KR102385691B1 - Electromagnetic wave shield film - Google Patents

Abstract

An object of the present invention is to realize an electromagnetic wave shielding film in which the transfer film can be easily peeled off. In order to solve the above problems, according to the present invention, the electromagnetic wave shielding film includes an insulating protective layer 112 , a transfer film 115 provided on the surface of the insulating protective layer 112 , and a transfer film of the insulating protective layer 112 . A conductive adhesive layer 111 provided on the opposite side to 115 is provided. The surface of the transfer film 115 on the insulating protective layer 112 side has a maximum trough depth Sv of 1 µm or more and 6 µm or less, and a maximum height Sz of 2 µm or more and 10 µm or less.

Description

Electromagnetic wave shielding film {ELECTROMAGNETIC WAVE SHIELD FILM}

The present disclosure relates to an electromagnetic wave shielding film.

In order to protect an electronic circuit from electromagnetic waves, an electromagnetic wave shielding film is used. The electromagnetic wave shielding film has a conductive adhesive layer and an insulating protective layer. The electromagnetic wave shielding film is generally manufactured by sequentially forming an insulating protective layer and a conductive adhesive layer on the surface of a base film. A base film is removed before a reflow process, after an electromagnetic wave shielding film is adhere|attached to a printed wiring board. In this case, the base film functions as a transfer film whose surface state is transferred to the insulating protective layer. Moreover, it functions also as a protective film which protects the insulating protective layer until the electromagnetic wave shielding film adheres to a printed wiring board.

In order to make the surface of the insulating protective layer a matte surface, it is common to provide unevenness on the surface of the transfer film. By providing an unevenness|corrugation, the adhesiveness of a transfer film and an insulating protective layer increases, and the force required when peeling a transfer film becomes large. In addition, when bonding an electromagnetic wave shielding film to a printed wiring board, it is a temperature of about 150 degreeC - 200 degreeC, and it is common to apply the pressure of several MPa. When exposed to such a temperature and pressure, peeling of a transfer film becomes more difficult, and a transfer film may fracture|rupture.

In order to prevent the fracture|rupture at the time of peeling, making the transfer film itself hard to tear is examined (for example, refer patent documents 1 and 2).

Japanese Laid-Open Patent Publication No. 2015-185659 Japanese Laid-Open Patent Publication No. 2016-97522

However, even if the transfer film itself becomes difficult to tear, if a large force is required at the time of peeling, productivity will fall. Moreover, there is a possibility that the side of the insulating protective layer may be damaged. In order to make the transfer film peelable easily, it is desired to control the interaction between the transfer film and the insulating protective layer.

An object of the present disclosure is to realize an electromagnetic wave shielding film in which the transfer film can be easily peeled off.

One aspect of the electromagnetic wave shielding film of the present disclosure includes an insulating protective layer, a transfer film provided on the surface of the insulating protective layer, and a conductive adhesive layer provided on the opposite side to the transfer film of the insulating protective layer, for insulation protection of the transfer film The layer-side surface has a maximum trough depth (Sv) of 1 µm or more and 6 µm or less, and a maximum height (Sz) of 2 µm or more and 10 µm or less.

In one aspect of the electromagnetic wave shielding film, the coefficient of variation of the maximum trough depth (Sv) and the coefficient of variation of the maximum height (Sz) on the surface of the transfer film on the insulating protective layer side may be 0.2 or less.

ADVANTAGE OF THE INVENTION According to the electromagnetic wave shielding film of this indication, peeling of a transfer film becomes easy, and productivity can be improved.

1 is a cross-sectional view showing an electromagnetic wave shielding film according to an embodiment.
2 is a cross-sectional view showing a modified example of the electromagnetic wave shielding film.
3 is a cross-sectional view showing a shielding printed wiring board using an electromagnetic wave shielding film according to an embodiment.

As shown in FIG. 1 , the electromagnetic wave shielding film of the present embodiment includes an insulating protective layer 112 , a transfer film 115 provided on the surface of the insulating protective layer 112 , and a transfer film of the insulating protective layer 112 . A conductive adhesive layer 111 provided on the opposite side to 115 is provided. Further, as shown in FIG. 2 , a shielding layer 113 may be provided between the insulating protective layer 112 and the conductive adhesive layer 111 .

The present inventors set the maximum trough depth (Sv) of the transfer film 115 on the insulating protective layer 112 side to 6 µm or less, preferably 5 µm or less, and set the maximum height (Sz) to 10 µm or less. , It was discovered that the transfer film 115 that can be easily peeled off is preferably set to 9 µm or less.

