Electromagnetic wave shielding film and method for manufacturing electromagnetic wave shielding film

Abstract

The invention provides an electromagnetic wave shielding film and a method for manufacturing the electromagnetic wave shielding film. Even if the electromagnetic wave shielding film is heated by reflow soldering and the like, the adhesion between an adhesive layer and a shielding layer is not easily damaged. The present invention relates to an electromagnetic wave shielding film which is provided with a conductive adhesive layer and a shielding layer laminated on the conductive adhesive layer, and which is characterized in that the conductive adhesive layer contains 50 wt% or less of a conductive filler, and the specific surface area of the conductive filler is 0.9 m2 / g or less.

Description

Technical Field

[0001] The present invention relates to an electromagnetic wave shielding film and a method for manufacturing the electromagnetic wave shielding film. Background Art

[0002] Hitherto, for example, an electromagnetic wave shielding film has been attached to a printed circuit board such as a flexible printed circuit board (FPC) to shield electromagnetic waves from the outside.

[0003] The electromagnetic wave shielding film generally has a structure in which an adhesive layer, a shielding layer formed of a metal film or the like, and an insulating layer are laminated in this order. By heating and pressing the electromagnetic wave shielding film in a state of overlapping the printed circuit board, the electromagnetic wave shielding film is adhered to the printed circuit board through the adhesive layer, and a shielded printed circuit board is manufactured. After this adhesion, components are mounted on the shielded printed circuit board by solder reflow. In addition, the printed circuit board has a structure in which a printed pattern on a base film is covered with an insulating film.

[0004] As such an electromagnetic wave shielding film, Patent Document 1 discloses a shielding film characterized by having a metal layer with a layer thickness of 0.5 μm to 12 μm and an anisotropic conductive adhesive layer in a laminated state.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: International Publication No. 2013 / 077108 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] When such an electromagnetic wave shielding film is disposed on a printed circuit board and then components are mounted by reflow soldering or the like, there is a problem that the interfacial adhesion between the adhesive layer and the metal layer of the electromagnetic wave shielding film is damaged and interfacial peeling occurs.

[0010] The reason for the above interfacial peeling is considered to be based on the following mechanism.

[0011] Figure 3A and Figure 3B FIG. is a schematic explanatory diagram showing the mechanism of interfacial peeling between the adhesive layer and the metal layer when manufacturing a shielded printed circuit board using a conventional electromagnetic wave shielding film.

[0012] As Figure 3A shown, when manufacturing a shielded printed circuit board, the electromagnetic wave shielding film 510 having an adhesive layer 520 and a shielding layer 530 formed of a metal layer laminated in this order is heated by heating and pressing and solder reflow.

[0013] By this heating, volatile components (mainly water) 560 are generated from the adhesive layer 520 of the electromagnetic wave shielding film 510 and the like, and accumulate between the adhesive layer 520 and the shielding layer 530.

[0014] If, in such a state, intense heating such as reflow soldering is performed for component mounting, then as Figure 3B shown, the volatile components 560 accumulated between the adhesive layer 520 and the shielding layer 530 expand, whereby the interfacial adhesion between the adhesive layer 520 and the shielding layer 530 is damaged, and delamination occurs.

[0015] The present invention has been made to solve the above problems, and an object of the present invention is to provide: an electromagnetic wave shielding film and a method for manufacturing an electromagnetic wave shielding film in which the interfacial adhesion between the adhesive layer and the shielding layer is not easily damaged even when heated by reflow soldering or the like.

[0016] Means for Solving the Problem

[0017] The present inventors found that the reason for the accumulation of volatile components between the adhesive layer and the shielding layer is that the adhesive layer absorbs moisture in the air during storage of the electromagnetic wave shielding film, and the above problems can be solved by reducing the hygroscopicity of the adhesive layer, thereby arriving at the present invention.

[0018] That is, the electromagnetic wave shielding film of the present invention is characterized in that it includes a conductive adhesive layer and a shielding layer laminated on the conductive adhesive layer, the conductive adhesive layer contains 50% by weight or less of a conductive filler, and the specific surface area of the conductive filler is 0.9 m 2 / g or less.

[0019] In the electromagnetic wave shielding film of the present invention, the conductive adhesive layer contains 50% by weight or less of a conductive filler, so that conductivity can be imparted to the conductive adhesive layer, and the adhesive strength of the conductive adhesive becomes high.

[0020] In addition, as will be described later, in the electromagnetic wave shielding film of the present invention, volatile components are not easily introduced around the conductive filler. Therefore, by including the conductive filler, the hygroscopicity of the entire adhesive layer is reduced. Therefore, for the electromagnetic wave shielding film of the present invention, even when heated by reflow soldering or the like, the interfacial adhesion between the conductive adhesive layer as the adhesive layer and the shielding layer is not easily damaged.

[0021] The reason why volatile components are not easily introduced around the conductive filler in the electromagnetic wave shielding film of the present invention will be described.

[0022] In the electromagnetic wave shielding film of the present invention, the specific surface area of the conductive filler is 0.9 m 2 / g or less.

[0023] When the specific surface area of the conductive filler is within the above range, the corners on the surface of the conductive filler become fewer (for example, approaching a perfect sphere), and volatile components such as moisture are less likely to accumulate around the conductive filler.

[0024] If the above specific surface area exceeds 0.9 m 2 / g, the surface of the conductive filler becomes uneven, the surface branches increase, and volatile components such as moisture become likely to accumulate between the branches. Therefore, the hygroscopicity of the entire conductive adhesive layer is likely to increase.

[0025] In the electromagnetic wave shielding film of the present invention, the tapped density of the above conductive filler is preferably 1 g / cm 3 or more.

[0026] When the tapped density is 1 g / cm 3 or more, the volume of the conductive filler becomes lower, the contacts between the conductive fillers become fewer, so volatile components are less likely to accumulate between the conductive fillers, and it becomes less likely to cause interlayer delamination caused by the above heating.

[0027] If the tapped density is less than 1 g / cm 3 , the volume of the conductive filler becomes higher, the contacts between the conductive fillers become more, so volatile components are likely to accumulate between the conductive fillers, and it becomes difficult to suppress interlayer delamination caused by the above heating.

[0028] It should be noted that the tapped density of the conductive filler is the density of the powder obtained by tapping the container under specified conditions, and it refers to the value measured according to JIS Z 2512:2012 (Metal Powders - Method for Determination of Tapped Density).

[0029] In the electromagnetic wave shielding film of the present invention, it is preferable that an insulating layer is further laminated on the above shielding layer.

[0030] By forming the insulating layer, the shielding layer and the adhesive layer can be protected. In addition, by the presence of the insulating layer, contact between the shielding layer and other conductive members can be prevented.

[0031] The manufacturing method of the electromagnetic wave shielding film of the present invention is characterized by including the following steps: a step of mixing a conductive filler and a resin to prepare a conductive adhesive containing 50% by weight or less of the above conductive filler; and a step of coating the above conductive adhesive on the shielding layer to form a conductive adhesive layer, wherein the specific surface area of the above conductive filler is 0.9 m 2 / g or less.

[0032] In the manufacturing method of the electromagnetic wave shielding film of the present invention, since the conductive adhesive contains 50% by weight or less of the conductive filler, conductivity can be imparted to the conductive adhesive layer, and the adhesive strength of the conductive adhesive becomes high.

[0033] In addition, in the method for manufacturing the electromagnetic wave shielding film of the present invention, the specific surface area of the conductive filler is 0.9 m 2 / g or less. Therefore, similar to the case of the electromagnetic wave shielding film of the present invention, even when heated by reflow soldering or the like, the interfacial adhesion between the conductive adhesive layer as the adhesive layer and the shielding layer is not easily damaged.

[0034] In the method for manufacturing the electromagnetic wave shielding film of the present invention, the tapped density of the above-mentioned conductive filler is preferably 1 g / cm 3 or more.

[0035] When the tapped density is 1 g / cm 3 or more, similar to the case of the electromagnetic wave shielding film of the present invention, it becomes more difficult to cause interfacial damage due to the above-mentioned heating.

[0036] If the tapped density is less than 1 g / cm 3 , then similar to the case of the electromagnetic wave shielding film of the present invention, it becomes difficult to suppress the interfacial damage caused by the above-mentioned heating.

[0037] Effects of the Invention

[0038] According to the present invention, it is possible to provide an electromagnetic wave shielding film and a method for manufacturing an electromagnetic wave shielding film in which the interfacial adhesion between the adhesive layer and the shielding layer is not easily damaged even when heated by reflow soldering or the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 FIG. is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention.

[0040] Figure 2 FIG. is a cross-sectional view schematically showing an example of a shielded printed circuit board using the electromagnetic wave shielding film of the present invention.

[0041] Figure 3A FIG. is an explanatory diagram schematically showing the mechanism of interfacial peeling between the adhesive layer and the metal layer when manufacturing a shielded printed circuit board using a conventional electromagnetic wave shielding film.

[0042] Figure 3B FIG. is an explanatory diagram schematically showing the mechanism of interfacial peeling between the adhesive layer and the metal layer when manufacturing a shielded printed circuit board using a conventional electromagnetic wave shielding film.

[0043] Figure 4A FIG. is a cross-sectional view schematically showing a sample used in the evaluation test of the adhesive strength.

[0044] Figure 4B FIG. is a cross-sectional view schematically showing a sample in the evaluation test of the adhesive strength. Detailed implementation mode

[0045] Hereinafter, the electromagnetic wave shielding film and the manufacturing method of the electromagnetic wave shielding film of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and can be appropriately changed and applied within the scope of not changing the gist of the present invention.

[0046] Figure 1 It is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention.

[0047] Figure 1 The shown electromagnetic wave shielding film 10 includes: a conductive adhesive layer 20, and a shielding layer 30 laminated on the conductive adhesive layer 20, and an insulating layer 40 is further laminated on the shielding layer 30.

[0048] Moreover, the conductive adhesive layer 20 contains a resin and a conductive filler.

[0049] In the electromagnetic wave shielding film 10, the conductive adhesive layer 20 contains 50% by weight or less of the conductive filler. Therefore, conductivity can be imparted to the conductive adhesive layer 20, and the adhesive strength of the conductive adhesive becomes high.

[0050] In the electromagnetic wave shielding film 10, the specific surface area of the conductive filler is 0.9 m 2 / g or less.

[0051] Since the conductive filler has such characteristics, volatile components are not easily introduced into the periphery of the conductive filler. Therefore, by including the conductive filler, the hygroscopicity of the entire conductive adhesive layer 20 is reduced. Therefore, for the electromagnetic wave shielding film 10, even when heated by reflow soldering or the like, the interfacial adhesion between the conductive adhesive layer 20 and the shielding layer 30 is not easily damaged.

[0052] Hereinafter, the reason why volatile components are not easily introduced into the periphery of the conductive filler when the conductive filler has the above characteristics will be described.

[0053] When the specific surface area of the conductive filler is 0.9 m 2 / g or less, the corners on the surface of the conductive filler become fewer (for example, approaching a perfect sphere), and volatile components such as moisture are not easily accumulated around the conductive filler.

[0054] If the above specific surface area exceeds 0.9 m 2 / g, the surface of the conductive filler becomes uneven, the surface branches increase, and volatile components such as moisture become easily accumulated between the branches. Therefore, the hygroscopicity of the entire conductive adhesive layer is easily increased.

[0055] It should be noted that the specific surface area of the conductive filler is preferably 0.25 m 2Above / g and 0.9m 2 Below / g, more preferably 0.25m 2 Above / g and less than 0.8m 2 / g, further preferably 0.25m 2 Above / g and 0.5m 2 Below / g.

[0056] The specific surface area of the above conductive filler can be measured by the nitrogen adsorption method using an elemental analyzer: Vari EL III (manufactured by Elementar).

[0057] In the electromagnetic wave shielding film 10, the tapped density of the above conductive filler is preferably 1 g / cm 3 Above, more preferably 1.5 g / cm 3 Above and 5.0 g / cm 3 Below, further preferably 2.0 g / cm 3 Above and 5.0 g / cm 3 Below.

[0058] When the tapped density is 1 g / cm 3 Above, the volume of the conductive filler becomes lower and the contacts between the conductive fillers become fewer. Therefore, the volatile components are less likely to accumulate between the conductive fillers, and it becomes more difficult to cause the interlayer breakdown caused by the above heating.

[0059] If the tapped density is less than 1 g / cm 3 , the volume of the conductive filler becomes higher and the contacts between the conductive fillers become more. Therefore, the volatile components are likely to accumulate between the conductive fillers, and it becomes difficult to suppress the interlayer breakdown caused by the above heating.

[0060] The conductive filler with a tapped density of 5.0 g / cm 3 Below is easy to manufacture.

[0061] In the electromagnetic wave shielding film 10, the conductive adhesive layer 20 contains 50% by weight or less of the conductive filler, preferably contains 3% by weight or more and 39% by weight or less of the conductive filler, more preferably contains 3% by weight or more and 35% by weight or less of the conductive filler, and further preferably contains 3% by weight or more and 30% by weight or less of the conductive filler.

[0062] If the proportion of the conductive filler exceeds 50% by weight, the proportion of the resin in the conductive adhesive layer becomes relatively small, and the adhesive strength of the conductive adhesive layer becomes likely to decrease. In addition, the conductive fillers are likely to come into contact with each other (it becomes easy to conduct current in the plane direction), so the electrical properties such as the transmission characteristics are likely to decrease.

[0063] In addition, when the proportion of the conductive filler is 3% by weight or more and 39% by weight or less, anisotropic conductivity can be imparted to the anisotropic conductive adhesive layer 20.

[0064] When the proportion of the conductive filler is less than 3% by weight, it becomes difficult to exhibit conductivity.

[0065] In this way, the anisotropic conductive adhesive layer 20 can have isotropic conductivity in which electrical conduction states are ensured in all three-dimensional directions composed of the thickness direction, the width direction, and the length direction, or can have anisotropic conductivity in which an electrical conduction state is ensured only in the thickness direction, but anisotropic conductivity is preferably provided.

[0066] As described later, the electromagnetic wave shielding film 10 is disposed on a printed circuit board.

[0067] When the anisotropic conductive adhesive layer 20 has anisotropic conductivity, the transmission characteristics of high-frequency signals transmitted through the signal circuit of the printed circuit board are improved as compared with the case of having isotropic conductivity.

[0068] In the electromagnetic wave shielding film 10, the particle diameter (D 50 ) of the conductive filler is preferably 3.0 μm or more and 15 μm or less, more preferably 5.0 μm or more and 11 μm or less, and still more preferably 5.0 μm or more and 8.0 μm or less.

[0069] When the particle diameter (D 50 ) of the conductive filler is less than 3.0 μm, the anisotropic conductive adhesive layer 20 is thicker than the conductive filler, and the conductive filler cannot come into contact with the ground circuit, and conductivity may not be obtained.

[0070] If the particle diameter (D 50 ) of the conductive filler exceeds 15 μm, there is a possibility that the conductive filler pierces the insulating layer 40 (possibility of causing poor appearance).

[0071] In the electromagnetic wave shielding film 10, the conductive filler is not particularly limited and may be metal fine particles, carbon nanotubes, carbon fibers, metal fibers, or the like.

[0072] When the conductive filler is metal fine particles, the metal fine particles are not particularly limited and may be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder obtained by plating copper powder with silver, fine particles obtained by covering polymer fine particles, glass beads, or the like with a metal.

[0073] Among these, from the viewpoint of economy, copper powder or silver-coated copper powder that can be obtained inexpensively is preferred.

[0074] The shape of the conductive filler is not particularly limited, and it can be appropriately selected from spherical, flat, scaly, dendritic, rod-shaped, fibrous, etc.

[0075] In the electromagnetic wave shielding film 10, the thickness of the conductive adhesive layer 20 is preferably 5 to 50 μm, more preferably 5 to 30 μm.

[0076] If the thickness of the conductive adhesive layer is less than 5 μm, the adhesiveness decreases due to its thinness.

[0077] If the thickness of the conductive adhesive layer exceeds 50 μm, the conductive adhesive layer becomes thick, and it becomes difficult to miniaturize the electromagnetic wave shielding film.

[0078] In the electromagnetic wave shielding film 10, as the resin material of the conductive adhesive layer 20, there is no particular limitation, and thermoplastic resin compositions such as styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, polyethylene-based resin compositions, polypropylene-based resin compositions, imide-based resin compositions, amide-based resin compositions, acrylic-based resin compositions, etc., and thermosetting resin compositions such as phenolic resin compositions, epoxy resin compositions, polyurethane resin compositions, melamine resin compositions, alkyd resin compositions, etc. can be used.

[0079] The resin material can be a single one of these, or a combination of two or more.

[0080] In the electromagnetic wave shielding film 10, in addition to the resin and the conductive filler, the conductive adhesive layer 20 may further contain a curing accelerator, an adhesion promoter, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, a viscosity regulator, etc. according to need.

[0081] In the electromagnetic wave shielding film 10, the shielding layer 30 is preferably formed of a metal layer.

[0082] In addition, the metal layer preferably contains at least one metal selected from the group consisting of copper, silver, gold, aluminum, nickel, tin, palladium, chromium, titanium, and zinc. In addition, the metal layer can be formed of an alloy of at least two selected from the group thereof.

[0083] The shielding layer 30 formed of these metals can appropriately shield electromagnetic waves.

[0084] In the electromagnetic wave shielding film 10, when the shielding layer 30 is formed of a metal layer, the metal layer can be a rolled metal foil, a metal plating layer, or a metal vapor deposition layer.

[0085] In the electromagnetic wave shielding film 10, when the shielding layer 30 is formed of a metal layer, its thickness is preferably 0.1 to 10 μm, more preferably 0.5 to 6 μm.

[0086] If the thickness of the shielding layer is less than 0.1 μm, the shielding layer is too thin, so the strength of the shielding layer becomes low. Therefore, the bending resistance is reduced. In addition, it is difficult to sufficiently reflect and absorb electromagnetic waves, so the electromagnetic wave shielding characteristics are likely to be reduced.

[0087] If the thickness of the shielding layer exceeds 10 μm, the entire electromagnetic wave shielding film becomes thick and difficult to handle.

[0088] In the electromagnetic wave shielding film 10, the insulating layer 40 is not particularly limited as long as it has sufficient insulation and can protect the shielding layer 30 and the conductive adhesive layer 20. For example, it is preferably composed of a thermoplastic resin composition, a thermosetting resin composition, an active energy ray curable composition, etc.

[0089] As the above-mentioned thermoplastic resin composition, there is no particular limitation, and examples thereof include styrene resin compositions, vinyl acetate resin compositions, polyester resin compositions, polyethylene resin compositions, polypropylene resin compositions, imide resin compositions, acrylic resin compositions, etc.

[0090] As the above-mentioned thermosetting resin composition, there is no particular limitation, and examples thereof include phenolic resin compositions, epoxy resin compositions, polyurethane resin compositions, melamine resin compositions, alkyd resin compositions, etc.

[0091] As the above-mentioned active energy ray curable composition, there is no particular limitation. For example, a polymerizable compound having at least 2 (meth)acryloyloxy groups in the molecule can be cited.

[0092] The insulating layer 40 may be composed of a single material or two or more materials.

[0093] The insulating layer 40 may further contain a curing accelerator, an adhesion promoter, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, a viscosity modifier, an anti-blocking agent, etc. as needed.

[0094] As the above-mentioned pigment, there is no particular limitation, and examples thereof include black pigments such as carbon black.

[0095] The thickness of the insulating layer 40 is not particularly limited and can be appropriately set as needed. It is preferably 1 to 15 μm, more preferably 3 to 10 μm.

[0096] If the thickness of the insulating layer 40 is less than 1 μm, it becomes difficult to sufficiently protect the shielding layer 30 and the conductive adhesive layer 20 due to being too thin.

[0097] If the thickness of the insulating layer 40 exceeds 15 μm, the electromagnetic wave shielding film 10 becomes difficult to bend due to excessive thickness, and in addition, the toughness of the insulating layer 40 decreases. Therefore, it is difficult to apply to members that require bending resistance.

[0098] It should be noted that in the electromagnetic wave shielding film of the present invention, the insulating layer may be formed as needed, or the insulating layer may not be formed.

[0099] Next, a method for manufacturing the electromagnetic wave shielding film of the present invention will be described.

[0100] The method for manufacturing the electromagnetic wave shielding film of the present invention includes the following steps: a step of mixing a conductive filler and a resin to prepare a conductive adhesive containing 50% by weight or less of the above-mentioned conductive filler; and a step of coating the above-mentioned conductive adhesive on a shielding layer to form a conductive adhesive layer, wherein the specific surface area of the above-mentioned conductive filler is 0.9 m 2 / g or less.

[0101] In the method for manufacturing the electromagnetic wave shielding film of the present invention, a step of forming the above-mentioned shielding layer on the insulating layer is performed before the above-mentioned conductive adhesive layer forming step, whereby the electromagnetic wave shielding film 10 can be manufactured.

[0102] Hereinafter, each step will be described in detail.

[0103] (Conductive Adhesive Preparation Step)

[0104] In this step, a conductive filler and a resin are mixed to prepare a conductive adhesive containing 50% by weight or less of the conductive filler. Here, the specific surface area of the above-mentioned conductive filler is 0.9 m 2 / g or less.

[0105] Since the conductive adhesive contains 50% by weight or less of the conductive filler, conductivity can be imparted to the conductive adhesive layer, and the adhesive strength of the conductive adhesive becomes high.

[0106] In addition, the specific surface area of the conductive filler is 0.9 m 2 / g or less. Therefore, even when heated by reflow soldering or the like, the interfacial adhesion between the conductive adhesive layer as the adhesive layer and the shielding layer is not easily damaged.

[0107] It should be noted that, as described above, the specific surface area of the conductive filler is preferably 0.25 m 2 / g or more and 0.9 m 2 / g or less, more preferably 0.25 m 2 / g or more and less than 0.8 m 2 / g, and further preferably 0.25 m2 above / g and 0.5 m or less 2 / g or less.

[0108] As described above, the above-mentioned conductive adhesive preferably contains 3% by weight or more and 39% by weight or less of a conductive filler, more preferably 3% by weight or more and 35% by weight or less of a conductive filler, and still more preferably 3% by weight or more and 30% by weight or less of a conductive filler.

[0109] As described above, the tapped density of the above-mentioned conductive filler is preferably 1 g / cm 3 or more, more preferably 1.5 g / cm 3 or more and 5.0 g / cm 3 or less, and still more preferably 2.0 g / cm 3 or more and 5.0 g / cm 3 or less.

[0110] Preferred materials of the conductive filler and the resin and the like have been described above, and thus the description thereof is omitted here.

[0111] (Shielding layer forming step)

[0112] In this step, a shielding layer is formed on the insulating layer.

[0113] At this time, as the shielding layer, a metal vapor deposition layer can be formed on the insulating layer by vapor deposition, a rolled metal foil can be attached to the insulating layer, or a metal plating layer can be formed on the insulating layer by electroplating.

[0114] Preferred materials of the insulating layer and the shielding layer and the like have been described above, and thus the description thereof is omitted here.

[0115] (Conductive adhesive layer forming step)

[0116] After the above-mentioned shielding layer forming step, in this step, a conductive adhesive is applied to the shielding layer to form a conductive adhesive layer.

[0117] As a method of disposing the conductive adhesive layer, conventionally known coating methods can be cited, such as gravure coating, kiss coating, die coating, lip coating, comma coating, knife coating, roll coating, blade coating, spraying, bar coating, spin coating, dip coating, etc.

[0118] Through the above steps, the electromagnetic wave shielding film 10 can be manufactured.

[0119] Next, a shielded printed circuit board using the electromagnetic wave shielding film of the present invention will be described.

[0120] Figure 2 A cross-sectional view schematically showing an example of a shielded printed circuit board using the electromagnetic wave shielding film of the present invention.

[0121] