin. The insulating layer 30 may be composed of only one of these resins, or may be composed of two or more kinds.

The thickness of the insulating layer 30 is preferably 0.5-10 μm, preferably 1-5 μm. If the thickness of the insulating layer is less than 0.5 μm, since the amount of the insulating layer is reduced, the metal layer is easily peeled off. If the thickness of the insulating layer exceeds 10 μm, since the insulating layer is thick, stress is easily applied to the metal layer when the electromagnetic wave shielding film is bent. Therefore, cracks are likely to occur in the metal layer during repeated bending.

(Isotropic conductive adhesive layer) The isotropic conductive adhesive layer 20 is composed of conductive particles and a resin composition.

As an electroconductive particle, silver particle, copper particle, nickel particle, aluminum particle, the silver-coated copper particle which silver-plated copper, etc. are mentioned, for example. Since these electroconductive particles are excellent in electroconductivity, electroconductivity can be favorably provided to the isotropic conductive adhesive layer 20 . These electroconductive particles may be contained in the isotropic conductive adhesive layer 20 individually by one type, and may contain several types.

The size of the conductive particles is not particularly limited, but the average particle diameter (d ₅₀ ) is preferably 0.5 to 20 μm. When the average particle diameter (d ₅₀ ) is 0.5 μm or more, the dispersibility of the conductive particles is good, aggregation is suppressed, and oxidation is difficult. When the average particle diameter (d ₅₀ ) is 20 μm or less, the connectivity to the ground circuit is good.

The weight ratio of the conductive particles contained in the isotropic conductive adhesive layer 20 is preferably 40-80 wt %, preferably 50-70 wt %. If the weight ratio of the conductive particles is less than 40 wt %, it is difficult to obtain isotropic conductivity. When the weight ratio of the electroconductive particles exceeds 80 wt %, the isotropic electroconductive adhesive layer becomes brittle, and the electromagnetic wave shielding film becomes easily damaged.

The material of the resin composition is not particularly limited, and can be used: styrene-based resin composition, vinyl acetate-based resin composition, polyester-based resin composition, polyethylene-based resin composition, polypropylene-based resin composition, Imide resin compositions, amide resin compositions, acrylic resin compositions and other thermoplastic resin compositions; and phenolic resin compositions, epoxy resin compositions, urethane resin compositions, Thermosetting resin compositions such as melamine-based resin compositions, alkyd-based resin compositions, and the like. Among them, the epoxy resin composition is preferable. The material of the adhesive resin composition may be used alone or in combination of two or more.

In addition, the isotropic conductive adhesive layer 20 may further contain a flame retardant, a flame retardant auxiliary, a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, and a defoaming agent. , Leveling agent, filler, viscosity regulator, etc.

The thickness of the isotropic conductive adhesive layer 20 is preferably 3-20 μm, preferably 5-10 μm. When the thickness of the isotropic conductive adhesive layer 20 is 3 μm or more, the filling property of the opening provided in the coverlay of the printed wiring board becomes more favorable. If the thickness of the isotropic conductive adhesive layer 20 is 20 μm or less, the thinning requirement of the electromagnetic wave shielding film can be satisfied.

In the electromagnetic wave shielding film 10 , a protective layer may be further formed on the metal layer 40 . By having the protective layer, the metal layer 40 can be prevented from being damaged by external shock or the like. Moreover, in the electromagnetic wave shielding film of this invention, a protective layer may not be formed.

The material of the protective layer is not particularly limited as long as it has insulating properties and can protect the metal layer 40, but is preferably composed of a thermoplastic resin composition, a thermosetting resin composition, an active energy ray curable composition, or the like.

The thermoplastic resin composition of the protective layer is not particularly limited, and examples thereof include styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, polyethylene-based resin compositions, and polypropylene-based resin compositions compounds, polyamide resin compositions, acrylic resin compositions, etc.

The thermosetting resin composition of the protective layer is not particularly limited, and examples thereof include phenol-based resin compositions, epoxy-based resin compositions, urethane-based resin compositions, melamine-based resin compositions, and alkyd-based resin compositions. Resin composition, polyimide resin composition, etc.

