JP7022573B2 - Printed wiring board with electromagnetic wave shielding film and its manufacturing method - Google Patents

Description

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

In order to shield electromagnetic noise generated from a printed wiring board and electromagnetic noise from the outside, an insulating film (coverlay film) is used as an electromagnetic shielding film composed of an insulating resin layer and a conductive layer adjacent to the insulating resin layer. It may be provided on the surface of the printed wiring board via (see, for example, Patent Document 1).
In the electromagnetic wave shielding film, for example, a paint containing a thermosetting resin, a curing agent, and a solvent is applied to one side of a carrier film and dried to form an insulating resin layer, and a conductive layer is provided on the surface of the insulating resin layer. Manufactured by The conductive layer is often formed of a metal thin film layer and a conductive adhesive layer.

In a printed wiring board with an electromagnetic wave shielding film, gas is generated in the conductive adhesive layer or the like when heated for solder reflow, and the expansion of the gas causes the conductive adhesive layer and the metal thin film layer to peel off. Sometimes.
As a method for preventing the peeling, it is disclosed that an air-permeable metal foil is used as a metal thin film layer constituting a printed wiring board with an electromagnetic wave shielding film (Patent Document 2).

Japanese Unexamined Patent Publication No. 2016-86120 Japanese Unexamined Patent Publication No. 2005-276873

However, in the conventional printed wiring board with an electromagnetic wave shielding film, the adhesive strength of the conductive adhesive layer may not be sufficient with respect to the metal thin film layer, and it may be peeled off. Further, since the insulating resin layer does not have strong adhesiveness, the adhesive strength to the metal thin film layer is insufficient, and the insulating resin layer may be peeled off.
An object of the present invention is to provide a printed wiring board with an electromagnetic wave shielding film capable of preventing peeling of an insulating resin layer and a conductive adhesive layer from a metal thin film layer, and a method for manufacturing the same.

The present invention includes the following aspects.
[1] A printed wiring board provided with a printed circuit on at least one side of a substrate, an insulating film adjacent to the side surface of the printed wiring board provided with the printed circuit, and the printed wiring board of the insulating film. Has an electromagnetic shielding film, which is provided on the opposite side,
The electromagnetic wave shielding film includes an insulating resin layer, a metal thin film layer adjacent to the insulating resin layer, and a conductive adhesive layer provided on a surface of the metal thin film layer opposite to the insulating resin layer. Have and
A plurality of through holes are formed in the metal thin film layer, and the amount of the through holes formed is 1000 pieces / cm ² or more and 100,000 pieces / cm ² or less.
The conductive adhesive layer is a printed wiring board with an electromagnetic wave shielding film containing conductive particles.
[2] The printed wiring board with an electromagnetic wave shielding film according to [1], wherein the diameter of the minimum circle including the through hole is 0.1 μm or more and 20 μm or less.
[3] The printed wiring board with an electromagnetic wave shielding film according to [1] or [2], wherein the thickness of the metal thin film layer is 0.01 μm or more and 3 μm or less.
[4] The printed wiring board with an electromagnetic wave shielding film according to any one of [1] to [3], wherein the average particle diameter of the conductive particles is 3 μm or more and 20 μm or less.
[5] The printed wiring board with an electromagnetic wave shielding film according to any one of [1] to [4], wherein the conductive particles are metal particles.

[6] The method for manufacturing a printed wiring board with an electromagnetic wave shielding film according to any one of [1] to [5].
It has an electromagnetic wave shielding film manufacturing process and a crimping process.
In the electromagnetic wave shielding film manufacturing step, the insulating resin layer, the non-perforated metal thin film layer adjacent to the insulating resin layer, and the conductive adhesive provided on the surface of the metal thin film layer on the side opposite to the insulating resin layer. An electromagnetic shielding film having an agent layer is prepared, and
In the crimping step, the electromagnetic wave shielding film having the non-perforated metal thin film layer and the printed wiring plate are crimped with the insulating film sandwiched between them, and the conductive particles contained in the conductive adhesive layer are pressed. A method for manufacturing a printed wiring board with an electromagnetic wave shielding film, which is pressed into a metal thin film layer to perforate the metal thin film layer to form the through hole.
[7] The method for manufacturing a printed wiring board with an electromagnetic wave shielding film according to [6], wherein in the crimping step, the pressure at the time of crimping is 1 MPa or more and 30 MPa or less.

The printed wiring board with an electromagnetic wave shielding film of the present invention can prevent the insulating resin layer and the conductive adhesive layer from peeling off from the metal thin film layer.
According to the method for manufacturing a printed wiring board with an electromagnetic wave shielding film of the present invention, a printed wiring board with an electromagnetic wave shielding film can be easily manufactured with good yield.

It is sectional drawing which shows the printed wiring board with the electromagnetic wave shielding film of 1st Embodiment. It is sectional drawing which shows the printed wiring board with the electromagnetic wave shielding film of 2nd Embodiment. It is sectional drawing which shows the electromagnetic wave shielding film used when manufacturing the printed wiring board with the electromagnetic wave shielding film of FIG. It is sectional drawing which shows the manufacturing process of the printed wiring board with the electromagnetic wave shielding film of FIG.

The definitions of the following terms apply throughout the specification and claims.
The "isotropic conductive adhesive layer" means a conductive adhesive layer having conductivity in the thickness direction and the surface direction.
The "anisotropic adhesive layer" means a conductive adhesive layer having conductivity in the thickness direction and not 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.
For the average particle size of the particles, 30 particles are randomly selected from the microscopic image of the particles, the minimum and maximum diameters are measured for each particle, and the median value between the minimum and maximum diameters is the particle of one particle. It is a value obtained by arithmetically averaging the particle diameters of the 30 measured particles as the diameter. The same applies to the average particle size of the conductive particles.
The thickness of the film (separation film, insulating film, etc.), coating film (insulating resin layer, conductive adhesive layer, etc.), metal thin film layer, etc. can be determined by observing the cross section of the measurement target using a microscope at 5 locations. The thickness is measured and averaged.
The storage elastic modulus is calculated from the stress applied to the measurement target and the detected strain, and is measured as one of the viscoelastic properties by using a dynamic viscoelastic measuring device that outputs as a function of temperature or time.
The 10% compressive strength of the conductive particles is obtained by the following formula (α) from the measurement results using the micro-compression tester.
C (x) = 2.48P / πd ² (α)
However, C (x) is the 10% compressive strength (MPa), P is the test force (N) when the particle size is displaced by 10%, and d is the particle size (mm).
For the surface resistance, two thin film metal electrodes (length 10 mm, width 5 mm, distance between electrodes 10 mm) formed by depositing gold on quartz glass are used, and an object to be measured is placed on the electrodes to be measured. It is the resistance between the electrodes measured from the object by pressing a region of 10 mm × 20 mm of the object to be measured with a load of 0.049 N and measuring a measurement current of 1 mA or less.
The dimensional ratios in FIGS. 1 to 4 are different from the actual ones for convenience of explanation.

<< Printed wiring board with electromagnetic wave shield film >>
An aspect of the printed wiring board with an electromagnetic wave shielding film of the present invention will be described.
The printed wiring board with an electromagnetic wave shielding film of this embodiment includes a printed wiring board provided with a printed circuit on at least one side of the substrate, and an insulating film adjacent to the surface of the printed wiring board on the side where the printed circuit is provided. The adhesive layer has an electromagnetic wave shielding film provided so as to be adjacent to the insulating film.

Hereinafter, embodiments of the printed wiring board with the electromagnetic wave shielding film of this embodiment will be described.
1 and 2 show a printed wiring board with an electromagnetic wave shielding film according to an embodiment. FIG. 1 is a cross-sectional view showing a printed wiring board 1a with an electromagnetic wave shielding film of the first embodiment, and FIG. 2 is a cross-sectional view showing a printed wiring board 1b with an electromagnetic wave shielding film of the second embodiment.
Both the printed wiring boards 1a and 1b with the electromagnetic wave shielding film of the first embodiment and the second embodiment include the electromagnetic wave shielding film 2, the flexible printed wiring board 50, and the insulating film 60. The flexible printed wiring board 50 includes a printed circuit 54. Through holes are formed in the insulating film 60.

