JP2020136437A - Electromagnetic wave shield film and circuit board - Google Patents

Abstract

To provide an electromagnetic wave shielding film excellent in both electromagnetic wave shielding property and solder heat resistance, and a circuit board provided with the electromagnetic wave shielding film.SOLUTION: An electromagnetic wave shielding film (1) includes an insulating resin layer (10), a shield layer (20) adjacent to the insulating resin layer, and a conductive adhesive layer (26) provided on the side opposite to the insulating resin layer of the shield layer, and the shield layer includes a plurality of metal layers having a thickness of 1 μm or less, and a non-metal layer interposed between the plurality of metal layers.SELECTED DRAWING: Figure 1

Description

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

In order to shield electromagnetic noise generated from a printed wiring board and electromagnetic noise from the outside, an insulating resin layer and an electromagnetic shielding film composed of a conductive layer adjacent to the insulating resin layer are provided with an insulating film (coverlay film). It may be provided on the surface of the printed wiring board via (see, for example, Patent Document 1).

JP-A-2018-177949

In the conventional electromagnetic wave shielding film, if the metal layer is thickened in order to enhance the electromagnetic wave shielding property, there is a problem that the heat resistance (solder heat resistance) when mounting the electronic component on the circuit board provided with the electromagnetic wave shielding film is lowered. On the contrary, if the thickness of the metal layer of the electromagnetic wave shielding film is reduced, the solder heat resistance is improved, but there is a problem that the electromagnetic wave shielding property is lowered.

The present invention provides an electromagnetic wave shielding film having excellent both electromagnetic wave shielding properties and solder heat resistance, and a circuit board provided with the electromagnetic wave shielding film.

[1] An electromagnetic wave shielding film comprising an insulating resin layer, a shield layer adjacent to the insulating resin layer, and a conductive adhesive layer provided on the opposite side of the shield layer to the insulating resin layer. The shield layer is an electromagnetic wave shielding film including a plurality of metal layers having a thickness of 1 μm or less and a non-metal layer interposed between the plurality of metal layers.
[2] The electromagnetic wave shielding film according to [1], wherein the non-metal layer is an insulating layer made of an insulating resin, or a conductive layer containing conductive particles or a conductive polymer.
[3] The electromagnetic wave shield according to [1] or [2], wherein at least one of the plurality of metal layers is a metal layer made of one or more metals selected from Ag, Cu, Al and Ni. the film.
[4] The electromagnetic wave shielding film according to any one of [1] to [3], wherein at least one of the plurality of metal layers is a physical vapor deposition layer.
[5] The electromagnetic wave shielding film according to any one of [1] to [4], wherein the thickness of the non-metal layer is 0.01 μm or more and 5 μm or less.
[6] A circuit board main body in which a circuit is provided on at least one surface of the substrate, an insulating film adjacent to the one surface, and an insulating film adjacent to the circuit board main body on the opposite side [1] to A circuit board comprising the electromagnetic wave shielding film according to any one of [5], wherein the conductive adhesive layer in the electromagnetic wave shielding film is adhered to the insulating film.

The electromagnetic wave shielding film and circuit board of the present invention are excellent in both electromagnetic wave shielding property and solder heat resistance.

It is sectional drawing which shows the 1st Embodiment of the electromagnetic wave shielding film of this invention. It is sectional drawing which shows the 2nd Embodiment of the electromagnetic wave shielding film of this invention. It is sectional drawing which shows the 3rd Embodiment of the electromagnetic wave shielding film of this invention. It is sectional drawing which shows an example of embodiment of the circuit board of this invention. It is sectional drawing which shows an example of the manufacturing process of the circuit board of this invention. It is the schematic of the measurement system of the KEC method. It is sectional drawing of the measuring jig of the KEC method.

The definitions of the following terms apply throughout the specification and claims.
The "isotropic conductive adhesive layer" means a conductive adhesive layer having conductivity in the thickness direction and the surface direction.
The "anisotropic adhesive layer" means a conductive adhesive layer that has conductivity in the thickness direction and does not have conductivity in the plane direction.
The “conductive adhesive layer having no conductivity in the plane direction” means that the surface resistance is 1 × 10 ⁴ Ω / sq. It means the above-mentioned conductive adhesive layer.
For the average particle size of the conductive particles, 30 particles are randomly selected from the microscopic image of the particles, the minimum and maximum diameters of each particle are measured, and the median value between the minimum and maximum diameters is one particle. It is a value obtained by arithmetically averaging the particle diameters of the 30 measured particles.
The 10% compressive strength of the conductive particles is determined by the following formula (α) from the measurement results using a microcompression tester.
C (x) = 2.48P / πd ² ... (α)
However, C (x) is the 10% compression strength (MPa), P is the test force (N) when the particle size is displaced by 10%, and d is the particle size (mm).
The thickness of each layer of the film (carrier film, protective film, etc.) and electromagnetic wave shielding film is the thickness of 5 places randomly selected using a digital length measuring machine (Mitutoyo, Lightmatic VL-50-B). It is the value measured and averaged.
The thickness of the metal layer is a value obtained by measuring the thicknesses of five randomly selected points using an eddy current film thickness meter and averaging them.
The storage elastic modulus is calculated from the stress applied to the measurement target and the detected strain, and is measured as one of the viscoelastic properties by using a dynamic viscoelastic measuring device that outputs as a function of temperature or time.
Surface resistance, if it is less than 10 ⁶ Ω / □, low resistivity resistivity meter (e.g., Mitsubishi Chemical Co., Loresta GP, ASP probe) using a four-terminal method (JIS K 7194: 1994 and JIS R 1637: a surface resistivity as measured by the method) that conforms to 1998, in the case of 10 ⁶ Ω / □ or more, high resistance resistivity meter (e.g., Mitsubishi Chemical Co., Hiresta UP, a URS probe) using double The surface resistivity measured by the ring method (a method conforming to JIS K 6911: 2006).
The dimensional ratios in FIGS. 1 to 7 are different from the actual ones for convenience of explanation.

≪Electromagnetic wave shield film≫
The first aspect of the present invention includes an insulating resin layer, a shield layer adjacent to the insulating resin layer, and a conductive adhesive layer provided on the opposite side of the shield layer from the insulating resin layer. It is an electromagnetic wave shielding film. The shield layer includes a plurality of metal layers having a thickness of 1 μm or less and a non-metal layer interposed between the plurality of metal layers.

FIG. 1 is a cross-sectional view showing the electromagnetic wave shielding film 1 of the first embodiment.
The electromagnetic wave shield film 1 of the first embodiment includes an insulating resin layer 10 and a shield layer 20 adjacent to the insulating resin layer 10.
The shield layer 20 has a first metal layer 21, a second metal layer 23, and a third metal layer 25 as a plurality of metal layers having a thickness of 1 μm or less, and is a non-metal layer interposed between the plurality of metal layers. It has a first non-metal layer 22 and a second non-metal layer 24.
The conductive adhesive layer 26 is provided on the side of the shield layer 20 opposite to the insulating resin layer 10, and is in contact with the third metal layer 25.
Further, the protective film 40 is attached to the surface of the conductive adhesive layer 26 opposite to the third metal layer 25.

<Insulation resin layer>
The insulating resin layer 10 functions as a protective layer for the shield layer 20.
As the insulating resin layer 10, a coating film (coating film) formed by applying a paint containing a photocurable resin and a photoradical polymerization initiator and semi-curing or curing the paint; a thermosetting resin and a curing agent are applied. A coating film formed by applying a coating material containing and semi-curing or curing; a coating film formed by applying a coating material containing a thermoplastic resin and drying it; from a film obtained by melt-molding a composition containing a thermoplastic resin. Layers and the like can be mentioned. From the viewpoint of heat resistance (solder heat resistance) when subjected to the solder reflow process, a coating film formed by applying a paint containing a photocurable resin and a photoradical polymerization initiator and semi-curing or curing it. Alternatively, a coating film formed by applying a paint containing a thermosetting resin and a curing agent and semi-curing or curing is preferable.
A coating film formed by applying the insulating resin layer 10 to the shield layer 20 is preferable because the adhesiveness of the insulating resin layer 10 to the shield layer 20 is improved.

Examples of the photocurable resin include compounds having a (meth) acryloyl group.
Examples of the photoradical polymerization initiator include known photoradical polymerization initiators depending on the type of photocurable resin.
Examples of the thermosetting resin include amide resin, epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, and ultraviolet curable acrylate resin.
As the thermosetting resin, an amide resin and an epoxy resin are preferable from the viewpoint of excellent heat resistance.
Examples of the curing agent include known curing agents depending on the type of thermosetting resin.
Examples of the thermoplastic resin include aromatic polyetherketone, polyimide, polyamideimide, polyamide, polysulfone, polyethersulfone, polyphenylene sulfide, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyphenylene sulfide ketone.

The insulating resin layer 10 contains one or both of a colorant (pigment, dye, etc.) and a filler in order to conceal the circuit of the circuit board and impart designability to the circuit board with the electromagnetic wave shielding film. You may be.
As one or both of the colorant and the filler, a pigment or a filler is preferable from the viewpoint of weather resistance, heat resistance and hiding property, and a black pigment or a black pigment and the like are used from the viewpoint of circuit hiding property and design property. The combination with the pigment or filler of is more preferable.
The insulating resin layer 10 may contain a flame retardant. The insulating resin layer 10 may contain other components, if necessary, as long as the effects of the present invention are not impaired.

The surface resistance of the insulating resin layer 10 is preferably 1 × 10 ⁶ Ω / □ or more from the viewpoint of electrical insulation. The surface resistance of the insulating resin layer 10 is preferably 1 × 10 ¹⁹ Ω / □ or less from a practical point of view.
The thickness of the insulating resin layer 10 is preferably 0.1 μm or more and 30 μm or less, and more preferably 0.5 μm or more and 20 μm or less. When the thickness of the insulating resin layer 10 is at least the lower limit of the above range, the insulating resin layer 10 can sufficiently exert the function as a protective layer. When the thickness of the insulating resin layer 10 is not more than the upper limit of the above range, the electromagnetic wave shielding film 1 can be thinned.

<Shield layer>
The shield layer 20 is a laminated body in which the first metal layer 21, the first non-metal layer 22, the second metal layer 23, the second non-metal layer 24, and the third metal layer 25 are laminated in this order. The insulating resin layer 10 is in contact with and laminated on the surface of the first metal layer 21 opposite to the first non-metal layer 22.

