CN115024029A - Electromagnetic wave shielding film - Google Patents
Electromagnetic wave shielding film Download PDFInfo
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- CN115024029A CN115024029A CN202180013589.7A CN202180013589A CN115024029A CN 115024029 A CN115024029 A CN 115024029A CN 202180013589 A CN202180013589 A CN 202180013589A CN 115024029 A CN115024029 A CN 115024029A
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- electromagnetic wave
- wave shielding
- layer
- shielding film
- conductive adhesive
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
- H05K9/0084—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising a single continuous metallic layer on an electrically insulating supporting structure, e.g. metal foil, film, plating coating, electro-deposition, vapour-deposition
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/02—Physical, chemical or physicochemical properties
- B32B7/025—Electric or magnetic properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/04—Interconnection of layers
- B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
- Polishing Bodies And Polishing Tools (AREA)
- Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
Abstract
The present invention provides an electromagnetic wave shielding film which is excellent in economy, excellent in bondability to a printed wiring board, capable of exhibiting excellent shielding performance after being subjected to a high-temperature environment, and excellent in connection stability between an electromagnetic wave shielding layer and a ground circuit. The electromagnetic wave shielding film 1 comprises an electromagnetic wave shielding layer 2 and a conductive adhesive layer 3 arranged on one surface of the electromagnetic wave shielding layer 2; the electromagnetic wave-shielding layer 2 includes aluminum as a constituent material; the conductive adhesive layer 3 includes nickel particles as conductive particles, and the average value of circularities of the nickel particles is 0.85 or less, and the 10% cumulative value of the circularities is 0.65 or less.
Description
Technical Field
The present disclosure relates to an electromagnetic wave shielding film.
Background
Conventionally, in portable devices such as smartphones and flat panel terminals, flexible printed circuit boards (FPCs) to which electromagnetic wave shielding films are attached have been used in order to shield electromagnetic waves generated from the inside and electromagnetic waves entering from the outside.
As an electromagnetic wave shielding film, for example, an electromagnetic wave shielding film including an electromagnetic wave shielding layer such as a metal thin film and a conductive adhesive layer including conductive particles is known. The electromagnetic wave shielding film and the printed wiring board are joined by hot pressing in a state where the conductive adhesive layer of the electromagnetic wave shielding film and the insulating layer of the printed wiring board covering the circuit pattern are superposed on each other, thereby producing a shielded printed wiring board.
The insulating layer is provided with an opening portion for exposing the ground circuit, and the conductive adhesive layer is fluidized by hot pressing in a state where the electromagnetic wave shielding film is mounted on the printed wiring board, and the opening portion is filled with the conductive adhesive. Thus, the electromagnetic wave shielding layer and the ground circuit included in the circuit pattern of the printed wiring board are electrically connected via the conductive adhesive, and the electromagnetic wave shielding film can exhibit shielding performance.
Thereafter, the component is mounted on the shield printed wiring board through a solder reflow process. In the solder reflow process, for example, the solder is exposed to a high temperature of 270 ℃.
In recent years, from the viewpoint of cost reduction, an electromagnetic wave shielding film using aluminum as an electromagnetic wave shielding layer is known (for example, see patent documents 1 and 2).
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open No. Hei 7-122883;
patent document 2: international publication No. 2017/164174.
Disclosure of Invention
Technical problem to be solved by the invention
However, the combination of the electromagnetic wave shielding layer using aluminum and the conductive particles in the electromagnetic wave shielding film described in patent document 1 has the following problems: after the solder reflow step, the on-resistance of the electromagnetic wave shielding layer and the ground circuit increases, and the original shielding performance cannot be exhibited. In addition, the combination of the electromagnetic wave shielding layer using aluminum and the conductive particles in the electromagnetic wave shielding film described in patent document 2 has the following problems: the adhesion to the printed wiring board is poor, and the connection stability between the electromagnetic wave shielding layer and the ground circuit cannot be obtained after the solder reflow step. Therefore, there is a need for an electromagnetic wave shielding film that has excellent adhesion to a printed wiring board, exhibits excellent shielding performance after being subjected to a high-temperature environment, and has excellent connection stability between an electromagnetic wave shielding layer and a ground circuit.
Accordingly, an object of the present disclosure is to provide an electromagnetic wave shielding film which is excellent in economy, excellent in bondability to a printed wiring board, capable of exhibiting excellent shielding performance after being subjected to a high-temperature environment, and excellent in connection stability between an electromagnetic wave shielding layer and a ground circuit.
Means for solving the problems
The inventors of the present invention have made extensive studies to achieve the above object, and as a result, have found that an electromagnetic wave shielding film using aluminum as an electromagnetic wave shielding layer and using specific nickel particles as conductive particles in a conductive adhesive layer is excellent in economical efficiency, excellent in adhesion to a printed wiring board, excellent in shielding performance after being subjected to a high-temperature environment, and excellent in connection stability between the electromagnetic wave shielding layer and a ground circuit. The present disclosure has been completed based on the present finding.
The present disclosure provides an electromagnetic wave shielding film comprising an electromagnetic wave shielding layer, a conductive adhesive layer provided on one surface of the electromagnetic wave shielding layer,
the above-mentioned electromagnetic wave-shielding layer includes aluminum as a constituent material,
the conductive adhesive layer includes nickel particles as conductive particles, and the average value of circularities of the nickel particles is 0.85 or less, and the 10% cumulative value of the circularities is 0.65 or less.