Although it does not specifically limit about the active energy ray curable composition of a protective layer, For example, the polymerizable compound etc. which have at least 2 (meth)acryloyloxy groups in a molecule|numerator are mentioned.

The protective layer may be composed of a single material, or may be composed of two or more materials.

The protective layer may also contain hardening accelerators, tackifiers, antioxidants, pigments, dyes, plasticizers, UV absorbers, defoamers, leveling agents, fillers, flame retardants, viscosity modifiers, Anti-caking agents, etc.

The thickness of the protective layer is not particularly limited, and can be appropriately set as needed, and is preferably 1 to 15 μm, preferably 3 to 10 μm.

Next, the manufacturing method of the electromagnetic wave shielding film of this invention is demonstrated. When the electromagnetic wave shielding film of the present invention is produced, a metal layer forming step, an insulating layer forming step, and an isotropic conductive adhesive layer forming step are performed.

FIG. 2A is a step diagram schematically showing an example of a metal layer forming step in the method of manufacturing the electromagnetic wave shielding film of the present invention. First, as shown in FIG. 2A, the release film 50 is prepared, and the metal layer 40 is formed thereon. The type of the release film 50 is not particularly limited, and conventionally used non-silicon-based release films, micro-adhesive films, and the like can be used. The method of forming the metal layer 40 is not particularly limited, and a rolled or electrolytic metal foil may be arranged, and it may be formed by vapor deposition or by plating.

FIG. 2B is a step diagram schematically showing an example of an insulating layer forming step in the method of manufacturing the electromagnetic wave shielding film of the present invention. Next, as shown in FIG. 2B , the insulating layer 30 is formed on the metal layer 40 . The method for forming the insulating layer 30 is not particularly limited, and for example, a bar coater can be used for coating.

2C is a step diagram schematically showing an example of a step of forming an isotropic conductive adhesive layer in the method for producing an electromagnetic wave shielding film of the present invention. Next, as shown in FIG. 2C , the isotropic conductive adhesive layer 20 is formed on the insulating layer 30 . The method for forming the isotropic conductive adhesive layer 20 is not particularly limited, and for example, it can be applied by a bar coater.

The electromagnetic wave shielding film 10 shown in FIG. 1 is obtained by inverting the laminate produced by the above steps by 180°. Moreover, the release film 50 can be peeled off at the time of use.

Next, the shielded printed wiring board 1 including the electromagnetic wave shielding film 10 will be described. The shielded printed wiring board 1 is also an example of the shielded printed wiring board of the present invention.

3 is a cross-sectional view schematically showing an example of the shielded printed wiring board of the present invention. The shielded printed wiring board 1 shown in FIG. 3 includes a printed wiring board 60 and an electromagnetic wave shielding film 10. The printed wiring board 60 is composed of a base film 61, a printed circuit 62 including a ground circuit 62a disposed on the base film 61, and A cover film 63 covering the printed circuit 62 is constituted. In the shielded printed wiring board 1 , the electromagnetic wave shielding film 10 is arranged on the printed wiring board 60 such that the isotropic conductive adhesive layer 20 is in contact with the coverlay 63 .

The shielded printed wiring board 1 includes an electromagnetic wave shielding film 10 . Therefore, in the shield printed wiring board 1 , the metal layer 40 is not easily peeled off, and even if the shield printed wiring board 1 is repeatedly bent, the metal layer 40 is less likely to be cracked.

Moreover, in the shield printed wiring board 1 shown in FIG. 3, the opening part 63a which exposes the ground circuit 62a is formed in the coverlay 63. As shown in FIG. The opening portion 63a is filled with the isotropically conductive adhesive layer 20, and the isotropically conductive adhesive layer 20 is brought into contact with the ground circuit 62a. In such a shielded printed wiring board 1, the isotropic conductive adhesive layer 20 and the ground circuit 62a are sufficiently contacted and electrically connected. In the shielded printed wiring board 1, since the isotropic conductive adhesive layer 20 has the function of shielding electromagnetic waves, the electromagnetic wave shielding effect becomes high.