<Electromagnetic wave shield film>
The electromagnetic wave shielding film 2 used in the first embodiment and the second embodiment has an insulating resin layer 10 and a conductive layer 20 adjacent to the insulating resin layer 10.
In the electromagnetic wave shielding film 2 of the first embodiment, the conductive layer 20 has a metal thin film layer 22 adjacent to the insulating resin layer 10 and an anisotropic conductive adhesive layer 24 (conductive adhesive layer 24) adjacent to the insulating film 60. ) And.
In the electromagnetic wave shielding film 2 of the second embodiment, the conductive layer 20 has a metal thin film layer 22 adjacent to the insulating resin layer 10 and an isotropic conductive adhesive layer 26 (conductive adhesive layer 26) adjacent to the insulating film 60. ) And.

(Insulating resin layer)
The insulating resin layer 10 serves as a protective layer for the conductive layer 20.
The insulating resin layer 10 is a coating film formed by applying a coating material containing a thermosetting resin and a curing agent and semi-curing or curing; a coating film formed by applying a coating material containing a thermoplastic resin; Examples thereof include a layer made of a film obtained by melt-molding a composition containing a thermoplastic resin. From the viewpoint of heat resistance at the time of soldering or the like, a coating film formed by applying a paint containing a thermosetting resin and a curing agent and semi-curing or curing is preferable.

Examples of the thermosetting resin include amide resin, epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, and ultraviolet curable acrylate resin. One type of thermosetting resin may be used alone, or two or more types may be used in combination. Among the thermosetting resins, amide resins and epoxy resins 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.

The insulating resin layer 10 contains a colorant (pigment, dye, etc.) and a colorant (pigment, dye, etc.) in order to conceal the printed circuit 54 of the flexible printed wiring board 50 and to impart designability to the printed wiring boards 1a and 1b with the electromagnetic wave shielding film. It may contain either or both of the fillers.
As one or both of the colorant and the filler, a pigment or a filler is preferable from the viewpoint of weather resistance, heat resistance and concealing property, and a black pigment or a black pigment is used from the viewpoint of concealing property and designability of a printed circuit. Combinations with other pigments or fillers are more preferred.

The insulating resin layer 10 may contain a flame retardant.
The insulating resin layer 10 may contain other components, if necessary, as long as the effects of the present invention are not impaired.

The storage elastic modulus of the insulating resin layer 10 at 180 ° C. is preferably 5 × 10 ⁶ Pa or more and 5 × 10 ⁹ Pa or less, and more preferably 1 × 10 ⁷ Pa or more and 1 × 10 ⁹ Pa or less. When the storage elastic modulus of the insulating resin layer 10 at 180 ° C. is equal to or higher than the lower limit of the above range, the insulating resin layer 10 has an appropriate hardness, and the pressure loss in the insulating resin layer 10 during hot pressing is increased. Can be reduced. As a result, the conductive adhesive layers 24 and 26 and the printed circuit 54 of the flexible printed wiring board 50 are sufficiently adhered, and the conductive adhesive layers 24 and 26 pass through the through holes of the insulating film 60 and the flexible printed wiring board. It is securely electrically connected by the printed circuit 54 of 50. When the storage elastic modulus of the insulating resin layer 10 at 180 ° C. is not more than the upper limit of the above range, the flexibility of the electromagnetic wave shielding film 2 is improved. As a result, the electromagnetic wave shielding film 2 tends to sink into the through hole of the insulating film 60, and the conductive adhesive layer passes through the through hole of the insulating film 60 and is reliably electrically operated by the printed circuit 54 of the flexible printed wiring board 50. Connected to.

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 at least the lower limit of the above range, the insulating resin layer 10 can sufficiently exert the function as a protective layer. When the thickness of the insulating resin layer 10 is not more than the upper limit of the above range, the electromagnetic wave shielding film 2 can be thinned.

(Conductive layer)
As described above, the conductive layer 20 in the first embodiment has a metal thin film layer 22 adjacent to the insulating resin layer 10 and an anisotropic conductive adhesive layer 24 adjacent to the insulating film 60.
The conductive layer 20 in the second embodiment has a metal thin film layer 22 adjacent to the insulating resin layer 10 and an isotropic conductive adhesive layer 26 adjacent to the insulating film 60.

[Metallic thin film layer]
The metal thin film layer 22 in the present embodiment is a porous metal thin film layer in which a plurality of through holes 22h are formed. Since the metal thin film layer 22 is formed so as to spread in the surface direction, it has conductivity in the surface direction and functions as an electromagnetic wave shielding layer or the like.

Examples of the metal constituting the metal thin film layer 22 include aluminum, silver, copper, gold, conductive ceramics, and the like, and silver or copper is preferable from the viewpoint of electrical conductivity.

The metal thin film layer 22 is a layer in which through holes are formed in the non-porous metal thin film layer.
Examples of the non-porous metal thin film layer include a vapor deposition film formed by physical vapor deposition (vacuum vapor deposition, sputtering, ion beam vapor deposition, electron beam vapor deposition, etc.) or chemical vapor deposition, a plating film formed by plating, a metal foil, and the like. A vapor-deposited film or a plated film is preferable as the non-porous metal thin film layer in terms of excellent surface conductivity. The non-porous metal thin film layer is more preferably a thin-film deposition film in that the metal thin film layer 22 can be made thin, has excellent surface conductivity even if it is thin, and can be easily formed by a dry process. A film is more preferable, and a silver-film-deposited layer or a copper-deposited layer is particularly preferable.

The number of through holes 22h formed in the metal thin film layer 22 is 1000 pieces / cm ² or more and 100,000 pieces / cm ² or less, preferably 5000 pieces / cm ² or more and 80,000 pieces / cm ² or less, preferably 6000. More preferably, the number of pieces / cm is ² or more and 60,000 pieces / cm ² or less. The number of through holes 22h is determined by measuring the number of through holes 22h using a microscope for a plurality of randomly selected areas having an area of 1 cm ² and averaging the number of through holes 22h in the measured areas. Can be done.
When the number of through holes 22h formed in the metal thin film layer 22 is equal to or greater than the lower limit of the above range, the insulating resin layer 10 and the conductive adhesive layers 24 and 26 can be bonded with sufficient adhesive strength. This makes it possible to prevent the insulating resin layer and the conductive adhesive layer from peeling off from the metal thin film layer 22. When the number of through holes 22h formed in the metal thin film layer 22 is not more than the upper limit of the above range, the electromagnetic wave shielding property of the electromagnetic wave shielding film 2 can be sufficiently improved.
The shape of the opening of the through hole 22h of the metal thin film layer 22 is not particularly limited, and may be, for example, a circular shape, an elliptical shape, a polygonal shape (for example, a triangular shape, a quadrangular shape, etc.), or an indefinite shape. good.
The diameter of the minimum circle including the through hole 22h of the metal thin film layer 22 is preferably 0.1 μm or more and 20 μm or less, more preferably 1 μm or more and 15 μm or less, and further preferably 5 μm or more and 15 μm or less. When the diameter of the through hole 22h of the metal thin film layer 22 is at least the lower limit of the above range, the adhesive strength between the insulating resin layer 10 and the conductive adhesive layers 24 and 26 can be further increased. When the diameter of the through hole 22h of the metal thin film layer 22 is not more than the upper limit of the above range, the electromagnetic wave shielding property of the electromagnetic wave shielding film 2 can be sufficiently ensured.
In a plan view, the through hole 22h overlaps with the conductive particles 24b and 26b contained in the conductive adhesive layers 24 and 26 described later.

The thickness of the metal thin film layer 22 is preferably 0.01 μm or more and 3 μm or less, more preferably 0.03 μm or more and 1 μm or less, further preferably 0.05 μm or more and 0.5 μm or less, and particularly preferably 0.07 μm or more and 0.4 μm or less. preferable. 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 shielding effect of electromagnetic noise is further improved. When the thickness of the metal thin film layer 22 is not more than the upper limit of the above range, the electromagnetic wave shielding film 2 can be thinned, and the productivity and flexibility of the electromagnetic wave shielding film 2 are improved.

