JP2017195278A - Electromagnetic wave shielding film and printed wiring board with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding film whose first release film (carrier film) is hardly peeled off before hot pressing and is easily peeled off after hot pressing.SOLUTION: An electromagnetic wave shielding film 1 includes: an insulating resin layer 10; a conductive layer 20 adjacent to the insulating resin layer 10; and a first release film 30 adjacent to the side opposite to the conductive layer 20 of the insulating resin layer 10. A peeling force X at an interface between the insulating resin layer 10 and the first release film 30 before hot pressing and a peeling force Y at the interface between the insulating resin layer 10 and the first release film 30 after hot pressing satisfy a relationship X>2×Y.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electromagnetic shielding film and a printed wiring board provided with the electromagnetic shielding film.

  In order to shield electromagnetic noise generated from a flexible printed wiring board and external electromagnetic noise, from an insulating resin layer and a conductive layer composed of a metal thin film layer and a conductive adhesive layer adjacent to the insulating resin layer An electromagnetic wave shielding film may be provided on the surface of the flexible printed wiring board (see, for example, Patent Document 1).

FIG. 7: is sectional drawing which shows an example of the manufacturing process of the conventional flexible printed wiring board with an electromagnetic wave shielding film.
The flexible printed wiring board 101 with an electromagnetic wave shielding film includes a flexible printed wiring board 130, an insulating film 140, and an electromagnetic wave shielding film 110 from which the first release film 118 has been peeled off.
The flexible printed wiring board 130 has a printed circuit 134 provided on one side of a base film 132.
The insulating film 140 is provided on the surface of the flexible printed wiring board 130 on the side where the printed circuit 134 is provided.
The electromagnetic wave shielding film 110 includes an insulating resin layer 112, a metal thin film layer 114 adjacent to the insulating resin layer 112, a conductive adhesive layer 116 adjacent to the metal thin film layer 114 on the side opposite to the insulating resin layer 112, and an insulating film. The resin layer 112 has a first release film 118 (carrier film) adjacent to the side opposite to the metal thin film layer 114.
The conductive adhesive layer 116 of the electromagnetic wave shielding film 110 is bonded to the surface of the insulating film 140 and cured. In addition, the conductive adhesive layer 116 is electrically connected to the printed circuit 134 through the through hole 142 formed in the insulating film 140.

For example, as shown in FIG. 7, the flexible printed wiring board 101 with the electromagnetic wave shielding film is manufactured through the following steps.
Step (i): A step of providing an insulating film 140 in which a through hole 142 is formed at a position corresponding to the ground of the printed circuit 134 on the surface of the flexible printed wiring board 130 on which the printed circuit 134 is provided.
Step (ii): The electromagnetic wave shielding film 110 is stacked on the surface of the insulating film 140 so that the conductive adhesive layer 116 of the electromagnetic wave shielding film 110 is in contact, and these are hot-pressed on the surface of the insulating film 140. Bonding the conductive adhesive layer 116 and electrically connecting the conductive adhesive layer 116 to the ground of the printed circuit 134 through the through hole 142;
Step (iii): Step of obtaining a flexible printed wiring board 101 with an electromagnetic wave shielding film by peeling and removing the first release film 118 that has finished its role as a carrier film after the heat pressing from the insulating resin layer 112. .

Japanese Patent No. 4201548

  In the step (iii), a release agent layer is often provided on the surface of the first release film 118 in order to make it easy to peel the first release film 118 from the insulating resin layer 112. However, since the adhesive force between the first release film 118 and the insulating resin layer 112 becomes insufficient, the surface of the conductive adhesive layer 116 is protected before hot pressing in the step (ii). When the second release film (not shown) is peeled off, the first release film 118 may be peeled off from the insulating resin layer 112 before the second release film.

  When the second release film is peeled from the conductive adhesive layer 116, the release agent is applied to the surface of the first release film 118 so that the first release film 118 does not peel from the insulating resin layer 112. It is conceivable to provide an adhesive layer instead of the layer. However, since the adhesive force between the first release film 118 and the insulating resin layer 112 becomes too high, it is difficult to peel the first release film 118 from the insulating resin layer 112 in the step (iii).

  In the present invention, the first release film (carrier film) is hardly peeled off before hot pressing, and the first release film is easily peeled off after hot pressing. The present invention provides a printed wiring board with an electromagnetic wave shielding film from which the release film of 1 is easily peeled off.

The present invention has the following aspects.
<1> having an insulating resin layer; a conductive layer adjacent to the insulating resin layer; and a first release film adjacent to the side of the insulating resin layer opposite to the conductive layer; The peeling force X at the interface between the insulating resin layer and the first release film and the peeling force Y at the interface between the insulating resin layer and the first release film after the following hot press are expressed by the following formula (1). An electromagnetic shielding film that satisfies the relationship.
X> 2 × Y (1)
(Heat press)
A 2 mm thick silicone rubber cushion material, a 50 μm thick polyethylene terephthalate film, a 12 μm thick polyimide film, a copper clad laminate with a 18 μm thick copper foil laminated on one side, and an electromagnetic shielding film To do. Silicone rubber cushioning material, polyethylene terephthalate film, copper-clad laminate, electromagnetic wave shielding film, polyethylene terephthalate film, silicone rubber cushioning material in this order and copper-clad lamination between the heating plates of a press equipped with a pair of heating plates It arrange | positions so that the copper foil of a board | substrate and the conductive layer of an electromagnetic wave shield film may contact | connect, and hot press is carried out for 120 second by hot plate temperature: 170 degreeC and pressure: 2MPa.
<2> The electromagnetic wave shielding film according to <1>, wherein the peeling force X is 2 N / cm or more and the peeling force Y is 20 N / cm or less.
<3> The electromagnetic wave shielding film according to <1> or <2>, wherein the insulating resin layer includes a semi-cured thermosetting resin.
<4> The electromagnetic wave shielding film according to <3>, wherein a degree of cure of the insulating resin layer before the hot pressing is 40% or more and 60% or less.
<5> The electromagnetic wave shielding film according to <3> or <4>, wherein a degree of cure of the insulating resin layer after the hot pressing is 70% or more and 99% or less.
<6> The conductive layer includes a metal thin film layer adjacent to the insulating resin layer, and a conductive adhesive layer serving as an outermost layer on the side opposite to the insulating resin layer in the conductive layer. The electromagnetic wave shielding film in any one of <5>.
<7> The electromagnetic wave shielding film according to any one of <1> to <5>, wherein the conductive layer includes an isotropic conductive adhesive layer.
<8> The electromagnetic wave shielding film according to any one of <1> to <7>, further including a second release film adjacent to the side of the conductive layer opposite to the insulating resin layer.
<9> a printed wiring board provided with a printed circuit on at least one side of the substrate; an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided; and the conductive layer adjacent to the insulating film And the electromagnetic wave shielding film according to any one of <1> to <7>, wherein the conductive layer is electrically connected to the printed circuit through a through hole formed in the insulating film. Printed wiring board with film.

In the electromagnetic wave shielding film of the present invention, the first release film (carrier film) is difficult to peel before hot pressing, and the first release film is easy to peel after hot pressing.
In the printed wiring board with an electromagnetic wave shielding film of the present invention, the first release film of the electromagnetic wave shielding film is easily peeled off.

It is sectional drawing which shows one Embodiment of the electromagnetic wave shield film of this invention. It is sectional drawing which shows other embodiment of the electromagnetic wave shielding film of this invention. It is sectional drawing which shows other embodiment of the electromagnetic wave shielding film of this invention. It is sectional drawing which shows the manufacturing process of the electromagnetic wave shielding film of FIG. It is sectional drawing which shows one Embodiment of the printed wiring board with an electromagnetic wave shield film of this invention. It is sectional drawing which shows the manufacturing process of the printed wiring board with an electromagnetic wave shielding film of FIG. It is sectional drawing which shows an example of the manufacturing process of the conventional flexible printed wiring board with an electromagnetic wave shielding film.

The following definitions of terms apply throughout this specification and the claims.
The “isotropic conductive adhesive layer” means a conductive adhesive layer having conductivity in the thickness direction and the surface direction.
The “anisotropic conductive adhesive layer” means a conductive adhesive layer having conductivity in the thickness direction and not having conductivity in the surface 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 “semi-cured state” means that the functional group amount is reduced by the reaction by heating at 170 ° C. for 120 seconds in a state where 30% or more of the functional groups contributing to curing remain.
The peel force is a peel force measured by performing a 180 degree peel test using a tensile tester.
The degree of cure of the insulating resin layer depends on the peak intensity of the reactive functional group of the thermosetting resin in the infrared spectrum of the insulating resin layer before semi-curing or curing, and the same reactive functionality after semi-curing or curing. Calculated from the ratio to the peak intensity of the group.
For the average particle diameter of the conductive particles, 30 conductive particles are randomly selected from the microscopic image of the conductive particles, and the minimum diameter and the maximum diameter are measured for each conductive particle. Is the value obtained by arithmetically averaging the measured particle diameters of the 30 conductive particles.
The thickness of the film (release film, insulating film, etc.), coating film (insulating resin layer, conductive adhesive layer, etc.), metal thin film layer, etc. is observed at a cross section of the object to be measured using a microscope. Thickness was measured and averaged.
The storage elastic modulus is calculated as one of the viscoelastic characteristics using a dynamic viscoelasticity measuring device that is calculated from the stress applied to the measurement object and the detected strain and outputs it as a function of temperature or time.
The surface resistance is measured by using two thin film metal electrodes (length 10 mm, width 5 mm, distance 10 mm between electrodes) formed by depositing gold on quartz glass, placing an object to be measured on the electrodes, and measuring the surface resistance. This is a resistance between electrodes measured by pressing a 10 mm × 20 mm region of the object to be measured with a load of 0.049 N from above the object with a measurement current of 1 mA or less.

<Electromagnetic wave shielding film>
FIG. 1 is a cross-sectional view showing a first embodiment of the electromagnetic wave shielding film of the present invention, FIG. 2 is a cross-sectional view showing a second embodiment of the electromagnetic wave shielding film of the present invention, and FIG. It is sectional drawing which shows 3rd Embodiment of the electromagnetic wave shield film of this invention.
The electromagnetic wave shielding film 1 of the first embodiment, the second embodiment, and the third embodiment includes an insulating resin layer 10; a conductive layer 20 adjacent to the insulating resin layer 10; and a conductive layer 20 of the insulating resin layer 10. A first release film 30 adjacent to the opposite side of the conductive layer 20; and a second release film 40 adjacent to the side of the conductive layer 20 opposite to the insulating resin layer 10.

In the electromagnetic wave shielding film 1 of the first embodiment, the conductive layer 20 includes a metal thin film layer 22 adjacent to the insulating resin layer 10 and an anisotropic conductive adhesive layer 24 adjacent to the second release film 40. This is an example.
In the electromagnetic wave shielding film 1 of the second embodiment, the conductive layer 20 includes a metal thin film layer 22 adjacent to the insulating resin layer 10 and an isotropic conductive adhesive layer 26 adjacent to the second release film 40. This is an example.
The electromagnetic wave shielding film 1 of the third embodiment is an example in which the conductive layer 20 is composed only of the isotropic conductive adhesive layer 26.

(Peeling power)
The electromagnetic wave shielding film 1 includes a peeling force X at the interface between the insulating resin layer 10 and the first release film 30 before hot pressing, and an interface between the insulating resin layer 10 and the first release film 30 after hot pressing. Satisfies the relationship of the following formula (1). The peeling force X and the peeling force Y preferably satisfy the relationship of the following formula (2), and more preferably satisfy the relationship of the following formula (3).
X> 2 × Y (1)
X> 3 × Y (2)
X> 5 × Y (3)

  The fact that the peeling force X and the peeling force Y satisfy the relationship of the above formula means that the insulation after the hot press is compared with the adhesive force at the interface between the insulating resin layer 10 and the first release film 30 before the hot press. It means that the adhesive force at the interface between the resin layer 10 and the first release film 30 is sufficiently low. Therefore, even if it is difficult to peel the first release film 30 from the insulating resin layer 10 before hot pressing, the first release film 30 is easily peeled from the insulating resin layer 10 after hot pressing.

The peeling force X is preferably 2 N / cm or more, more preferably 4 N / cm or more, and further preferably 6 N / cm or more. If the peeling force X is not less than the lower limit of the above range, the first release film 30 is more difficult to peel from the insulating resin layer 10 before hot pressing.
When the peeling force X is too high, the insulating resin layer may not be sufficiently cured even by hot pressing. Therefore, the peeling force Y after hot pressing is not sufficiently reduced, and it may be difficult to peel the first release film 30 from the insulating resin layer 10. Recently, due to the shortening of the manufacturing time, the hot pressing time tends to be shortened, which is particularly remarkable in this case. Therefore, the peeling force X is preferably 50 N / cm or less, more preferably 40 N / cm or less, and further preferably 30 N / cm or less.

The peeling force Y is preferably 20 N / cm or less, more preferably 10 N / cm or less, and even more preferably 5 N / cm or less. If the peeling force Y is less than or equal to the upper limit of the above range, the first release film 30 is more likely to peel from the insulating resin layer 10 after hot pressing.
In addition, when the peeling force Y is too low, when conveying the printed wiring board with the electromagnetic wave shielding film obtained after hot press, the 1st release film 30 may drop | omit and it may become impossible to protect the insulating resin layer 10. FIG. . Therefore, the peeling force Y is preferably 0.1 N / cm or more, more preferably 0.3 N / cm or more, and further preferably 0.5 N / cm or more.

(Insulating resin layer)
The insulating resin layer 10 becomes a base (base) for forming the metal thin film layer 22, and after the electromagnetic wave shielding film 1 is attached to the surface of the insulating film provided on the surface of the flexible printed wiring board, the metal thin film It becomes the protective layer of the layer 22.

The insulating resin layer 10 is preferably a layer containing a semi-cured thermosetting resin from the viewpoint that the peeling force X and the peeling force Y easily satisfy the relationship of the above formula. In the semi-cured state before hot pressing, the peeling force X at the interface between the insulating resin layer 10 and the first release film 30 is sufficiently high due to the adhesive force, and after being cured by hot pressing, the insulating resin layer 10 The peel force Y at the interface between the first release film 30 and the first release film 30 is sufficiently reduced.
The insulating resin layer 10 is preferably a coating film formed by applying and semi-curing a coating containing a thermosetting resin and a curing agent from the viewpoint of heat resistance during reflow soldering.