In the electromagnetic wave shielding film, aluminum, which is less expensive than silver or copper, is used as a constituent material of the electromagnetic wave shielding layer, and therefore, the electromagnetic wave shielding film is economically advantageous. The conductive particles in the conductive adhesive layer are nickel particles having an average roundness value of 0.85 or less and a 10% cumulative roundness value of 0.65 or less. The circularity is an index indicating the degree of approximation between the two-dimensional shape of the nickel particle and a circle, and a circularity of 1.0 indicates that the two-dimensional shape is more approximate to a circle. That is, an average value of the circularities of the nickel particles of 0.85 or less indicates that the two-dimensional shape of the nickel particles greatly differs from the perfect circle to some extent, and a cumulative value of 10% of the circularities of the nickel particles of 0.65 or less indicates that the proportion of nickel particles having small circularities is large to some extent. By using the nickel particles as the conductive particles, the electromagnetic wave shielding film described above uses aluminum as a constituent material of the electromagnetic wave shielding layer, and is excellent in bondability to the printed wiring board, can exhibit excellent shielding performance after being subjected to a high-temperature environment, and is excellent in connection stability between the electromagnetic wave shielding layer and the ground circuit.
Preferably: the nickel particles are filamentous.
Preferably: the nickel particles have an average aspect ratio of 0.70 or less.
Preferably: the nickel particles have an aspect ratio of 0.50 or less in a 10% cumulative value.
Preferably: the nickel particles have a median diameter of 1 to 30 μm.
Preferably: the content ratio of the nickel particles in the conductive adhesive layer is 2 to 80 mass%.
Effects of the invention
The electromagnetic wave shielding film of the present disclosure is excellent in economy, excellent in bondability with a printed wiring board, capable of exerting excellent shielding performance after experiencing a high-heat environment, and excellent in connection stability of an electromagnetic wave shielding layer and a ground circuit.
Drawings
Fig. 1 is a schematic cross-sectional view of an embodiment of the electromagnetic wave shielding film of the present disclosure.
Detailed Description
[ electromagnetic wave shielding film ]
The electromagnetic wave shielding film of the present disclosure includes at least: an electromagnetic wave shielding layer, and a conductive adhesive layer provided on at least one surface of the electromagnetic wave shielding layer. The electromagnetic wave shielding film may include a layer other than the electromagnetic wave shielding layer and the conductive adhesive layer. The other layer may include an insulating layer on the opposite side of the electromagnetic wave shielding layer from the conductive adhesive layer.
An embodiment of the electromagnetic wave shielding film is described below. Fig. 1 is a schematic cross-sectional view of an embodiment of the electromagnetic wave-shielding film.
The electromagnetic wave shielding film 1 shown in fig. 1 includes: an electromagnetic wave shielding layer 2, a conductive adhesive layer 3 provided adjacent to one surface of the electromagnetic wave shielding layer 2, and an insulating layer 4 provided adjacent to the other surface of the electromagnetic wave shielding layer 2. In other words, the electromagnetic wave shielding film 1 includes the conductive adhesive layer 3, the electromagnetic wave shielding layer 2, and the insulating layer 4 in this order.
(electromagnetic wave shielding layer)
The electromagnetic wave shielding layer includes aluminum as a constituent material. The electromagnetic wave shielding layer including aluminum as a constituent material can be exemplified by: an aluminum layer (a layer made of aluminum) or a metal layer made of a metal such as an alloy layer made of an alloy of aluminum and another metal, a layer formed on the surface of another layer (a film, another metal layer, or the like) (a layer to which metal plating is applied), or the like. The method for forming the metal layer such as the aluminum layer or the alloy layer is not particularly limited, and examples thereof include electrolysis, vapor deposition (e.g., vacuum vapor deposition), sputtering, Chemical Vapor Deposition (CVD), metal organic growth (MO), plating, and rolling. The electromagnetic wave shielding layer may be a single layer or a plurality of layers (e.g., metal-plated layers).
The thickness of the electromagnetic wave shielding layer is not particularly limited, but is preferably 0.01 μm or more, and more preferably 0.1 μm or more. When the thickness is 0.01 μm or more, the shielding performance is further improved. The thickness is preferably 12 μm or less, more preferably 10 μm or less, and further preferably 3 μm or less, from the viewpoint of excellent flexibility, excellent transmission characteristics of high-frequency signals of 10MHz or more, and excellent electromagnetic wave shielding performance. And the thickness of the aluminum layer is preferably within the above range.
(conductive adhesive layer)
The conductive adhesive layer contains, for example, bondability and conductivity for bonding the electromagnetic wave shielding film to a printed wiring board. The conductive adhesive layer is preferably formed adjacent to the electromagnetic wave-shielding layer. The conductive adhesive layer may be a single layer or a plurality of layers.
The conductive adhesive layer includes nickel particles as conductive particles. Aluminum used for the electromagnetic wave shielding layer is easily oxidized to form an oxide film on the surface, and nickel particles break through the oxide film due to the effect of hardness or the like, and can stably maintain good electrical connection. In the case of other soft metal particles, even if the particles have a shape such as a protrusion, the oxide film is hardly broken through, and it is difficult to obtain a good electrical connection. The nickel particles may be used alone, or two or more kinds may be used as long as the object of the present disclosure is not impaired.
The average roundness of the nickel particles is 0.85 or less, preferably 0.84 or less, and more preferably 0.83 or less. The average value of the circularity is preferably small, and is, for example, 0.60 or more, preferably 0.70 or more, and more preferably 0.75 or more, from the viewpoint of obtaining more favorable conductivity in the thickness direction and the surface direction of the conductive adhesive layer.
The nickel particles have a 10% cumulative value of circularity of 0.65 or less, preferably 0.64 or less, and more preferably 0.63 or less. The cumulative value of 10% of the circularity is preferably small, and is, for example, 0.40 or more, preferably 0.45 or more, and more preferably 0.50 or more, from the viewpoint of obtaining more favorable conductivity in the thickness direction and the surface direction of the conductive adhesive layer.
The circularity is a value obtained by dividing the circumference of a circle equal to the area of the projected image of the particle by the circumference of the projected image of the particle. The 10% cumulative value of the circularity is a value corresponding to 10% cumulative at a cumulative frequency of 100%. The various values relating to the above-mentioned circularity can be measured by the method described in examples.
In the electromagnetic wave shielding film, aluminum, which is less expensive than silver and copper, is used as a constituent material of the electromagnetic wave shielding layer, and thus the electromagnetic wave shielding film is economically superior. In addition, as the conductive particles in the conductive adhesive layer, nickel particles are used, the average value of circularity of which is 0.85 or less and the 10% cumulative value of circularity of which is 0.65 or less. The circularity is an index indicating the degree of approximation between a projection image (two-dimensional shape) of the nickel particle and a circle, and a circularity of 1.0 indicates that the two-dimensional shape is more approximate to a circle as the height is higher. That is, an average value of the circularities of the nickel particles of 0.85 or less indicates that the two-dimensional shape of the nickel particles greatly differs from the perfect circle to some extent, and a cumulative value of 10% of the circularities of the nickel particles of 0.65 or less indicates that the proportion of nickel particles having small circularities is large to some extent. By using the nickel particles as the conductive particles, the electromagnetic wave shielding film described above uses aluminum as a constituent material of the electromagnetic wave shielding layer, is excellent in bondability to a printed wiring board, can exhibit excellent shielding performance after being subjected to a high-temperature environment, and is excellent in connection stability between the electromagnetic wave shielding layer and a ground circuit.
The average aspect ratio of the nickel particles is preferably 0.70 or less, and more preferably 0.69 or less. The average aspect ratio is, for example, 0.60 or more, preferably 0.65 or more.
The aspect ratio of the nickel particles is preferably 0.50 or less, more preferably 0.49 or less in a 10% cumulative value. The aspect ratio has a 10% cumulative value of, for example, 0.35 or more, preferably 0.40 or more.
The aspect ratio is a ratio (aspect ratio) of a length to a width of a rectangle circumscribed about the smallest rectangle when the particle pattern of nickel particles in a projection image is surrounded by the rectangle. The average aspect ratio of 0.70 or less indicates that the length is longer to a certain extent with respect to the width in the minimum rectangle, and the 10% cumulative value of the aspect ratio of 0.50 or less indicates that the proportion of nickel particles having a small aspect ratio is large to a certain extent. When the nickel particles are used as the conductive particles, the conductive particles extending in the thickness direction are in contact with each other in the conductive adhesive layer, and thus the conductivity in the thickness direction is more excellent. It is also presumed that the nickel particles are also arranged in the plane direction in the conductive adhesive layer, and as a result, the number of joints between the electromagnetic wave shielding layer and the ground circuit increases, and therefore, the conductive adhesive layer can exhibit excellent shielding performance after being subjected to a high-temperature environment, and the resistance value is stabilized. The various values relating to the aspect ratio described above can be measured by the methods described in the examples.
The nickel particles are preferably filamentous in shape. The wire-like nickel particles are, for example, particles mainly composed of nickel in which 10 to 1000 primary particles are linked in a chain form to form wire-like secondary particles. When the nickel particles are filamentous, the effects of the shape are: the oxide film is easier to break through, and the connection stability after the oxide film is subjected to a high-temperature environment is better.
The nickel particles preferably have a median diameter (D50) of 1 to 30 μm, more preferably 2 to 20 μm, and still more preferably 3 to 13 μm. When the median diameter is 1 μm or more, the resistance value described later becomes low, and the shielding performance becomes further excellent. When the median diameter is 30 μm or less (particularly 13 μm or less), the nickel particles are more dispersed in the conductive adhesive layer, and the adhesiveness to the printed wiring board is more excellent, and the connection stability between the electromagnetic wave shielding layer and the ground circuit is more excellent after the conductive adhesive layer is subjected to a high-temperature environment. The median diameter is a circle-equivalent diameter measured by a laser diffraction particle size analyzer.
The content of the nickel particles in the conductive adhesive layer is not particularly limited, but is preferably 2 to 60 mass%, more preferably 3 to 50 mass%, even more preferably 4 to 40 mass%, even more preferably 4.5 to 30 mass%, and particularly preferably 5 to 25 mass% with respect to 100 mass% of the total amount of the conductive adhesive layer. When the content is 2% by mass or more, the conductivity is further improved. In addition, even in the case where the electromagnetic wave shielding film is blended in a large amount at a content ratio of 30 mass% or more, the electromagnetic wave shielding film can exhibit bondability to a printed wiring board after being subjected to a high-temperature environment. When the content is 60% by mass or less, the binder component can be sufficiently contained, and the bondability to the printed wiring board is further improved. In addition, even if the content ratio is a small amount of 25 mass% or less, the electromagnetic wave shielding film can exhibit excellent shielding performance and connection stability between the electromagnetic wave shielding layer and the ground circuit after being subjected to a high-temperature environment.
