JP2020064927A - Electromagnetic wave shield film, manufacturing method of the same, and printed wiring board with electromagnetic wave shield film - Google Patents

Abstract

To provide an electromagnetic wave shield film having excellent adhesion between an insulating resin layer and a metal thin film layer, a method of manufacturing the same, and a printed wiring board with the electromagnetic wave shield film.SOLUTION: An electromagnetic wave shield film 1 includes: an insulating resin layer 10; a porous black chrome plating layer 5; a metal thin film layer 22; and a conductive adhesive layer 24, stacked in this order. The insulating resin layer 10 is in contact with a surface of the black chrome plating layer 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electromagnetic wave shield film, a method for manufacturing the same, and a printed wiring board with an electromagnetic wave shield film.

  In order to shield the electromagnetic noise generated from the flexible printed wiring board and the electromagnetic noise from the outside, an electromagnetic shielding film formed by laminating an insulating resin layer, a metal thin film layer, and a conductive adhesive layer is used as an insulating film ( It may be provided on the surface of the flexible printed wiring board via a cover lay film) (for example, refer to Patent Document 1).

  When the electromagnetic wave shielding film is provided on the surface of the printed wiring board, the printed wiring board with an insulating film and the electromagnetic wave shielding film are stacked so that the insulating film and the conductive adhesive layer are in contact with each other, and these are heat pressed and pressure bonded. To do. At this time, the conductive adhesive layer of the electromagnetic wave shielding film comes into contact with the printed circuit (ground) of the printed wiring board through the through hole formed in the insulating film, so that the metal thin film layer and the printed circuit of the printed wiring board are contacted. And are electrically connected.

JP, 2017-220592, A

  However, the insulating resin layer and the metal thin film layer of the electromagnetic wave shielding film may peel off when the electromagnetic wave shielding film is pressure-bonded to the through hole of the insulating film by heat pressing or when the electromagnetic wave shielding film is handled. There is.

  The present invention provides an electromagnetic wave shield film having excellent adhesiveness between an insulating resin layer and a metal thin film layer, a method for producing the same, and a printed wiring board with an electromagnetic wave shield film.

The present invention has the following aspects.
[1] An insulating resin layer, a porous black chrome plating layer, a metal thin film layer, and a conductive adhesive layer are laminated in this order, and the insulating resin layer is formed on the surface of the black chrome plating layer. The electromagnetic wave shield film that is in contact.
[2] The electromagnetic wave shielding film according to [1], wherein the metal thin film layer is a metal foil.
[3] The electromagnetic wave shielding film according to [1] or [2], wherein the black chrome plating layer has a thickness of 0.1 μm or more and 1 μm or less.
[4] The electromagnetic wave shield film according to any one of [1] to [3], wherein the black chrome plating layer contains an oxide or hydroxide of chromium.
[5] The electromagnetic wave shield film manufacturing method according to any one of [1] to [4], wherein the porous black chrome plating layer and the metal thin film layer are laminated in this order. And preparing an insulating resin layer by applying an insulating resin to the surface of the black chrome plated layer of the laminate.
[6] A printed wiring board having a printed circuit provided on at least one surface of a substrate, an insulating film adjacent to a surface of the printed wiring board on which the printed circuit is provided, and the printed wiring board having the insulating film. And the electromagnetic wave shielding film according to any one of [1] to [4] provided on the opposite side, wherein the conductive adhesive layer of the electromagnetic wave shielding film is adjacent to the insulating film. Printed wiring board with electromagnetic wave shielding film.

In the electromagnetic wave shielding film of the present invention, since the porous black chrome plating layer is interposed between the insulating resin layer and the metal thin film layer, the adhesiveness between the insulating resin layer and the metal thin film layer is excellent.
According to the method for producing an electromagnetic wave shielding film of the present invention, the above electromagnetic wave shielding film can be easily produced.

It is sectional drawing which shows an example of the electromagnetic wave shield film of this invention. It is sectional drawing which shows the other example of the electromagnetic wave shield film of this invention. It is sectional drawing which shows an example of the printed wiring board with an electromagnetic wave shield film of this invention. It is sectional drawing which shows the other example of the printed wiring board with an electromagnetic wave shield film of this invention. It is sectional drawing which shows an example of the manufacturing process of the printed wiring board with an electromagnetic wave shield film.

The following definitions of 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 plane direction.
The “anisotropic conductive 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 a conductive adhesive layer having a surface resistance of 1 × 10 ⁴ Ω / □ or more.
The average particle diameter of particles is 30 particles randomly selected from a microscopic image of particles, the minimum diameter and the maximum diameter of each particle are measured, and the median of the minimum diameter and the maximum diameter is the particle of one particle. The diameter is a value obtained by arithmetically averaging the measured particle diameters of 30 particles. The same applies to the average particle diameter of the conductive particles.
The thickness of the film (carrier film, release film, insulating film, etc.), coating film (conductive adhesive layer, etc.), metal thin film layer, plating layer, etc. can be determined by observing the cross section of the measurement object with a microscope. It is a value obtained by measuring and averaging the thickness of the place. The thickness measurement points are five points corresponding to points that divide the entire width of the measurement object into six equal parts.
The storage elastic modulus is calculated as one of the viscoelastic properties by using a dynamic viscoelasticity measuring device that is calculated from the stress applied to the measurement target and the detected strain and outputs as a function of temperature or time.
Among the various resistivity meters manufactured by Mitsubishi Chemical Corporation, when the surface resistance is less than 10 ⁶ Ω / □, the product name: Loresta (Loresta GP, ASP probe) is used, and the four-terminal method (JIS K 7194: 1994 and Surface resistivity measured by JIS R 1637: 1998). When the surface resistivity is 10 ⁶ Ω / □ or more, the product name: Hiresta (Hiresta UP, URS probe) is used and the double ring method (JIS K 6911: 2006).
The dimensional ratios in FIGS. 1 to 5 are different from actual ones for convenience of explanation.