Examples of the thermosetting resin include amide resin, epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, and ultraviolet curable acrylate resin. As the thermosetting resin, an amide resin and an epoxy resin are preferable from the viewpoint of excellent heat resistance.
As a hardening | curing agent, the well-known hardening | curing agent according to the kind of thermosetting resin is mentioned. As the curing agent, a slow curing type curing agent is preferable from the viewpoint that the thermosetting resin is easily made into a semi-cured state. A normal curing agent and a curing retarder may be used in combination.

The degree of cure of the insulating resin layer 10 before hot pressing is preferably 60% or less, and more preferably 50% or less. If the degree of cure of the insulating resin layer 10 is not more than the upper limit of the above range, the peeling force X at the interface between the insulating resin layer 10 and the first release film 30 is sufficiently high due to the adhesive force.
In addition, when the cure degree of the insulating resin layer 10 is too low, the curing of the insulating resin layer may not sufficiently proceed even by hot pressing. Therefore, the peeling force Y after hot pressing is not sufficiently reduced, and it may be difficult to peel the first release film 30 from the insulating resin layer 10. Recently, due to the shortening of the manufacturing time, the hot pressing time tends to be shortened, which is particularly remarkable in this case. Therefore, the degree of cure of the insulating resin layer 10 before hot pressing is preferably 40% or more, and more preferably 50% or more.

The degree of cure of the insulating resin layer 10 after hot pressing is preferably 70% or more, and more preferably 75% or more. If the degree of cure of the insulating resin layer 10 is equal to or higher than the lower limit of the above range, the peeling force Y is sufficiently reduced and the first release film 30 is easily peeled from the insulating resin layer 10.
The degree of cure of the insulating resin layer 10 after hot pressing is preferably 99% or less, and more preferably 98% or less. If the degree of cure of the insulating resin layer 10 is not more than the upper limit of the above range, the first release film 30 is unlikely to drop off when the printed wiring board with an electromagnetic wave shielding film obtained after hot pressing is conveyed.

The storage elastic modulus at 180 ° C. of the insulating resin layer 10 before hot pressing 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. If the storage elastic modulus at 180 ° C. of the insulating resin layer 10 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 reduced. Can be reduced. If the storage elastic modulus at 180 ° C. of the insulating resin layer 10 is not more than the upper limit of the above range, the insulating resin layer 10 does not become too hard, and the peeling force X and the peeling force Y easily satisfy the relationship of the above formula. .

The insulating resin layer 10 may be colored in order to impart designability to the printed wiring board with an electromagnetic wave shielding film.
In order to make the surface of the insulating resin layer 10 inconspicuous, scratches and the like of the first release film 30 that has been embossed or blasted may be transferred to the surface of the insulating resin layer 10. .
The insulating resin layer 10 may contain other components (such as a flame retardant).

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

(Conductive layer)
As the conductive layer 20, a metal thin film layer 22 adjacent to the insulating resin layer 10 and a conductive adhesive layer (an anisotropic conductive adhesive layer 24) that is the outermost layer on the opposite side of the conductive layer 20 from the insulating resin layer 10. Alternatively, a conductive layer (I) having an isotropic conductive adhesive layer 26); or a conductive layer (II) consisting only of the isotropic conductive adhesive layer 26 may be mentioned. As the conductive layer 20, the conductive layer (I) is preferable because it can sufficiently function as an electromagnetic wave shielding layer.

(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 surface direction, it has conductivity in the surface direction and functions as an electromagnetic wave shielding 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, a plating film formed by plating, a metal foil, and the like. From the point of excellent surface direction conductivity, a vapor deposition film and a plating film are preferable, the thickness can be reduced, and even if the thickness is small, the surface direction conductivity is excellent and can be easily formed by a dry process. A vapor deposition film is more preferable, and a vapor deposition film formed by physical vapor deposition is more preferable.

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

  The surface resistance of the metal thin film layer 22 is preferably 0.001Ω to 1Ω, and more preferably 0.001Ω to 0.1Ω. If the surface resistance of the metal thin film layer 22 is not less than the lower limit of the above range, the metal thin film layer 22 can be made sufficiently thin. If the surface resistance of the metal thin film layer 22 is less than or equal to the upper limit of the above range, the metal thin film layer 22 can sufficiently function as an electromagnetic wave shielding layer.

  The thickness of the metal thin film layer 22 is preferably 0.01 μm or more and 1 μm or less, and more preferably 0.05 μm or more and 1 μm or less. When the thickness of the metal thin film layer 22 is 0.01 μm or more, the surface conductivity is further improved. If the thickness of the metal thin film layer 22 is 0.05 μm or more, the electromagnetic noise shielding effect is further improved. If the thickness of the metal thin film layer 22 is equal to or less than the upper limit 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.

(Conductive adhesive layer)
The conductive adhesive layer has conductivity at least in the thickness direction and has adhesiveness.
As the conductive adhesive layer, an anisotropic conductive adhesive layer 24 having conductivity in the thickness direction and having no conductivity in the surface direction, or having conductivity in the thickness direction and the surface direction, etc. An electrically conductive adhesive layer 26 is exemplified. As the conductive adhesive layer in the conductive layer (I), the conductive adhesive layer can be made thin and the amount of conductive particles can be reduced. As a result, the electromagnetic wave shielding film 1 can be made thin, and the electromagnetic wave shielding film 1 is flexible. From the viewpoint of improving the properties, the anisotropic conductive adhesive layer 24 is preferable. As the conductive adhesive layer in the conductive layer (I), the isotropic conductive adhesive layer 26 is preferable in that it can sufficiently function as an electromagnetic wave shielding layer.

As the conductive adhesive layer, a thermosetting conductive adhesive layer is preferable because heat resistance can be exhibited 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 anisotropic conductive adhesive layer 24 may contain a flame retardant as necessary.
The thermosetting isotropic conductive adhesive layer 26 includes, for example, a thermosetting adhesive 26a and conductive particles 26b. The thermosetting isotropic conductive adhesive layer 26 may contain a flame retardant as necessary.

Examples of the thermosetting adhesive include an epoxy resin, a phenol resin, an amino resin, an alkyd resin, a urethane resin, a synthetic rubber, and an ultraviolet curable acrylate resin. An epoxy resin is preferable from the viewpoint of excellent heat resistance. The epoxy resin may contain a rubber component for imparting flexibility (carboxy-modified nitrile rubber, acrylic rubber, etc.), a tackifier, and the like.
The thermosetting adhesive may contain a cellulose resin and microfibrils (such as glass fibers) in order to increase the strength of the conductive adhesive layer and improve the punching characteristics.

  Examples of the conductive particles include metal (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.) particles, graphite powder, calcined carbon particles, plated calcined carbon particles, and the like. As the conductive particles, metal particles are preferable and copper particles are preferable from the viewpoint that the conductive adhesive layer has an appropriate hardness and can reduce pressure loss in the conductive adhesive layer during hot pressing. More preferred.