(Metal layer)
The number of metal layers included in the shield layer 20 is not limited to the three layers exemplified in this embodiment, and may be two or more layers, for example, 2 to 10 layers are preferable, and 2 to 6 layers are more preferable. ~ 4 layers are more preferable. By having a plurality of metal layers, the number of reflection interfaces of electromagnetic waves is larger than that of the case where one metal layer is provided, and the electromagnetic wave shielding property is excellent even though the thickness of each metal layer is thin.

The thickness of all the metal layers of the shield layer 20 is 1 μm or less, and the lower limit of the thickness is not particularly limited. For example, each of them is independently preferably 0.01 μm or more and 1 μm or less, and 0.05 μm or more and 0.6 μm. The following is more preferable, and 0.1 μm or more and 0.4 μm or less is further preferable. The thickness of each metal layer may be the same or different.
When the thickness of each metal layer is not more than the upper limit of the above range, the gas permeability in each metal layer is increased, and the gas generated during the solder reflow treatment (for example, the gas generated from the conductive adhesive layer 26) is permeated. It is possible to prevent delamination and swelling due to the retention of gas.
When the thickness of each metal layer is at least the lower limit of the above range, the electromagnetic wave shielding property at the interface of each metal layer is improved.

The total thickness of the plurality of metal layers included in the shield layer 20 is, for example, preferably 0.1 μm or more and 5 μm or less, more preferably 0.2 μm or more and 2 μm or less, further preferably 0.3 μm or more and 1.2 μm or less, and 0. Most preferably, it is 5.5 μm or more and 1 μm or less.
When the total thickness is not more than the lower limit of the above range, the gas permeability in the shield layer 20 is increased, and the gas generated during the solder reflow treatment (for example, the gas generated from the conductive adhesive layer) is easily permeated. Therefore, it is possible to prevent delamination and swelling due to the retention of gas.
When the total thickness is not more than the upper limit of the above range, the electromagnetic wave shielding film can be made thinner.

Since the metal layer is a thin film of metal and is formed so as to spread in the plane direction, it has conductivity in the plane direction and functions as a layer that shields electromagnetic waves.

Examples of the metal layer include a vapor deposition film formed by physical vapor deposition (vacuum vapor deposition, sputtering, ion beam deposition, electron beam deposition, etc.) or chemical vapor deposition, a plating film formed by plating, a metal foil, and the like. The metal layer is preferably a vapor-deposited film or a plated film in terms of excellent surface conductivity. The metal layer is more preferably a thin-film vapor deposition film, and is vapor-deposited by physical vapor deposition in that the metal layer can be made thin, has excellent conductivity in the plane direction even if the thickness is thin, and can be easily formed by a dry process. It is more preferably a membrane. It is also preferable that the physical vapor deposition film can easily reduce the density of the metal layer for the purpose of increasing gas permeability.

Examples of the metal constituting the metal layer include one or more selected from silver, copper, aluminum, nickel and gold, and silver or copper is preferable from the viewpoint of electrical conductivity.
Among the metal layers, a physical vapor deposition layer is preferable, and a silver vapor deposition layer or a copper vapor deposition layer is more preferable, because a metal layer having high electromagnetic wave shielding property and excellent gas permeability can be easily formed.

The surface resistance of the metal layer is preferably 0.001Ω or more and 1Ω or less, and more preferably 0.001Ω or more and 0.5Ω or less. When it is at least the lower limit of the above range, the metal layer can be sufficiently thinned. If it is not more than the upper limit of the above range, it can sufficiently function as an electromagnetic wave shield layer.

The thickness, constituent materials, physical properties, and the like of each metal layer constituting the shield layer 20 may be the same as or different from each other.

(Non-metal layer)
In the shield layer 20, a non-metal layer is always interposed between the metal layers. In other words, when a group of metal layers is multi-layered without interposing a non-metal layer (for example, when a metal layer B is laminated on the metal layer A by vapor deposition or the like), the group of metals The metal layer is considered to be one metal layer.

In this embodiment, one surface of the shield layer 20 is formed by the first metal layer 21, and the other surface of the shield layer 20 is formed by the third metal layer 25. The shield layer 20 is not limited to this example, and a non-metal layer (not shown) may be provided between the insulating resin layer 10 and the first metal layer 21, and the third metal layer 25 and the conductive adhesive layer 26 may be provided. A non-metal layer (not shown) may be provided between the two.

The metal layer of the shield layer 20 is a layer made of only metal. On the other hand, the non-metal layer interposed between the metal layers is not a layer composed only of metal, but a layer containing at least a resin. Examples of the non-metal layer include an insulating layer made of an insulating resin (resin that is electrically insulating), a conductive layer containing conductive particles or a conductive polymer.

The thickness of the non-metal layer is preferably 0.01 μm or more and 5 μm or less, more preferably 1 μm or more and 4 μm or less, and further preferably 2 μm or more and 3 μm or less.
When the thickness of the non-metal layer is not less than the lower limit of the above range, the adhesive force to the adjacent metal layer is increased, and when it is not more than the upper limit of the above range, the gas permeability of the non-metal layer is increased, and as a result, the solder heat resistance It is preferable because it improves the properties.

Examples of the insulating resin constituting the insulating layer include known thermosetting resins and thermoplastic resins, and thermosetting resins are preferable from the viewpoint of heat resistance. The thermosetting resin constituting the non-metal layer may be in any of an uncured state, a B-staged state, and a cured state.
The insulating layer may contain components other than the insulating resin, if necessary.

Examples of the thermosetting resin include epoxy resin, phenol resin, imide resin, urethane resin, condensation curable silicone, addition curable silicone, thermosetting acrylic resin and the like. Of these, epoxy resin is preferable because it has excellent heat resistance.
The insulating resin may contain a curing agent of a thermosetting resin. Examples of the curing agent include an isocyanate compound having two or more isocyanate groups, an epoxy compound having two or more epoxy groups, and the like, which are appropriately selected depending on the type of the thermosetting resin.

Examples of the thermoplastic resin include a thermoplastic acrylic resin, an ethylene-vinyl acetate copolymer, an ethylene-acrylic copolymer, a polyvinyl chloride, a polyvinyl acetate, a polyamide, a chloroprene, a styrene-butadiene copolymer, and a styrene-. Examples thereof include a butadiene-styrene block copolymer or a hydrogenated product thereof, a styrene-isoprene-styrene block copolymer or a hydrogenated product thereof, and the like.

Examples of the resin contained in the conductive layer include the above-mentioned thermosetting resin and thermoplastic resin, and a thermosetting resin is preferable from the viewpoint of heat resistance. Further, a conductive polymer is also suitable in that it imparts conductivity to the conductive layer.

When the conductive layer contains conductive particles and an insulating resin, a preferred embodiment of the conductive adhesive layer is an isotropic conductive adhesive layer or isotropic conductive adhesive, which is exemplified as a conductive adhesive layer described later. The agent layer can be mentioned.
Hereinafter, particularly preferable embodiments of the conductive layer will be illustrated.

The average particle size of the conductive particles contained in the conductive layer is preferably 0.2 μm or more and 10 μm or less, more preferably 0.5 μm or more and 8 μm or less, and further preferably 0.8 μm or more and 5 μm or less. The thickness of the conductive layer can be maintained as long as it is equal to or higher than the lower limit of the above range. When it is not more than the upper limit of the above range, the adhesive strength between the metal layers can be increased.

The proportion of the conductive particles in the conductive layer is preferably 1% by volume or more and 30% by volume or less, more preferably 2% by volume or more and 15% by volume or less, out of 100% by volume of the conductive layer. When it is at least the lower limit value in the above range, the conductivity of the conductive layer becomes good. When it is not more than the upper limit value of the above range, the adhesiveness of the conductive layer becomes good. In addition, the flexibility of the electromagnetic wave shield film 1 is improved.

The conductive thickness including the conductive particles is preferably 0.2 μm or more and 10 μm or less, more preferably 0.5 μm or more and 8 μm or less, and further preferably 0.8 μm or more and 5 μm or less. When it is at least the lower limit of the above range, the adhesive strength between the metal layers can be increased. If it is not more than the upper limit of the above range, the electromagnetic wave shield film 1 can be thinned. In addition, the flexibility of the electromagnetic wave shield film 1 is improved.

When the conductive layer contains a conductive polymer, the conductive layer may or may not contain a resin other than the conductive polymer. Examples of the resin other than the conductive polymer include the thermosetting resin and the thermoplastic resin. The conductive layer may contain the conductive particles in addition to the conductive polymer.

Examples of the conductive polymer include a conductive composite containing a known π-conjugated conductive polymer and polyanion.

The π-conjugated conductive polymer is not particularly limited as long as it is an organic polymer whose main chain is composed of a π-conjugated system. For example, a polypyrrole-based conductive polymer, a polythiophene-based conductive polymer, or a polyacetylene-based polymer is used. Conductive polymer, polyphenylene-based conductive polymer, polyphenylene vinylene-based conductive polymer, polyaniline-based conductive polymer, polyacene-based conductive polymer, polythiophene vinylene-based conductive polymer, and copolymers thereof, etc. Can be mentioned. From the viewpoint of stability in air, polypyrrole-based conductive polymer, polythiophene-based conductive polymer, and polyaniline-based conductive polymer are preferable, and polythiophene-based conductive polymer is more preferable.