On the other hand, it was found that there is a film that is difficult to peel even if the arithmetic mean height (Sa) is small. It is considered that even if it is an unevenness|corrugation which becomes the same grade as an average value, if there is a deep valley or a high mountain at a pinpoint, the adhesiveness will become high in that part, and peeling will become difficult. For this reason, it becomes important to control Sv and Sz of the transfer film 115 . In addition, Sa, Sv, and Sz of the transfer film 115 can be measured by the method demonstrated in an Example.

From the viewpoint of facilitating peeling, it is preferable that the maximum trough depth on the surface of the transfer film 115 on the insulating protective layer 112 side is small, but from the viewpoint of making the surface of the insulating protective layer 112 a matte surface and printing From the viewpoint of preventing the transfer film 115 from peeling off before fixing to the wiring board, Sv is 1 µm or more, preferably 2 µm or more, and Sz is 2 µm or more, preferably 3 µm or more.

The peel strength of the transfer film 115 is preferably 5.0 N/50 mm or less, more preferably 1.5 N/50 mm or less, from the viewpoint of easy peeling, and from the viewpoint of preventing the transfer film 115 from peeling before use. In, preferably 0.2N/50mm or more, more preferably 0.5N/50mm or more. In addition, the peeling strength of the transfer film 115 can be measured by the method shown in an Example.

From the viewpoint of facilitating peeling, the coefficient of variation of Sv and the coefficient of variation (CV) of Sz on the surface of the transfer film 115 on the insulating protective layer 112 side are preferably 0.2 or less, more preferably 0.15 or less. The coefficient of variation here is a value obtained from the arithmetic mean and standard deviation of 10 points as shown in Examples.

Moreover, it is preferable to also control parameters which show surface properties other than Sv and Sz from a viewpoint of making peeling further easier. For example, kurtosis (Sku) becomes like this. Preferably it is 2.0 or more, More preferably, it is 3.0 or more, Preferably it is 8.5 or less, More preferably, it is 7.5 or less. The minimum autocorrelation length (Sal) is preferably 7.5 µm or more, more preferably 8.5 µm or more, preferably 20.0 µm or less, still more preferably 15.0 µm or less. The aspect ratio (Str) of the surface properties is preferably 0.55 or more, more preferably 0.60 or more, and preferably 0.75 or less. The projecting valley height (Svk) is preferably 0.20 or more, more preferably 0.25 or more, preferably 0.75 or less, and more preferably 0.70 or less. The load area ratio (Smr2) that separates the protruding valley portion and the core portion is preferably 90.0% or more, more preferably 94.0% or more. The parameter which shows this surface property can also be measured by the method shown in an Example.

The material of the transfer film 115 is not specifically limited, Polyester, polyolefin, polyimide, polyethylene naphthalate, polyphenylene sulfide, etc. can be used. Although the thickness of the transfer film 115 is not specifically limited, From a viewpoint of making peeling easy, Preferably it is 25 micrometers or more, Preferably it is 100 micrometers or less.

At least one surface of the transfer film 115 may be subjected to a sandblaster treatment or the like in order to set Sv and Sz to predetermined values. Moreover, Sv and Sz can also be made into predetermined values by containing microparticles|fine-particles. The microparticles|fine-particles added to the transfer film 115 are not specifically limited, For example, amorphous silica (colloidal silica), silica, talc, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, phosphoric acid. Inorganic particles such as calcium, magnesium phosphate, alumina, carbon black, titanium dioxide, kaolin, and synthetic zeolite, and organic particles such as crosslinked polystyrene particles and crosslinked acrylic particles can be used.

A release agent layer (not shown) can be provided between the transfer film 115 and the insulating protective layer 112 . The release agent layer can be formed by applying a silicone-based or non-silicone-based release agent to the surface of the transfer film 115 on the insulating protective layer 112 side. When forming a mold release agent layer, the thickness can be made into about several micrometers - about several tens of micrometers.

In the present embodiment, the insulating protective layer 112 is not particularly limited as long as it has sufficient insulation and can protect the conductive adhesive layer 111 and, if necessary, the shielding layer 113. For example, a thermoplastic resin , a thermosetting resin, an active energy ray-curable resin, or the like.