  The average particle diameter of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 2 μm to 26 μm, and more preferably 4 μm to 16 μm. If the average particle diameter of the conductive particles 24b is equal to or greater than the lower limit of the above range, the thickness of the anisotropic conductive adhesive layer 24 can be ensured, and sufficient adhesive strength can be obtained. If the average particle diameter of the conductive particles 24b is equal to or less than the upper limit of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (followability to the shape of the through holes 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 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 greater than 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. If the average particle diameter of the conductive particles 26b is less than or equal to the upper limit of the above range, the fluidity of the isotropic conductive adhesive layer 26 (followability to the shape of the through holes 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 to 30% by volume, and preferably 2% by volume to 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 equal to or higher than the lower limit of the above range, the conductivity of the anisotropic conductive adhesive layer 24 is improved. When the ratio of the conductive particles 24b is equal to or less than the upper limit of the above range, the adhesiveness and fluidity (followability to the shape of the through hole of the insulating film) of the anisotropic conductive adhesive layer 24 are improved. 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 in 100% by volume of the isotropic conductive adhesive layer 26, and 60% by volume or more and 70% by volume. 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 is improved. When the ratio of the conductive particles 26b is equal to or less than the upper limit of the above range, the adhesiveness and fluidity of the isotropic conductive adhesive layer 26 (followability to the shape of the through hole of the insulating film) are improved. 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 to 1 × 10 ¹⁶ Ω, more preferably 1 × 10 ⁶ Ω to 1 × 10 ¹⁴ Ω. If the surface resistance of the anisotropic conductive adhesive layer 24 is not less than the lower limit of the above range, the content of the conductive particles 24b can be kept low. 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 anisotropy in practice.

  The surface resistance of the isotropic conductive adhesive layer 26 is preferably 0.05Ω to 2.0Ω, more preferably 0.1Ω to 1.0Ω. If the surface resistance of the isotropic conductive adhesive layer 26 is equal to or greater than the lower limit of the above range, the content of the conductive particles 26b can be kept low, the viscosity of the conductive adhesive does not become too high, and the coatability is further increased. It becomes good. Further, the fluidity of the isotropic conductive adhesive layer 26 (followability to the shape of the through hole of the insulating film) can be further ensured. If the surface resistance of the isotropic conductive adhesive layer 26 is less than or equal to the upper limit of the above range, the entire surface of the isotropic conductive adhesive layer 26 has uniform conductivity.

The storage elastic modulus at 180 ° C. of the conductive adhesive layer 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. If the storage elastic modulus at 180 ° C. of the conductive adhesive layer is not less than the lower limit of the above range, the conductive adhesive layer has an appropriate hardness, and in the conductive adhesive layer at the time of hot pressing. Pressure loss can be reduced. If the storage elastic modulus at 180 ° C. of the conductive adhesive layer is less than or equal to the upper limit of the above range, the fluidity of the conductive adhesive layer (followability to the shape of the through hole of the insulating film) can be secured, and the insulating film The through hole can be sufficiently filled with a conductive adhesive.

  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 equal to or greater than the lower limit of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (followability to the shape of the through hole of the insulating film) can be secured, The through hole of the insulating film can be sufficiently filled with the conductive adhesive. If the thickness of the anisotropic conductive adhesive layer 24 is equal to or less than the upper limit 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, and more preferably 7 μm or more and 17 μm or less. If the thickness of the isotropic conductive adhesive layer 26 is equal to or greater than the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 becomes good and can sufficiently function as an electromagnetic wave shielding layer. Further, the fluidity of the isotropic conductive adhesive layer 26 (followability to the shape of the through hole of the insulating film) can be ensured, and the through hole of the insulating film can be sufficiently filled with the conductive adhesive. The bendability can be secured and the isotropic conductive adhesive layer 26 will not be torn even if it is repeatedly bent. If the thickness of the isotropic conductive adhesive layer 26 is equal to or less than the upper limit 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.

(First release film)
The first release film 30 serves as a carrier film when forming the insulating resin layer 10 and the conductive layer 20, and improves the handling properties of the electromagnetic wave shielding film 1. The first release film 30 is peeled from the insulating resin layer 10 after the electromagnetic wave shielding film 1 is attached to a printed wiring board or the like.

  The first release film 30 includes, for example, a release film main body 32 and a release agent layer 34 provided on the surface of the release film main body 32 on the insulating resin layer 10 side.

  As the resin material of the release film main body 32, polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, Examples thereof include polyvinylidene chloride, synthetic rubber, liquid crystal polymer, and the like, and polyethylene terephthalate is preferable from the viewpoint of heat resistance (dimensional stability) and cost when the electromagnetic wave shielding film 1 is produced.

The storage elastic modulus of the release film body 32 at 180 ° C. is preferably 8 × 10 ⁷ Pa or more and 5 × 10 ⁹ Pa, more preferably 1 × 10 ⁸ Pa or more and 8 × 10 ⁸ Pa. If the storage elastic modulus at 180 ° C. of the release film body 32 is equal to or higher than the lower limit of the above range, the first release film 30 has an appropriate hardness, and the first release at the time of hot pressing. The pressure loss in the mold film 30 can be reduced. If the storage elastic modulus at 180 ° C. of the release film main body 32 is equal to or less than the upper limit of the above range, the flexibility of the first release film 30 is good.

  The thickness of the release film main body 32 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. If the thickness of the release film main body 32 is not less than the lower limit of the above range, the handling property of the electromagnetic wave shielding film 1 will be good. If the thickness of the release film main body 32 is equal to or less than the upper limit of the above range, heat is easily transmitted to the conductive adhesive layer when the conductive adhesive layer of the electromagnetic wave shielding film 1 is hot-pressed on the surface of the insulating film. .

The release agent layer 34 is formed by performing a release treatment with a release agent on the surface of the release film main body 32. Since the first release film 30 has the release agent layer 34, when the first release film 30 is peeled from the insulating resin layer 10, the first release film 30 is easily peeled off, and the insulating resin The layer 10 and the conductive adhesive layer after curing are not easily broken.
As the release agent, a known release agent may be used.

  The thickness of the release agent layer 34 is preferably 0.05 μm or more and 2.0 μm or less, and more preferably 0.1 μm or more and 1.5 μm or less. If the thickness of the release agent layer 34 is within the above range, the first release film 30 is more easily peeled off.

(Second release film)
The second release film 40 protects the conductive adhesive layer and improves the handling properties of the electromagnetic wave shielding film 1. The second 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 second release film 40 includes, 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 for the release film main body 42 include the same resin materials as those for the release film main body 32.
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 performing release treatment with a release agent on the surface of the release film main body 42. When the second release film 40 has the release agent layer 44, the second release film 40 can be easily peeled off when the second release film 40 is peeled off from the conductive adhesive layer. The adhesive layer becomes difficult to break.
As the release agent, a known release agent may be used.

  The thickness of the release agent layer 34 is preferably 0.05 μm or more and 2.0 μm or less, and more preferably 0.1 μm or more and 1.5 μm or less. If the thickness of the release agent layer 34 is within the above range, the second release film 40 is more easily peeled off.

(Thickness of electromagnetic shielding film)
The thickness of the electromagnetic shielding film 1 (excluding the release film) is preferably 10 μm or more and 45 μm or less, and more preferably 10 μm or more and 30 μm or less. When the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is equal to or greater than the lower limit of the above range, it is difficult to break when the first release film 30 is peeled off. If the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is not more than the upper limit of the above range, the printed wiring board with the electromagnetic wave shielding film can be thinned.

(Method for producing electromagnetic shielding film)
The electromagnetic wave shielding film of this invention can be manufactured by the method ((alpha)) which has the following process (a)-(c), for example.
Step (a): A step of forming an insulating resin layer on one side of the first release film.
Step (b): A step of forming a conductive layer on the surface of the insulating resin layer after the step (a).
Step (c): A step of attaching a second release film to the surface of the conductive layer after the step (b).

Moreover, the electromagnetic wave shielding film of this invention can be manufactured by the method ((beta)) which has the following process (a '), (b'1), (b'2), (c'), for example.
Step (a ′): a step of forming an insulating resin layer on one side of the first release film.
Step (b′1): By forming a metal thin film layer on the surface of the insulating resin layer, a first laminate including a first release film, an insulating resin layer, and a metal thin film layer in order is obtained. Process.
Step (b′2): a second laminate comprising a second release film and a conductive adhesive layer in this order by forming a conductive adhesive layer on one side of the second release film. Obtaining.
Step (c ′): A step of bonding the first laminate and the second laminate so that the metal thin film layer and the conductive adhesive layer are in contact with each other.

  Hereinafter, a method for producing the electromagnetic wave shielding film 1 shown in FIG. 1 by the method (α) will be described with reference to FIG.

Step (a):
As shown in FIG. 4, the insulating resin layer 10 is formed on one side of the first release film 30.
As a method for forming the insulating resin layer 10, from the viewpoint of heat resistance during reflow soldering or the like, a method of applying and semi-curing a paint containing a thermosetting resin and a curing agent is preferable.
The paint containing a thermosetting resin and a curing agent may contain a solvent and other components (such as a flame retardant) as necessary.

  The peel force at the interface between the insulating resin layer 10 and the first release film 30, the degree of cure of the insulating resin layer 10, and the storage elastic modulus are controlled by selecting the type and composition of the thermosetting resin, the curing agent, etc. It can be carried out by adjusting the curing conditions such as temperature and time when semi-curing the curable resin, or by adding a thermoplastic resin such as a thermoplastic elastomer as a component that does not have thermosetting properties.

Step (b):
As shown in FIG. 4, a metal thin film layer 22 is formed on the surface of the insulating resin layer 10 (step (b1)), and an anisotropic conductive adhesive layer 24 is formed on the surface of the metal thin film layer 22 (step (b2). )).

  Examples of the method for forming the metal thin film layer 22 include physical vapor deposition, a method of forming a vapor deposition film formed by CVD, a method of forming a plating film by plating, and a method of attaching a metal foil. From the viewpoint that the metal thin film layer 22 having excellent surface conductivity can be formed, a method of forming a vapor deposition film by physical vapor deposition, CVD, or a method of forming a plating film by plating is preferable, and the thickness of the metal thin film layer 22 is reduced. The metal thin film layer 22 having excellent conductivity in the plane direction can be formed even when the thickness is small, and the metal thin film layer 22 can be easily formed by a dry process. Therefore, the vapor deposition film is formed by physical vapor deposition or CVD. A method is more preferable, and a method of forming a deposited film by physical vapor deposition is further preferable.

Examples of the method for 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 a thermosetting conductive adhesive composition, what contains the thermosetting adhesive 24a and the electroconductive particle 24b is used.
The storage elastic modulus of the anisotropic conductive adhesive layer 24 can be controlled in the same manner as the storage elastic modulus of the insulating resin layer 10.

Step (c):
As shown in FIG. 4, the second release film 40 is attached to the surface of the anisotropic conductive adhesive layer 24 to obtain the electromagnetic wave shielding film 1.

(Function and effect)
In the electromagnetic wave shielding film 1 described above, the peeling force X at the interface between the insulating resin layer 10 and the first release film 30 before hot pressing, and the insulating resin layer 10 and first separation after the hot pressing. Since the peeling force Y at the interface with the mold film 30 satisfies the relationship of the above formula, compared to the adhesive force at the interface between the insulating resin layer 10 and the first release film 30 before hot pressing, after hot pressing The adhesive force at the interface between the insulating resin layer 10 and the first release film 30 is sufficiently low. Therefore, the first release film 30 is difficult to peel off before hot pressing, and the first release film 30 is easy to peel off after hot pressing.

(Other embodiments)
The electromagnetic wave shielding film of the present invention is an electromagnetic wave shielding film having a first release film, an insulating resin layer, and a conductive layer in this order, at the interface between the insulating resin layer and the first release film before hot pressing. The peeling force X and the peeling force Y at the interface between the insulating resin layer and the first release film after hot pressing need only satisfy the relationship of the above formula, and are limited to the illustrated embodiment. Not.
For example, the insulating resin layer may be two or more layers.
When the tackiness of the surface of the conductive adhesive layer is small, the second release film 40 may be omitted.
In the case where the release film has sufficient release properties only with the release film main body, the release film may not have a release agent layer.
The release film may have an adhesive layer instead of the release agent layer.

<Printed wiring board with electromagnetic shielding film>
FIG. 5 is a cross-sectional view showing an embodiment of a printed wiring board with an electromagnetic wave shielding film of the present invention.
The flexible printed wiring board 2 with an electromagnetic wave shielding film includes a flexible printed wiring board 50, an insulating film 60, and the electromagnetic wave shielding film 1 of the first embodiment.
The flexible printed wiring board 50 has a printed circuit 54 provided on at least one side 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 to the surface of the insulating film 60 and cured. 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 an electromagnetic wave shielding film, the second release film 40 is peeled from the anisotropic conductive adhesive layer 24.
When the first release film 30 becomes unnecessary in the flexible printed wiring board 2 with the electromagnetic wave shielding film, the first release film 30 is peeled off from the insulating resin layer 10.

In the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) excluding the portion having the through hole, the metal thin film layer 22 of the electromagnetic wave shielding film 1 is provided with the insulating film 60 and the anisotropic conductive adhesive layer 24. Are arranged opposite to each other.
The separation 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 sum of the thickness of the insulating film 60 and the thickness of 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. When the separation distance is smaller than 30 μm, the impedance of the signal circuit is lowered. Therefore, in order to have a characteristic impedance such as 100Ω, the line width of the signal circuit has to be reduced, and the variation in the line width causes the variation in the characteristic impedance. Thus, the reflection resonance noise due to the impedance mismatch is easily applied to 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 is insufficient.

(Flexible printed wiring board)
The flexible printed wiring board 50 is a printed circuit (a power circuit, a ground circuit, a ground layer, etc.) formed by processing a copper foil of a copper clad laminate into a desired pattern by a known etching method.
As the copper-clad laminate, one or both surfaces of the base film 52 are bonded with copper foil via an adhesive layer (not shown); a resin solution or the like that forms the base film 52 is cast on the surface of the copper foil And the like.
Examples of the material for the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenol resin, polyurethane, 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)
The base film 52 is preferably a heat resistant film, more preferably a polyimide film or a liquid crystal polymer film, and even more preferably a polyimide film.
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 a 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 constituting 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 preferred from the viewpoint of flexibility.
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.
An end (terminal) in the length direction of the printed circuit 54 is not covered with the insulating film 60 or the electromagnetic wave shielding film 1 for solder connection, connector connection, component mounting, or the like.

(Insulating film)
The insulating film 60 is obtained by forming an adhesive layer (not shown) on one surface of a base film (not shown) by applying an adhesive, attaching an adhesive sheet, or the like.
The surface resistance of the base film is preferably 1 × 10 ⁶ Ω or more from the viewpoint of electrical insulation. The surface resistance of the base film is preferably 1 × 10 ¹⁹ Ω or less from a practical point of view.
As a base film, the film which has heat resistance is preferable, a polyimide film and a liquid crystal polymer film are more preferable, and a polyimide film is further more preferable.
The thickness of the base film 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 for the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenol resin, polyurethane, acrylic resin, melamine resin, polystyrene, and polyolefin. The epoxy resin may contain a rubber component (carboxyl-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, and 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 62 include a circle, an ellipse, and a quadrangle.

(Method for producing printed wiring board with electromagnetic shielding film)
The printed wiring board with an electromagnetic wave shielding film of the present invention can be produced by, for example, a method having the following steps (d) to (g).
Step (d): A step of obtaining a printed wiring board with an insulating film by providing an insulating film having through holes formed at positions corresponding to the printed circuit on the surface of the printed wiring board on which the printed circuit is provided.
Step (e): After step (d), the printed wiring board with an insulating film and the electromagnetic wave shielding film of the present invention from which the second release film has been peeled are contacted with the conductive adhesive layer on the surface of the insulating film. The conductive adhesive layer is adhered to the surface of the insulating film, and the conductive adhesive layer is electrically connected to the printed circuit through the through-holes by stacking and heat-pressing them. A step of obtaining a printed wiring board with a shield film.
Step (f): A step of peeling off the first release film after the step (e) when the first release film becomes unnecessary.
Step (g): A step of fully curing the anisotropic conductive adhesive layer between the steps (e) and (f) or after the step (f) as necessary.

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

(Process (d))
As shown in FIG. 6, an insulating film 60 in which a through hole 62 is formed at a position corresponding to the printed circuit 54 is overlaid on the flexible printed wiring board 50, and an adhesive layer of the insulating film 60 is placed on the surface of the flexible printed wiring board 50. A flexible printed wiring board 3 with an insulating film is obtained by bonding (not shown) and curing the adhesive layer. The adhesive layer of the insulating film 60 may be temporarily bonded to the surface of the flexible printed wiring board 50, and the adhesive layer may be fully cured in the step (g).
Adhesion and curing of the adhesive layer are performed by, for example, hot pressing with a press machine (not shown) or the like.

(Process (e))
As shown in FIG. 6, the electromagnetic shielding film 1 from which the second release film 40 is peeled is superimposed on the flexible printed wiring board 3 with an insulating film, and heat-pressed, whereby the surface of the insulating film 60 is anisotropically conductive. The flexible printed wiring board 2 with the electromagnetic wave shielding film is obtained in which the adhesive layer 24 is bonded and the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through the through hole 62.

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

  The temperature of the hot press (the temperature of the hot platen 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. If the temperature of the hot press is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is bonded to the surface of the insulating film 60. Also, the time for hot pressing can be shortened. Further, the insulating resin layer 10 is sufficiently cured, and the peeling force Y at the interface between the insulating resin layer 10 and the first release film 30 is sufficiently reduced. If the temperature of the hot press is not more than the upper limit of the above range, deterioration of the electromagnetic wave shielding film 1, the flexible printed wiring board 50, etc. can be suppressed.

  The pressure of the hot press is preferably 0.5 MPa or more and 20 MPa or less, and more preferably 1 MPa or more and 16 MPa or less. If the pressure of the hot press 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. Also, the time for hot pressing can be shortened. If the pressure of the hot press is not more than the upper limit of the above range, damage to the electromagnetic wave shielding film 1, the flexible printed wiring board 50, etc. can be suppressed.

(Process (f))
As shown in FIG. 6, when the first release film becomes unnecessary, the first release film 30 is peeled from the insulating resin layer 10.

(Process (g))
When the time of the hot press in the step (e) is a short time of 20 seconds or more and 10 minutes or less, the anisotropic conductive adhesive layer between the step (e) and the step (f) or after the step (f) It is preferable to perform 24 main curing.
The main curing of the anisotropic conductive adhesive layer 24 is performed using a heating device such as an oven, for example.
The heating time is from 15 minutes to 120 minutes, preferably from 30 minutes to 60 minutes. If the heating time is not less than the lower limit of the above range, the anisotropic conductive adhesive layer 24 can be sufficiently cured. If heating time is below the upper limit of the said range, the manufacturing time of the flexible printed wiring board 2 with an electromagnetic wave shielding film can be shortened.
The heating temperature (atmosphere temperature in the oven) is preferably 120 ° C. or higher and 180 ° C. or lower, and preferably 120 ° C. or higher and 150 ° C. or lower. If heating temperature is more than the lower limit of the said range, heating time can be shortened. If heating temperature is below the upper limit of the said range, deterioration etc. of the electromagnetic wave shielding film 1, the flexible printed wiring board 50, etc. can be suppressed.
Heating is preferably performed without pressure from the point that a special apparatus need not be used.

(Function and effect)
In the flexible printed wiring board 2 with the electromagnetic wave shielding film described above, since the electromagnetic wave shielding film 1 is used, the first release film 30 of the electromagnetic wave shielding film 1 is easily peeled off.

(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 conductive. Any layer may be used as long as it has an electromagnetic wave shielding film electrically connected to a printed circuit through a through-hole formed in the insulating film, and is not limited to the illustrated embodiment.
For example, the flexible printed wiring board may have a ground layer on the back side. The flexible printed wiring board may have a printed circuit 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, a rigid printed board having no flexibility may be used.
Instead of the electromagnetic shielding film 1 of the first embodiment, the electromagnetic shielding film 1 of the second embodiment, the electromagnetic shielding film 1 of the third embodiment, or the like may be used.

  Examples are shown below. In addition, this invention is not limited to an Example.

(Curing degree)
The degree of cure of the insulating resin layer was measured as follows.
About the insulating resin layer before making it harden | cure or harden | cure, the infrared spectroscopy spectrum was measured using the infrared spectrophotometer (JASCO company make, FT-IR-4600). After semi-curing or curing the insulating resin layer, the infrared spectrum was measured in the same manner. The degree of cure is calculated from the peak intensity of the epoxy group in the infrared spectrum after semi-curing or curing, assuming that the peak intensity of the epoxy group near 918 cm ⁻¹ in the infrared spectrum before semi-curing or curing is 100%. did.

(Storage modulus)
The storage elastic modulus was measured using a dynamic viscoelasticity measuring device (Rheometric Scientific, Inc., RSAII) under the conditions of temperature: 180 ° C., frequency: 1 Hz, and heating rate: 10 ° C./min.

(Peeling power)
Tensile test is conducted on the peel force X at the interface between the first release film and the insulating resin layer before the following hot press and the peel force Y at the interface between the first release film and the insulating resin layer after the following hot press. A 180 degree peel test of the first release film was performed using a machine.

(Heat press)
Silicone rubber cushion material (made by Shin-Etsu Polymer Co., Ltd.) having a thickness of 2 mm, polyethylene terephthalate film (made by Toray Industries, Lumirror (registered trademark)) having a thickness of 50 μm, and a thickness of 18 μm on one side of a polyimide film having a thickness of 12 μm A copper-clad laminate (manufactured by Shin-Etsu Chemical Co., Ltd., KN12SR18P) and an electromagnetic wave shielding film were prepared.
An electromagnetic wave in which a silicone rubber cushion material, a polyethylene terephthalate film, a copper-clad laminate, and a second release film are peeled between hot plates of a hot press apparatus (G-12 manufactured by Orihara Seisakusho Co., Ltd.) having a pair of hot plates. A shield film, a polyethylene terephthalate film, and a silicone rubber cushion material are arranged in this order so that the copper foil of the copper-clad laminate and the conductive layer of the electromagnetic wave shield film are in contact with each other, and the heating plate temperature is 170 ° C. and the pressure is 2 MPa. Hot pressed for 120 seconds.

(Peelability)
Before the hot pressing in the step (e), a part of the first release film 30 was peeled off, and the ease of peeling was evaluated. After the hot pressing in the step (e), a part of the first release film 30 was peeled off, and the ease of peeling was evaluated.
○ (good): The first release film 30 is easily peeled off.
X (defect): It is difficult to peel the first release film 30.

Example 1
As the first release film 30 and the second release film 40, a polyethylene terephthalate film whose one side was release-treated with a non-silicone release agent (manufactured by Lintec, T157, thickness: 50 μm, at 180 ° C. Storage elastic modulus: 5 × 10 ⁸ Pa) was prepared.

  As a paint, 100 parts by mass of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER (registered trademark) 828), 20 parts by mass of a curing agent (N-aminoethylpiperazine), 2 of 2-ethyl-4-methylimidazole A coating material in which 2 parts by mass of carbon black and 2 parts by mass of carbon black were dissolved in 200 parts by mass of a solvent (methyl ethyl ketone) was prepared.

  As a thermosetting conductive adhesive composition, 20 parts by mass of thermosetting adhesive 24a (epoxy resin (DIC, EXA-4816) and curing agent (Ajinomoto Fine-Techno, PN-23). And 40 parts by weight of conductive particles 24b (copper particles having an average particle diameter of 7.5 μm) were dissolved or dispersed in 200 parts by weight of a solvent (methyl ethyl ketone). I prepared something.

Step (a):
A coating material is applied to the surface of the release agent layer 34 of the first release film 30, heated at 60 ° C. for 2 minutes, dried and semi-cured, and the insulating resin layer 10 (thickness: 10 μm, degree of curing) : 56%, storage elastic modulus at 180 ° C .: 1.8 × 10 ⁷ Pa).

Step (b1):
Copper was physically vapor-deposited on the surface of the insulating resin layer 10 by an electron beam vapor deposition method to form a metal thin film layer 22 (deposition film, thickness: 0.07 μm, surface resistance: 0.3Ω).

Step (b2):
By applying a thermosetting conductive adhesive composition to the surface of the metal thin film layer 22 using a die coater and evaporating the solvent to form a B stage, the anisotropic conductive adhesive layer 24 (thickness: 7 μm, copper particles: 4.5% by volume, storage elastic modulus at 180 ° C .: 1 × 10 ⁴ Pa).

Step (c):
The 2nd release film 40 was affixed on the surface of the anisotropic conductive adhesive layer 24, and the electromagnetic wave shielding film 1 was obtained. Table 1 shows the measurement results of the peeling force X and the peeling force Y. Table 1 shows the measurement results of the degree of cure of the insulating resin layer 10 after measuring the peeling force Y, that is, after hot pressing.

Step (d):
An insulating adhesive composition made of a nitrile rubber-modified epoxy resin is applied to the surface of a polyimide film (surface resistance: 1 × 10 ¹⁷ Ω) (base film) with a thickness of 25 μm so that the dry film thickness is 25 μm. Then, an adhesive layer was formed to obtain an insulating film 60 (thickness: 50 μm). A through hole 62 (hole diameter: 150 μm) was formed at a position corresponding to the ground of the printed circuit 54.

A flexible printed wiring board 50 having a printed circuit 54 formed on the surface of a polyimide film (surface resistance: 1 × 10 ¹⁷ Ω) (base film 52) having a thickness of 12 μm was prepared.
The insulating film 60 was affixed on the flexible printed wiring board 50 by hot press, and the flexible printed wiring board 3 with an insulating film was obtained.

Step (e):
The electromagnetic wave shielding film 1 from which the second release film 40 has been peeled is stacked on the flexible printed wiring board 3 with an insulating film, and a hot press apparatus (G-12 manufactured by Orihara Seisakusho Co., Ltd.) is used. Pressure: hot pressing at 2 MPa for 120 seconds, the anisotropic conductive adhesive layer 24 was temporarily bonded to the surface of the insulating film 60, and the flexible printed wiring board 2 with an electromagnetic wave shielding film was obtained. Table 1 shows the evaluation results of the peelability of the first release film 30 before and after hot pressing.

Steps (f) and (g):
The anisotropic conductive adhesive layer 24 was fully cured by heating the flexible printed wiring board 2 with the electromagnetic wave shielding film at a temperature of 160 ° C. for 1 hour using a high temperature thermostat (manufactured by Enomoto Kasei Co., Ltd., HT210). . The first release film 30 was peeled from the insulating resin layer 10.
The conduction between the ground of the printed circuit 54 corresponding to the position where the through-hole 62 is formed and the metal thin film layer 22 of the electromagnetic wave shielding film 1 is examined, and the anisotropic conductive adhesive cured with the ground of the printed circuit 54. It was confirmed that the layer 24 was electrically connected.

(Example 2)
As the first release film 30 and the second release film 40, a polyethylene terephthalate film whose one side was release-treated with a non-silicone release agent (manufactured by Lintec, T157, thickness: 50 μm, at 180 ° C. Storage elastic modulus: 5 × 10 ⁸ Pa) was prepared.

  As paint, 90 parts by mass of bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, jER (registered trademark) 828), 10 parts by mass of bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, jER (registered trademark) 1001), curing A coating material was prepared by dissolving 30 parts by mass of an agent (isophoronediamine) and 4 parts by mass of carbon black in 200 parts by mass of a solvent (methyl ethyl ketone).

  As a thermosetting conductive adhesive composition, 20 parts by mass of thermosetting adhesive 24a (epoxy resin (DIC, EXA-4816) and curing agent (Ajinomoto Fine-Techno, PN-23). And 40 parts by weight of conductive particles 24b (copper particles having an average particle diameter of 7.5 μm) were dissolved or dispersed in 200 parts by weight of a solvent (methyl ethyl ketone). I prepared something.

After the step (a), the electromagnetic wave shielding film 1 was obtained in the same manner as in Example 1. Table 1 shows the measurement results of the degree of cure of the insulating resin layer 10 before and after hot pressing, the storage elastic modulus at 180 ° C., and the peel force X and peel force Y.
Moreover, except having changed the electromagnetic wave shielding film 1, it carried out similarly to Example 1, and obtained the flexible printed wiring board 2 with an electromagnetic wave shielding film. Table 1 shows the evaluation results of the peelability of the first release film 30 before and after the hot pressing in the step (e).

(Comparative Example 1)
As the first release film 30 and the second release film 40, a polyethylene terephthalate film whose one side was release-treated with a non-silicone release agent (manufactured by Lintec, T157, thickness: 50 μm, at 180 ° C. Storage elastic modulus: 5 × 10 ⁸ Pa) was prepared.

  As paints, 100 parts by mass of bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, jER (registered trademark) 828), 80 parts by mass of curing agent (Mitsubishi Chemical Corporation, jER Cure QX21), and 4 parts by mass of carbon black A paint dissolved in 200 parts by mass of (methyl ethyl ketone) was prepared.

  As a thermosetting conductive adhesive composition, 20 parts by mass of thermosetting adhesive 24a (epoxy resin (DIC, EXA-4816) and curing agent (Ajinomoto Fine-Techno, PN-23). And 40 parts by weight of conductive particles 24b (copper particles having an average particle diameter of 7.5 μm) were dissolved or dispersed in 200 parts by weight of a solvent (methyl ethyl ketone). I prepared something.

After the step (a), the electromagnetic wave shielding film 1 was obtained in the same manner as in Example 1. Table 1 shows the measurement results of the degree of cure of the insulating resin layer 10 before and after hot pressing, the storage elastic modulus at 180 ° C., and the peel force X and peel force Y.
Moreover, except having changed the electromagnetic wave shielding film 1, it carried out similarly to Example 1, and obtained the flexible printed wiring board 2 with an electromagnetic wave shielding film. Table 1 shows the evaluation results of the peelability of the first release film 30 before and after the hot pressing in the step (e).

(Comparative Example 2)
As the first release film 30 and the second release film 40, a polyethylene terephthalate film whose one side was release-treated with a non-silicone release agent (manufactured by Lintec, T157, thickness: 50 μm, at 180 ° C. Storage elastic modulus: 5 × 10 ⁸ Pa) was prepared.

  As paint, 10 parts by mass of bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, jER (registered trademark) 828), 90 parts by mass of bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, jER (registered trademark) 1010), curing A paint was prepared by dissolving 30 parts by mass of an agent (manufactured by Mitsubishi Chemical Corporation, jER Cure YN100) and 4 parts by mass of carbon black in 200 parts by mass of a solvent (methyl ethyl ketone).

  As a thermosetting conductive adhesive composition, 20 parts by mass of thermosetting adhesive 24a (epoxy resin (DIC, EXA-4816) and curing agent (Ajinomoto Fine-Techno, PN-23). And 40 parts by weight of conductive particles 24b (copper particles having an average particle diameter of 7.5 μm) were dissolved or dispersed in 200 parts by weight of a solvent (methyl ethyl ketone). I prepared something.

After the step (a), the electromagnetic wave shielding film 1 was obtained in the same manner as in Example 1. Table 1 shows the measurement results of the degree of cure of the insulating resin layer 10 before and after hot pressing, the storage elastic modulus at 180 ° C., and the peel force X and peel force Y.
Moreover, except having changed the electromagnetic wave shielding film 1, it carried out similarly to Example 1, and obtained the flexible printed wiring board 2 with an electromagnetic wave shielding film. Table 1 shows the evaluation results of the peelability of the first release film 30 before and after the hot pressing in the step (e).

  In Examples 1 and 2 in which the peeling force X and the peeling force Y satisfy the above-described relationship, the first release film 30 is difficult to peel from the insulating resin layer 10 before hot pressing, and after hot pressing. The first release film 30 is easy to peel off from the insulating resin layer 10.

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

DESCRIPTION OF SYMBOLS 1 Electromagnetic wave shielding film 2 Flexible printed wiring board with electromagnetic wave shielding film 3 Flexible printed wiring board with an insulating film 10 Insulating resin layer 20 Conductive layer 22 Metal thin film layer 24 Anisotropic conductive adhesive layer 24a Thermosetting adhesive 24b Conductive particle 26 Isotropic Conductive Adhesive Layer 26a Thermosetting Adhesive 26b Conductive Particles 30 First Release Film 32 Release Film Main Body 34 Release Agent Layer 40 Second Release Film 42 Release Film Main Body 44 Release Agent layer 50 Flexible printed wiring board 52 Base film 54 Printed circuit 60 Insulating film 62 Through-hole 101 Flexible printed wiring board with electromagnetic shielding film 110 Electromagnetic shielding film 112 Insulating resin layer 114 Metal thin film layer 116 Conductive adhesive layer 118 First Mold release Irumu 130 flexible printed circuit board 132 the base film 134 printed circuit 140 insulating film 142 through hole

Claims (9)

An insulating resin layer;
A conductive layer adjacent to the insulating resin layer;
A first release film adjacent to the side of the insulating resin layer opposite to the conductive layer;
The peeling force X at the interface between the insulating resin layer and the first release film before the following hot press, and the peeling force Y at the interface between the insulating resin layer and the first release film after the following hot press are as follows: An electromagnetic wave shielding film that satisfies the relationship of formula (1).
X> 2 × Y (1)
(Heat press)
A 2 mm thick silicone rubber cushion material, a 50 μm thick polyethylene terephthalate film, a 12 μm thick polyimide film, a copper clad laminate with a 18 μm thick copper foil laminated on one side, and an electromagnetic shielding film To do. Silicone rubber cushioning material, polyethylene terephthalate film, copper-clad laminate, electromagnetic wave shielding film, polyethylene terephthalate film, silicone rubber cushioning material in this order and copper-clad lamination between the heating plates of a press equipped with a pair of heating plates It arrange | positions so that the copper foil of a board | substrate and the conductive layer of an electromagnetic wave shield film may contact | connect, and hot press is carried out for 120 second by hot plate temperature: 170 degreeC and pressure: 2MPa. The peeling force X is 2 N / cm or more,
The electromagnetic wave shielding film according to claim 1, wherein the peeling force Y is 20 N / cm or less.   The electromagnetic wave shielding film according to claim 1 or 2, wherein the insulating resin layer is a layer containing a semi-cured thermosetting resin.   The electromagnetic wave shielding film according to claim 3, wherein a degree of cure of the insulating resin layer before the hot pressing is 40% or more and 60% or less.   The electromagnetic wave shielding film according to claim 3 or 4, wherein a degree of cure of the insulating resin layer after the hot pressing is 70% or more and 99% or less.   The said conductive layer has a metal thin film layer adjacent to the said insulating resin layer, and the conductive adhesive layer used as the outermost layer on the opposite side to the said insulating resin layer in the said conductive layer. The electromagnetic wave shielding film according to claim 1.   The electromagnetic wave shielding film according to any one of claims 1 to 5, wherein the conductive layer comprises an isotropic conductive adhesive layer.   The electromagnetic wave shielding film according to claim 1, further comprising a second release film adjacent to the side of the conductive layer opposite to the insulating resin layer. A printed wiring board provided with a printed circuit on at least one side of the substrate;
An insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided;
The said conductive layer is adjacent to the said insulating film, and the said conductive layer is electrically connected to the said printed circuit through the through-hole formed in the said insulating film. A printed wiring board with an electromagnetic wave shielding film, comprising:

Images