Furthermore, in the shielded printed wiring board of the present invention, the cover film may not have an opening for exposing the ground circuit. At this time, the ground circuit and the isotropic conductive adhesive layer can also be electrically connected by conductive bumps or conductive pins.

In the shielded printed wiring board 1, the metal layer 40 is electrically connected to the external ground GND. In the shielded printed wiring board 1, since the metal layer 40 has the function of shielding electromagnetic waves, if the metal layer 40 is electrically connected to the external ground GND, the electromagnetic wave shielding effect will be enhanced.

The method of electrically connecting the external ground GND and the metal layer 40 is not particularly limited.

Moreover, the case where a protective layer is further formed on the metal layer of the electromagnetic wave shielding film in the shielding printed wiring board of this invention is demonstrated using drawings. 4A to 4D are cross-sectional views schematically showing another example of the shielded printed wiring board of the present invention.

The shielded printed wiring board 1A shown in FIG. 4A includes a printed wiring board 60 and an electromagnetic wave shielding film 11. The printed wiring board 60 is composed of a base film 61, a printed circuit 62 including a ground circuit 62a disposed on the base film 61, and a cover film 63 covering the printed circuit 62 . In the electromagnetic wave shielding film 11, the isotropic conductive adhesive layer 20, the insulating layer 30, the metal layer 40, and the protective layer 70 are laminated in this order. In the shielded printed wiring board 1A, the electromagnetic wave shielding film 11 is arranged on the printed wiring board 60 such that the isotropic conductive adhesive layer 20 and the coverlay 63 are in contact with each other.

The shielded printed wiring board 1A is provided on the protective layer 70 of the electromagnetic wave shielding film 11 and further includes a ground member 80A having a flat conductive external connection member 81 and a conductive external connection member 81 protruding from one surface of the ground member 80A. The conductive protrusions 82 . The conductive protrusion 82 penetrates through the protective layer 70 to contact the metal layer 40 , and the conductive external connection member 81 is electrically connected to the external ground GND. That is, in the shielded printed wiring board 1A, the metal layer 40 is connected to the external ground GND via the ground member 80A.

The conductive external connection member 81 and the conductive protrusion 82 of the ground member 80A may be formed of any material as long as they have conductivity, and may be formed of, for example, copper, silver, aluminum, or the like.

In the ground member 80A, the conductive external connection member 81 and the conductive protrusion 82 may be connected by soldering or welding. In addition, the conductive protrusions 82 may be formed by etching, and the conductive external connection member 81 and the conductive protrusions 82 may be integrated.

The shielded printed wiring board 1B shown in FIG. 4B includes a printed wiring board 60 and an electromagnetic wave shielding film 11. The printed wiring board 60 is composed of a base film 61, a printed circuit 62 including a ground circuit 62a disposed on the base film 61, and a cover film 63 covering the printed circuit 62 . In the electromagnetic wave shielding film 11, the isotropic conductive adhesive layer 20, the insulating layer 30, the metal layer 40, and the protective layer 70 are laminated in this order. In the shielded printed wiring board 1B, the electromagnetic wave shielding film 11 is arranged on the printed wiring board 60 such that the isotropic conductive adhesive layer 20 and the coverlay 63 are in contact with each other.

The shielded printed wiring board 1B is provided on the protective layer 70 of the electromagnetic wave shielding film 11 and further includes a ground member 80B having a flat conductive external connection member 81 and a conductive external connection member 81 arranged on one side. Conductive particles 83 . The conductive particles 83 penetrate through the protective layer 70 to be in contact with the metal layer 40 , and the conductive external connection member 81 is electrically connected to the external ground GND. That is, in the shielded printed wiring board 1B, the metal layer 40 is connected to the external ground GND via the ground member 80B.