Although the thermoplastic resin is not specifically limited, Styrene-type resin, vinyl acetate-type resin, polyester-type resin, polyethylene-type resin, polypropylene-type resin, imide-type resin, an acrylic resin, etc. can be used. Although it does not specifically limit as a thermosetting resin, A phenol-type resin, an epoxy-type resin, a urethane-type resin, a melamine-type resin, a polyamide-type resin, an alkyd-type resin, etc. can be used. Although it does not specifically limit as active energy ray-curable resin, For example, the polymeric compound etc. which have at least two (meth)acryloyloxy groups in a molecule|numerator can be used. The protective layer may be formed of a single material, or may be formed of two or more types of materials.

In the insulating protective layer 112, it is not limited to a colorant, and if necessary, a curing accelerator, a tackifier, an antioxidant, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, a viscosity One or more of a regulator, an antiblocking agent, etc. may be contained.

The insulating protective layer 112 may be a laminate of two or more layers different in material or physical properties such as hardness or elastic modulus. For example, when a laminate of an outer layer with low hardness and an inner layer with high hardness is used as a laminate, the outer layer has a cushioning effect. 113) can be relieved. For this reason, it can suppress that the shielding layer 113 is destroyed by the level|step difference provided in the printed wiring board 102. As shown in FIG.

The insulating protective layer 112 can be formed by applying a composition for an insulating protective layer to the surface of the transfer film 115 . The composition for an insulating protective layer may be prepared, for example, by adding an appropriate amount of a solvent to the resin for the insulating protective layer.

The thickness of the insulating protective layer 112 is not particularly limited and can be appropriately set as needed. Preferably, it is 1 µm or more, more preferably 4 µm or more, and preferably 20 µm or less, and more preferably may be 10 µm or less, more preferably 5 µm or less. When the thickness of the insulating protective layer 112 is 1 μm or more, the conductive adhesive layer 111 and the shielding layer 113 can be sufficiently protected. By making the thickness of the insulating protective layer 112 into 20 micrometers or less, it becomes easy to make the elastic modulus and breaking elongation of the electromagnetic wave shielding film 101 into predetermined values.

When the shielding layer 113 is provided, the shielding layer 113 can be formed of metal foil, a vapor deposition film, a conductive filler, or the like.

The metal foil is not particularly limited, but a foil made of an alloy containing any one or two or more of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc. there is.

Although the thickness of metal foil is not specifically limited, 0.5 micrometer or more is preferable, and 1.0 micrometer or more is more preferable. When the high frequency signal of 10 MHz - 100 GHz is transmitted to the shielding printed wiring board as thickness of metal foil is 0.5 micrometer or more, the attenuation amount of a high frequency signal can be suppressed. Moreover, 12 micrometers or less are preferable, as for the thickness of metal foil, 10 micrometers or less are more preferable, and 7 micrometers or less are still more preferable. When the thickness of a metal layer is 12 micrometers or less, raw material cost can be suppressed and break elongation of a shielding film becomes favorable.

The vapor-deposited film is not particularly limited, and can be formed by vapor-depositing nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, or the like. For vapor deposition, an electrolytic plating method, an electroless plating method, a sputtering method, an electron beam vapor deposition method, a vacuum vapor deposition method, a chemical vapor deposition (CVD) method, or a metal organic deposition (MOCVD) method can be used.

Although the thickness of a vapor deposition film is not specifically limited, 0.05 micrometer or more is preferable, and 0.1 micrometer or more is more preferable. It is excellent in the characteristic which an electromagnetic wave shielding film shields electromagnetic waves in a shielding printed wiring board as the thickness of a metal vapor deposition film is 0.05 micrometer or more. Moreover, it is preferable that it is less than 0.5 micrometer, and, as for the thickness of a metal vapor deposition film, it is more preferable that it is less than 0.3 micrometer. When the thickness of the deposited metal film is less than 0.5 µm, the electromagnetic wave shielding film has excellent bending resistance, and it can suppress that the shielding layer is destroyed by the step provided on the printed wiring board.

In the case of the conductive filler, the shielding layer 113 can be formed by applying a solvent containing the conductive filler to the surface of the insulating protective layer 112 and drying it. As the conductive filler, a metal filler, a metal-coated resin filler, a carbon filler, and mixtures thereof can be used. As the metal filler, copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder, and the like can be used. These metal powders can be prepared by an electrolysis method, an atomization method, or a reduction method. Examples of the shape of the metal powder include spherical, flake, fibrous, and dendritic shapes.

In this embodiment, the thickness of the shielding layer 113 is preferably selected according to the required electromagnetic shielding effect and repeated bending/sliding resistance, but in the case of metal foil, the viewpoint of securing the elongation at break It is preferable to set it to 12 μm or less.