Examples of the polythiophene-based conductive polymer include polythiophene, poly (3-methylthiophene), poly (3-ethylthiophene), poly (3-propylthiophene), poly (3-butylthiophene), and poly (3-hexyl). Thiophene), poly (3-heptylthiophene), poly (3-octylthiophene), poly (3-decylthiophene), poly (3-dodecylthiophene), poly (3-octadecylthiophene), poly (3-bromothiophene) , Poly (3-chlorothiophene), poly (3-iodothiophene), poly (3-cyanothiophene), poly (3-phenylthiophene), poly (3,4-dimethylthiophene), poly (3,4-dibutyl) Thiophene), poly (3-hydroxythiophene), poly (3-methoxythiophene), poly (3-ethoxythiophene), poly (3-butoxythiophene), poly (3-hexyloxythiophene), poly (3-heptyloxy) Thiophene), poly (3-octyloxythiophene), poly (3-decyloxythiophene), poly (3-dodecyloxythiophene), poly (3-octadecyloxythiophene), poly (3,4-dihydroxythiophene), poly (3,4-dimethoxythiophene), poly (3,4-diethoxythiophene), poly (3,4-dipropoxythiophene), poly (3,4-dibutoxythiophene), poly (3,4-dihexyloxy) Thiophene), poly (3,4-diheptyloxythiophene), poly (3,4-dioctyloxythiophene), poly (3,4-didecyloxythiophene), poly (3,4-didodecyloxythiophene), Poly (3,4-ethylenedioxythiophene), poly (3,4-propylenedioxythiophene), poly (3,4-butylenedioxythiophene), poly (3-methyl-4-methoxythiophene), poly (3-methyl-4-methoxythiophene) 3-Methyl-4-ethoxythiophene), poly (3-carboxythiophene), poly (3-methyl-4-carboxythiophene), poly (3-methyl-4-carboxyethylthiophene), poly (3-methyl-4) -Carboxybutylthiophene).

Examples of the polypyrrole-based conductive polymer include polypyrrole, poly (N-methylpyrrole), poly (3-methylpyrrole), poly (3-ethylpyrrole), poly (3-n-propylpyrrole), and poly (3). -Butylpyrrole), poly (3-octylpyrrole), poly (3-decylpyrrole), poly (3-dodecylpyrrole), poly (3,4-dimethylpyrrole), poly (3,4-dibutylpyrrole), poly (3-carboxypyrrole), poly (3-methyl-4-carboxypyrrole), poly (3-methyl-4-carboxyethylpyrrole), poly (3-methyl-4-carboxybutylpyrrole), poly (3-hydroxy) Pyrrole), poly (3-methoxypyrrole), poly (3-ethoxypyrrole), poly (3-butoxypyrrole), poly (3-hexyloxypyrrole), poly (3-methyl-4-hexyloxypyrrole). Be done.

Examples of the polyaniline-based conductive polymer include polyaniline, poly (2-methylaniline), poly (3-isobutylaniline), poly (2-aniline sulfonic acid), and poly (3-aniline sulfonic acid).
Among the π-conjugated conductive polymers exemplified above, poly (3,4-ethylenedioxythiophene) is particularly preferable from the viewpoint of conductivity and heat resistance.
One type of π-conjugated conductive polymer may be used alone, or two or more types may be used in combination.

The polyanion is a polymer having two or more monomer units having an anionic group in the molecule. The anionic group of this polyanion functions as a dopant for the π-conjugated conductive polymer, and can improve the conductivity of the π-conjugated conductive polymer.
The anionic group of the polyanion is preferably a sulfonic acid group or a carboxy group.
Specific examples of the polyanion include a sulfonic acid group bonded to the ester moiety of polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, and polyacrylic acid ester, and a sulfonic acid group bonded to the ester moiety of polymethacrylic acid ester. (For example, polysulfoethyl methacrylate, poly (4-sulfobutyl methacrylate), polymethacryloxybenzene sulfonic acid), poly (2-acrylamide-2-methylpropane sulfonic acid), polyisoprene sulfonic acid and other sulfonic acid groups. Polymers, polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacrylic carboxylic acid, polymethacrylcarboxylic acid, poly (2-acrylamide-2-methylpropanecarboxylic acid), polyisoprenecarboxylic acid, polyacrylic acid Examples thereof include polymers having a carboxylic acid group such as. These homopolymers may be used, or two or more kinds of copolymers may be used.
Among these polyanions, a polymer having a sulfonic acid group is preferable, and polystyrene sulfonic acid is more preferable, because the conductivity can be made higher.
One type of polyanion may be used alone, or two or more types may be used in combination.
The mass average molecular weight of the polyanion is preferably 20,000 or more and 1 million or less, and more preferably 100,000 or more and 500,000 or less.
The mass average molecular weight in the present specification is a value obtained by measuring by gel permeation chromatography and using polystyrene as a standard substance.

The content ratio of the polyanion in the conductive composite is preferably in the range of 1 part by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the π-conjugated conductive polymer, and is 10 parts by mass or more and 700 parts by mass. It is more preferably in the following range, and further preferably in the range of 100 parts by mass or more and 500 parts by mass or less. When the content ratio of the polyanion is at least the above lower limit value, the doping effect on the π-conjugated conductive polymer tends to be strong, sufficient conductivity can be easily obtained, and the conductivity in the conductive polymer dispersion is further increased. The dispersibility of the complex is increased. Further, when the content of the polyanion is not more than the upper limit value, the relative content of the π-conjugated conductive polymer increases, and sufficient conductivity can be easily obtained.

A conductive composite is formed by coordinating and doping a π-conjugated conductive polymer with a polyanion. From the viewpoint of improving the conductivity and dispersibility of the conductive composite, it is preferable that all the anion groups have a surplus anion group that does not contribute to the doping, rather than doping the π-conjugated conductive polymer.

It is preferable that at least one of the amine compound and the epoxy compound reacts with at least a part of the surplus anionic group to coordinate or bond. That is, the polyanion is preferably a product obtained by reacting a part of its own anion group with an amine compound or an epoxy compound. If at least one of the amine compound and the epoxy compound is coordinated or bonded to the excess anion group of the polyanion, the conductive complex can be made hydrophobic.

The amine compound is at least one selected from the group consisting of primary amines, secondary amines and tertiary amines. One type of amine compound may be used alone, or two or more types may be used in combination.
Examples of the primary amine include aniline, toluidine, benzylamine, ethanolamine and the like.
Examples of the secondary amine include diethanolamine, dimethylamine, diethylamine, dipropylamine, diphenylamine, dibenzylamine, dinaphthylamine and the like.
Examples of the tertiary amine include triethanolamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trioctylamine, triphenylamine, tribenzylamine, trinaphthylamine and the like.
Among the amine compounds, a tertiary amine is preferable, and at least one of tributylamine and trioctylamine is more preferable because the conductive complex can be easily hydrophobized.

Examples of the epoxy compound include compounds having one or more epoxy groups in one molecule. It is believed that the epoxy compound reacts with the excess anionic group of the polyanion to form a hydrophobic substituent. For example, when the anionic group is a sulfonic acid group, it is considered to form a sulfonic acid ester.

When the conductive layer contains a conductive polymer, the conductive layer can be formed by applying a conductive polymer-containing liquid containing the conductive polymer and drying it.

The conductive layer containing the conductive polymer may further contain an additive. Examples of the additive include a conductivity improver, a binder component, a surfactant, an inorganic conductive agent, a defoamer, a coupling agent, an antioxidant, an ultraviolet absorber, and conductive particles.

The conductivity improver includes an acrylic compound, a nitrogen-containing aromatic cyclic compound, a compound having two or more hydroxyl groups, a compound having two or more carboxyl groups, one or more hydroxyl groups, and one or more hydroxyl groups. Examples thereof include at least one compound selected from the group consisting of a compound having a carboxy group, a compound having an amide group, a compound having an imide group, a lactam compound, a compound having a glycidyl group, and a water-soluble organic solvent.
Specific examples of these compounds are described in, for example, Japanese Patent Application Laid-Open No. 2010-87401.

As the binder component, a polymer other than the π-conjugated conductive polymer and the polyanion or a compound forming the polymer is used. Specific examples of the binder component include resins, thermosetting compounds, and active energy ray-curable compounds. When the conductive polymer-containing liquid contains a thermosetting compound, it is preferable that a thermosetting initiator is also contained, and when an active energy ray-curable compound is contained, a photopolymerization initiator is also contained. It is preferably contained.
Examples of the resin that can be used as the binder component include acrylic resin, polyester resin, epoxy resin, oxetane resin, polyurethane resin, polyimide resin, melamine resin, silicone resin, vinyl acetate resin and the like.
Examples of the thermosetting compound and the active energy ray-curable compound include a compound having a vinyl group, a compound having an epoxy group, and a compound having an oxetane group. These may be monomers or oligomers.

Examples of the surfactant include nonionic, anionic and cationic surfactants, and nonionic surfactants are preferable from the viewpoint of storage stability. Further, a polymer-based surfactant such as polyvinyl alcohol or polyvinylpyrrolidone may be added.
Examples of the inorganic conductive agent include metal ions and conductive carbon. Metal ions can be generated by dissolving a metal salt in water.
Examples of the defoaming agent include silicone resin, polydimethylsiloxane, silicone oil and the like.
Examples of the coupling agent include a silane coupling agent having a vinyl group, an amino group, an epoxy group and the like.
Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, sugars and the like.
Examples of UV absorbers include benzotriazole-based UV absorbers, benzophenone-based UV absorbers, salicylate-based UV absorbers, cyanoacrylate-based UV absorbers, oxanilide-based UV absorbers, hindered amine-based UV absorbers, benzoate-based UV absorbers, etc. Can be mentioned.

The content of the conductive polymer with respect to the total mass of the conductive layer containing the conductive polymer is not particularly limited, and is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 30% by mass or less. , 15% by mass or more and 25% by mass or less is more preferable.

The thickness of the conductive layer containing the conductive polymer is preferably 0.1 μm or more and 10 μm or less, more preferably 0.5 μm or more and 8 μm or less, and further preferably 0.8 μm or more and 5 μm or less. When it is at least the lower limit of the above range, the adhesion between the metal layers can be strengthened and the electrical connectivity between the metal layers can be improved. If it is equal to or less than the upper limit of the above range, the flexibility of the electromagnetic wave shielding film 2 can be increased and the thickness can be reduced.

When there are a plurality of non-metal layers constituting the shield layer 20, the thickness, constituent materials, physical properties, etc. of each non-metal layer may be the same as or different from each other.

<Conductive adhesive layer>
The electromagnetic wave shield film 1 includes a conductive adhesive layer 26 laminated in contact with the surface of the shield layer 20 opposite to the second non-metal layer 24 of the third metal layer 25.
The conductive adhesive layer 26 is an essential layer in the electromagnetic wave shielding film 1, and is distinguished from the conductive adhesive layer arbitrarily provided as a non-metal layer in the shield layer 20.
The conductive adhesive layer 26 may be an anisotropic conductive adhesive layer as shown in FIG. 2 or an isotropic conductive adhesive layer as shown in FIG.