The conductive external connection member 81 of the ground member 80B may be formed of any material as long as it has conductivity, and may be formed of, for example, copper, silver, aluminum, or the like. Moreover, the electroconductive particle 83 of the grounding member 80B may be made of any material as long as it has electroconductivity, and may be made of, for example, copper, silver, aluminum, or the like.

In the ground member 80B, the conductive particles 83 can be attached to the conductive external connection member 81 by a conductive adhesive.

The shielded printed wiring board 1C shown in FIG. 4C includes a printed wiring board 60 and an electromagnetic wave shielding film 11. The printed wiring board 60 is composed of a base film 61, a printed circuit 62 including a ground circuit 62a disposed on the base film 61, and a cover film 63 covering the printed circuit 62 . In the electromagnetic wave shielding film 11, the isotropic conductive adhesive layer 20, the insulating layer 30, the metal layer 40, and the protective layer 70 are laminated in this order. In the shielded printed wiring board 1C, the electromagnetic wave shielding film 11 is disposed on the printed wiring board 60 such that the isotropic conductive adhesive layer 20 and the coverlay 63 are in contact with each other.

The shield printed wiring board 1C is provided on the protective layer 70 of the electromagnetic wave shielding film 11 and further includes a ground member 80C, which is constituted by a conductive external connection member 84 . The conductive external connection member 84 has a shape formed by bending a flat plate a plurality of times, and has a protruding convex portion 84a. The protruding portion 84a penetrates through the protective layer 70 and is in contact with the metal layer 40, and the conductive external connection member 84 is electrically connected to the external ground GND. That is, in the shielded printed wiring board 1C, the metal layer 40 is connected to the external ground GND via the ground member 80C.

The conductive external connection member 84 of the ground member 80C may be formed of any material as long as it has conductivity, and may be formed of, for example, copper, nickel, silver, aluminum, or the like.

The shielded printed wiring board 1D shown in FIG. 4D includes a printed wiring board 60 and an electromagnetic wave shielding film 12. The printed wiring board 60 is composed of a base film 61, a printed circuit 62 including a ground circuit 62a disposed on the base film 61, and a cover film 63 covering the printed circuit 62 . In the electromagnetic wave shielding film 12, the isotropic conductive adhesive layer 20, the insulating layer 30, the metal layer 40, and the protective layer 71 are laminated in this order. In the shielded printed wiring board 1D, the electromagnetic wave shielding film 12 is arranged on the printed wiring board 60 such that the isotropic conductive adhesive layer 20 and the coverlay 63 are in contact with each other.

In the shield printed wiring board 1D, an opening 71 a for exposing the metal layer 40 is formed in the protective layer 71 of the electromagnetic wave shielding film 12 . Then, the metal layer 40 is electrically connected to the external ground GND through the opening 71a.

Furthermore, in the shielded printed wiring board 1D, the opening 71a of the protective layer 71 may be filled with a conductive adhesive, and the metal layer 40 may be connected to the external ground GND through the conductive adhesive.

The materials of the base film 61 and the cover film 63 are not particularly limited, but are preferably made of engineering plastics. The above-mentioned engineering plastics include, for example, polyethylene terephthalate, polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide, and polyetherimide. Amine, polyphenylene sulfide and other resins. In addition, among these engineering plastics, a polyphenylene sulfide film is preferable when flame retardancy is required, and a polyimide film is preferable when heat resistance is required. Furthermore, the thickness of the base film 61 is preferably 10 to 40 μm. In addition, the thickness of the cover film 63 is preferably 20 to 50 μm.

The printed circuit 62 and the ground circuit 62a are not particularly limited, and can be formed by etching a conductive material or the like. As a conductive material, copper, nickel, silver, gold, etc. are mentioned.

As a method of manufacturing the shielded printed wiring board 1 , a method of preparing the printed wiring board 60 and the electromagnetic wave shielding film 10 and disposing the electromagnetic wave shielding film 10 on the printed wiring board 60 is exemplified. More specifically, the method of thermocompression-bonding the electromagnetic wave shielding film 10 to the printed wiring board 60 such that the isotropic conductive adhesive layer 20 and the coverlay 63 are in contact with each other can be mentioned. The conditions for thermocompression bonding are not particularly limited, and examples thereof include conditions of 150 to 200° C., 2 to 5 MPa, and 1 to 60 minutes.