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. When the surface resistance of the metal thin film layer 22 is at least the lower limit of the above range, the metal thin film layer 22 can be sufficiently thinned. If the surface resistance of the metal thin film layer 22 is not more than the upper limit of the above range, it can sufficiently function as an electromagnetic wave shielding layer.

[Anteroconductive adhesive layer]
The anisotropic conductive adhesive layer 24 in the first embodiment has conductivity in the thickness direction, does not have conductivity in the plane direction, and has adhesiveness.
The anisotropic conductive adhesive layer 24 can easily thin the conductive adhesive layer and reduce the amount of the conductive particles described later, and as a result, the electromagnetic wave shielding film 2 can be thinned, and the electromagnetic wave shielding film 2 can be used. It has the advantage of being highly sexual.

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

Examples of the thermosetting adhesive 24a include epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, ultraviolet curable acrylate resin and the like. Epoxy resin is preferable because it has excellent heat resistance. The epoxy resin may contain a rubber component (carboxy-modified nitrile rubber, acrylic rubber, etc.) for imparting flexibility, a tackifier, and the like.
The thermosetting adhesive 24a may contain a cellulose resin, microfibrils (glass fiber, etc.) in order to increase the strength of the anisotropic conductive adhesive layer 24 and improve the punching characteristics. The thermosetting adhesive may contain other components, if necessary, as long as the effects of the present invention are not impaired.

Examples of the conductive particles 24b include metal particles (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.), graphite powder, calcined carbon particles, plated calcined carbon particles, and the like. As the conductive particles 24b, metal particles are preferable because the anisotropic conductive adhesive layer 24 has a more appropriate hardness and can suppress the loss of pressure applied during the crimping step described later. , Copper particles are more preferred.

The 10% compressive strength of the conductive particles 24b is preferably 30 MPa or more and 200 MPa or less, more preferably 50 MPa or more and 150 MPa or less, and further preferably 70 MPa or more and 100 MPa or less. When the 10% compressive strength of the conductive particles is equal to or higher than the lower limit of the above range, it can be used for drilling a non-porous metal thin film layer without losing the pressure applied during the crimping step described later. Further, when the 10% compressive strength of the conductive particles is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 24 sufficiently penetrates into the through hole of the insulating film 60 to sufficiently penetrate the printed circuit of the flexible printed wiring board 50. The 54 ensures an electrical connection. When the 10% compressive strength of the conductive particles 24b is not more than the upper limit of the above range, the contact with the metal thin film layer 22 is improved and the electrical connection is ensured.

The average particle diameter of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 3 μm or more and 20 μm or less, and more preferably 5 μm or more and 10 μm or less. When the average particle diameter of the conductive particles 24b is at least the lower limit 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 of the above range, the anisotropic conductive adhesive layer 24 sufficiently penetrates into the through hole of the insulating film 60 by the printed circuit 54 of the flexible printed wiring board 50. Securely electrically connected.

The proportion of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 1% by volume or more and 50% by volume or less, preferably 10% by volume or more and 30% 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 equal to or higher than the lower limit of the above range, the conductivity of the anisotropic conductive adhesive layer 24 becomes good. When the ratio of the conductive particles 24b is not more than the upper limit of the above range, the adhesiveness and fluidity (following the shape of the through hole of the insulating film 60) of the anisotropic conductive adhesive layer 24 are good. In addition, the flexibility of the electromagnetic wave shielding film 2 is improved.

The storage elastic modulus of the anisotropic conductive adhesive layer 24 at 180 ° C. is preferably 1 × 10 ³ Pa or more and 5 × 10 ⁷ Pa or less, and more preferably 5 × 10 ³ Pa or more and 1 × 10 ⁷ Pa or less. When the storage elastic modulus of the anisotropic conductive adhesive layer 24 at 180 ° C. is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 24 has a more appropriate hardness, and the crimping step described later The loss of pressure applied at the time can be suppressed. As a result, the conductive adhesive layer and the printed circuit 54 of the flexible printed wiring board 50 are sufficiently adhered, and the anisotropic conductive adhesive layer 24 enters the through hole of the insulating film 60 to form the flexible printed wiring board 50. It is securely electrically connected by the printed circuit 54. When the storage elastic modulus of the conductive adhesive layer at 180 ° C. is not more than the upper limit of the above range, the flexibility of the electromagnetic wave shielding film 2 is improved. As a result, the electromagnetic wave shielding film 2 easily sinks into the through hole of the insulating film 60, and the anisotropic conductive adhesive layer 24 sufficiently penetrates into the through hole of the insulating film 60 to sufficiently penetrate the printed circuit of the flexible printed wiring board 50. The 54 ensures an electrical connection.

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. When the surface resistance of the anisotropic conductive adhesive layer 24 is at least the lower limit of the above range, the content of the conductive particles 24b can be suppressed to a low level. If the surface resistance of the anisotropic conductive adhesive layer 24 is not more than the upper limit of the above range, there is no problem in practically anisotropy.

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. When the thickness of the anisotropic conductive adhesive layer 24 is at least the lower limit of the above range, the fluidity of the anisotropic conductive adhesive layer 24 becomes high, and the anisotropic conductive adhesive layer 24 is the insulating film 60. It penetrates sufficiently into the through hole and is securely electrically connected by the print circuit 54 of the flexible printed wiring board 50. When the thickness of the anisotropic conductive adhesive layer 24 is not more than the upper limit of the above range, the electromagnetic wave shielding film 2 can be thinned. In addition, the flexibility of the electromagnetic wave shielding film 2 is improved.

[Isotropic conductive adhesive layer]
The isotropic conductive adhesive layer 26 in the second embodiment has conductivity in the thickness direction and the surface direction, and has adhesiveness.
The isotropic conductive adhesive layer 26 has an advantage that the electromagnetic wave shielding property of the electromagnetic wave shielding film 2 can be further enhanced.

As the isotropic conductive adhesive layer 26, a thermosetting conductive adhesive layer is preferable because it can exhibit heat resistance after curing. The thermosetting isotropic conductive adhesive layer 26 may be in an uncured state or may be in a B-staged state.
The thermosetting isotropic conductive adhesive layer 26 contains, for example, a thermosetting adhesive 26a and conductive particles 26b. The thermosetting isotropic conductive adhesive layer 26 may contain a flame retardant, if necessary.
The components of the thermosetting adhesive 26a contained in the isotropic conductive adhesive layer 26 and the materials of the conductive particles 26b are the components of the thermosetting adhesive 24a contained in the anisotropic conductive adhesive layer 24 and the conductivity. It is the same as the material of the particle 24b.

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 at least the lower limit 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 of the above range, the isotropic conductive adhesive layer 26 sufficiently penetrates into the through holes of the insulating film 60 and is formed by the printed circuit 54 of the flexible printed wiring board 50. Securely electrically connected.

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, out 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 equal to or higher than the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 becomes good. When the ratio of the conductive particles 26b is equal to or less than the upper limit of the above range, the isotropic conductive adhesive layer 26 sufficiently penetrates into the through hole of the insulating film 60 and is surely formed by the printed circuit 54 of the flexible printed wiring board 50. It is electrically connected.

The storage elastic modulus of the isotropic conductive adhesive layer 26 at 180 ° C. is preferably 1 × 10 ³ Pa or more and 5 × 10 ⁷ Pa or less, and more preferably 5 × 10 ³ Pa or more and 1 × 10 ⁷ Pa or less. The reason why the above range is preferable is the same as that of the anisotropic conductive adhesive layer 24.

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

The thickness of the isotropic conductive adhesive layer 26 is preferably 5 μm or more and 20 μm or less, and more preferably 7 μm or more and 17 μm or less. When the thickness of the isotropic conductive adhesive layer 26 is at least the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 becomes good, and the isotropic conductive adhesive layer 26 can sufficiently function as an electromagnetic wave shielding layer. In addition, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through hole of the insulating film) can be ensured, and the inside of the through hole of the insulating film can be sufficiently filled with the conductive adhesive, and the resistance can be increased. Foldability can be ensured, and the isotropic conductive adhesive layer 26 does not tear even when repeatedly bent.
When the thickness of the isotropic conductive adhesive layer 26 is not more than the upper limit of the above range, the electromagnetic wave shielding film 2 can be thinned. In addition, the flexibility of the electromagnetic wave shielding film 2 is improved.