In this embodiment, the conductive adhesive layer 111 contains resin components, such as a thermoplastic resin and a thermosetting resin, and a conductive filler.

When the conductive adhesive layer 111 contains a thermoplastic resin, as a thermoplastic resin, for example, a styrene-based resin, a vinyl acetate-based resin, a polyester-based resin, a polyethylene-based resin, a polypropylene-based resin, an imide-based resin, and An acrylic resin or the like can be used. These resins may be used individually by 1 type, and may use 2 or more types together.

When the conductive adhesive layer 111 includes a thermosetting resin, as the thermosetting resin, for example, a phenol-based resin, an epoxy-based resin, a urethane-based resin, a melamine-based resin, a polyamide-based resin, and an alkyd-based resin may be used. . Although it does not specifically limit as an active energy ray-curable composition, For example, the polymeric compound etc. which have at least two (meth)acryloyloxy groups in a molecule|numerator can be used. These compositions may be used individually by 1 type, and may use 2 or more types together.

A thermosetting resin contains the 1st resin component which has a reactive 1st functional group, and the 2nd resin component which reacts with a 1st functional group, for example. The first functional group can be, for example, an epoxy group, an amide group, or a hydroxyl group. What is necessary is just to select a 2nd functional group according to a 1st functional group, for example, when a 1st functional group is an epoxy group, it can be set as a hydroxyl group, a carboxyl group, an epoxy group, an amino group, etc. Specifically, for example, when the first resin component is an epoxy resin, as the second resin component, an epoxy group-modified polyester resin, an epoxy group-modified polyamide resin, an epoxy group-modified acrylic resin, an epoxy group-modified polyurethane polyurea resin, A carboxyl group-modified polyester resin, a carboxyl group-modified polyamide resin, a carboxyl group-modified acrylic resin, a carboxyl group-modified polyurethane polyurea resin, and a urethane-modified polyester resin can be used. Among these, a carboxyl group-modified polyester resin, a carboxyl group-modified polyamide resin, a carboxyl group-modified polyurethane polyurea resin, and a urethane-modified polyester resin are preferable. When the first resin component is a hydroxyl group, the second resin component is an epoxy group-modified polyester resin, an epoxy group-modified polyamide resin, an epoxy group-modified acrylic resin, an epoxy group-modified polyurethane polyurea resin, a carboxyl group-modified polyester resin, and a carboxyl group-modified polyester resin. A polyamide resin, a carboxyl group-modified acrylic resin, a carboxyl group-modified polyurethane polyurea resin, a urethane-modified polyester resin, etc. can be used. Among these, a carboxyl group-modified polyester resin, a carboxyl group-modified polyamide resin, a carboxyl group-modified polyurethane polyurea resin, and a urethane-modified polyester resin are preferable.

A thermosetting resin may contain the hardening|curing agent which accelerates|stimulates a thermosetting reaction. When a thermosetting resin has a 1st functional group and a 2nd functional group, a hardening|curing agent can be suitably selected according to the kind of 1st functional group and 2nd functional group. When the first functional group is an epoxy group and the second functional group is a hydroxyl group, an imidazole-based curing agent, a phenol-based curing agent, a cationic curing agent, or the like can be used. These may be used individually by 1 type, and may use 2 or more types together. In addition, an antifoaming agent, an antioxidant, a viscosity modifier, a diluent, an anti-settling agent, a leveling agent, a coupling agent, a colorant, a flame retardant, and the like may be included as optional components.

Although the electroconductive filler is not specifically limited, For example, a metal filler, a metal-coated resin filler, a carbon filler, and these mixtures can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. These metal powders can be produced by an electrolysis method, an atomization method, a reduction method, or the like. Among these, any one of silver powder, silver-coated copper powder, and copper powder is preferable.

The conductive filler preferably has an average particle diameter of 1 µm or more, more preferably 3 µm or more, preferably 50 µm or less, and more preferably 40 µm or less from the viewpoint of contact between the fillers. The shape of the conductive filler is not particularly limited, and it can be spherical, flaky, resinous, or fibrous.

The content of the conductive filler can be appropriately selected depending on the application, but in the total solid content, preferably 5 mass% or more, more preferably 10 mass% or more, preferably 95 mass% or less, more preferably 90 mass% is below. From a viewpoint of embedding, Preferably it is 70 mass % or less, More preferably, it is 60 mass % or less. Moreover, when realizing anisotropic conductivity, Preferably it is 40 mass % or less, More preferably, it is 35 mass % or less.