The conductive adhesive layer preferably contains a binder component capable of functioning as an adhesive. Examples of the binder component include thermoplastic resins, thermosetting resins, and active energy ray-curable compounds. The binder component may be used alone or in combination of two or more.
Examples of the thermoplastic resin include polystyrene resin, vinyl acetate resin, polyester resin, polyolefin resin (e.g., polyethylene resin, polypropylene resin composition, etc.), polyimide resin, and acrylic resin. The thermoplastic resin may be used alone or in combination of two or more.
Examples of the thermosetting resin include both a resin having thermosetting properties (thermosetting resin) and a resin obtained by curing the thermosetting resin. Examples of the thermosetting resin include phenol resins, epoxy resins, polyurethane resins, melamine resins, alkyd resins, and the like. The thermosetting resin may be used alone or in combination of two or more.
Examples of the epoxy resin include a bisphenol epoxy resin, a spiro epoxy resin, a naphthalene epoxy resin, a biphenyl epoxy resin, a terpene epoxy resin, a glycidyl ether epoxy resin, a glycidyl amine epoxy resin, and a (novolac) novolac epoxy resin.
Examples of the bisphenol epoxy resin include bisphenol a epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, tetrabromobisphenol a epoxy resin, and the like. Examples of the glycidyl ether type epoxy resin include tris (glycidyl ether oxyphenyl) methane and tetrakis (glycidyl ether oxyphenyl) ethane. Examples of the glycidyl amine type epoxy resin include tetraglycidyl diaminodiphenylmethane and the like. Examples of the (novolac) type epoxy resin include cresol (novolac) type epoxy resin, phenol (novolac) type epoxy resin, α -naphthol (novolac) type epoxy resin, and brominated phenol (novolac) type epoxy resin.
Examples of the active energy ray-curable compound include both a compound curable by irradiation with an active energy ray (active energy ray-curable compound) and a compound obtained by curing the active energy ray-curable compound. The active energy ray-curable compound is not particularly limited, and examples thereof include polymerizable compounds containing 1 or more (preferably 2 or more) radical-reactive groups (e.g., (meth) acryloyl groups) in the molecule. The active energy ray-curable compound may be used alone or in combination of two or more.
Among them, the binder component is preferably a thermosetting resin. In this case, after the electromagnetic wave shielding film is disposed on the printed wiring board, the adhesive component can be cured by applying pressure and heat, and the adhesiveness is further improved.
When the binder component includes a thermosetting resin, a curing agent for promoting a thermosetting reaction may be included as a component constituting the binder component. The curing agent can be appropriately selected according to the kind of the thermosetting resin. The curing agent may be used alone or in combination of two or more.
The content ratio of the binder component in the conductive adhesive layer is not particularly limited, but is preferably 40 to 98 mass%, more preferably 50 to 97 mass%, even more preferably 60 to 96 mass%, even more preferably 70 to 95.5 mass%, and particularly preferably 75 to 95 mass%, relative to 100 mass% of the total amount of the conductive adhesive layer. When the content is 40% by mass or more, the adhesiveness to a printed wiring board is more excellent. When the content ratio is 98% by mass or less, the conductive particles can be sufficiently contained.
The conductive adhesive layer may be a layer having isotropic conductivity or anisotropic conductivity, as required. Among them, the conductive adhesive layer preferably has anisotropic conductivity from the viewpoint of improving the transmission characteristics of a high-frequency signal transmitted through a signal circuit of a printed wiring board.
The conductive adhesive layer may contain other components than the above components within a range not to impair the effects of the present disclosure. The other components may be those contained in a known or conventional adhesive layer. Examples of the other components include a curing accelerator, a plasticizer, a flame retardant, an antifoaming agent, a viscosity adjuster, an antioxidant, a diluent, an anti-settling agent, a filler, a colorant, a leveling agent, a coupling agent, an ultraviolet absorber, a tackifying resin, and an anti-blocking agent. The other components may be used alone or in combination of two or more. The proportion of nickel particles having an average value of circularity and a cumulative value of 10% in all conductive particles contained in the conductive adhesive layer within the above ranges is preferably 90 mass% or more, more preferably 95 mass% or more, and still more preferably 98 mass% or more.
The thickness of the conductive adhesive layer is preferably 3 to 20 μm, and more preferably 5 to 15 μm. In order to provide anisotropy to the conductive adhesive layer, the thickness of the conductive adhesive layer is preferably equal to or less than the median diameter of the nickel particles. In this case, the electromagnetic wave shielding film and the printed wiring board are electrically connected well.
(insulating layer)
The insulating layer has a function of protecting the conductive adhesive layer and/or the electromagnetic wave shielding layer in the electromagnetic wave shielding film.
The insulating layer preferably includes a binder component. Examples of the binder component include thermoplastic resins, thermosetting resins, and active energy ray-curable compounds. The thermoplastic resin, the thermosetting resin, and the active energy ray-curable compound are exemplified by the fact that the conductive adhesive layer may contain a binder component. The binder component may be used alone or in combination of two or more.