(Thickness of electromagnetic wave shield film)
The thickness of the electromagnetic wave shielding film 2 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 of the electromagnetic wave shielding film 2 is at least the lower limit of the above range, it is difficult to break when the carrier film 30 is peeled off. When the thickness of the electromagnetic wave shielding film 2 is not more than the upper limit of the above range, the printed wiring boards 1a and 1b with the electromagnetic wave shielding film can be thinned.

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

(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 50 μm or less, and more preferably 10 μm or more and 25 μm or less from the viewpoint of flexibility.

(Print circuit)
Examples of the copper foil constituting the printed circuit 54 include rolled copper foil, electrolytic copper foil, and the like, and rolled copper foil is preferable from the viewpoint of flexibility. The print circuit 54 is used, for example, as a signal circuit, a ground circuit, a ground layer, or the like.
The thickness of the copper foil is preferably 1 μm or more and 50 μm or less, and more preferably 18 μm or more and 35 μm or less.
The end portion (terminal) in the length direction of the print circuit 54 is not covered with the insulating film 60 or the electromagnetic wave shielding film 2 and is exposed because of solder connection, connector connection, component mounting, and the like.

<Insulation film>
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 insulating film 60 (coverlay film) is formed by forming an adhesive layer (not shown) on one side of an insulating film main body (not shown) by applying an adhesive, attaching an adhesive sheet, or the like.
The surface resistance of the insulating film body is 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 main body of the insulating film, 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, polyamide-imide, polyamide, phenol resin, urethane resin, acrylic resin, melamine resin, polystyrene, polyolefin and the like. The epoxy resin may contain a rubber component (carboxy-modified nitrile rubber, etc.) for imparting flexibility.
The thickness of the adhesive layer is preferably 1 μm or more and 100 μm or less, and more preferably 1.5 μm or more and 60 μm or less.

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

An anisotropic conductive adhesive layer 24 or an isotropic conductive adhesive layer 26 is adhered and cured on the surface of the insulating film 60. Further, the anisotropic conductive adhesive layer 24 or the isotropic conductive adhesive layer 26 enters into a through hole (not shown) formed in the insulating film 60 and is electrically connected to the printed circuit 54.
In the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) excluding the portion having a through hole, the metal thin film layer 22 of the electromagnetic wave shielding film 2 is formed on the insulating film 60 and the anisotropic conductive adhesive layer 24 or. They are spaced apart and opposed to each other via an isotropic conductive adhesive layer 26.
The separation distance between the printed circuit 54 and the metal thin film layer 22 excluding the portion having the through hole is the sum of the thickness of the insulating film 60 and the thickness of the anisotropic conductive adhesive layer 24 or the isotropic conductive adhesive layer 26. Almost equal. The separation distance is preferably 30 μm or more and 200 μm or less, and more preferably 60 μm or more and 200 μm or less. If the separation distance is smaller than 30 μm, the impedance of the signal circuit becomes low. Therefore, in order to have a characteristic impedance such as 100Ω, the line width of the signal circuit must be reduced, and the variation in the line width is the variation in the characteristic impedance. Therefore, the reflected resonance noise due to the impedance mismatch can easily get on the electric signal. If the separation distance is larger than 200 μm, the printed wiring boards 1a and 1b with the electromagnetic wave shielding film become thick, and the flexibility becomes insufficient.

<Action effect>
In the printed wiring boards 1a and 1b with the electromagnetic wave shielding film of the above embodiment, the through holes 22h are formed in the metal thin film layer 22 arranged between the insulating resin layer 10 and the conductive adhesive layers 24 and 26. Inside the through hole 22h of the metal thin film layer 22, the insulating resin layer 10 and the conductive adhesive layers 24 and 26, particularly the thermosetting adhesives 24a and 26a, enter and come into contact with each other. By contacting the insulating resin layer 10 and the conductive adhesive layers 24 and 26 inside the through hole 22h, the insulating resin layer 10 and the conductive adhesive layers 24 and 26 can be adhered to each other. In particular, when the number of holes in the metal thin film layer 22 is equal to or greater than the lower limit of the above range, the adhesive area between the insulating resin layer 10 and the conductive adhesive layers 24 and 26 becomes sufficiently large, so that the insulating resin layer 10 And the adhesive strength of the conductive adhesive layers 24 and 26 can be sufficiently increased.
As a result of the insulating resin layer 10 and the conductive adhesive layers 24 and 26 being bonded with sufficient adhesive strength, the insulating resin layer 10 and the conductive adhesive layers 24 and 26 are prevented from peeling off from the metal thin film layer 22. can.
Further, since the through holes 22h are formed in the metal thin film layer 22, the printed wiring boards 1a and 1b with the electromagnetic wave shielding film are generated from the conductive adhesive layers 24 and 26 when heated by the solder float treatment or the like. The gas can be removed through the through hole 22h. The gas that has passed through the through hole 22h enters the insulating resin layer 10. Since the insulating resin layer 10 is more permeable to gas than the metal thin film layer 22, it is easily discharged to the outside of the insulating resin layer 10. Therefore, for example, even if the volatile matter is vaporized inside the electromagnetic wave shielding film 2 when heated, the generation of bubbles can be prevented. If air bubbles are generated between the electromagnetic wave shielding film 2 and the insulating film 60, the electromagnetic wave shielding film 2 and the insulating film 60 may be peeled off. However, in the present embodiment, since the through hole 22h is formed in the metal thin film layer 22 to prevent the generation of bubbles, it is possible to prevent the electromagnetic wave shielding film 2 from peeling off from the insulating film 60.

<< Manufacturing method of printed wiring board with electromagnetic wave shielding film >>
The method for manufacturing a printed wiring board with an electromagnetic wave shielding film according to this embodiment includes a step of manufacturing an electromagnetic wave shielding film for manufacturing an electromagnetic wave shielding film and a crimping step of crimping the electromagnetic wave shielding film and the printed wiring board with an insulating film sandwiched between them. Have.
Hereinafter, as an example of the method for manufacturing a printed wiring board with an electromagnetic wave shielding film according to this embodiment, the printed wiring board 1a with an electromagnetic wave shielding film according to the first embodiment is manufactured in which the conductive adhesive layer is an anisotropic conductive adhesive layer. An example of manufacturing to be performed will be described.

In the following production examples, a carrier film and a release film are used as process films. Therefore, in this production example, as shown in FIG. 3, the electromagnetic wave shielding film 2 is obtained in a state where the carrier film 30 and the release film 40 are laminated.
Specifically, the carrier film 30 and the release film 40 are the following films.

[Carrier film]
The carrier film 30 is a support that reinforces and protects the insulating resin layer 10 and the conductive layer 20, and improves the handleability of the laminated body 2a for producing an electromagnetic wave shielding film.
Since the carrier film 30 is unnecessary for the printed wiring board 1a with the electromagnetic wave shielding film, it is peeled off from the insulating resin layer 10 after the crimping step.

The carrier film 30 used in this production example has a carrier film main body 32 and an adhesive layer 34 provided on the surface of the carrier film main body 32 on the insulating resin layer 10 side.

The resin material of the carrier film body 32 includes polyethylene terephthalate (hereinafter, also referred to as “PET”), polyethylene naphthalate, polyethylene isophthalate, polyvinylidene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, and ethylene. -Vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, liquid crystal polymer and the like can be mentioned. As the resin material, PET is preferable from the viewpoint of heat resistance (dimensional stability) and price when manufacturing the electromagnetic wave shielding film 2.

The carrier film body 32 may contain one or both of a colorant (pigment, dye, etc.) and a filler.
One or both of the colorant and the filler can be clearly distinguished from the insulating resin layer 10, and the carrier film 30 has a different color from the insulating resin layer 10 in that it is easy to notice the unpeeled residue after hot pressing. Preferred are white pigments, fillers, or combinations of white pigments with other pigments or fillers.