<Electromagnetic wave shielding film>
A first aspect of the present invention is an electromagnetic wave shield film in which an insulating resin layer, a porous black chrome plating layer, a metal thin film layer, and a conductive adhesive layer are laminated in this order. The layer is in contact with the surface of the black chrome plated layer.

FIG. 1 is a sectional view showing an example of the electromagnetic wave shielding film of the present invention.
The electromagnetic wave shield film 1 includes an insulating resin layer 10, a porous black chrome plating layer 5 adjacent to the insulating resin layer 10, a conductive layer 20, and a separating layer adjacent to the conductive layer 20 on the opposite side of the insulating resin layer 10. And a mold film 40.
The conductive layer 20 has a metal thin film layer 22 adjacent to the black chrome plated layer 5 and an anisotropic conductive adhesive layer 24 adjacent to the release film 40.
Although not shown, a carrier film may be provided adjacent to the side of the insulating resin layer 10 opposite to the conductive layer 20.

The thickness of the electromagnetic wave shielding film 1 (excluding the carrier film and the release 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 value of the above range, the carrier film or the release film 40 is less likely to break when peeled.
When the thickness is equal to or less than the upper limit value of the range, the printed wiring board with the electromagnetic wave shielding film can be thinned.

(Insulating resin layer)
The insulating resin layer 10 adheres the electromagnetic wave shielding film 1 to the surface of the insulating film provided on the surface of the flexible printed wiring board, and serves as a protective layer for the black chrome plating layer 5 and the conductive layer 20.

  The insulating resin layer 10 is formed by applying a coating material containing a thermosetting resin and a curing agent and semi-curing or curing the coating material; applying a coating material containing a thermoplastic resin and drying it. Coating film; a layer formed of a film obtained by melt-molding a composition containing a thermoplastic resin, and the like. From the viewpoint of heat resistance when subjected to the solder reflow step, a coating film formed by applying a coating material containing a thermosetting resin and a curing agent and semi-curing or curing it is preferable.

Examples of the thermosetting resin include amide resin, epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, and ultraviolet curing 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 polyether ketone, polyimide, polyamideimide, polyamide, polysulfone, polyether sulfone, polyphenylene sulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyphenylene sulfide ketone.

The insulating resin layer 10 hides the printed circuit of the printed wiring board or imparts design characteristics to the printed wiring board with the electromagnetic wave shielding film, so that either one of a coloring agent (pigment, dye, etc.) and a filler, or Both may be included.
As one or both of the colorant and the filler, from the viewpoint of weather resistance, heat resistance, and hiding properties, pigments or fillers are preferable, and from the viewpoint of hiding properties of printed circuits and design, black pigments, black pigments and others. It is more preferable to use a combination of the above pigment or a black pigment and a filler.
The insulating resin layer 10 may include a flame retardant.
The insulating resin layer 10 may include other components as needed, 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 the 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 equal to or more than the lower limit value of the above range, the insulating resin layer 10 can sufficiently exhibit the function as a protective layer. If the thickness of the insulating resin layer 10 is less than or equal to the upper limit value of the above range, the electromagnetic wave shielding film 1 can be thinned.

(Black chrome plating layer)
The black chrome plating layer 5 is a plating layer including black chrome plating on the surface that contacts the insulating resin layer 10. The surface of the black chrome plating layer 5 is porous and has a complicated sponge-like fine structure. Therefore, since the surface area for adhering to the adjacent insulating resin layer 10 is large, the adhesiveness with the insulating resin layer 10 is excellent.

Components of the black chrome plating include metal chromium, chromium oxide, and chromium hydroxide. Of these three components, it is preferable that metallic chromium and at least one of chromium oxide and chromium hydroxide are contained, because a plated layer having a porous and heavy texture is formed.
The porous black chrome plating layer is formed by a known plating method. Specific examples include low-temperature black chrome plating, hard black chrome plating, trivalent black chrome plating, and the like.

The thickness of the black chrome plating layer 5 is, for example, 0.01 μm or more and 10 μm or less, preferably 0.1 μm or more and 5 μm or less, and more preferably 0.3 μm or more and 1 μm or less.
When the thickness of the black chrome plating layer 5 is at least the lower limit value of the above range, a porous fine structure is sufficiently formed, and the adhesiveness with the insulating resin layer 10 is further improved.
When the thickness of the black chrome plating layer 5 is less than or equal to the upper limit value of the above range, the structural fragility of the black chrome plating layer 5 does not appear, and the adhesiveness with the insulating resin layer 10 is further improved.

The black chrome plating layer 5 may be a single layer or two or more layers.
Another plating layer may be interposed between the black chrome plating layer 5 and the metal thin film layer 22. However, the black chrome plating layer 5 adheres to the insulating resin layer 10.
An example of another plating layer interposed between the black chrome plating layer 5 and the metal thin film layer 22 is, for example, a nickel plating layer. It is preferable to have a nickel plating layer on the surface of the metal thin film layer 22 because the adhesion between the black chrome plating layer 5 and the metal thin film layer 22 is excellent.

(Conductive layer)
Since the conductive layer 20 has the metal thin film layer 22 adjacent to the black chrome plated layer 5 and the anisotropic conductive adhesive layer 24 adjacent to the release film 40, the electromagnetic wave shielding property is sufficiently high.

Metal thin film layer:
The metal thin film layer 22 is a layer made of a metal thin film. Since the metal thin film layer 22 is formed so as to spread in the plane direction, it has conductivity in the plane direction and functions as an electromagnetic wave shield layer or the like.

Examples of the metal thin film layer 22 include a vapor deposition film formed by physical vapor deposition (vacuum vapor deposition, sputtering, ion beam vapor deposition, electron beam vapor deposition, etc.) or CVD (chemical vapor deposition), a metal foil, and the like.
A metal foil formed by rolling is preferable because it has high adhesiveness to the black chrome plating layer 5. The thickness of the metal foil may be adjusted by etching.

  Examples of the metal forming the metal thin film layer 22 include aluminum, silver, copper, gold, conductive ceramics, and the like. From the viewpoint of electrical conductivity, silver or copper is preferable, and the adhesiveness to the black chrome plating layer 5 is high. Copper is more preferable because of its high price.

  The surface resistance of the metal thin film layer 22 is preferably 0.001 Ω / □ or more and 1 Ω / □ or less, and more preferably 0.001 Ω / □ or more and 0.5 Ω / □ or less. If the surface resistance of the metal thin film layer 22 is at least the lower limit value of the above range, the metal thin film layer 22 can be made sufficiently thin. When the surface resistance of the metal thin film layer 22 is equal to or less than the upper limit value of the above range, it can sufficiently function as an electromagnetic wave shield layer.

  The thickness of the metal thin film layer 22 is preferably 0.01 μm or more and 5 μm or less, more preferably 0.05 μm or more and 3 μm or less. When the thickness of the metal thin film layer 22 is 0.01 μm or more, the conductivity in the plane direction is further improved. When the thickness of the metal thin film layer 22 is 0.05 μm or more, the effect of shielding electromagnetic wave noise is further improved. When the thickness of the metal thin film layer 22 is not more than the upper limit value of the above range, the electromagnetic wave shielding film 1 can be thinned. Further, the productivity and flexibility of the electromagnetic wave shielding film 1 are improved.

  The thickness ratio represented by (thickness of black chrome plating layer 5 / thickness of metal thin film layer 22) is preferably 0.01 to 1, more preferably 0.02 to 0.6, and 0.05. ~ 0.3 is more preferable. When the above ratio is in the above range, the adhesiveness between the insulating resin layer 10 and the metal thin film layer 22 is enhanced with the black chrome plating layer 5 interposed, and the function as an electromagnetic wave shield layer is sufficiently obtained.

(Conductive adhesive layer)
The conductive adhesive layer that forms the conductive layer 20 has conductivity and adhesiveness at least in the thickness direction.
As the conductive adhesive layer, an anisotropic conductive adhesive layer 24 having conductivity in the thickness direction and having no conductivity in the plane direction, or having conductivity in the thickness direction and the plane direction, etc. The one-way conductive adhesive layer 26 is included. The electromagnetic wave shielding film 1 including the anisotropic conductive adhesive layer 24 is shown in FIG. The electromagnetic wave shielding film 1 including the isotropic conductive adhesive layer 26 is shown in FIG.
The conductive adhesive layer can be made thin, the amount of conductive particles can be reduced, and as a result, the electromagnetic wave shielding film 1 can be made thin, and the flexibility of the electromagnetic wave shielding film 1 can be improved. 24 is preferred. The isotropic conductive adhesive layer 26 is preferable because it can sufficiently function as an electromagnetic wave shield layer.

As the conductive adhesive layer, a thermosetting conductive adhesive layer is preferable because it can exhibit heat resistance after curing. The thermosetting conductive adhesive layer may be in an uncured state or in a B-staged state.
The thermosetting anisotropic conductive adhesive layer 24 includes, for example, a thermosetting adhesive 24a and conductive particles 24b.
The thermosetting isotropic conductive adhesive layer 26 includes, for example, a thermosetting adhesive 26a and conductive particles 26b.

Examples of the thermosetting adhesive include those containing a thermosetting resin having adhesiveness and a curing agent.
Examples of the thermosetting resin include epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, and ultraviolet curing acrylate resin. As the thermosetting resin, an epoxy resin is preferable because it has excellent heat resistance.
Examples of the curing agent include known curing agents depending on the type of thermosetting resin.

When the thermosetting resin is an epoxy resin, the thermosetting adhesive may include a rubber component (carboxy-modified nitrile rubber, acrylic rubber, etc.) for imparting flexibility, a tackifier, and the like.
The thermosetting adhesive may contain a flame retardant, if necessary.
The thermosetting adhesive may contain a cellulose resin or microfibril (glass fiber or the like) in order to enhance the strength of the conductive adhesive layer and improve the punching property.
The thermosetting adhesive may contain other components, if necessary, within a range that does not impair the effects of the present invention.

  Examples of the conductive particles include particles of metal (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.), graphite powder, fired carbon particles, plated fired carbon particles, and the like. As the conductive particles, the conductive adhesive layer comes to have an appropriate hardness, from the viewpoint that the pressure loss in the conductive adhesive layer at the time of hot pressing can be reduced, metal particles are preferable, and copper particles are More preferable.

  The average particle diameter of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 2 μm or more and 26 μm or less, and more preferably 4 μm or more and 16 μm or less. When the average particle diameter of the conductive particles 24b is equal to or larger than the lower limit value of the above range, the thickness of the anisotropic conductive adhesive layer 24 can be secured and sufficient adhesive strength can be obtained. When the average particle diameter of the conductive particles 24b is equal to or less than the upper limit value of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (following the shape of the through holes of the insulating film) can be secured, and The inside of the through hole can be sufficiently filled with a conductive adhesive.

  The average particle diameter of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 0.1 μm or more and 10 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 26b is equal to or more than the lower limit value of the above range, the number of contact points of the conductive particles 26b increases, and the conductivity in the three-dimensional direction can be stably increased. When the average particle diameter of the conductive particles 26b is equal to or less than the upper limit value of the above range, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through hole of the insulating film) can be secured, and the insulating film The inside of the through hole can be sufficiently filled with a conductive adhesive.

  The proportion of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 1% by volume or more and 30% by volume or less, preferably 2% by volume or more and 10% by volume, out of 100% by volume of the anisotropic conductive adhesive layer 24. The following is more preferable. When the ratio of the conductive particles 24b is at least the lower limit value of the above range, the conductivity of the anisotropic conductive adhesive layer 24 will be good. When the ratio of the conductive particles 24b is equal to or less than the upper limit value of the above range, the anisotropic conductive adhesive layer 24 has good adhesiveness and fluidity (following the shape of the through holes of the insulating film). Moreover, the flexibility of the electromagnetic wave shielding film 1 is improved.

  The proportion of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 50% by volume or more and 80% by volume or less, and 60% by volume or more and 70% by volume, of 100% by volume of the isotropic conductive adhesive layer 26. The following is more preferable. When the ratio of the conductive particles 26b is at least the lower limit value of the above range, the conductivity of the isotropic conductive adhesive layer 26 will be good. When the ratio of the conductive particles 26b is equal to or less than the upper limit value of the above range, the adhesiveness and fluidity of the isotropic conductive adhesive layer 26 (the conformability to the shape of the through hole of the insulating film) will be good. Moreover, the flexibility of the electromagnetic wave shielding film 1 is improved.

The surface resistance of the anisotropic conductive adhesive layer 24 is preferably 1 × 10 ⁴ Ω / □ or more and 1 × 10 ¹⁶ Ω / □ or less, and more preferably 1 × 10 ⁶ Ω / □ or more and 1 × 10 ¹⁴ Ω / □ or less. preferable. When the surface resistance of the anisotropic conductive adhesive layer 24 is at least the lower limit value of the above range, the content of the conductive particles 24b can be suppressed low. When the surface resistance of the anisotropic conductive adhesive layer 24 is not more than the upper limit value of the above range, there is no problem in anisotropy in practical use.

  The surface resistance of the isotropic conductive adhesive layer 26 is preferably 0.05 Ω / □ or more and 2.0 Ω / □ or less, and more preferably 0.1 Ω / □ or more and 1.0 Ω / □ or less. When the surface resistance of the isotropic conductive adhesive layer 26 is at least the lower limit value of the above range, the content of the conductive particles 26b is suppressed to be low, the viscosity of the conductive adhesive does not become too high, and the coating property 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 secured. When the surface resistance of the isotropic conductive adhesive layer 26 is not more than the upper limit value of the above range, the entire surface of the isotropic conductive adhesive layer 26 has uniform conductivity.

  The thickness of the anisotropic conductive adhesive layer 24 is preferably 3 μm or more and 25 μm or less, and more preferably 5 μm or more and 15 μm or less. If the thickness of the anisotropic conductive adhesive layer 24 is not less than the lower limit value of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (following the shape of the through hole of the insulating film) can be secured, The through holes of the insulating film can be sufficiently filled with the conductive adhesive. If the thickness of the anisotropic conductive adhesive layer 24 is not more than the upper limit value of the above range, the electromagnetic wave shielding film 1 can be thinned. Moreover, the flexibility of the electromagnetic wave shielding film 1 is improved.

The thickness of the isotropic conductive adhesive layer 26 is preferably 5 μm or more and 20 μm or less, more preferably 7 μm or more and 17 μm or less. When the thickness of the isotropic conductive adhesive layer 26 is not less than the lower limit value 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 shield layer. In addition, the fluidity of the isotropic conductive adhesive layer 26 (the conformability to the shape of the through hole of the insulating film) can be secured, and the through hole of the insulating film can be sufficiently filled with the conductive adhesive to improve the resistance. Foldability can be ensured and the isotropic conductive adhesive layer 26 will not be broken even if it is repeatedly bent.
If the thickness of the isotropic conductive adhesive layer 26 is not more than the upper limit value of the above range, the electromagnetic wave shielding film 1 can be thinned. Moreover, the flexibility of the electromagnetic wave shielding film 1 is improved.

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

  The release film 40 has, for example, a release film body 42 and a release agent layer 44 provided on the surface of the release film body 42 on the side of the conductive adhesive layer.

Examples of the resin material of the release film main body 42 include polyethylene terephthalate (hereinafter sometimes referred to as “PET”), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, Examples thereof include ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, and liquid crystal polymer. As the resin material, PET is preferable from the viewpoint of heat resistance (dimensional stability) when manufacturing the electromagnetic wave shielding film 1 and price.
The release film main body 42 may include a colorant, a filler, and the like.
The thickness of the release film main 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 release agent layer 44 is formed by treating the surface of the release film main body 42 with a release agent. When the release film 40 has the release agent layer 44, when the release film 40 is released from the conductive adhesive layer, the release film 40 is easily released and the conductive adhesive layer is less likely to be broken. .
As the release agent, a known release agent may be used.

  The thickness of the release agent layer 44 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 release agent layer 44 is within the above range, the release film 40 can be more easily peeled off.

(Method for manufacturing electromagnetic wave shielding film)
The electromagnetic wave shielding film of the present invention can be produced, for example, by a method (A) in which the following steps (I) to (IV) are sequentially performed. Hereinafter, a method for producing the electromagnetic wave shielding film 1 shown in FIG. 1 in the case where the conductive adhesive layer is an anisotropic conductive adhesive layer will be described.
Step (I): A step of forming the black chrome plating layer 5 on one surface of the metal thin film layer 22.
Step (II): A step of forming the insulating resin layer 10 on the surface of the black chrome plating layer 5 opposite to the metal thin film layer 22.
Step (III): A step of forming the anisotropic conductive adhesive layer 24 on the other surface of the metal thin film layer 22.
Step (IV): A step of attaching the release film 40 to the surface of the anisotropic conductive adhesive layer 24 opposite to the metal thin film layer 22.

  Step (I): A metal foil is prepared as the metal thin film layer 22, and a laminated body in which a porous black chrome plating layer 5 is formed on one surface of the metal thin film layer 22 is obtained. As a method for forming the black chrome plating layer 5, a known method is applied, and examples thereof include an electrolytic plating method and an electroless plating method. When plating is performed, masking is performed with a film or the like so that the other surface of the metal thin film layer 22 is not plated.

  Step (II): The insulating resin layer 10 is formed by applying the resin material of the insulating resin layer 10 on the surface of the porous black chrome plating layer 5 and curing the resin. The coating method is not particularly limited, and examples include coating using various coaters, spray coating, dip coating, and the like. The method of curing the resin contained in the coating film is not particularly limited, and for example, in the case of a thermoplastic resin, the temperature of the coating film can be lowered to be cured, and in the case of a thermosetting resin, a curing agent of It can be cured by heating or light irradiation depending on the type.

Step (III): An anisotropic conductive adhesive layer 24 is formed on the other surface of the metal thin film layer 22. Examples of the method of forming the anisotropic conductive adhesive layer 24 include a method of applying a thermosetting conductive adhesive composition to the surface of the metal thin film layer 22.
As the thermosetting conductive adhesive composition, a composition containing the thermosetting adhesive 24a and the conductive particles 24b can be used.

  Step (IV): The adhesive surface of the release film 40 is attached to the surface of the anisotropic conductive adhesive layer 24 to obtain the electromagnetic wave shielding film 1.

(Other embodiments)
The electromagnetic wave shielding film of the present invention is not limited to the illustrated embodiment.
For example, when the tackiness of the surface of the conductive adhesive layer is small, the release film may have an adhesive layer instead of the release agent layer. Alternatively, the release film may be omitted.
When the release film main body has a high releasability, the release film may be composed of only the release film main body without a release agent layer.

<Printed wiring board with electromagnetic wave shielding film>
A second aspect of the present invention is a printed wiring board having a printed circuit provided on at least one surface of a substrate, an insulating film adjacent to a surface of the printed wiring board on the side where the printed circuit is provided, and a second aspect of the first aspect. A printed wiring board with an electromagnetic wave shielding film, comprising an electromagnetic wave shielding film.
It is preferable that the conductive adhesive layer of the electromagnetic wave shielding film is adjacent to the insulating film and that the conductive adhesive layer is electrically connected to the printed circuit through the through hole formed in the insulating film.

The flexible printed wiring board 2 with an electromagnetic wave shielding film illustrated in FIG. 3 includes a flexible printed wiring board 50, an insulating film 60, and the electromagnetic wave shielding film 1.
The flexible printed wiring board 50 is one in which a printed circuit 54 is provided on at least one surface of a 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 anisotropic conductive adhesive layer 24 of the electromagnetic wave shielding film 1 is adhered and cured on the surface of the insulating film 60. Further, the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through a through hole (not shown) formed in the insulating film 60.
In the flexible printed wiring board 2 with the electromagnetic wave shield film, the release film 40 is peeled off from the anisotropic conductive adhesive layer 24.

In the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) except for the portion having the through holes, the metal thin film layer 22 of the electromagnetic wave shielding film 1 includes the insulating film 60 and the anisotropic conductive adhesive layer 24. They are spaced apart and are opposed to each other.
The distance between the printed circuit 54 and the metal thin film layer 22 excluding the portion having the through hole is substantially equal to the total thickness of the insulating film 60 and the anisotropic conductive adhesive layer 24. 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 of 100Ω or the like, the line width of the signal circuit must be made small, and the variation in the line width causes the variation in the characteristic impedance. Then, the reflected resonance noise due to the impedance mismatch becomes easy to be carried on the electric signal. When the separation distance is larger than 200 μm, the flexible printed wiring board 2 with the electromagnetic wave shielding film becomes thick and the flexibility becomes insufficient.

(Flexible printed wiring board)
The flexible printed wiring board 50 is a printed circuit (power circuit, ground circuit, ground layer, etc.) 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 surface or both surfaces of the base film 52 via an adhesive layer (not shown); a resin solution for forming the base film 52 is cast on the surface of the copper foil. The thing etc. are mentioned.
Examples of the material of the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenol resin, urethane resin, acrylic resin, and melamine resin.
The thickness of the adhesive layer is preferably 0.5 μm or more and 30 μm or less.

(Base film)
As the base film 52, a film having heat resistance is preferable, a polyimide 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 preferably 1 × 10 ⁶ Ω / □ or more from the viewpoint of electrical insulation. The surface resistance of the base film 52 is preferably 1 × 10 ¹⁹ Ω / □ or less from the practical point of view.
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 25 μm or less, and more preferably 10 μm or more and 25 μm or less from the viewpoint of flexibility.

(Printed circuit)
Examples of the copper foil forming the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) include rolled copper foil, electrolytic copper foil and the like, and rolled copper foil is preferable from the viewpoint of flexibility.
The thickness of the copper foil is preferably 1 μm or more and 50 μm or less, more preferably 18 μm or more and 35 μm or less.
The lengthwise ends (terminals) of the printed circuit 54 are not covered with the insulating film 60 or the electromagnetic wave shielding film 1 because of solder connection, connector connection, component mounting, and the like.

(Insulating film)
The insulating film 60 (coverlay film) is one in which an adhesive layer (not shown) is formed on one surface of the insulating film body by applying an adhesive, attaching an adhesive sheet, or the like.
The surface resistance of the insulating film body is preferably 1 × 10 ⁶ Ω / □ or more from the viewpoint of electrical insulation. The surface resistance of the insulating film body is preferably 1 × 10 ¹⁹ Ω / □ or less from the practical point of view.
As the insulating film body, a film having heat resistance is preferable, a polyimide 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, polyamideimide, polyamide, phenol resin, urethane resin, acrylic resin, melamine resin, polystyrene and polyolefin. The epoxy resin may include a rubber component (carboxy-modified nitrile rubber or the like) for imparting flexibility.
The thickness of the adhesive layer is preferably 1 μm or more and 100 μm or less, more preferably 1.5 μm or more and 60 μm or less.

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

  The printed wiring board 2 with an electromagnetic wave shielding film illustrated in FIG. 4 is the same as the printed wiring board 2 with an electromagnetic wave shielding film in FIG. 3 except that the printed wiring board 2 with an isotropic conductive adhesive layer 26 is provided.

(Method for manufacturing printed wiring board with electromagnetic wave shielding film)
The printed wiring board with an electromagnetic wave shielding film of the present invention can be manufactured by, for example, a method of sequentially performing the following steps (a) to (c). Hereinafter, a manufacturing method in the case where the electromagnetic wave shielding film includes the anisotropic conductive adhesive layer will be described.
Step (a): A step of providing a printed wiring board with an insulating film by providing an insulating film having through holes at positions corresponding to the printed circuit on the surface of the printed wiring board on which the printed circuit is provided.
Step (b): A printed wiring board with an insulating film and the electromagnetic wave shielding film of the present invention from which the release film has been peeled off are stacked so that the conductive adhesive layer contacts the surface of the insulating film, and these are hot pressed. Thus, a step of adhering a conductive adhesive layer to the surface of the insulating film, and electrically connecting the conductive adhesive layer to the printed circuit through the through hole to obtain a printed wiring board with an electromagnetic wave shielding film.
Step (c): A step of main curing the anisotropic conductive adhesive layer, if necessary.

  Hereinafter, a method for manufacturing a flexible printed wiring board with an electromagnetic wave shielding film will be described with reference to FIG.

(Process (a))
An insulating film 60 having through holes 62 formed at positions corresponding to the printed circuit 54 is placed on the flexible printed wiring board 50, and an adhesive layer (not shown) of the insulating film 60 is adhered to the surface of the flexible printed wiring board 50. By curing the adhesive layer, the flexible printed wiring board 3 with an insulating film is obtained. 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 fully cured in the step (c). Adhesion and curing of the adhesive layer can be performed, for example, by hot pressing with a pressing machine (not shown) or the like.

(Process (b))
The electromagnetic shielding film 1 from which the release film 40 has been peeled off is placed on the flexible printed wiring board 3 with an insulating film, and hot pressed to bond the anisotropic conductive adhesive layer 24 to the surface of the insulating film 60, and The flexible printed wiring board 2 with the electromagnetic wave shielding film in which the one-way conductive adhesive layer 24 is electrically connected to the printed circuit 54 through the through hole 62 is obtained.

The anisotropic conductive adhesive layer 24 is adhered and cured by, for example, hot pressing using a pressing machine (not shown) or the like.
The time of hot pressing is 20 seconds or more and 60 minutes or less, and more preferably 30 seconds or more and 30 minutes or less. If the time of hot pressing is not less than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is bonded to the surface of the insulating film 60. Further, the insulating resin layer 10 is sufficiently cured, and the peeling force at the interface between the insulating resin layer 10 and the carrier film 30 is sufficiently reduced. If the time of hot pressing is not more than the upper limit value of the above range, the manufacturing time of the flexible printed wiring board 2 with the electromagnetic wave shielding film can be shortened.

  The temperature of hot pressing (temperature of hot plate of press) 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 hot pressing is not less than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is sufficiently adhered to the surface of the insulating film 60. Also, the time of heat pressing can be shortened. Moreover, the insulating resin layer 10 is sufficiently cured. When the temperature of the hot press is equal to or lower than the upper limit value of the above range, deterioration of the electromagnetic wave shielding film 1, the flexible printed wiring board 50 and the like can be suppressed.

  The pressure of the hot press is preferably 0.5 MPa or more and 20 MPa or less, more preferably 1 MPa or more and 16 MPa or less. When the pressure of the hot press is not less than the lower limit value of the above range, the anisotropic conductive adhesive layer 24 is sufficiently adhered to the surface of the insulating film 60. Also, the time of heat pressing can be shortened. When the pressure of the hot press is equal to or lower than the upper limit value of the above range, it is possible to suppress damage to the electromagnetic wave shielding film 1, the flexible printed wiring board 50 and the like.

(Process (c))
When the time of hot pressing in the step (b) is a short time of 20 seconds or more and 10 minutes or less, it is preferable to perform the main curing of the anisotropic conductive adhesive layer 24 after the step (b).
The main curing of the anisotropic conductive adhesive layer 24 is performed using a heating device such as an oven.
The heating time is 15 minutes or more and 120 minutes or less, and preferably 30 minutes or more and 60 minutes or less. When the heating time is at least the lower limit value of the above range, the anisotropic conductive adhesive layer 24 can be sufficiently cured. If the heating time is not more than the upper limit value of the above range, the manufacturing time of the flexible printed wiring board 2 with the electromagnetic wave shielding film can be shortened.
The heating temperature (ambient 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 at least the lower limit value of the above range, the heating time can be shortened. When the heating temperature is equal to or lower than the upper limit value of the above range, deterioration of the electromagnetic wave shielding film 1, the flexible printed wiring board 50 and the like can be suppressed.
It is preferable to perform heating without pressurization, because a special device does not have to be used.

(Other embodiments)
The printed wiring board with an electromagnetic wave shielding film of the present invention includes a printed wiring board, an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided, a conductive layer adjacent to the insulating film, and a conductive layer. The layer is not limited to the illustrated embodiment, as long as the layer has the electromagnetic wave shielding film of the present invention electrically connected to the printed circuit through the through hole formed in the insulating film.
For example, the flexible printed wiring board may have a ground layer on the back surface side. Further, the flexible printed wiring board may have a printed circuit on both sides and have an insulating film and an electromagnetic wave shielding film attached to both sides.
Instead of the flexible printed wiring board, an inflexible rigid printed board may be used.
The anisotropic conductive adhesive layer 24 may be an isotropic conductive adhesive layer 26.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Coating for forming insulating resin layer>
100 parts by mass of bisphenol A type epoxy resin (Mitsubishi Chemical Co., jER (registered trademark) 828), 20 parts by mass of a curing agent (Showa Denko KK, Shoamine X (registered trademark)), 2-ethyl-4- 2 parts by mass of methylimidazole and 2 parts by mass of carbon black were dissolved in 200 parts by mass of a solvent (methyl ethyl ketone) to prepare a coating material for forming an insulating resin layer.

<Coating for forming conductive adhesive layer>
100 parts by mass of a thermosetting adhesive (EXA-4816, manufactured by DIC Co., Ltd.) made of an epoxy resin and 20 parts by mass of a curing agent (PN-23, manufactured by Ajinomoto Fine-Techno Co., Ltd.) are mixed to obtain latent curability. An epoxy resin composition was obtained.
The latent curable epoxy resin composition and 40 parts by mass of copper particles (average particle diameter: 7.5 μm) are dispersed in 200 parts by mass of a solvent (methyl ethyl ketone) to prepare a conductive adhesive layer forming coating material. did.

<Release film>
As a release film, a PET film (T157 manufactured by Lintec Co., Ltd.) having one surface subjected to a release treatment with a non-silicone release agent was prepared.

[Example 1]
<Production of electromagnetic wave shielding film>
First, after forming a nickel plating layer (thickness: 0.1 μm) on one surface of a rolled copper foil (thickness: 5 μm), a black chrome plating layer (thickness: 0.3 μm) is further formed by a conventional method. The formed laminated body was obtained. During this plating, a masking film was attached to the other surface of the rolled copper foil to prevent the formation of a plated layer. When the surface of the formed black chrome plating layer was observed with a magnifying glass, it was found to be a complex sponge-like porosity.
On the surface of the black chrome plated layer of the rolled copper foil obtained above, the above-mentioned coating material for forming an insulating resin layer is applied, heated at 60 ° C. for 2 minutes, and the coating material is dried and semi-cured to form an insulating resin layer S: 10 μm) was formed.
Next, the masking film was peeled off from the other surface of the rolled copper foil having the insulating resin layer formed thereon, and the surface of the rolled copper foil where the copper was exposed was coated with the above-mentioned conductive adhesive layer-forming coating by Daiko. Then, the solvent was volatilized to form a B-stage to form an anisotropic conductive adhesive layer (thickness: 7 μm, copper particles: 4.5% by volume).
The release film was attached to the surface of the anisotropic conductive adhesive layer formed above opposite to the metal thin film layer to obtain an electromagnetic wave shielding film of Example 1.

[Example 2]
An electromagnetic wave shield film was prepared in the same manner as in Example 1 except that the thickness of the black chrome plating layer formed on one surface of the rolled copper foil was changed to 3.0 μm.

[Comparative Example 1]
An electromagnetic wave shielding film was prepared in the same manner as in Example 1 except that only the nickel plating layer (thickness: 0.3 μm) was formed on one surface of the rolled copper foil, and the black chrome plating layer was not formed. did.

[Comparative Example 2]
An electromagnetic wave shield film was prepared in the same manner as in Comparative Example 1 except that the thickness of the nickel plating layer formed on one surface of the rolled copper foil was changed to 3.0 μm.