The insulating layer may contain other components than the binder component within a range not to impair the effect of the present disclosure. Examples of the other components include a curing agent, a curing accelerator, a plasticizer, a flame retardant, an antifoaming agent, a viscosity adjuster, an antioxidant, a diluent, an anti-settling agent, a filler, a coloring agent, a leveling agent, a coupling agent, an ultraviolet absorber, a tackifying resin, and an anti-blocking agent. The other components may be used alone or in combination of two or more.
The insulating layer may be a single layer or a plurality of layers. When the insulating layer is a plurality of layers, for example, a laminate of 2 or more layers having different physical and chemical properties such as material, hardness, elastic modulus, and the like may be used. For example, in a laminate of an outer layer having low hardness and an inner layer having high hardness, the outer layer has a cushioning effect, and therefore, in the step of heating and pressing the electromagnetic wave shielding film on the printed wiring board, the pressure applied to the electromagnetic wave shielding layer can be relaxed. Therefore, the electromagnetic wave shielding layer can be prevented from being damaged by the level difference provided on the printed wiring board.
The thickness of the insulating layer is not particularly limited, and can be appropriately set as needed, and is preferably 1 to 20 μm, more preferably 2 to 15 μm, and further preferably 3 to 10 μm. When the thickness is 1 μm or more, the electromagnetic wave shielding layer and the conductive adhesive layer can be more sufficiently protected. When the thickness is 20 μm or less, flexibility and flexibility are excellent, and economical efficiency is also advantageous.
The electromagnetic wave shielding film may include a separator (release film) on the insulating layer side and/or the conductive adhesive layer side. The separator is laminated so as to be peelable from the electromagnetic wave shielding film. The separator is an element for covering and protecting the insulating layer and the conductive adhesive layer, and is peeled off when the electromagnetic wave shielding film is used.
Examples of the separator include a polyethylene terephthalate (PET) film, a polyethylene film, a polypropylene film, and a plastic film or paper coated with a release agent such as a fluorine-based release agent or a long-chain alkyl acrylate-based release agent.
The thickness of the separator is preferably 10 to 200 μm, more preferably 15 to 150 μm. When the thickness is 10 μm or more, the protective performance is more excellent. When the thickness is 200 μm or less, the separator is easily peeled off at the time of use.
The electromagnetic wave shielding film may further include an anchor coat layer formed between the insulating layer and the electromagnetic wave shielding layer. With the above configuration, the electromagnetic wave shielding layer and the insulating layer can be more favorably bonded to each other.
Examples of the material for forming the anchor coat layer include urethane resins, acrylic resins, core-shell type composite resins in which urethane resins are used as a shell and acrylic resins are used as a core, epoxy resins, polyimide resins, polyamide resins, melamine resins, phenol resins, urea resins, blocked isocyanates obtained by reacting a blocking agent such as phenol with polyisocyanate, polyvinyl alcohol, and polyvinyl pyrrolidone. The above-mentioned material may be used alone or in combination of two or more.
The resistance value (initial resistance value) of the electromagnetic wave shielding film obtained by the conductivity test described below is not particularly limited, but is preferably 500m Ω or less, more preferably 400m Ω or less, and further preferably less than 300m Ω. When the initial resistance value is 500m Ω or less, the electromagnetic wave shielding film and the ground circuit are well connected.
[ conductivity test ]
The following printed wiring boards were used as the printed wiring boards: a base member made of a polyimide film was provided with 2 copper foil patterns simulating a ground circuit, and a cover film made of an insulating adhesive layer and a polyimide film having a thickness of 25 μm was formed thereon. A circular opening simulating a ground connection portion having a diameter of 1mm is formed in the cover film. Then, using a press at a temperature: 170 ℃ and pressure: the electromagnetic wave shielding film and the printed wiring board were evacuated at 3.0MPa for 60 seconds, then joined by heating and pressurizing for 180 seconds, heated at 150 ℃ for 60 minutes in an oven, and the resistance value between 2 copper foil patterns was measured by a resistance meter and used as the resistance value.
The resistance value (resistance value after reflow) of the electromagnetic wave shielding film obtained by a conductivity test after the reflow step of setting a temperature profile of exposure to hot air of 265 ℃ for 5 seconds for 3 cycles is not particularly limited, but is preferably 1000m Ω or less, more preferably 700m Ω or less, and further preferably less than 500m Ω. When the resistance value is 1000m Ω or less, the electromagnetic wave shielding film and the ground circuit are well connected after the film is exposed to a high-temperature environment. The resistance value after reflow soldering was measured for the electromagnetic wave shielding film after the reflow soldering process for 3 cycles in the same manner as the conductivity test for the initial resistance value.
The bonding force of the electromagnetic wave shielding film obtained by the following bonding test is not particularly limited, but is preferably 3.0N/10 mm or more, more preferably 3.5N/10 mm or more, and further preferably more than 4.0N/10 mm. If the bonding force is 3.0N/10 mm or more, the bonding property with the printed wiring board after the high temperature environment is excellent.