The storage elastic modulus of the carrier film main body 32 at 180 ° C. is preferably 8 × 10 ⁷ Pa or more and 5 × 10 ⁹ Pa, and more preferably 1 × 10 ⁸ Pa or more and 8 × 10 ⁸ Pa. When the storage elastic modulus of the carrier film main body 32 at 180 ° C. is equal to or higher than the lower limit of the above range, the carrier film 30 has an appropriate hardness, and the pressure loss in the carrier film 30 during hot pressing can be reduced. .. When the storage elastic modulus of the carrier film main body 32 at 180 ° C. is not more than the upper limit of the above range, the flexibility of the carrier film 30 is good.

The thickness of the carrier film main body 32 is preferably 3 μm or more and 75 μm or less, and more preferably 12 μm or more and 50 μm or less. When the thickness of the carrier film main body 32 is at least the lower limit of the above range, the handling property of the electromagnetic wave shielding film 2 is good. When the thickness of the carrier film main body 32 is not more than the upper limit of the above range, the anisotropic conductive adhesive layer 24 is hot-pressed on the surface of the insulating film 60 when the anisotropic conductive adhesive layer 24 of the electromagnetic wave shielding film is hot-pressed. Heat is easily transferred to the film.

The pressure-sensitive adhesive layer 34 is formed, for example, by applying a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive to the surface of the carrier film body 32. Since the carrier film 30 has the adhesive layer 34, the carrier is used when the release film 40 is peeled from the anisotropic conductive adhesive layer 24 or when the electromagnetic wave shielding film 2 is attached to a printed wiring board or the like by a hot press. The film 30 is prevented from peeling from the insulating resin layer 10. Therefore, the carrier film 30 can sufficiently serve as a protective film.

The pressure-sensitive adhesive layer has an appropriate adhesiveness to the extent that the carrier film 30 does not easily peel off from the insulating resin layer 10 before hot pressing and the carrier film 30 can be peeled off from the insulating resin layer 10 after hot pressing. It is preferable that it is given to 34.
Examples of the pressure-sensitive adhesive include an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, and a rubber-based pressure-sensitive adhesive.
The glass transition temperature of the pressure-sensitive adhesive is preferably −100 ° C. or higher and 60 ° C. or lower, and more preferably −60 ° C. or higher and 40 ° C. or lower.

The thickness of the carrier film 30 is preferably 25 μm or more and 125 μm or less, and more preferably 38 μm or more and 100 μm or less. When the thickness of the carrier film 30 is at least the lower limit of the above range, the handling property of the electromagnetic wave shielding film 2 is good. When the thickness of the carrier film 30 is not more than the upper limit of the above range, the anisotropic conductive adhesive layer 24 is hot-pressed on the surface of the insulating film 60 when the anisotropic conductive adhesive layer 24 of the electromagnetic wave shielding film 2 is hot-pressed. Heat is easily transferred to the film.

[Release film]
The release film 40 protects the anisotropic conductive adhesive layer 24 and improves the handleability of the electromagnetic wave shielding film 2. The release film 40 is peeled off from the anisotropic conductive adhesive layer 24 before the electromagnetic wave shielding film 2 is attached to the printed wiring board.

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

Examples of the resin material of the release film main body 42 include the same resin materials as those of the carrier film main body 32.
The release film main body 42 may contain a colorant, a filler and the like.
The thickness of the release film body 42 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and further preferably 25 μm or more and 100 μm or less.

The release agent layer 44 is formed by treating the surface of the release film main body 42 with a release agent. Since the release film 40 has the release agent layer 44, when the release film 40 is peeled from the conductive adhesive layer, the release film 40 is easily peeled off and the conductive adhesive layer is less likely to break. ..
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.

An example of manufacturing the printed wiring board 1a with an electromagnetic wave shielding film is a method having the following steps (a) to (e) (see FIGS. 3 and 4).
Step (a): A step of manufacturing the electromagnetic wave shielding film 2 shown in FIG. 3 (electromagnetic wave shielding film manufacturing step).
Step (b): An insulating film 60 having a through hole 62 formed at a position corresponding to the printed circuit 54 is provided on the surface of the flexible printed wiring board 50 on the side where the printed circuit 54 is provided, and the flexible printed wiring with an insulating film is provided. The process of obtaining the plate 3.
Step (c): After the step (b), the flexible printed wiring board 3 with an insulating film and the electromagnetic wave shielding film 2 from which the release film 40 is peeled off are placed on the surface of the insulating film 60 with an anisotropic conductive adhesive layer 24. The process of stacking the films so that they come into contact with each other and crimping them (crimping process). In this step, the metal thin film layer 22 is perforated by the conductive particles 24b contained in the anisotropic conductive adhesive layer 24, and the insulating resin layer 10 and the anisotropic conductive adhesive layer 24 are adhered to each other.
Step (d): A step of peeling off the carrier film 30 when the carrier film 30 is no longer needed after the step (c).
Step (e): A step of main curing the anisotropic conductive adhesive layer 24 between the steps (b) and the step (c), or after the step (d), if necessary.
Hereinafter, each step will be described in detail with reference to FIGS. 3 and 4.

(Step (a))
The electromagnetic wave shielding film 2 formed in the step (a) is provided on the surface of the insulating resin layer 10, the metal thin film layer 22 adjacent to the insulating resin layer 10, and the surface of the metal thin film layer 22 opposite to the insulating resin layer 10. It also has an anisotropic conductive adhesive layer 24. However, the metal thin film layer 22 obtained in the step (a) is a non-perforated metal thin film layer in which through holes are not formed.

The method for forming the electromagnetic wave shielding film 2 shown in FIG. 3 includes a step of forming the insulating resin layer 10, a step of forming the non-porous metal thin film layer 22, and a step of forming the anisotropic conductive adhesive layer 24. A method having and is mentioned.
Specifically, as a method for manufacturing the electromagnetic wave shielding film 2 shown in FIG. 3, a method (a1) and a method (a2) described later can be mentioned.

[Method (a1)]
The method (a1) is a method having the following steps (a1-1) to (a1-4).
Step (a1-1): A step of laminating the insulating resin layer 10 on the carrier film 30.
Step (a1-2): A step of forming the metal thin film layer 22 on the surface of the insulating resin layer 10 opposite to the carrier film 30.
Step (a1-3): A step of forming the anisotropic conductive adhesive layer 24 on the surface of the metal thin film layer 22 opposite to the insulating resin layer 10.
Step (a1-4): A step of laminating the release film 40 on the surface of the anisotropic conductive adhesive layer 24 opposite to the metal thin film layer 22.
Hereinafter, each step of the method (a1) will be described in detail.

Examples of the method for forming the insulating resin layer 10 in the step (a1-1) include the following methods.
A method of applying a paint containing a thermosetting resin and a curing agent to the surface of the carrier film 30 on the side of the pressure-sensitive adhesive layer 34, and semi-curing or curing the paint.
A method of applying a paint containing a thermoplastic resin to the surface of the carrier film 30 on the side of the pressure-sensitive adhesive layer 34 and drying it.
A method of directly laminating a film formed by extrusion molding a composition containing a thermoplastic resin on the surface of the carrier film 30 on the side of the pressure-sensitive adhesive layer 34.
Among the above methods, from the viewpoint of heat resistance during soldering or the like, a paint containing a thermosetting resin and a curing agent is applied to the surface of the carrier film 30 on the pressure-sensitive adhesive layer 34 side, and semi-cured or cured. The method of causing is preferable.
Examples of the method for applying the paint include a die coater, a gravure coater, a roll coater, a curtain flow coater, a spin coater, a bar coater, a reverse coater, a kiss coater, a fountain coater, a rod coater, an air doctor coater, a knife coater, and a blade coater. A method using various coaters such as a cast coater and a screen coater can be applied.
When the thermosetting resin is semi-cured or cured, it may be heated using a heater such as a heater or an infrared lamp.