The conductive adhesive layer 111 can be formed, for example, by applying a composition for a conductive adhesive layer on the insulating protective layer 112 or the shielding layer 113 formed on the insulating protective layer 112 . The composition for conductive adhesive layers may be prepared by adding an appropriate amount of a solvent to the resin and filler for conductive adhesive layers.

It is preferable that the thickness of the conductive adhesive layer 111 shall be 1 micrometer - 50 micrometers from a viewpoint of controlling embedding property.

And if necessary, a peelable protective film can also be bonded to the surface of the conductive adhesive layer 111 .

The electromagnetic wave shielding film 101 of this embodiment can be combined with the printed wiring board 102 as the shielding wiring board 103 as shown in FIG. The electromagnetic wave shielding film 101 may have a shielding layer 113 .

The printed wiring board 102 has, for example, a printed circuit including a base member 122 and a ground circuit 125 provided on the base member 122 . An insulator layer 121 is adhered to the base member 122 by an adhesive layer 123 . An opening exposing the ground circuit 125 is formed in the insulator layer 121 . A surface layer such as a plating layer may be formed on the exposed portion of the ground circuit 125 . In addition, the printed wiring board 102 may be a flexible board|substrate or a rigid board|substrate may be sufficient as it.

When the electromagnetic wave shielding film 101 is adhered to the printed wiring board 102 , the electromagnetic wave shielding film 101 is disposed on the printed wiring board 102 so that the conductive adhesive layer 111 is positioned over the opening. Then, the electromagnetic wave shielding film 101 and the printed wiring board 102 are sandwiched from the vertical direction by two heating plates (not shown) heated to a predetermined temperature (for example, 120° C.), and a predetermined pressure is applied. (For example, 0.5 MPa) for a short time (for example, 5 second) is pressed. Thereby, the electromagnetic wave shielding film 101 is temporarily fixed to the printed wiring board 102 .

Subsequently, the temperature of the two heating plates is set to a predetermined temperature (for example, 170° C.) higher than the time of temporary fixing, and a predetermined time (for example, 30 MPa) at a predetermined pressure (for example, 3 MPa) min) pressurize. Thereby, the electromagnetic wave shielding film 101 can be fixed to the printed wiring board 102 . When the pressure is applied, since the conductive adhesive layer 111 is sufficiently filled in the opening, the strength and conductivity required for the electromagnetic wave shielding film 101 can be realized.

After fixing the electromagnetic wave shielding film 101 to the printed wiring board 102 , the transfer film 115 is peeled off. After that, solder reflow for component mounting is performed. Since the electromagnetic wave shielding film 101 of this embodiment can peel the transfer film 115 easily after fixing the electromagnetic wave shielding film 101 to the printed wiring board 102, productive efficiency can be improved.

[Example]

Hereinafter, the electromagnetic wave shielding film of the present disclosure will be described in more detail using Examples. The following examples are illustrative and are not intended to limit the present invention.

<Production of electromagnetic wave shielding film>

A release agent was applied to the surface of a predetermined transfer film. On the surface of the transfer film to which the mold release agent was applied, the composition for an insulation protective layer was apply|coated using a wire bar, and it heat-dried, and formed the insulation protective layer. Next, after apply|coating the composition for conductive adhesive layers with a wire bar on the insulation protective layer, 100 degreeC x 3 minutes was dried and the electromagnetic wave shielding film was produced.

The composition for an insulating protective layer had a two-layer structure of a hard coating layer of a polyester-based transparent resin having a thickness of 2 µm and a soft coating layer of a carbon black-containing epoxy-based black resin having a thickness of 3 µm. The composition for conductive adhesive layers was prepared by adding dendritic silver-coated copper powder having an average particle diameter of 5 µm as conductive fine particles to a phosphorus-based flame retardant-containing epoxy resin. The thickness of the conductive adhesive layer was 15 µm.

<Measurement of surface properties>

The parameters about the surface properties were measured in accordance with ISO25178 using a laser microscope (VK-X210, manufactured by Keyence Corporation, lens magnification 50 times). The measurement was performed with respect to the surface on which the insulation protective layer of the unused transfer film cut out to 5.0 cm x 5.0 cm was formed. Measurement was performed at 10 arbitrary locations within the plane, and the arithmetic mean value was used as the measured value. In addition, standard deviation (SD) and coefficient of variation (CV) were calculated.