By performing the above thermocompression bonding, the isotropic conductive adhesive layer 20 fills the openings 63a. As a result, the ground circuit 62a is electrically connected to the isotropic conductive adhesive layer 20 . Thereby, the electromagnetic wave shielding effect improves. [Example]

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

(Example 1) (Metal layer forming step) Silver (Ag) was vapor-deposited on the surface of the release film formed of the non-silicon-based release agent to form a metal layer with a thickness of 0.1 μm.

(Insulating layer forming step) Epoxy resin was coated on the metal layer to form an insulating layer with a thickness of 1.0 μm.

(Isotropic conductive adhesive layer forming step) An isotropic conductive adhesive containing 60 wt % of conductive particles composed of silver-coated copper powder and 40 wt % of epoxy resin was prepared. The isotropic conductive adhesive layer was applied on the insulating layer to form an isotropic conductive adhesive layer with a thickness of 15 μm.

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

(Examples 2 to 13) and (Comparative Examples 1 to 6) The electromagnetic wave shielding films of Examples 2 to 13 and Comparative Examples 1 to 3 were produced in the same manner as in Example 1, except that the material and thickness of the metal layer and the thickness of the insulating layer were changed as shown in Table 1. In addition, the electromagnetic wave shielding films of Comparative Examples 4 to 6 were produced in the same manner as in Example 1, except that the material and thickness of the metal layer were changed as shown in Table 1, and the insulating layer was not provided.

[Table 1]

(MIT trial) The bending resistance of the electromagnetic wave shielding film of each Example and each comparative example after peeling the peeling film was measured by the following method. Each electromagnetic wave shielding film was placed on the polyimide film so that the isotropic conductive adhesive layer was in contact with the polyimide film with a thickness of 50 μm, and was bonded by thermocompression (170°C, 3MPa, 30 minutes) be fitted. Then, it was cut into the size of vertical x horizontal = 130 mm x 15 mm, the peeling film was peeled off, and it was set as a test piece. The bending resistance of each test piece was measured according to the method prescribed|regulated by JIS P8115:2001 using the MIT folding endurance tester (No. 307 MIT type folding endurance tester made by Yasuda Seiki Co., Ltd.). The test conditions are as follows. Front end R of the bending jig: 0.38mm Bending angle: ±135° Bending speed: 175cpm Load: 500gf Detection method: use the built-in electrical device to sense the rupture of the shielding film

The evaluation criteria of the MIT test are as follows. The results are shown in Table 1. ○: When the number of bending times was 1000 times or more, the fracture of the metal layer was confirmed. Δ: When the number of bending times was 300 or more and less than 999, fracture of the metal layer was confirmed. ╳: When the number of bending times is less than 300 times, the fracture of the metal layer is confirmed.

(Adhesion Strength Test) The adhesion strength of the electromagnetic wave shielding film of each Example and each comparative example after peeling the peeling film was measured by the following method. Each electromagnetic wave shielding film was placed on the polyimide film so that the isotropic conductive adhesive layer was in contact with the polyimide film with a thickness of 25 μm, and the temperature was 170°C, time: 30 minutes, pressure: 3MPa conditions for thermocompression bonding. The metal layer side of the electromagnetic wave shielding film was fixed with double-sided tape, and the polyimide film was peeled off at a stretching speed of 50 mm/min and a peeling angle of 180° at room temperature. The peel strength during peeling was measured, and the maximum and minimum values were determined. The average value is used as the adhesion strength.

The evaluation criteria of the adhesion strength test are as follows. The results are shown in Table 1. ○: The metal layer is peeled off under a tensile force of 4.0 N/cm or more. △: The metal layer is peeled off under a tensile force of 3.0 N/cm or more and less than 4.0 N/cm. ╳: The metal layer is peeled off under the tensile force less than 3.0N/cm.

As shown in Table 1, the electromagnetic wave shielding films of Examples 1 to 13 in which an insulating layer is included between the isotropic conductive adhesive layer and the metal layer, and the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm , both the MIT test and the adhesion strength test were good.

On the other hand, the electromagnetic wave shielding films of Comparative Examples 1 to 3 in which the total thickness of the insulating layer and the metal layer exceeded 20 μm were found to be unsatisfactory in the MIT test, and cracks were likely to occur in the metal layer during repeated bending. In addition, the electromagnetic wave shielding films of Comparative Examples 4 to 6 which did not contain an insulating layer between the isotropic conductive adhesive layer and the metal layer were found to be poor in the adhesion strength test, and the metal layer was easily peeled off.

1, 1A, 1B, 1C, 1D: Shielded printed wiring board 10, 11, 12: Electromagnetic wave shielding film 20: Isotropic conductive adhesive layer 30: Insulation layer 40: Metal layer 50: peel off film 60: Printed wiring board 61: substrate film 62: Printed Circuits 62a: Ground circuit 63: Cover film 63a: Opening 70,71: Protective layer 71a: Opening 80A, 80B, 80C: Grounding member 81, 84: Conductive external connection members 82: Conductive protrusions 83: Conductive particles 84a: convex part GND: External ground

FIG. 1 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention. FIG. 2A is a step diagram schematically showing an example of a metal layer forming step in the method of manufacturing the electromagnetic wave shielding film of the present invention. FIG. 2B is a step diagram schematically showing an example of an insulating layer forming step in the method of manufacturing the electromagnetic wave shielding film of the present invention. 2C is a step diagram schematically showing an example of a step of forming an isotropic conductive adhesive layer in the method for producing an electromagnetic wave shielding film of the present invention. 3 is a cross-sectional view schematically showing an example of the shielded printed wiring board of the present invention. 4A is a cross-sectional view schematically showing another example of the shielded printed wiring board of the present invention. 4B is a cross-sectional view schematically showing another example of the shielded printed wiring board of the present invention. 4C is a cross-sectional view schematically showing another example of the shielded printed wiring board of the present invention. 4D is a cross-sectional view schematically showing another example of the shielded printed wiring board of the present invention.

10: Electromagnetic wave shielding film

20: Isotropic conductive adhesive layer

30: Insulation layer

40: Metal layer

Claims (10)

An electromagnetic wave shielding film is characterized in that: an isotropic conductive adhesive layer, an insulating layer and a metal layer are sequentially laminated, and The total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm. The electromagnetic wave shielding film of claim 1, wherein the thickness of the aforementioned metal layer is 0.1-8 μm. The electromagnetic wave shielding film according to claim 1 or 2, wherein the thickness of the aforementioned insulating layer is 0.5-10 μm. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the metal layer includes at least one selected from the group consisting of copper, silver, and aluminum. The electromagnetic wave shielding film according to any one of claims 1 to 4, wherein through holes are formed in the metal layer. The electromagnetic wave shielding film of claim 5, wherein the opening area of each of the aforementioned through holes is 10-80000 μm ² . The electromagnetic wave shielding film according to claim 5 or 6, wherein the aperture ratio of the aforementioned through holes is 0.05-30%. A shielded printed wiring board is characterized by having: A printed wiring board comprising a base film, a printed circuit including a ground circuit disposed on the base film, and a cover film covering the printed circuit; and An electromagnetic wave shielding film, which is sequentially laminated with an isotropic conductive adhesive layer, an insulating layer and a metal layer, and the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm; And the said electromagnetic wave shielding film is arrange|positioned on the said printed wiring board so that the said isotropically conductive adhesive agent layer may contact the said coverlay film. The shielded printed wiring board according to claim 8, wherein the cover film is formed with an opening for exposing the ground circuit, And the said isotropically conductive adhesive layer is filled in the said opening part, and the said isotropically conductive adhesive layer is made to contact the said ground circuit. The shielded printed wiring board of claim 8 or 9, wherein the aforementioned metal layer is electrically connected to an external ground.

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