(Iteroconductive adhesive layer)
The anisotropic conductive adhesive layer has conductivity in the thickness direction, does not have conductivity in the surface direction, and has adhesiveness.
In the anisotropic conductive adhesive layer, the conductive adhesive layer can be easily thinned, the amount of conductive particles described later can be reduced, and as a result, the electromagnetic wave shielding film can be thinned, and the electromagnetic wave shielding film has high flexibility. Has the advantage of

As the anisotropic conductive adhesive layer, a thermosetting conductive adhesive layer is preferable because it can exhibit heat resistance after curing. The thermosetting anisotropic conductive adhesive layer may be in an uncured state or in a B-staged state.
The thermosetting anisotropic conductive adhesive layer contains, for example, a thermosetting adhesive 26a and conductive particles 26b, as shown in FIG. The thermosetting anisotropic conductive adhesive layer 26 may contain a flame retardant, if necessary.

Examples of the thermosetting adhesive 26a include epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, ultraviolet curable acrylate resin and the like. Epoxy resin is preferable because it has excellent heat resistance. The epoxy resin may contain a rubber component (carboxy-modified nitrile rubber, acrylic rubber, etc.) for imparting flexibility, a tackifier, and the like.
The thermosetting adhesive 26a may contain a cellulose resin, microfibrils (glass fiber, etc.) in order to increase the strength of the anisotropic conductive adhesive layer 26 and improve the punching characteristics. The thermosetting adhesive 26a may contain other components (hardener and the like), if necessary, as long as the effects of the present invention are not impaired.

Examples of the conductive particles 26b include metal (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.) particles, graphite powder, calcined carbon particles, plated calcined carbon particles, and the like. As the conductive particles 26b, the anisotropic conductive adhesive layer 26 has a more appropriate hardness, and the pressure loss in the anisotropic conductive adhesive layer 26 at the time of hot pressing can be further reduced. , Metal particles are preferable, and copper particles are more preferable.

The 10% compressive strength of the conductive particles 26b is preferably 30 MPa or more and 200 MPa or less, more preferably 50 MPa or more and 150 MPa or less, and further preferably 70 MPa or more and 100 MPa or less. When the 10% compressive strength of the conductive particles 26b is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 26 is an insulating film without significantly losing the pressure applied to the metal thin film layer during hot pressing. It is securely electrically connected by the printed circuit of the printed wiring board through the through hole of. When the 10% compressive strength of the conductive particles 26b is not more than the upper limit of the above range, the contact with the metal thin film layer is improved and the electrical connection is ensured.

The average particle diameter of the conductive particles 26b in the anisotropic conductive adhesive layer 26 is preferably 0.2 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 8 μm or less. When the average particle diameter of the conductive particles 26b is at least the lower limit of the above range, the thickness of the anisotropic conductive adhesive layer 26 can be secured, and sufficient adhesive strength can be obtained. When the average particle diameter of the conductive particles 26b is equal to or less than the upper limit of the above range, the fluidity of the anisotropic conductive adhesive layer 26 can be ensured, and the anisotropic conductive adhesive layer 26 is formed of the insulating film as described later. When pushed into the through hole, the inside of the through hole of the insulating film can be sufficiently filled with the conductive adhesive.

The proportion of the conductive particles 26b in the anisotropic conductive adhesive layer 26 is preferably 1% by volume or more and 30% by volume or less, preferably 2% by volume or more and 15% by volume, out of 100% by volume of the anisotropic conductive adhesive layer 26. The following is more preferable. When the ratio of the conductive particles 26b is equal to or higher than the lower limit of the above range, the conductivity of the anisotropic conductive adhesive layer 26 becomes good. When the ratio of the conductive particles 26b is not more than the upper limit of the above range, the adhesiveness and fluidity (following the shape of the through hole of the insulating film) of the anisotropic conductive adhesive layer 26 are improved. In addition, the flexibility of the electromagnetic wave shield film 1 is improved.

The storage elastic modulus of the anisotropic conductive adhesive layer 26 at 180 ° C. is preferably 1 × 10 ³ Pa or more and 5 × 10 ⁷ Pa or less, and more preferably 5 × 10 ³ Pa or more and 1 × 10 ⁷ Pa or less. When the storage elastic modulus of the anisotropic conductive adhesive layer 26 at 180 ° C. is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 26 has a more appropriate hardness, and is subjected to hot pressing. The pressure loss in the anisotropic conductive adhesive layer 26 can be reduced. As a result, the anisotropic conductive adhesive layer 26 and the printed circuit of the printed wiring board are sufficiently adhered, and the anisotropic conductive adhesive layer 26 is surely passed through the through hole of the insulating film by the printed circuit of the printed wiring board. Is electrically connected to. When the storage elastic modulus of the anisotropic conductive adhesive layer 26 at 180 ° C. is not more than the upper limit of the above range, the flexibility of the electromagnetic wave shielding film 1 is improved. As a result, the electromagnetic wave shielding film 1 easily sinks into the through hole of the insulating film, and the anisotropic conductive adhesive layer 26 is reliably electrically connected through the through hole of the insulating film by the printed circuit of the printed wiring board. Will be done.

The surface resistance of the anisotropic conductive adhesive layer 26 is 1 × 10 ⁴ Ω / sq. 1 × 10 ¹⁶ Ω / sq. The following is preferable, 1 × 10 ⁶ Ω / sq. 1 × 10 ¹⁴ Ω / sq. The following is more preferable. When the surface resistance of the anisotropic conductive adhesive layer 26 is equal to or higher than the lower limit of the above range, the content of the conductive particles 26b can be suppressed to a low level. If the surface resistance of the anisotropic conductive adhesive layer 26 is equal to or less than the upper limit of the above range, there is no problem in anisotropy in practical use.

The thickness of the anisotropic conductive adhesive layer 26 is preferably 0.2 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 8 μm or less. When the thickness of the anisotropic conductive adhesive layer 26 is equal to or greater than the lower limit of the above range, the fluidity of the anisotropic conductive adhesive layer 26 (following the shape of the through hole of the insulating film) can be ensured. The inside of the through hole of the insulating film can be sufficiently filled with the conductive adhesive. When the thickness of the anisotropic conductive adhesive layer 26 is not more than the upper limit of the above range, the electromagnetic wave shielding film can be thinned. In addition, the flexibility of the electromagnetic wave shielding film is improved.

(Isotropic conductive adhesive layer)
The isotropic conductive adhesive layer has conductivity in the thickness direction and the surface direction, and has adhesiveness.
The isotropic conductive adhesive layer has an advantage that the electromagnetic wave shielding property of the electromagnetic wave shielding film can be improved.

As the isotropic conductive adhesive layer, a thermosetting conductive adhesive layer is preferable because it can exhibit heat resistance after curing. The thermosetting isotropic conductive adhesive layer may be in an uncured state or in a B-staged state.
The thermosetting isotropic conductive adhesive layer contains, for example, a thermosetting adhesive 26a and conductive particles 26c, as shown in FIG. The thermosetting isotropic conductive adhesive layer 26 may contain a flame retardant, if necessary.
The component of the thermosetting adhesive 26a and the material of the conductive particles 26c contained in the isotropic conductive adhesive layer 26 are the component of the thermosetting adhesive 26a contained in the anisotropic conductive adhesive layer 26 and the conductive material. It is the same as the material of the particle 26c.

The average particle diameter of the conductive particles 26c in the isotropic conductive adhesive layer 26 is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.2 μm or more and 1 μm or less. When the average particle diameter of the conductive particles 26c is equal to or greater than the lower limit of the above range, the number of contact points of the conductive particles 26c increases, and the conductivity in the three-dimensional direction can be stably increased. When the average particle diameter of the conductive particles 26c is equal to or less than the upper limit of the above range, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through holes of the insulating film) can be ensured, and the insulating film The inside of the through hole can be sufficiently filled with the conductive adhesive.

The proportion of the conductive particles 26c in the isotropic conductive adhesive layer 26 is preferably 50% by volume or more and 80% by volume or less, preferably 60% by volume or more and 70% by volume, out of 100% by volume of the isotropic conductive adhesive layer 26. The following is more preferable. When the ratio of the conductive particles 26c is equal to or higher than the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 becomes good. When the proportion of the conductive particles 26c is not more than the upper limit of the above range, the adhesiveness and fluidity (following the shape of the through hole of the insulating film) of the isotropic conductive adhesive layer 26 are improved. In addition, the flexibility of the electromagnetic wave shield film 1 is improved.

The storage elastic modulus of the isotropic conductive adhesive layer 26 at 180 ° C. is preferably 1 × 10 ³ Pa or more and 5 × 10 ⁷ Pa or less, and more preferably 5 × 10 ³ Pa or more and 1 × 10 ⁷ Pa or less. The reason why the above range is preferable is the same as that of the anisotropic conductive adhesive layer 26.

The surface resistance of the isotropic conductive adhesive layer 26 is 0.05 Ω / sq. 2.0Ω / sq. The following is preferable, and 0.1 Ω / sq. 1.0Ω / sq. The following is more preferable. When the surface resistance of the isotropic conductive adhesive layer 26 is equal to or higher than the lower limit of the above range, the content of the conductive particles 26c is suppressed to a low level, the viscosity of the conductive adhesive does not become too high, and the coatability is further improved. It will be good. Further, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through hole of the insulating film) can be further ensured. When the surface resistance of the isotropic conductive adhesive layer 26 is equal to or less than the upper limit of the above range, the entire surface of the isotropic conductive adhesive layer 26 has uniform conductivity.

The thickness of the isotropic conductive adhesive layer 26 is preferably 0.2 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 8 μm or less. When the thickness of the isotropic conductive adhesive layer 26 is equal to or greater than the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 becomes good, and the isotropic conductive adhesive layer 26 can sufficiently function as an electromagnetic wave shielding layer. In addition, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through hole of the insulating film) can be ensured, and the inside of the through hole of the insulating film can be sufficiently filled with the conductive adhesive, and the resistance Foldability can be ensured, and the isotropic conductive adhesive layer 26 does not tear even when repeatedly bent. When the thickness of the isotropic conductive adhesive layer 26 is not more than the upper limit of the above range, the electromagnetic wave shielding film can be thinned. In addition, the flexibility of the electromagnetic wave shielding film is improved.

<Carrier film>
In the electromagnetic wave shield film 1, a carrier film may be provided on the surface of the insulating resin layer 10 opposite to the shield layer 20 (not shown).
The carrier film is a support that reinforces and protects the insulating resin layer 10 and the shield layer 20, and improves the handleability of the electromagnetic wave shield film 1. In particular, when a thin film, specifically a film having a thickness of 1 μm or more and 10 μm or less is used as the insulating resin layer 10, the carrier film can prevent the insulating resin layer 10 from breaking.
The carrier film is peeled off from the insulating resin layer 10 after the electromagnetic wave shielding film 1 is attached to a printed wiring board or the like.

The carrier film used in the present embodiment has a carrier film main body and an adhesive layer provided on the surface of the carrier film main body on the insulating resin layer 10 side.

As the resin material of the carrier film body, polyethylene terephthalate (hereinafter, also referred to as "PET"), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, ethylene- Examples thereof include vinyl acetate copolymers, polyvinyl chloride, polyvinylidene chloride, synthetic rubbers, and liquid crystal polymers. As the resin material, PET is preferable from the viewpoint of heat resistance (dimensional stability) and price when manufacturing the electromagnetic wave shielding film 1.

The carrier film body may contain one or both of a colorant (pigment, dye, etc.) and a filler.
As one or both of the colorant and the filler, those having a color different from that of the insulating resin layer 10 are preferable because they can be clearly distinguished from the insulating resin layer 10 and it is easy to notice the unpeeled residue of the carrier film after hot pressing. , White pigments, fillers, or combinations of white pigments with other pigments or fillers are more preferred.

The storage elastic modulus of the carrier film body at 180 ° C. is preferably 8 × 10 ⁷ Pa or more and 5 × 10 ⁹ Pa, and more preferably 1 × 10 ⁸ Pa or more and 8 × 10 ⁸ Pa. When the storage elastic modulus of the carrier film body at 180 ° C. is equal to or higher than the lower limit of the above range, the carrier film has an appropriate hardness, and the pressure loss in the carrier film during hot pressing can be reduced. When the storage elastic modulus of the carrier film body at 180 ° C. is not more than the upper limit of the above range, the flexibility of the carrier film is good.

The thickness of the carrier film body is preferably 3 μm or more and 75 μm or less, and more preferably 12 μm or more and 50 μm or less. When the thickness of the carrier film body is at least the lower limit of the above range, the handleability of the electromagnetic wave shield film 1 is good. When the thickness of the carrier film body is not more than the upper limit of the above range, heat is easily transferred to the conductive adhesive layer when the electromagnetic wave shield film 1 is hot-pressed on the printed wiring board 50.

The pressure-sensitive adhesive layer is formed, for example, by applying a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive to the surface of a carrier film body. By having the adhesive layer on the carrier film, it is possible to prevent the carrier film from being unintentionally peeled from the insulating resin layer 10 when the electromagnetic wave shielding film 1 is handled. As a result, the carrier film can sufficiently serve as a protective film.

The pressure-sensitive adhesive imparts an appropriate degree of adhesiveness to the pressure-sensitive adhesive layer so that the carrier film does not easily peel off from the insulating resin layer 10 before hot pressing and the carrier film can be peeled off from the insulating resin layer 10 after heat-pressing. It is preferable that the film is used.
Examples of the adhesive include acrylic adhesives, urethane adhesives, rubber adhesives and the like.
The glass transition temperature of the pressure-sensitive adhesive is preferably −100 ° C. or higher and 60 ° C. or lower, and more preferably −60 ° C. or higher and 40 ° C. or lower.

The thickness of the carrier film is preferably 25 μm or more and 125 μm or less, and more preferably 38 μm or more and 100 μm or less. When the thickness of the carrier film is at least the lower limit of the above range, the handleability of the electromagnetic wave shielding film 1 is good. When the thickness of the carrier film is not more than the upper limit of the above range, heat is easily transferred to the conductive adhesive layer 26 when the electromagnetic wave shield film 1 is hot-pressed on the printed wiring board.

(Protective film)
The protective film 40 protects the conductive adhesive layer 26 and improves the handleability of the electromagnetic wave shielding film 1. The protective film 40 is peeled off from the conductive adhesive layer 26 before the electromagnetic wave shielding film 1 is attached to the printed wiring board or the like.

The protective film 40 has, for example, a protective film main body 42 and an adhesive layer 41 provided on the surface of the protective film main body 42 on the conductive adhesive layer 26 side.

Examples of the resin material of the protective film main body 42 include the same resin materials as those of the carrier film main body.
The protective film body 42 may contain a colorant, a filler and the like.
The thickness of the protective film body 42 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and further preferably 25 μm or more and 100 μm or less.

The pressure-sensitive adhesive layer 41 is formed by treating the surface of the protective film body 42 with a pressure-sensitive adhesive. Since the protective film 40 has the pressure-sensitive adhesive layer 41, when the protective film 40 is peeled from the conductive adhesive layer 26, the protective film 40 is easily peeled off and the conductive adhesive layer 26 is less likely to break.
As the pressure-sensitive adhesive, a known pressure-sensitive adhesive may be used.

The thickness of the pressure-sensitive adhesive layer 41 is preferably 0.05 μm or more and 30 μm or less, and more preferably 0.1 μm or more and 20 μm or less. When the thickness of the pressure-sensitive adhesive layer 41 is within the above range, the protective film 40 can be more easily peeled off.

<Thickness of electromagnetic wave shield film>
The thickness of the electromagnetic wave shielding film 1 (excluding the carrier film and the protective film 40) is preferably 3 μm or more and 50 μm or less, and more preferably 5 μm or more and 30 μm or less.
When the thickness is at least the lower limit of the above range, it is unlikely to break when the carrier film or the protective film 40 is peeled off. When the thickness is not more than the upper limit of the above range, the circuit board to which the electromagnetic wave shielding film is attached can be thinned.

(Action effect)
In the electromagnetic wave shield film 1 described above, since the shield layer 20 has a plurality of metal layers, the number of electromagnetic wave reflection interfaces is larger than that in the case of providing one metal layer, and the thickness of each metal layer is 1 μm. Despite its thinness of the following, it has excellent electromagnetic wave shielding properties.
Further, since the thickness of each metal layer of the shield layer 20 is 1 μm or less, the gas permeability of each metal layer is good, and the gas generated from the conductive adhesive layer 26 or the like by heating such as solder reflow treatment. Is more likely to permeate, so gas is less likely to stay between the metal layers, and delamination and swelling can be prevented.
As described above, the electromagnetic wave shielding film of the present invention is excellent in both electromagnetic wave shielding property and solder heat resistance.

(Other embodiments)
The electromagnetic wave shielding film of the present invention is not limited to the illustrated examples.
In order to protect the insulating resin layer 10 of the electromagnetic wave shielding film, a carrier film may be provided on the surface of the insulating resin layer 10. The carrier film does not have to have an adhesive layer when the carrier film body is a self-adhesive film. The carrier film may have a release agent layer instead of the pressure-sensitive adhesive layer.
When it is less necessary to protect the surface of the conductive adhesive layer 26 of the electromagnetic wave shielding film, the protective film 40 may be omitted. The protective film 40 does not have to have the pressure-sensitive adhesive layer 41 when the protective film main body 42 alone has sufficient adhesiveness.

<Manufacturing method of electromagnetic wave shield film>
The electromagnetic wave shielding film of the present invention can be produced by applying a known method for forming a laminated film. From the viewpoint of easily producing a uniform electromagnetic wave shielding film with a good yield, for example, the following suitable production method can be mentioned.

Hereinafter, an example of a method for manufacturing the electromagnetic wave shielding film 1 of FIG. 1 will be shown.
A commercially available metal thin film can be applied as the first metal layer 21. For example, a metal vapor deposition film deposited on one surface of a base film can be mentioned. The resin composition forming the insulating resin layer 10 is applied to the surface of the metal vapor deposition film opposite to the base film, dried and cured to obtain the insulating resin layer 10 / first metal layer 21 / base material. A laminated body A in which the films are laminated in this order is obtained. If necessary, a carrier film is attached to the surface of the insulating resin layer 10 opposite to the first metal layer 21, and then the base film is peeled off to form the carrier film / insulating resin layer 10 / first metal layer 21. A laminated body B laminated in order is obtained.
The first non-metal layer 22, the second metal layer 23, the second non-metal layer 24, and the third metal layer 25 are sequentially laminated on the surface of the first metal layer 21 of the laminate B opposite to the insulating resin layer 10. As a result, the laminated body C in which the carrier film / insulating resin layer 10 / first metal layer 21 / first non-metal layer 22 / second metal layer 23 / second non-metal layer 24 / third metal layer 25 is laminated in this order is formed. can get. Each metal layer can be formed by a known method for forming a metal thin film, and the film thickness can be easily adjusted, so that the physical vapor deposition method is suitable. Since each non-metal layer is basically a layer containing a resin, it can be formed by a known method for forming a resin layer, for example, by applying a resin composition, drying and curing. By increasing or decreasing the number of metal layers and non-metal layers alternately laminated in the laminated body C, the shield layer 20 having a desired number of layers can be formed.
A target electromagnetic wave shielding film 1 is obtained by forming a conductive adhesive layer 26 on the surface of the third metal layer 25 of the laminate C opposite to the second non-metal layer 24 and further attaching the protective film 40. Be done. The anisotropic conductive adhesive layer or the isotropic conductive adhesive layer constituting the conductive adhesive layer 26 can be formed by a known method, for example, with reference to the above-mentioned Patent Document 1 and the like.

In addition to the method for manufacturing the electromagnetic wave shield film 1 described above, the following manufacturing method can also be mentioned.
First, the insulating resin layer 10 is formed on the surface of the pressure-sensitive adhesive layer of the carrier film, and the first metal layer 21 / first non-metal layer 22 / second is formed on the surface of the insulating resin layer 10 opposite to the carrier film. A first laminated body is obtained in which the metal layer 23 / the second non-metal layer 24 / the third metal layer 25 are laminated in this order. Next, the conductive adhesive layer 26 is laminated on the surface of the pressure-sensitive adhesive layer 41 of the protective film 40 to obtain a second laminated body. Subsequently, the electromagnetic wave shielding film is formed by contacting and attaching the conductive adhesive layer 26 of the second laminate to the surface of the third metal layer 25 of the first laminate opposite to the second non-metal layer 24. 1 is obtained.

In addition to the method for manufacturing the electromagnetic wave shield film 1 described above, the following manufacturing method can also be mentioned.
The insulating resin layer 10 is formed on the surface of the carrier film, and the first metal layer 21 / first non-metal layer 22 / second metal layer 23 / second is formed on the surface of the insulating resin layer 10 on the side opposite to the carrier film. The shield layer 20 is laminated in the order of the non-metal layer 24 / the third metal layer 25, and the conductive adhesive layer 26 is further laminated so as to be in contact with the third metal layer 25, and then the protective film 40 is attached to obtain an electromagnetic wave. Shield film 1 is obtained.

(Action effect)
In the method for producing an electromagnetic wave shielding film described above, an electromagnetic wave shielding film having a plurality of thin metal layers can be easily produced.

<Circuit board>
In the second aspect of the present invention, a circuit board main body in which a circuit is provided on at least one surface of the substrate, an insulating film adjacent to the one surface, and the insulating film adjacent to the circuit board main body on the opposite side. It is a circuit board provided with the electromagnetic wave shielding film of the first aspect. In the circuit board, a conductive adhesive layer provided on the side of the shield layer of the electromagnetic wave shielding film opposite to the insulating resin layer is adhered to the insulating film.

FIG. 4 is a cross-sectional view showing an embodiment of the circuit board of this embodiment.
The circuit board 4 includes a flexible printed wiring board 50, which is an example of a circuit board main body, and an electromagnetic wave shielding film 3.
The flexible printed wiring board 50 is provided with a printed circuit 54 on at least one side of the base film 52.
The insulating film 60 is provided on the surface of the flexible printed wiring board 50 on the side where the printed circuit 54 is provided.
The conductive adhesive layer 26 of the electromagnetic wave shielding film 3 is adhered to and cured on the surface of the insulating film 60. Further, the conductive adhesive layer 26 is electrically connected to the print circuit 54 through a through hole (not shown) formed in the insulating film 60.
In the printed wiring board 4 with the electromagnetic wave shielding film, the carrier film and the release film are peeled off from the electromagnetic wave shielding film 3.

In the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) excluding the portion having the through hole, the shield layer 20 of the electromagnetic wave shielding film 3 is separated via the insulating film 60 and the conductive adhesive layer 26. And are placed facing each other.
The separation distance between the printed circuit 54 and the shield layer 20 excluding the portion having the through hole is substantially equal to the sum of the thickness of the insulating film 60 and the thickness of the conductive adhesive layer 26. The separation distance is preferably 30 μm or more and 200 μm or less, and more preferably 60 μm or more and 200 μm or less. If the separation distance is smaller than 30 μm, the impedance of the signal circuit becomes low. Therefore, in order to have a characteristic impedance such as 100Ω, the line width of the signal circuit must be reduced, and the variation in the line width is the variation in the characteristic impedance. Therefore, the reflected resonance noise due to the impedance mismatch can easily get on the electric signal. If the separation distance is larger than 200 μm, the printed wiring board 2 with the electromagnetic wave shielding film becomes thick, and the flexibility becomes insufficient.

(Circuit board body)
The flexible printed wiring board 50, which is an example of the main body of the circuit board, is a printed circuit 54 obtained by processing a copper foil of a copper-clad laminate into a desired pattern by a known etching method.
As the copper-clad laminate, a copper foil is attached to one side or both sides of the base film 52 via an adhesive layer (not shown); a resin solution or the like forming the base film 52 is cast on the surface of the copper foil. Things etc. can be mentioned.
Examples of the material of the adhesive layer include epoxy resin, polyester, polyimide, polyamide-imide, polyamide, phenol resin, urethane resin, acrylic resin, melamine resin and the like.
The thickness of the adhesive layer is preferably 0.5 μm or more and 30 μm or less.

As the base film 52, a film having heat resistance is preferable, a polyimide film, a polyetherimide film, a polyphenylene sulfide film, and a liquid crystal polymer film are more preferable, and a polyimide film is further preferable.
The surface resistance of the base film 52 is 1 × 10 ⁶ Ω / sq. From the viewpoint of electrical insulation. The above is preferable. The surface resistance of the base film 52 is 1 × 10 ¹⁹ Ω / sq. From a practical point of view. The following is preferable.
The thickness of the base film 52 is preferably 5 μm or more and 200 μm or less, more preferably 6 μm or more and 50 μm or less, and more preferably 10 μm or more and 25 μm or less from the viewpoint of flexibility.

Examples of the copper foil constituting the printed circuit 54 include rolled copper foil and electrolytic copper foil, and rolled copper foil is preferable from the viewpoint of flexibility. The print circuit 54 is used as a signal circuit, a ground circuit, a ground layer, and the like.
The thickness of the copper foil is preferably 1 μm or more and 50 μm or less, and more preferably 18 μm or more and 35 μm or less.
The end (terminal) of the print circuit 54 in the length direction is not covered with the insulating film 60 or the electromagnetic wave shielding film 1 and is exposed because of solder connection, connector connection, component mounting, and the like.

(Insulation film)
The insulating film 60 (coverlay film) is formed by forming an adhesive layer (not shown) on one side of an insulating film main body (not shown) by applying an adhesive, attaching an adhesive sheet, or the like.
The surface resistance of the insulating film body is 1 × 10 ⁶ Ω / sq. From the viewpoint of electrical insulation. The above is preferable. The surface resistance of the insulating film body is 1 × 10 ¹⁹ Ω / sq. From a practical point of view. The following is preferable.
As the insulating film main body, a film having heat resistance is preferable, a polyimide film, a polyetherimide film, a polyphenylene sulfide film, and a liquid crystal polymer film are more preferable, and a polyimide film is further preferable.
The thickness of the insulating film body is preferably 1 μm or more and 100 μm or less, and more preferably 3 μm or more and 25 μm or less from the viewpoint of flexibility.
Examples of the material of the adhesive layer include epoxy resin, polyester, polyimide, polyamide-imide, polyamide, phenol resin, urethane resin, acrylic resin, melamine resin, polystyrene, polyolefin and the like. The epoxy resin may contain a rubber component (carboxy-modified nitrile rubber, etc.) for imparting flexibility.
The thickness of the adhesive layer is preferably 1 μm or more and 100 μm or less, and more preferably 1.5 μm or more and 60 μm or less.

The shape of the opening of the through hole formed in the insulating film 60 is not particularly limited. Examples of the shape of the opening of the through hole include a circle, an ellipse, and a quadrangle.

(Manufacturing method of printed wiring board with electromagnetic wave shield film)
The printed wiring board 4 with an electromagnetic wave shielding film can be manufactured, for example, by a method having the following steps (g) to (j) (see FIG. 5).
Step (g): An insulating film 60 having a through hole 62 formed at a position corresponding to the printed circuit 54 is provided on the surface of the flexible printed wiring board 50 on the side where the printed circuit 54 is provided, and the printed wiring board with the insulating film is provided. The process of obtaining.
Step (h): After the step (g), the printed wiring board with the insulating film and the electromagnetic wave shielding film 2 from which the protective film 40 has been peeled off are brought into contact with the surface of the insulating film 60 so that the conductive adhesive layer 26 comes into contact with the surface. The process of stacking and crimping these.
Step (i): A step of peeling the carrier film 30 when the carrier film 30 is no longer needed after the step (h).
Step (j): A step of main curing the conductive adhesive layer 26 between the steps (g) and the step (h), or after the step (i), if necessary.
Hereinafter, each step will be described in detail with reference to FIG. In FIG. 5, the second non-metal layer 24 and the third metal layer 25 are not shown.

Step (g):
The step (g) is a step of laminating the insulating film 60 on the flexible printed wiring board 50 to obtain a printed wiring board with an insulating film.
Specifically, first, an insulating film 60 having a through hole 62 formed at a position corresponding to the printed circuit 54 is superposed on the flexible printed wiring board 50. Next, an adhesive layer (not shown) of the insulating film 60 is adhered to the surface of the flexible printed wiring board 50, and the adhesive layer is cured to obtain a printed wiring board with an insulating film. The adhesive layer of the insulating film 60 may be temporarily adhered to the surface of the flexible printed wiring board 50, and the adhesive layer may be mainly cured in the step (j).
Adhesion and curing of the adhesive layer are performed, for example, by hot pressing with a press machine (not shown) or the like.

Step (h):
The step (h) is a step of crimping the electromagnetic wave shield film 2 onto the printed wiring board with an insulating film.
Specifically, the electromagnetic wave shield film 2 from which the protective film 40 has been peeled off is placed on the printed wiring board with an insulating film and crimped by a hot press or the like. As a result, the conductive adhesive layer 26 is adhered to the surface of the insulating film 60, and the conductive adhesive layer 26 is pushed into the through hole 62 to fill the through hole 62 and electrically connect to the print circuit 54. .. As a result, a printed wiring board with an electromagnetic wave shielding film is obtained.

Adhesion and curing of the conductive adhesive layer 26 are performed, for example, by hot pressing with a press machine (not shown) or the like.
The heat pressing time is preferably 20 seconds or more and 60 minutes or less, and more preferably 30 seconds or more and 30 minutes or less. When the heat pressing time is equal to or greater than the lower limit of the above range, the conductive adhesive layer 26 can be easily adhered to the surface of the insulating film 60. When the heat pressing time is equal to or less than the upper limit of the above range, the manufacturing time of the printed wiring board with the electromagnetic wave shielding film can be shortened.

The temperature of the hot press (the temperature of the hot plate of the press machine) is preferably 140 ° C. or higher and 190 ° C. or lower, and more preferably 150 ° C. or higher and 175 ° C. or lower. When the temperature of the hot press is equal to or higher than the lower limit of the above range, the conductive adhesive layer 26 can be easily adhered to the surface of the insulating film 60. Moreover, the time of heat pressing can be shortened. When the temperature of the hot press is not more than the upper limit of the above range, deterioration of the electromagnetic wave shielding film 2, the flexible printed wiring board 50, and the like can be easily suppressed.

The pressure of the hot press is preferably 0.5 MPa or more and 20 MPa or less, and more preferably 1 MPa or more and 16 MPa or less. When the pressure of the hot press is equal to or higher than the lower limit of the above range, the conductive adhesive layer 26 is easily adhered to the surface of the insulating film 60. Moreover, the time of heat pressing can be shortened. When the pressure of the hot press is equal to or less than the upper limit of the above range, damage to the electromagnetic wave shielding film 2, the flexible printed wiring board 50, etc. can be suppressed.

Step (i):
The step (i) is a step of peeling off the carrier film 30.
Specifically, when the carrier film is no longer needed, the carrier film 30 is peeled off from the insulating resin layer 10.

Step (j):
The step (j) is a step of main curing the conductive adhesive layer 26.
When the heat pressing time in the step (h) is as short as 20 seconds or more and 10 minutes or less, the conductive adhesive layer 26 of the conductive adhesive layer 26 is used between the steps (h) and the step (i) or after the step (i). It is preferable to perform the main curing. When the shield layer 20 contains a thermosetting resin, the thermosetting resin constituting the shield layer 20 can be main-cured together with the main curing of the conductive adhesive layer 26.
The main curing of the conductive adhesive layer 26 is performed using, for example, a heating device such as an oven.
The heating time is 15 minutes or more and 120 minutes or less, more preferably 30 minutes or more and 60 minutes or less.
When the heating time is at least the lower limit of the above range, the conductive adhesive layer 26 can be sufficiently cured. When the heating time is not more than the upper limit of the above range, the manufacturing time of the printed wiring board with the electromagnetic wave shielding film can be shortened.
The heating temperature (atmospheric temperature in the oven) is preferably 120 ° C. or higher and 180 ° C. or lower, and more preferably 120 ° C. or higher and 150 ° C. or lower. When the heating temperature is equal to or higher than the lower limit of the above range, the heating time can be shortened. When the heating temperature is not more than the upper limit of the above range, deterioration of the electromagnetic wave shielding film 2, the flexible printed wiring board 50, and the like can be suppressed.

(Action effect)
In the printed wiring board with the electromagnetic wave shield film described above, since the electromagnetic wave shield film 2 has the shield layer 20, the electromagnetic wave shield film 2 is excellent in electromagnetic wave shielding property and solder heat resistance.

(Other embodiments)
The circuit board of this embodiment is opposite to the circuit board main body in which the circuit is provided on at least one side of the board, the insulating film adjacent to the surface of the circuit board main body on which the circuit is provided, and the circuit board main body of the insulating film. It is not limited to the embodiment of the illustrated example as long as it has the electromagnetic wave shielding film of the first aspect of the present invention which is adjacent to the side and the conductive adhesive layer is in contact with the insulating film.
For example, the illustrated flexible printed wiring board 50 may have a ground layer on the back surface side. Further, the flexible printed wiring board 50 may have printed circuits 54 on both sides, and an insulating film 60 and an electromagnetic wave shielding film may be attached to both sides.
Further, an inflexible rigid printed circuit board may be used instead of the flexible printed wiring board 50.

<Material>
Hereinafter, description will be made using the reference numerals of the electromagnetic wave shielding films illustrated in FIGS.
As a carrier film, a polyethylene terephthalate film (manufactured by Toyobo, CN100, thickness 50 μm) was prepared.
As a coating material for forming the insulating resin layer 10, a solution of a compound having a (meth) acryloyl group (manufactured by Asia Industries, Ltd., EXCELATE RUA-054, acrylic polymer acrylate, solid content: 73% by mass, solvent: butyl acetate, methyl isobutyl ketone ), 1.71 g of photoradical polymerization initiator (BASF, Irgacure (registered trademark) 184), black dye (Orient Chemical Industry, ORIPACS (registered trademark) B-20, azo compound chromium complex). Was prepared.
As a coating material for forming the "insulating layer" constituting the non-metal layers 22 and 24, 100 parts by mass of a thermosetting adhesive (epoxy resin (DIC, EXA-4816)) and a curing agent (Ajinomoto Fine-Techno, Inc., A coating material prepared by mixing 20 parts by mass of PN-23) with a latent curable epoxy resin) and 200 parts by mass of a solvent (methyl ethyl ketone) was prepared.
As a paint for forming the "conductive adhesive layer" constituting the non-metal layers 22 and 24, 100 parts by mass of a thermosetting adhesive (epoxy resin (made by DIC, EXA-4816)) and a curing agent (Ajinomoto Fine Techno) Potentially curable epoxy resin made by mixing 20 parts by mass of PN-23) manufactured by the company, 40 parts by mass of conductive particles (copper particles with an average particle diameter of 5 μm), and 200 parts by mass of solvent (methyl ethyl ketone). A paint mixed with the particles was prepared.
As a paint for forming the conductive adhesive layer 26, 100 parts by mass of a thermosetting adhesive (epoxy resin (made by DIC, EXA-4816) and 20 parts by mass of a curing agent (manufactured by Ajinomoto Fine Techno, PN-23)). A coating material was prepared in which 40 parts by mass of conductive particles (copper particles having an average particle diameter of 5 μm) and 200 parts by mass of a solvent (methyl ethyl ketone) were mixed with a latent curable epoxy resin obtained by mixing the parts. ..
As the protective film 40, an adhesive film (manufactured by Panac, Panaprotect (registered trademark) ET, adhesive strength: 0.08 N / cm, PET film thickness: 50 μm) was prepared.
As a circuit board, a copper foil having a thickness of 18 μm is laminated on a polyimide film having a thickness of 50 μm via an epoxy adhesive having a thickness of 15 μm, and a polyimide film having a thickness of 25 μm is further laminated through an epoxy adhesive having a thickness of 15 μm. A circuit board (manufactured by Shin-Etsu Chemical Industry Co., Ltd.) on which (insulating film) was formed was prepared.

[Example 1]
The coating liquid for forming the insulating resin layer 10 was applied to the surface of the carrier film using a # 4 bar coater. The coating film was dried at 100 ° C. for 1 minute and then irradiated with ultraviolet rays of 400 mJ to provide an insulating resin layer 10 (thickness: 10 μm, surface resistance: 1.0 × 10 ¹² Ω / □ or more).
Next, copper was physically vapor-deposited on the surface of the insulating resin layer 10 by an electron beam vapor deposition method to form a copper-deposited film (thickness: 0.1 μm) which is the first metal layer 21.
Next, the coating material for forming the "insulating layer" is applied to the surface of the copper vapor deposition film opposite to the insulating resin layer 10 using a die coater, and the solvent is volatilized to form a B stage. An insulating layer (thickness: 2 μm) which is a non-metal layer 22 was formed.
Subsequently, copper is physically vapor-deposited on the surface of the insulating layer, which is the first non-metal layer 22, opposite to the copper-deposited film by an electron beam vapor deposition method, and the copper-deposited film (thickness:: 0.1 μm) was formed.
Finally, the coating material for forming the conductive adhesive layer 26 is applied to the surface of the copper vapor deposition film, which is the second metal layer 23, opposite to the first non-metal layer 22, using a die coater to volatilize the solvent. The anisotropic conductive adhesive layer (thickness: 4.5 μm, copper particles: 18.3% by volume, surface resistance: ^10-1 Ω / sq.) Was formed by forming a B stage.
A protective film was attached to the surface of the anisotropic conductive adhesive layer to obtain an electromagnetic wave shielding film 2 as shown in FIG.

A hot press device (manufactured by Orihara Seisakusho Co., Ltd., G- Using 12), hot pressing was performed at a hot plate temperature: 170 ° C. and a pressure: 15 MPa for 120 seconds. As a result, a circuit board with an electromagnetic wave shielding film was obtained by temporarily adhering an anisotropic conductive adhesive layer to the surface of the insulating film of the circuit board.
The anisotropic conductive adhesive layer in the electromagnetic wave shielding film is finally cured by putting the insulating film with the electromagnetic wave shielding film in a high temperature incubator (manufactured by Kusumoto Kasei Co., Ltd., HT210) and heating at a temperature of 150 ° C. for 1 hour. I let you.
A circuit board with an electromagnetic wave shielding film was cut to a predetermined size to prepare a measurement sample, and the electromagnetic wave shielding property and solder heat resistance were evaluated. The results are shown in Table 1.

[Example 2]
Circuit board with electromagnetic wave shielding film in the same manner as in Example 1 except that the thickness of the insulating layer which is the first non-metal layer 22 is 5 μm and the thickness of the copper vapor deposition film which is the second metal layer 23 is 1 μm. Was prepared, and the electromagnetic wave shielding property and solder heat resistance were evaluated. The results are shown in Table 1.

[Example 3]
The coating liquid for forming the insulating resin layer 10 was applied to the surface of the carrier film using a # 4 bar coater. The coating film was dried at 100 ° C. for 1 minute and then irradiated with ultraviolet rays of 400 mJ to provide an insulating resin layer 10 (thickness: 10 μm, surface resistance: 1.0 × 10 ¹² Ω / □ or more).
Next, copper was physically vapor-deposited on the surface of the insulating resin layer 10 by an electron beam vapor deposition method to form a copper-deposited film (thickness: 0.1 μm) which is the first metal layer 21.
Next, the coating material for forming the "insulating layer" is applied to the surface of the copper vapor deposition film on the side opposite to the insulating resin layer 10 using a die coater, and the solvent is volatilized to form a B stage. An insulating layer (thickness: 2 μm) which is one non-metal layer 22 was formed.
Next, copper is physically vapor-deposited on the surface of the insulating layer, which is the first non-metal layer 22, opposite to the copper-deposited film by an electron beam vapor deposition method, and the copper-deposited film (thickness:: 0.1 μm) was formed.
Next, the coating material for forming the "insulating layer" is applied to the surface of the copper vapor deposition film, which is the second metal layer 23, opposite to the first non-metal layer 2, using a die coater to volatilize the solvent. By forming the B stage, an insulating layer (thickness: 2 μm), which is the second non-metal layer 24, was formed.
Subsequently, copper is physically vapor-deposited on the surface of the insulating layer, which is the second non-metal layer 24, opposite to the copper-deposited film by an electron beam vapor deposition method, and the copper-deposited film (thickness:: 0.1 μm) was formed.
Finally, the coating material for forming the conductive adhesive layer 26 is applied to the surface of the copper vapor deposition film, which is the third metal layer 25, opposite to the second non-metal layer 24 using a die coater to volatilize the solvent. The anisotropic conductive adhesive layer (thickness: 4.5 μm, copper particles: 18.3% by volume, surface resistance: ^10-1 Ω / sq.) Was formed by B-stage formation.
A protective film was attached to the surface of the anisotropic conductive adhesive layer to obtain an electromagnetic wave shielding film 2 as shown in FIG.
A circuit board was bonded to the obtained anisotropic conductive adhesive layer of the electromagnetic wave shield film 2 in the same manner as in Example 1, a circuit board with an electromagnetic wave shield film was prepared, and the electromagnetic wave shielding property and solder heat resistance were evaluated. .. The results are shown in Table 1.