<Measurement of Peel Strength>

The electromagnetic wave shielding film was pressed using a press under the conditions of temperature: 170°C, time: 30 minutes, and pressure: 2-3 MPa. After the electromagnetic wave shielding film returned to room temperature, the peeling strength of the transfer film was measured for the peeling film on the surface using a peeling strength tester (manufactured by Palmec Co., Ltd., PFT50S). The measurement was performed at room temperature under the conditions of a tensile rate of 1000 mm/min and a peeling angle of 170°. The measurement was performed 10 times, and the minimum value, maximum value, and average value were calculated|required.

(Example 1)

A PET film having a thickness of 50 µm was used as the transfer film. The surface of the insulating protective layer after peeling the transfer film had become a matte surface. Sv on the insulating protective layer formation surface of the transfer film was 3.1 µm, Sz was 8.0 µm, and Sa was 0.69 µm. The coefficient of variation of Sv was 0.15 and that of Sz was 0.02. The minimum value of peeling strength was 0.51N/50mm, the maximum value was 0.75N/50mm, and the average value was 0.63N/50mm.

(Example 2)

A PET film having a thickness of 50 µm was used as the transfer film. The surface of the insulating protective layer after peeling the transfer film had become a matte surface. Sv on the insulating protective layer formation surface of the transfer film was 2.5 mu m, Sz was 6.6 mu m, and Sa was 0.41 mu m. The coefficient of variation of Sv was 0.12 and the coefficient of variation of Sz was 0.08. The minimum value of peeling strength was 0.60N/50mm, the maximum value was 0.76N/50mm, and the average value was 0.68N/50mm.

(Example 3)

A PET film having a thickness of 50 µm was used as the transfer film. The surface of the insulating protective layer after peeling the transfer film had become a matte surface. Sv on the insulating protective layer formation surface of the transfer film was 5.9 µm, Sz was 9.6 µm, and Sa was 0.69 µm. The coefficient of variation of Sv was 0.07 and that of Sz was 0.09. The minimum value of peeling strength was 0.98N/50mm, the maximum value was 1.50N/50mm, and the average value was 1.25N/50mm.

(Comparative Example 1)

A PET film having a thickness of 50 µm was used as the transfer film. The surface of the insulating protective layer after peeling the transfer film had become a matte surface. Sv on the insulating protective layer formation surface of the transfer film was 6.8 µm, Sz was 11.4 µm, and Sa was 0.48 µm. The coefficient of variation of Sv was 0.43 and that of Sz was 0.40. The minimum value of peeling strength exceeded 7.0N/50mm, and the maximum value exceeded 10N/50mm, and could not be measured.

(Comparative Example 2)

A PET film having a thickness of 50 µm was used as the transfer film. The surface of the insulating protective layer after peeling the transfer film had become a glossy surface. Sv on the insulating protective layer formation surface of the transfer film was 0.8 µm, Sz was 1.3 µm, and Sa was 0.06 µm. The coefficient of variation of Sv was 0.23 and that of Sz was 0.13. The minimum value of peeling strength was 0.08N/50mm, the maximum value was 0.15N/50mm, and the average value was 0.10N/50mm.

Table 1 summarizes the results of each Example and Comparative Example. In addition to Sv and Sz, data on kurtosis (Sku), minimum autocorrelation length (Sal), aspect ratio of surface properties (Str), height of protruding troughs (Svk), and load area ratio (Smr2) separating protruding troughs and cores was described.

[Table 1]

The electromagnetic wave shielding film of the present disclosure can easily peel the transfer film, and thus productivity can be improved.

101: electromagnetic wave shielding film
102: printed wiring board
103: shielded wiring board
111: conductive adhesive layer
112: insulating protective layer
113: shielding layer
115: transfer film
121: insulator film
122: base member
123: adhesive layer
125: ground circuit

Claims (2)

insulating protective layer,
a transfer film installed on the surface of the insulating protective layer; and
a conductive adhesive layer provided on the opposite side to the transfer film of the insulating protective layer;
The surface of the transfer film on the side of the insulating protective layer has a maximum trough depth (Sv) of 1 µm or more and 5 µm or less, a maximum height (Sz) of 2 µm or more and 9 µm or less, and a minimum autocorrelation length ( Sa1) is 8.5 μm or more and 20.0 μm or less, the electromagnetic wave shielding film. According to claim 1,
The electromagnetic wave shielding film, wherein the coefficient of variation of the maximum trough depth (Sv) and the coefficient of variation of the maximum height (Sz) of the transfer film on the insulating protective layer side are 0.2 or less.

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