[ test of bondability ]
A polyimide film having a thickness of 25 μm was laminated on the conductive adhesive layer surface of the electromagnetic wave shielding film, and the thickness was measured using a press at a temperature: 170 ℃ and pressure: vacuum was applied for 60 seconds under the condition of 3.0MPa, and then the resultant was heated and pressurized for 180 seconds to bond the substrates. Then, the sample was heated at 150 ℃ for 60 minutes to prepare a measurement sample. Next, the measurement sample was cut into a width of 10mm, and the contact surface between the conductive adhesive layer and the polyimide film was peeled off at a peeling speed of 50 mm/min and a peeling angle of 180 ° using a tensile tester, whereby the bonding strength was measured and used as the bonding force.
The above electromagnetic wave shielding film is preferably used for a printed wiring board, and particularly preferably used for a flexible printed wiring board (FPC).
(method for producing electromagnetic wave shielding film)
An embodiment of the method for manufacturing the electromagnetic wave shielding film will be described. In the step of manufacturing the electromagnetic wave shielding film 1 shown in fig. 1, first, a laminate of the insulating layer 4 and the electromagnetic wave shielding layer 2 and the conductive adhesive layer 3 are separately manufactured. Then, the separately produced laminate and the conductive adhesive layer 3 are bonded (lamination method).
In the production of the laminate, the insulating layer 4 is formed, for example, as follows: the resin composition for forming the insulating layer 4 is applied (coated) on a temporary substrate such as a release film or a substrate, and, if necessary, desolvated and/or partially cured.
The resin composition may contain a solvent (solvent) in addition to the components contained in the insulating layer. Examples of the solvent include toluene, acetone, methyl ethyl ketone, methanol, ethanol, propanol, and dimethylformamide. The solid content concentration of the resin composition is appropriately set according to the thickness of the insulating layer to be formed, and the like.
The resin composition can be applied by a known coating method. For example, a gravure roll coater, a reverse roll coater, an oil feed roll coater, a lip coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater, a direct coater, a slit coater, or the like can be used.
Next, the electromagnetic wave shielding layer 2 is formed on the surface of the insulating layer 4 formed on the separator. The electromagnetic wave shielding layer 2 is preferably formed by a vapor deposition method or a sputtering method. The vapor deposition method and the sputtering method can be any known or conventional methods. In this way, a laminate of the insulating layer 4/electromagnetic wave shielding layer 2 was produced.
On the other hand, when the conductive adhesive 3 is produced, the conductive adhesive layer 3 is formed, for example, as follows: the adhesive composition for forming the conductive adhesive layer 3 is applied (coated) on a temporary substrate such as a release film or a substrate, and if necessary, desolvation and/or partial curing are performed.
The adhesive composition may contain a solvent (solvent) in addition to the components contained in the conductive adhesive layer. The solvent is exemplified by the resin composition containing a solvent. The solid content concentration of the adhesive composition is appropriately set according to the thickness of the conductive adhesive layer to be formed, and the like.
The adhesive composition can be applied by a known coating method. Examples thereof include coaters used for coating the resin composition.
Next, the exposed surface (electromagnetic wave shielding layer 2 side) of each of the laminates thus produced and the conductive adhesive layer 3 were bonded to each other, thereby producing an electromagnetic wave shielding film 1.
As another embodiment other than the above-described lamination method, the electromagnetic wave-shielding film 1 can be manufactured by a method of sequentially laminating the respective layers (direct coating method). For example, the electromagnetic wave-shielding film 1 shown in fig. 1 can be manufactured as follows: the adhesive composition for forming the conductive adhesive layer 3 is applied (coated) on the surface of the electromagnetic wave shielding layer 2 of the laminate, and the conductive adhesive layer 3 is formed by removing the solvent and/or partially curing, if necessary.
The electromagnetic wave shielding film can be used for manufacturing a shielding printed wiring board. For example, a shielded printed wiring board in which the electromagnetic wave shielding film is laminated on a printed wiring board can be obtained by laminating the conductive adhesive layer of the electromagnetic wave shielding film on a printed wiring board (for example, a cover film). In the above-described shield printed wiring board, the conductive adhesive layer may be thermally cured by, for example, a subsequent heat and pressure treatment.
Examples
An embodiment of the electromagnetic wave shielding film of the present disclosure will be described in further detail below based on examples, but the electromagnetic wave shielding film of the present disclosure is not limited to these examples.
Example 1
(formation of insulating layer)
When the amount of solid content was 20% by mass, 100 parts by mass of a bisphenol a type epoxy resin (trade name "jER 1256", manufactured by mitsubishi chemical corporation) and 0.1 part by mass of a curing agent (trade name "ST 14", manufactured by mitsubishi chemical corporation) were mixed with toluene and stirred to prepare a resin composition. The obtained resin composition was applied to a release-treated surface of a polyethylene terephthalate (PET) film whose surface was subjected to release treatment, and heated to remove a solvent, thereby forming an insulating layer (thickness 6 μm).
(formation of electromagnetic wave-shielding layer)
An aluminum layer having a thickness of 0.1 μm was formed on the surface of the obtained insulating layer by a vapor deposition method, and a laminate of the insulating layer and the electromagnetic wave shielding layer was obtained. Specifically, a PET film with an insulating layer formed thereon was placed in a batch type vacuum deposition apparatus (trade name "EBH-800", manufactured by ULVAC corporation), and the degree of vacuum was adjusted to 5X 10 in an argon atmosphere -1 Pa or less, and aluminum was deposited by a magnetron sputtering method (DC power output: 3.0 kW) to a thickness of 0.1. mu.m.