[Comparative Example 3]
An electromagnetic wave shielding film was prepared in the same manner as in Example 1 except that the plated layer was not formed on one surface of the rolled copper foil and the coating material for forming the insulating resin layer was applied to the exposed copper surface.

[Comparative Example 4]
An electromagnetic wave shield film was prepared in the same manner as Comparative Example 3 except that one surface of the rolled copper foil was roughened in advance using sandpaper, and the roughened copper surface was coated with the insulating resin layer-forming coating material. It was created.

[Peeling strength measurement method]
With respect to the electromagnetic wave shielding film of each example, the adhesiveness between the insulating resin layer and the metal thin film layer was evaluated by the following method.
A 25 μm-thick polyimide film was laminated with an electromagnetic wave shielding film from which the release film had been peeled off, and a hot press machine (G-12 manufactured by Orihara Manufacturing Co., Ltd.) was used to heat the platen temperature: 180 ° C., load: 2 MPa for 120 seconds. Pressed. In this way, the anisotropic conductive adhesive layer was temporarily adhered to the surface of the insulating film to obtain a polyimide with an electromagnetic wave shielding film.
The anisotropic conductive adhesive layer was fully cured by heating the polyimide film with an electromagnetic wave shielding film in a high temperature tank (HT210 manufactured by Kusumoto Kasei Co., Ltd.) at a temperature of 160 ° C. for 1 hour.
Next, a polyimide reinforcing plate having a thickness of 25 μm was thermocompression bonded to the surface of the insulating resin layer of the electromagnetic wave shielding film via a bonding sheet (D3410 manufactured by Dexerials Co., Ltd.) to prepare a test piece for tensile test.
A chuck of a tensile tester was attached to the polyimide film and the polyimide reinforcing plate of the test piece, and a peeling test was performed according to JIS Z0237 under the conditions of a 180 ° peeling direction and a pulling speed of 50 mm / min.

[Peel strength measurement results]
The test piece using the electromagnetic wave shielding film of Example 1 had a peel strength of 4.8 N / cm, and peeling occurred at the interface between the insulating resin layer and the black chrome plating layer.
In the test piece using the electromagnetic wave shielding film of Example 2, the peel strength was 4.4 N / cm, peeling occurred between the insulating resin layer and the metal thin film layer, and part of the layer structure of the black chrome plating layer. Was destroyed.
The test piece using the electromagnetic wave shielding film of Comparative Example 1 had a peel strength of 3.2 N / cm, and peeling occurred at the interface between the insulating resin layer and the nickel plating layer.
The test piece using the electromagnetic wave shielding film of Comparative Example 2 had a peel strength of 3.2 N / cm, and peeling occurred at the interface between the insulating resin layer and the nickel plating layer.
The test piece using the electromagnetic wave shielding film of Comparative Example 3 had a peel strength of 3.1 N / cm, and peeling occurred at the interface between the insulating resin layer and the metal thin film layer.
The test piece using the electromagnetic wave shielding film of Comparative Example 4 had a peel strength of 3.2 N / cm, and peeling occurred at the interface between the insulating resin layer and the metal thin film layer.

  From the above results, in Examples 1 and 2 in which the porous black chrome plating layer is interposed between the insulating resin layer and the metal thin film layer, the peel strength of the insulating resin layer is high and the insulating resin layer and the metal thin film layer are It was found that the adhesive strength of was excellent.

  The electromagnetic wave shielding film of the present invention is useful as an electromagnetic wave shielding member in a flexible printed wiring board for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game machines, notebook computers, and medical equipment.

1 Electromagnetic Wave Shield Film 2 Flexible Printed Wiring Board with Electromagnetic Wave Shielding Film 3 Flexible Printed Wiring Board with Insulating Film 5 Black Chrome Plating Layer 10 Insulating Resin Layer 22 Metal Thin Film Layer 24 Anisotropic Conductive Adhesive Layer 24a Thermosetting Adhesive 24b Conductive Particles 26 isotropic conductive adhesive layer 26a thermosetting adhesive 26b conductive particles 40 release film 42 release film body 44 release agent layer 50 flexible printed wiring board 52 base film 54 printed circuit 60 insulating film 62 through Hole

Claims (6)

  An insulating resin layer, a porous black chrome plating layer, a metal thin film layer, and a conductive adhesive layer are laminated in this order, and the insulating resin layer is in contact with the surface of the black chrome plating layer. , Electromagnetic wave shielding film.   The electromagnetic wave shielding film according to claim 1, wherein the metal thin film layer is a metal foil.   The electromagnetic wave shielding film according to claim 1, wherein the black chrome plating layer has a thickness of 0.1 μm or more and 1 μm or less.   The electromagnetic wave shield film according to any one of claims 1 to 3, wherein the black chromium plating layer contains chromium oxide or hydroxide. It is a manufacturing method of the electromagnetic wave shield film according to any one of claims 1 to 4,
The insulating resin layer is prepared by preparing a laminate in which a porous black chrome plating layer and a metal thin film layer are laminated in this order, and applying an insulating resin to the surface of the black chrome plating layer of the laminate. A method for producing an electromagnetic wave shielding film, the method including the step of forming. A printed wiring board provided with a printed circuit on at least one surface of a substrate, an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided, and the opposite side of the insulating film from the printed wiring board. The electromagnetic wave shielding film according to any one of claims 1 to 4 provided in,
A printed wiring board with an electromagnetic wave shielding film, wherein the conductive adhesive layer of the electromagnetic wave shielding film is adjacent to the insulating film.

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