Examples of the method for forming the metal thin film layer in the step (a1-2) include a method of forming a vapor-deposited film by physical vapor deposition and CVD (chemical vapor deposition), a method of forming a plating film by plating, a method of pasting a metal foil, and the like. Can be mentioned. From the viewpoint that a metal thin film layer having excellent surface conductivity can be formed, a method of forming a vapor-filmed film by physical vapor deposition or CVD, or a method of forming a plated film by plating is preferable. Physical vapor deposition and CVD are possible because the thickness of the metal thin film layer can be reduced, and even if the thickness is thin, a metal thin film layer having excellent surface conductivity can be formed, and the metal thin film layer can be easily formed by a dry process. A method of forming a thin-film deposition film by physical vapor deposition is more preferable, and a method of forming a thin-film deposition film by physical vapor deposition is further preferable.
A non-porous metal thin film layer can be formed by the step (a1-2).

The thickness of the metal thin film layer 22 formed by the step (a1-2) is preferably 0.01 μm or more and 3 μm or less, more preferably 0.03 μm or more and 1 μm or less, and 0.05 μm or more and 0.5 μm or more. It is more preferably 0.07 μm or more, and particularly preferably 0.4 μm or less. When the thickness of the metal thin film layer 22 is set to be equal to or greater than the lower limit of the above range, sufficient electromagnetic wave shielding properties can be obtained. When the thickness of the metal thin film layer 22 is set to be equal to or less than the upper limit of the above range, the metal thin film layer 22 can be easily perforated by pushing the conductive particles 24b into the metal thin film layer 22 during the crimping step. That is, if the thickness of the metal thin film layer 22 is not more than the upper limit of the above range, the porous metal thin film layer 22 can be easily formed.

In the step (a1-3), the conductive adhesive paint is applied to the surface of the metal thin film layer 22 opposite to the insulating resin layer 10. The conductive adhesive coating material contains a thermosetting adhesive 24a, conductive particles 24b, and a solvent. The anisotropic conductive adhesive layer 24 is formed by volatilizing the solvent from the applied conductive adhesive paint.
The conductive particles contained in the conductive adhesive coating material are preferably metal particles and more preferably copper particles from the viewpoint that the metal thin film layer 22 is more easily perforated.
The average particle size of the conductive particles is preferably 3 μm or more and 20 μm or less, and more preferably 5 μm or more and 10 μm or less. When the average particle diameter of the conductive particles is at least the lower limit of the above range, the metal thin film layer 22 can be easily perforated. When the average particle diameter of the conductive particles is not more than the upper limit of the above range, the fluidity of the anisotropic conductive adhesive layer 24 can be ensured.
The content ratio of the conductive particles in the conductive adhesive paint is such that the content of the conductive particles in the anisotropic conductive adhesive layer 24 formed from the conductive adhesive paint is 1% by volume or more and 50% by volume or less. It is preferable, 10% by volume or more and 30% by volume or less is more preferable. When the content ratio of the conductive particles in the conductive adhesive paint is within the above range, the amount of through holes 22h formed in the metal thin film layer 22 can be easily reduced to 1000 / cm ² or more and 100,000 / cm ² or less.

Examples of the solvent contained in the conductive adhesive coating material include esters (butyl acetate, ethyl acetate, methyl acetate, isopropyl acetate, ethylene glycol monoacetate, etc.) and ketones (methyl ethyl ketone, methyl isobutyl ketone, acetone, methyl isobutyl ketone, cyclohexanone). Etc.), alcohols (methanol, ethanol, isopropanol, butanol, propylene glycol monomethyl ether, propylene glycol, etc.) and the like.
Examples of the method of applying the conductive adhesive include a die coater, a gravure coater, a roll coater, a curtain flow coater, a spin coater, a bar coater, a reverse coater, a kiss coater, a fountain coater, a rod coater, an air doctor coater, a knife coater, and a blade. A method using various coaters such as a coater, a cast coater, and a screen coater can be applied.

In the step (a1-4), the release film 40 is placed on the surface of the anisotropic conductive adhesive layer 24 opposite to the metal thin film layer 22, and the release agent layer 44 is placed on the anisotropic conductive adhesive layer 24. Laminate so that they are in contact with each other.
After the release film 40 is laminated on the anisotropic conductive adhesive layer 24, the laminate is composed of the carrier film 30, the insulating resin layer 10, the metal thin film layer 22, the anisotropic conductive adhesive layer 24, and the release film 40. In addition, a pressure treatment may be applied to enhance the adhesion between the layers.
The pressure in the pressurizing treatment is preferably 0.1 kPa or more and 100 kPa or less, more preferably 0.1 kPa or more and 20 kPa or less, and further preferably 1 kPa or more and 10 kPa or less.
It may be heated at the same time as the pressure treatment. The heating temperature at that time is preferably 50 ° C. or higher and 100 ° C. or lower.

[Method (a2)]
The method (a2) is a method having the following steps (a2-1) to (a2-4).
Step (a2-1): A step of laminating the insulating resin layer 10 on the carrier film 30.
Step (a2-2): A step of forming the metal thin film layer 22 on the surface of the insulating resin layer 10 opposite to the carrier film 30 to form the laminated body (I).
Step (a2-3): A step of forming the anisotropic conductive adhesive layer 24 on the release film 40 to form the laminate (II).
Step (a2-4): The laminated body (I) and the laminated body (II) are brought into contact with the metal thin film layer 22 of the laminated body (I) and the anisotropic conductive adhesive layer 24 of the laminated body (II). The process of bonding to.

The step (a2-1) and the step (a2-2) are the same as the step (a1-1) and the step (a1-2) in the method (a1).

In the step (a2-3), the conductive adhesive paint is applied to the surface of the release film 40 provided with the release agent layer 44. The anisotropic conductive adhesive layer 24 is formed by volatilizing the solvent from the applied conductive adhesive paint. The conductive adhesive coating material and the coating method are the same as those in the step (a1-3) in the method (a).

In the step (a2-4), in the bonding of the laminated body (I) and the laminated body (II), a pressure treatment is applied to enhance the adhesion between the laminated body (I) and the laminated body (II). May be good. The pressurizing conditions are the same as the pressurizing treatment in the step (a1-4). Further, in the step (a2-4), heating may be performed in the same manner as in the step (a1-4).

(Step (b))
The step (b) is a step of laminating the insulating film 60 on the flexible printed wiring board 50 to obtain the flexible printed wiring board 3 with the insulating film.
Specifically, first, an insulating film 60 having a through hole 62 formed at a position corresponding to the printed circuit 54 is superposed on the flexible printed wiring board 50. Next, the adhesive layer (not shown) of the insulating film 60 is adhered to the surface of the flexible printed wiring board 50, and the adhesive layer is cured to obtain the flexible printed wiring board 3 with the insulating film. The adhesive layer of the insulating film 60 may be temporarily adhered to the surface of the flexible printed wiring board 50, and the adhesive layer may be mainly cured in the step (e).
Adhesion and curing of the adhesive layer are performed, for example, by hot pressing with a press machine (not shown) or the like.

(Step (c))
The step (c) is a step of crimping the electromagnetic wave shielding film 2 to the flexible printed wiring board 3 with an insulating film.
Specifically, the electromagnetic wave shielding film 2 from which the release film 40 has been peeled off is superposed on the flexible printed wiring board 3 with an insulating film, and is pressure-bonded by a hot press. As a result, the anisotropic conductive adhesive layer 24 is adhered to the surface of the insulating film 60, the anisotropic conductive adhesive layer 24 is pushed into the through hole 62, the inside of the through hole 62 is filled, and electricity is supplied to the printed circuit 54. Connect. Further, the anisotropic conductive adhesive layer 24 is cured by a hot press. As a result, a printed wiring board 1a with an electromagnetic wave shielding film is obtained.
During the crimping in the step (c), each layer is compressed so that the adjacent layers of the electromagnetic wave shielding film 2 are closer to each other. At this time, since the conductive particles 24b contained in the anisotropic conductive adhesive layer 24 are hard and difficult to be compression-deformed, they are pushed into the metal thin film layer 22. Since the metal thin film layer 22 is thin, when the conductive particles 24b are pushed into the metal thin film layer 22, the metal thin film layer 22 is cleaved. As a result, the metal thin film layer 22 is perforated to form a through hole 22h in the metal thin film layer 22. Further, the insulating resin layer 10 and the anisotropic conductive adhesive layer 24 adhere to each other inside the formed through hole 22h.
After the hot pressing is completed and the pressure is released, the through holes 22h are formed in the metal thin film layer 22, and the insulating resin layer 10 and the anisotropic conductive adhesive layer 24 are adhered to each other. , Each layer is restored to its original shape.