[Example 4]
The thickness of the copper vapor deposition film of the first metal layer 21 is 0.3 μm, the thickness of the insulating layer of the first non-metal layer 22 is 1 μm, and the thickness of the copper vapor deposition film of the second metal layer 23 is 0.7 μm. A circuit board with an electromagnetic wave shielding film was produced in the same manner as in Example 1, and the electromagnetic wave shielding property and solder heat resistance were evaluated. The results are shown in Table 1.

[Example 5]
The coating liquid for forming the insulating resin layer 10 was applied to the surface of the carrier film using a # 4 bar coater. The coating film was dried at 100 ° C. for 1 minute and then irradiated with ultraviolet rays of 400 mJ to provide an insulating resin layer 10 (thickness: 10 μm, surface resistance: 1.0 × 10 ¹² Ω / □ or more).
Next, copper was physically vapor-deposited on the surface of the insulating resin layer 10 by an electron beam vapor deposition method to form a copper-deposited film (thickness: 0.1 μm) which is the first metal layer 21.
Next, the coating material for forming the "conductive adhesive layer" is applied to the surface of the copper vapor deposition film opposite to the insulating resin layer 10 using a die coater, and the solvent is volatilized to form a B stage. , An anisotropic conductive adhesive layer (thickness: 3 μm, copper particles: 18.3% by volume), which is the first non-metal layer 22, was formed.
Subsequently, copper is physically vapor-deposited on the surface of the insulating layer, which is the first non-metal layer 22, opposite to the copper-deposited film by an electron beam vapor deposition method, and the copper-deposited film (thickness:: 0.8 μm) was formed.
Finally, the coating material for forming the conductive adhesive layer 26 is applied to the surface of the copper vapor deposition film, which is the second metal layer 23, opposite to the first non-metal layer 22, using a die coater to volatilize the solvent. The anisotropic conductive adhesive layer (thickness: 4.5 μm, copper particles: 18.3% by volume, surface resistance: ^10-1 Ω / sq.) Was formed by forming a B stage.
A protective film was attached to the surface of the anisotropic conductive adhesive layer to obtain an electromagnetic wave shielding film 2 as shown in FIG.
A circuit board was bonded to the obtained anisotropic conductive adhesive layer of the electromagnetic wave shield film 2 in the same manner as in Example 1, a circuit board with an electromagnetic wave shield film was prepared, and the electromagnetic wave shielding property and solder heat resistance were evaluated. .. The results are shown in Table 1.

[Comparative Example 1]
A copper foil with a base film (manufactured by Mitsui Metal Mining Co., Ltd., copper foil thickness: 5 μm) was prepared, and a coating material for forming the conductive adhesive layer 26 was applied to the surface of the copper foil opposite to the base film. By applying with a tar and volatilizing the solvent to form a B stage, the anisotropic conductive adhesive layer (thickness: 4.5 μm, copper particles: 18.3% by volume, surface resistance: 10 ^-1 Ω / sq.) Was formed.
A protective film was attached to the surface of the anisotropic conductive adhesive layer to obtain an electromagnetic wave shielding film of Comparative Example 1.
A hot press device (Orihara Seisakusho Co., Ltd.) in which an electromagnetic wave shielding film from which the base film and the protective film have been peeled off is overlaid on the insulating film of the circuit board, and the anisotropic conductive adhesive layer is in contact with the insulating film of the circuit board. The film was hot-pressed at a hot plate temperature: 170 ° C. and a pressure of 15 MPa for 120 seconds using G-12). As a result, a circuit board with an electromagnetic wave shielding film was obtained by temporarily adhering an anisotropic conductive adhesive layer to the surface of the circuit board.
A circuit board with an electromagnetic wave shielding film is placed in a high-temperature incubator (manufactured by Kusumoto Kasei Co., Ltd., HT210) and heated at a temperature of 150 ° C. for 1 hour to cure the anisotropic conductive adhesive layer in the electromagnetic wave shielding film. I let you.
A circuit board with an electromagnetic wave shielding film was cut to a predetermined size to prepare a measurement sample, and the electromagnetic wave shielding property and solder heat resistance were evaluated. The results are shown in Table 1.

[Comparative Example 2]
A circuit board with an electromagnetic wave shielding film of Comparative Example 2 was obtained in the same manner as in Example 1 except that the first non-metal layer 22 and the second metal layer 23 were not provided.
The circuit board with the electromagnetic wave shielding film of Comparative Example 2 was cut to a predetermined size to prepare a measurement sample, and the electromagnetic wave shielding property and the solder heat resistance were evaluated. The results are shown in Table 1.

<Evaluation>
The electromagnetic wave shielding property and solder heat resistance of the circuit boards with the electromagnetic wave shielding film of each example were evaluated by the following methods.

(Electromagnetic wave shielding property)
Using the KEC method measurement system shown in FIG. 6 (KEC method shield characteristic measurement system manufactured by Technoscience Japan) and the KEC method measurement jig shown in FIG. 7, the electromagnetic wave of the measurement sample (vertical x horizontal = 10 cm x 11 cm). The shielding property was evaluated. The KEC method is a known method developed at the Kansai Electronics Industry Promotion Center.
As shown in FIG. 7, the KEC method jig 104 is divided into a transmitting jig (side provided with the transmitting antenna 107) and a receiving jig (side provided with the receiving antenna 109), and the measurement sample 108 is inserted between them. It has become. The KEC method is a method of evaluating how much the signal is attenuated on the receiving side by using the KEC method jig.
First, as shown in FIG. 6, the signal output from the signal generator 102 was input to the transmitting antenna 107 of the KEC method jig 104 through the attenuator 103. On the receiving side, the signal reaching the receiving antenna 109 was amplified by the preamplifier 105, and then the signal level was measured by the spectrum analyzer 106. The above operation was controlled by the personal computer 101.
The electromagnetic wave shielding property of the measurement sample was evaluated according to the following evaluation criteria.
⊚: The amount of radio wave attenuation at 1 GHz is 70 dB or more.
◯: The amount of radio wave attenuation at 1 GHz is 60 dB or more and less than 70 dB.
X: The amount of radio wave attenuation at 1 GHz is less than 60 dB.

(Solder heat resistance)
According to JIS C 6481, each measurement sample of 25 mm was humidity-controlled for 24 hours in an atmosphere of 22 ° C and 90% RH, and then floated on a 260 ° C solder bath for 30 seconds with the electromagnetic wave shield film prepared in each example. In the circuit board, the occurrence of peeling and swelling between each layer was evaluated according to the following criteria.
〇: No peeling or swelling occurs.
X: Peeling or swelling occurred.

<Discussion of evaluation results>
Since the electromagnetic wave shield films of Examples 1 to 5 have a plurality of metal layers, the electromagnetic wave reflection interfaces are larger than those of the case where one metal layer is provided, and the thickness of each metal layer is thin. , Excellent electromagnetic wave shielding property. Further, since the thickness of each metal layer is 1 μm or less, the gas generated from the conductive adhesive layer does not stay between the metal layers and swelling is prevented, so that the solder heat resistance is also excellent. ..
Compared with Example 1, Examples 2 to 5 show better electromagnetic wave shielding properties than Example 1 because the total thickness (total thickness) of each metal layer is thicker.
Since the electromagnetic wave shielding film of Comparative Example 1 is much thicker than that of Examples 1 to 5, it exhibits excellent electromagnetic wave shielding property, but since the solder heat resistance test result is poor, it is electron after being attached to the circuit board. It is clear that the solder reflow treatment at the time of mounting the component deteriorates and the adhesiveness to the insulating film is impaired.
The electromagnetic wave shielding film of Comparative Example 2 is inferior in electromagnetic wave shielding property because the total thickness of the metal layer is thinner and the reflection interface of electromagnetic waves is smaller than that of Examples 1 to 5.

From the above, in the electromagnetic wave shield film according to the present invention having a shield layer having a plurality of metal layers, the conventional electromagnetic wave shield film having one metal layer cannot be compatible with the electromagnetic wave shielding property and solder. It is clear that it is excellent in both heat resistance.

1 Electromagnetic wave shield film 2 Electromagnetic wave shield film 3 Electromagnetic wave shield film 4 Circuit board 10 Insulation resin layer 20 Shield layer 21, 23, 25 Metal layer 22, 24 Non-metal layer 26 Conductive adhesive layer 40 Protective film 41 Adhesive layer 42 Protection Film body 50 Flexible printed wiring board 52 Base film 54 Printed circuit 60 Insulation film 62 Through hole 100 KEC method measurement system 101 PC 102 Signal generator 103 Attenuator 104 KEC method jig 105 Preamplifier 106 Spectrum analyzer 107 Transmission antenna 108 Measurement sample 109 Reception antenna

Claims (6)

An electromagnetic wave shielding film comprising an insulating resin layer, a shield layer adjacent to the insulating resin layer, and a conductive adhesive layer provided on the opposite side of the shield layer from the insulating resin layer.
The shield layer is an electromagnetic wave shielding film including a plurality of metal layers having a thickness of 1 μm or less and a non-metal layer interposed between the plurality of metal layers. The electromagnetic wave shielding film according to claim 1, wherein the non-metal layer is an insulating layer made of an insulating resin, or a conductive layer containing conductive particles or a conductive polymer. The electromagnetic wave shielding film according to claim 1 or 2, wherein at least one of the plurality of metal layers is a metal layer made of one or more metals selected from Ag, Cu, Al and Ni. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein at least one of the plurality of metal layers is a physical vapor deposition layer. The electromagnetic wave shielding film according to any one of claims 1 to 4, wherein the thickness of the non-metal layer is 0.01 μm or more and 5 μm or less. A circuit board body with circuits on at least one side of the board,
With an insulating film adjacent to one of the surfaces,
The electromagnetic wave shielding film according to any one of claims 1 to 5, which is adjacent to the side of the insulating film opposite to the circuit board main body, is provided.
A circuit board in which the conductive adhesive layer of the electromagnetic wave shielding film is adhered to the insulating film.

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