(formation of conductive adhesive layer)
When the amount of solid content was 20 mass%, 95 parts by mass of a bisphenol a type epoxy resin (trade name "jER 1256", manufactured by mitsubishi chemical corporation), 0.1 part by mass of a curing agent (trade name "ST 14", manufactured by mitsubishi chemical corporation), and 5 parts by mass of conductive particles composed of filiform nickel particles (No. 1) were mixed with toluene, and stirred and mixed to prepare an adhesive composition. The properties of the conductive particles used are shown in Table 2. The obtained adhesive composition was applied to a release-treated surface of a PET film whose surface was subjected to release treatment, and heated to remove the solvent, thereby forming a conductive adhesive layer (thickness 12 μm).
(production of electromagnetic wave-shielding film)
The obtained conductive adhesive layer was bonded to the electromagnetic wave shielding layer surface of the laminate composed of the insulating layer and the electromagnetic wave shielding layer, to produce the electromagnetic wave shielding film of example 1 having a structure of conductive adhesive layer/electromagnetic wave shielding layer/insulating layer.
Examples 2 to 4 and comparative examples 1 to 8
An electromagnetic wave shielding film was produced in the same manner as in example 1, except that the kind and content ratio of nickel particles in the conductive adhesive layer were changed as shown in table 1. The properties of the conductive particles used in each example are shown in table 2.
(evaluation)
The electromagnetic wave-shielding films obtained in examples and comparative examples were evaluated as follows. The evaluation results are set forth in Table 1.
(1) Roundness, aspect ratio, and median diameter
The circularity, aspect ratio, and median diameter of the conductive particles were measured using a flow particle image analyzer (trade name "FPIA-3000", manufactured by shimexican corporation). Specifically, measurement was performed using a 10-fold objective lens in a bright field optical system in an LPF measurement mode with a concentration of 4000 to 20000 particles/. mu.l of a conductive particle dispersion liquid adjusted. The conductive particle dispersion is prepared by adding 0.1 to 0.5ml of a surfactant to a 0.2 mass% aqueous solution of sodium hexametaphosphate and adding 0.1 + -0.01 g of conductive particles as a measurement sample. The suspension in which the conductive particles are dispersed is subjected to a dispersing treatment for 1 to 3 minutes in an ultrasonic disperser, and subjected to measurement. The average value of circularity, the 10% cumulative value of circularity, the average aspect ratio, the 10% cumulative value of aspect ratio, and the median diameter of the obtained conductive particles are shown in table 2.
(2) Conductivity test
The electromagnetic wave-shielding films produced in examples and comparative examples were laminated on a printed wiring board for evaluation, and then subjected to a press at a temperature of: 170 ℃ and pressure: vacuum was applied for 60 seconds under the condition of 3.0MPa, and then the resultant was heated and pressurized for 180 seconds to bond the substrates. After that, the PET film on the insulating layer was peeled off, and the resultant was heated in an oven at 150 ℃ for 60 minutes to prepare a base material for evaluation. The printed wiring board comprises 2 copper foil patterns extending in parallel with each other with a space therebetween and an insulating protective layer (thickness: 25 μm) made of polyimide and covering the copper foil patterns, and the insulating protective layer is provided with openings (diameter: 1 mm) for exposing the copper foil patterns. When the conductive adhesive layer of the electromagnetic wave shielding film and the printed wiring board are stacked, the opening is completely covered with the electromagnetic wave shielding film. Then, the resistance value between the 2 copper foil patterns of the obtained evaluation substrate was measured by a resistance meter, and the measured resistance value was used as the resistance value (initial resistance value) between the printed wiring board and the electromagnetic wave shielding layer before reflow soldering.
Next, heat treatment assuming reflow treatment was performed, and the resistance value after reflow (resistance value after reflow) was measured. The heat treatment and the measurement of the resistance value were repeated 3 times. The heat treatment assumes the use of lead-free solder, and the temperature profile is set such that the electromagnetic wave shielding film in the base material for evaluation is exposed to 265 ℃ for 5 seconds. Then, the initial resistance value and the resistance value after reflow soldering were evaluated based on the following evaluation criteria.
(initial resistance value)
O (good): less than 300m omega
Δ (optional): 300m omega to 500m omega
X (bad): over 500m omega
(post reflow resistance value)
O (good): less than 500m omega
And (b): 500m omega to 1000m omega
X (bad): over 1000m omega.
(3) Bonding property
Polyimide films (trade name "Kapton 100 EN", manufactured by DU PONT-TORAY) having a thickness of 25 μm were laminated on the conductive adhesive layer of the electromagnetic wave shielding films prepared in examples and comparative examples, and the film was laminated on the conductive adhesive layer using a press at a temperature of: 170 ℃ and pressure: vacuum was applied for 60 seconds under the condition of 3.0MPa, and then the resultant was heated and pressurized for 180 seconds to bond the substrates. Then, the sample was heated in an oven at 150 ℃ for 60 minutes to prepare a measurement sample. Then, in order to measure the bonding strength, the measurement sample was cut into a width of 10mm, and the contact surface between the conductive adhesive layer and the polyimide film was peeled off at a peeling speed of 50 mm/min and a peeling angle of 180 ° using a tensile tester (trade name "AGS-X50N", manufactured by Shimadzu corporation), thereby measuring the bonding strength.
O (good): more than 4.0N/10 mm
Δ (optional): 3.0N/10 mm to 4.0N/10 mm
X (bad): less than 3.0N/10 mm.
The electromagnetic wave shielding film of the embodiment has excellent bondability, a low initial resistance value, and a low resistance value after reflow processing in the case of using an aluminum layer as an electromagnetic wave shielding layer. Therefore, the electromagnetic wave shielding film of the embodiment is judged to be superior in economy, superior in bondability to a printed wiring board, capable of exerting superior shielding performance after being subjected to a high-temperature environment, and superior in connection stability of the electromagnetic wave shielding layer and the ground circuit. On the other hand, when nickel particles having an average roundness value and a 10% cumulative value exceeding a specific value were used as the conductive particles in the conductive adhesive layer (comparative example), even if the content ratio of the conductive particles was changed, the bondability and the resistance value after the reflow process could not be both excellent.
Description of the numbering
1 electromagnetic wave shielding film
2 electromagnetic wave shielding layer
3 conductive adhesive layer
4 insulating layer
Claims (6)
1. An electromagnetic wave shielding film, characterized in that:
comprises an electromagnetic wave shielding layer and a conductive adhesive layer arranged on one surface of the electromagnetic wave shielding layer;
the electromagnetic wave-shielding layer includes aluminum as a constituent material,
the conductive adhesive layer includes nickel particles as conductive particles, an average value of circularities of the nickel particles is 0.85 or less, and a 10% cumulative value of the circularities is 0.65 or less.
2. The electromagnetic wave shielding film according to claim 1, characterized in that:
the nickel particles are filamentous in shape.
3. The electromagnetic wave shielding film according to claim 1 or 2, characterized in that:
the nickel particles have an average aspect ratio of 0.70 or less.
4. The electromagnetic wave shielding film according to any one of claims 1 to 3, characterized in that:
the nickel particles have an aspect ratio of 0.50 or less in a 10% cumulative value.
5. The electromagnetic wave shielding film according to any one of claims 1 to 4, characterized in that:
the median diameter of the nickel particles is 1-30 μm.
6. The electromagnetic wave shielding film according to any one of claims 1 to 5, wherein:
the content ratio of the nickel particles in the conductive adhesive layer is 2-80 mass%.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2020035598 | 2020-03-03 | ||
| JP2020-035598 | 2020-03-03 | ||
| PCT/JP2021/008033 WO2021177328A1 (en) | 2020-03-03 | 2021-03-03 | Electromagnetic wave shielding film |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115024029A true CN115024029A (en) | 2022-09-06 |
Family
ID=77613530
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202180013589.7A Pending CN115024029A (en) | 2020-03-03 | 2021-03-03 | Electromagnetic wave shielding film |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JP7506150B2 (en) |
| KR (1) | KR20220148802A (en) |
| CN (1) | CN115024029A (en) |
| TW (1) | TWI812889B (en) |
| WO (1) | WO2021177328A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116669410B (en) * | 2023-07-03 | 2024-02-20 | 广州方邦电子股份有限公司 | Electromagnetic shield cover and circuit board |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07122883A (en) | 1993-10-21 | 1995-05-12 | Nitto Denko Corp | Electromagnetic-wave shielding material |
| JP4759899B2 (en) * | 2001-09-28 | 2011-08-31 | 大日本印刷株式会社 | Electromagnetic shielding material and flat cable with electromagnetic shielding |
| JP6196131B2 (en) * | 2013-11-15 | 2017-09-13 | 三井金属鉱業株式会社 | Metal foil for press bonding and electronic component package |
| JP7023836B2 (en) * | 2016-03-23 | 2022-02-22 | タツタ電線株式会社 | Electromagnetic wave shield film |
| US10224304B2 (en) * | 2016-09-22 | 2019-03-05 | Apple Inc. | Conductive adhesive film structures |
| TW201841559A (en) * | 2017-02-10 | 2018-11-16 | 日商東洋油墨Ｓｃ控股股份有限公司 | Component-mounted board, manufacturing method thereof, laminate, electromagnetic wave-shielding sheet, and electronic device which have high in productivity, high in quality and high in coatability |
| JP6546975B2 (en) * | 2017-10-16 | 2019-07-17 | タツタ電線株式会社 | Conductive adhesive |
| JP6970025B2 (en) * | 2018-01-10 | 2021-11-24 | タツタ電線株式会社 | Electromagnetic wave shield film |
| JP6511550B1 (en) * | 2018-01-30 | 2019-05-15 | タツタ電線株式会社 | Electromagnetic shielding film |
| SG11202006816YA (en) | 2018-02-14 | 2020-09-29 | Threebond Co Ltd | Conductive adhesive and cured product thereof |
-
2020
- 2020-10-14 TW TW109135565A patent/TWI812889B/en active
-
2021
- 2021-03-03 JP JP2022504413A patent/JP7506150B2/en active Active
- 2021-03-03 KR KR1020227024885A patent/KR20220148802A/en not_active Application Discontinuation
- 2021-03-03 CN CN202180013589.7A patent/CN115024029A/en active Pending
- 2021-03-03 WO PCT/JP2021/008033 patent/WO2021177328A1/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| TWI812889B (en) | 2023-08-21 |
| JP7506150B2 (en) | 2024-06-25 |
| KR20220148802A (en) | 2022-11-07 |
| TW202135638A (en) | 2021-09-16 |
| JPWO2021177328A1 (en) | 2021-09-10 |
| WO2021177328A1 (en) | 2021-09-10 |
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