Adhesion and curing of the anisotropic conductive adhesive layer 24 are performed, for example, by hot pressing with a press machine (not shown) or the like.
The pressure of the hot press in the step (c) is preferably 1 MPa or more and 30 MPa or less, more preferably 10 MPa or more and 30 MPa or less, and further preferably 15 MPa or more and 20 MPa or less. When the pressure of the hot press is equal to or higher than the lower limit of the above range, the conductive particles 24b can be sufficiently pushed into the metal thin film layer 22, and the through holes 22h can be easily formed by the metal thin film layer 22. Further, when the pressure of the hot press is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is adhered to the surface of the insulating film 60. In addition, the time for hot pressing can be shortened. When the pressure of the hot press is not more than the upper limit of the above range, damage to the electromagnetic wave shielding film 2, the flexible printed wiring board 50, etc. can be suppressed.

The hot pressing time is preferably 20 seconds or more and 60 minutes or less, and more preferably 30 seconds or more and 30 minutes or less. When the hot pressing time is equal to or longer than the lower limit of the above range, the through hole 22h can be easily formed by the metal thin film layer 22, and the anisotropic conductive adhesive layer 24 can be easily adhered to the surface of the insulating film 60. .. When the heat pressing time is not more than the upper limit of the above range, the manufacturing time of the printed wiring board 1a with the electromagnetic wave shielding film can be shortened.

The temperature of the hot press (the temperature of the hot plate of the press machine) is preferably 140 ° C. or higher and 190 ° C. or lower, and more preferably 150 ° C. or higher and 175 ° C. or lower. When the temperature of the hot press is equal to or higher than the lower limit of the above range, the through hole 22h can be easily formed by the metal thin film layer 22, and the anisotropic conductive adhesive layer 24 can be easily adhered to the surface of the insulating film 60. .. Furthermore, the time for hot pressing can be shortened. When the temperature of the hot press is not more than the upper limit of the above range, deterioration of the electromagnetic wave shielding film 2, the flexible printed wiring board 50, and the like can be easily suppressed.

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

(Step (e))
The step (e) is a step of main curing the anisotropic conductive adhesive layer 24.
When the heat pressing time in the step (c) is a short time of 20 seconds or more and 10 minutes or less, the anisotropic conductive adhesive layer is formed between the step (c) and the step (d) or after the step (d). It is preferable to perform the main curing of 24.
The main curing of the anisotropic conductive adhesive layer 24 is performed using, for example, a heating device such as an oven.
The heating time is 15 minutes or more and 120 minutes or less, more preferably 30 minutes or more and 60 minutes or less. When the heating time is at least the lower limit of the above range, the anisotropic conductive adhesive layer 24 can be sufficiently cured. When the heating time is not more than the upper limit of the above range, the manufacturing time of the printed wiring board 1a with the electromagnetic wave shielding film can be shortened.
The heating temperature (atmospheric temperature in the oven) is preferably 120 ° C. or higher and 180 ° C. or lower, and more preferably 120 ° C. or higher and 150 ° C. or lower. When the heating temperature is equal to or higher than the lower limit of the above range, the heating time can be shortened. When the heating temperature is not more than the upper limit of the above range, deterioration of the electromagnetic wave shielding film 2, the flexible printed wiring board 50, and the like can be suppressed.

(Other manufacturing examples)
The manufacturing example was a manufacturing example for manufacturing the printed wiring board 1a with the electromagnetic wave shielding film of the first embodiment, but the printed wiring board 1b with the electromagnetic wave shielding film of the second embodiment is almost the same as the manufacturing example. Can be manufactured. That is, in the above-mentioned production example, the conductive adhesive paint is changed to a paint containing the heat-curable adhesive 26a, the conductive particles 26b, and the solvent to form the isotropic conductive adhesive layer 26. The printed wiring board 1b with the electromagnetic wave shielding film of the second embodiment can be manufactured.
However, the average particle diameter of the conductive particles 26b contained in the conductive adhesive coating material 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 at least the lower limit of the above range, the metal thin film layer 22 can be easily perforated. When the average particle diameter of the conductive particles 26b is not more than the upper limit of the above range, the fluidity of the isotropic conductive adhesive layer 26 can be ensured.
The content of the conductive particles 26b in the conductive adhesive paint is such that the content of the conductive particles 26b in the isotropic conductive adhesive layer 26 formed from the conductive adhesive paint is 50% by volume or more and 80% by volume or less. Is preferable, and the ratio of 60% by volume or more and 70% by volume or less is more preferable. When the content ratio of the conductive particles 26b in the conductive adhesive paint is within the above range, the amount of through holes 22h formed in the metal thin film layer 22 can be easily reduced to 1000 / cm ² or more and 100,000 / cm ² or less.

The electromagnetic wave shielding film may have a blackening layer. The metal thin film layer such as the silver-deposited layer and the copper-deposited layer has high light reflectivity and has a metallic luster. In order to suppress the metallic luster, a blackening layer may be provided on the surface of the metal thin film layer on the insulating resin layer side. For example, when an electromagnetic shielding film is used for a flexible printed wiring board for a display, in order to prevent the gloss of the metal thin film layer from affecting the visibility of the display, between the metal thin film layer and the insulating resin layer. It is preferable to provide a blackening layer. Normally, a blackening layer is formed on the surface of the insulating resin layer on the metal thin film layer side.
The blackening layer is a black layer which is composed of a light-absorbing material and has a light antireflection property. Specifically, the blackened layer preferably has a brightness L ^* defined in JIS Z8781-5 of 5 or less. The smaller the value of the lightness L ^* , the larger the blackness, and the more the light reflection tends to be suppressed.
When the electromagnetic wave shielding film has a blackening layer, it is preferable that through holes are formed in the blackening layer as well as the metal thin film layer.

The blackened layer is composed of, for example, any of the following light-absorbing materials (i) to (iii).
(I) Silver oxide or copper oxide (ii) At least one selected from the group consisting of copper nitride, copper oxide, nickel nitride and nickel oxide (iii) Zinc, copper-zinc alloy, silver-zinc When the blackening layer of any one of the alloys is composed of the above (i), a method of forming a layer made of a silver oxide or a copper oxide by vapor deposition or plating can be mentioned. As the vapor deposition method, for example, a known vapor deposition method such as a vacuum vapor deposition method or a sputtering method can be applied.
When the blackened layer is composed of the above (ii), a method of forming a layer consisting of at least one selected from the group consisting of copper nitride, copper oxide, nickel nitride and nickel oxide by vapor deposition or plating can be mentioned. Be done.
When the blackened layer is composed of the above (iii), a method of forming a layer composed of any one of zinc, an alloy of copper and zinc, and an alloy of silver and zinc by vapor deposition or plating can be mentioned.
The thickness of the blackened layer is not particularly limited, but is preferably 5 nm or more and 20 μm or less, and more preferably 10 nm or more and 1 μm or less. When the thickness of the blackening layer is not less than the lower limit of the above range, the reflection of light can be sufficiently suppressed, and when it is not more than the upper limit of the above range, the blackening layer can be easily formed.

The flexible printed wiring board may have a ground layer on the back surface side. Further, the flexible printed wiring board may have printed circuits on both sides, and an insulating film and an electromagnetic wave shielding film may be attached to both sides.
Instead of the flexible printed wiring board, an inflexible rigid printed circuit board may be used.

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.
In the following examples, the following materials were used.
As the carrier film, a polyethylene terephthalate film having an adhesive layer on one side was used.
As a release film, a polyethylene terephthalate film (T157 manufactured by Lintec Corporation, T157, release film body thickness: 50 μm, release agent layer thickness: 0.1 μm) whose one side is release-treated with a non-silicone release agent. ) Was used.
As an insulating film, an insulating adhesive composition made of a nitrile rubber-modified epoxy resin was applied to the surface of a 25 μm-thick polyimide film (Capton 100H, manufactured by Toray Dupont Co., Ltd.) so that the dry film thickness was 25 μm. A film (total thickness: 50 μm) obtained by forming an adhesive layer was used.
As the copper-clad laminate, a laminate in which a copper foil was attached to one side of the polyimide plate was used.

(Example 1)
A paint for forming an insulating resin layer containing a thermosetting epoxy resin is applied to the surface of the pressure-sensitive adhesive layer of the carrier film, heated at 60100 ° C. for 2 minutes, and the paint is dried and semi-cured to obtain an insulating resin layer ( Thickness: 10 μm) was formed.
Copper was physically vapor-deposited on the surface of the insulating resin layer by an electron beam vapor deposition method to form a metal thin film layer (deposited film, thickness: 70 nm).
A thermosetting conductive adhesive composition containing copper particles (conductive particles) having an average particle diameter of 5 μm is applied to the surface of the metal thin film layer using a die coater applicator, and the solvent is volatilized to cause the B stage. The anisotropic conductive adhesive layer (thickness: 6 μm, copper particles: 20% by volume) was formed.
A release film was attached to the surface of the anisotropic conductive adhesive layer to obtain an electromagnetic wave shielding film.
An electromagnetic wave shield film from which the release film was peeled off was superposed on the insulating film, and heat-pressed for 120 seconds at a hot plate temperature: 170 ° C. and a pressure: 15 MPa using a hot press device (G-12 manufactured by Orihara Seisakusho Co., Ltd.). As a result, the anisotropic conductive adhesive layer was temporarily adhered to the surface of the insulating film to obtain an insulating film with an electromagnetic wave shielding film.
Then, the carrier film was peeled off from the insulating resin layer. Next, the anisotropic conductive adhesive layer was finally cured by heating the insulating film with an electromagnetic wave shielding film at a temperature of 150 ° C. for 1 hour using a high-temperature thermostat (manufactured by Kusumoto Kasei Co., Ltd., HT210). Then, the carrier film was peeled off from the insulating resin layer.

(Examples 2 to 5 and Comparative Examples 1 and 2)
An insulating film with an electromagnetic wave shielding film was obtained in the same manner as in Example 1 except that the thickness of the metal thin film layer and the average particle diameter of the conductive particles were changed as shown in Table 1.

Since the product obtained in the above embodiment does not have a printed wiring board, it is not the printed wiring board with the electromagnetic wave shielding film of the present invention. However, since it is within the scope of the present invention except that it does not have a printed wiring board, it is regarded as an embodiment. Since the amount of through holes formed is outside the scope of the present invention, the comparative example is used as a comparative example.

<Evaluation>
(Measurement of the number of through holes in the metal thin film layer and the diameter of the minimum circle of the through holes)
For the obtained insulating film with an electromagnetic wave shielding film, observe the through holes from the insulating resin layer side while irradiating the insulating film with light, and determine the number of through holes formed in the metal thin film layer and the diameter of the minimum circle of the through holes. It was measured. Since light is transmitted through the through hole, the through hole can be visually recognized.

(Adhesive strength)
The obtained insulating film with electromagnetic wave shielding film was subjected to tensile strength using a tensile tester (Shimadzu Corporation, AGS-50NX) based on JIS K 6854-2: 1999 (corresponding international standard ISO 8510-2: 1990). It was measured. The obtained tensile strength was taken as the adhesive strength.

(Evaluation of peeling prevention during solder reflow)
An anisotropic conductive adhesive layer of an electromagnetic wave shielding film was adhered to a polyimide plate of a copper-clad laminate instead of an insulating film to obtain a copper-clad laminate with an electromagnetic wave shielding film.
About the obtained copper-clad laminate with electromagnetic wave shielding film, the insulating resin layer side was immersed in a solder bath at 288 ° C. three times for 10 seconds. After the immersion, the floating, that is, the peeling of the electromagnetic wave shielding film with respect to the copper-clad laminate was visually observed. The less the electromagnetic wave shield film floats, the better the peeling prevention property.
A: There was one or less floats on 5 cm ^squares .
B: There were 2 to 5 floats on 5 cm ^squares .
C: Floating occurred on the entire 5 cm ^square .

In each embodiment, since the through holes were formed in the metal thin film layer in the range of 1000 pieces / cm ² or more and 100,000 pieces / cm ² or less, peeling of the electromagnetic wave shielding film during solder reflow was prevented. In addition, each example had high adhesive strength.
In each comparative example, since the amount of through holes formed in the metal thin film layer was less than 1000 pieces / cm ² , peeling of the electromagnetic wave shielding film during solder reflow was not prevented. In addition, each example had insufficient adhesive strength.

1a, 1b Flexible printed wiring board with electromagnetic wave shielding film 2 Electromagnetic wave shielding film 3 Flexible printed wiring board with insulating film 10 Insulation resin layer 22 Metal thin film layer 22h Through hole 20 Conductive layer 24 anisotropic conductive adhesive layer (conductive adhesive) layer)
24a Thermosetting Adhesive 24b Conductive Particles 26 Isotropic Conductive Adhesive Layer (Conductive Adhesive Layer)
26a Thermo-curable adhesive 26b Conductive particles 30 Carrier film 32 Carrier film body 34 Adhesive layer 40 Release film 42 Release film body 44 Release agent layer 50 Flexible printed wiring board (printed wiring board)
52 Base film 54 Print circuit 60 Insulation film 62 Through hole

Claims (6)

A printed wiring board provided with a printed circuit on at least one side of the board, an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided, and a side opposite to the printed wiring board of the insulating film. With the electromagnetic wave shielding film provided in
The electromagnetic wave shielding film includes an insulating resin layer, a metal thin film layer adjacent to the insulating resin layer, and an anisotropic conductive adhesive layer provided on a surface of the metal thin film layer opposite to the insulating resin layer. Have,
A plurality of through holes are formed in the metal thin film layer, and the amount of the through holes formed is 5000 pieces / cm ² or more and 80,000 pieces / cm ² or less.
The anisotropic conductive adhesive layer contains conductive particles and contains conductive particles.
A method for manufacturing a printed wiring board with an electromagnetic wave shielding film, wherein the content of the conductive particles in the anisotropic conductive adhesive layer is 10% by volume or more and 30% by volume or less.
It has an electromagnetic wave shielding film manufacturing process and a crimping process.
In the electromagnetic wave shielding film manufacturing step, the insulating resin layer, the non-porous metal thin film layer adjacent to the insulating resin layer, and the anisotropic conductivity provided on the surface of the metal thin film layer opposite to the insulating resin layer. An electromagnetic shielding film having a sex adhesive layer was prepared.
In the crimping step, the electromagnetic wave shielding film and the printed wiring board are crimped with an insulating film sandwiched between them, and the conductive particles contained in the anisotropic conductive adhesive layer are pushed into the metal thin film layer to push the metal. A method for manufacturing a printed wiring board with an electromagnetic wave shielding film, in which a thin film layer is perforated to form the through hole . The method for manufacturing a printed wiring board with an electromagnetic wave shielding film according to claim 1, wherein the diameter of the minimum circle including the through hole is 0.1 μm or more and 20 μm or less. The method for manufacturing a printed wiring board with an electromagnetic wave shielding film according to claim 1 or 2, wherein the thickness of the metal thin film layer is 0.01 μm or more and 3 μm or less. The method for manufacturing a printed wiring board with an electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the average particle diameter of the conductive particles is 3 μm or more and 20 μm or less. The method for manufacturing a printed wiring board with an electromagnetic wave shielding film according to any one of claims 1 to 4, wherein the conductive particles are metal particles. The method for manufacturing a printed wiring board with an electromagnetic wave shielding film according to any one of claims 1 to 5, wherein in the crimping step, the pressure at the time of crimping is 1 MPa or more and 30 MPa or less.

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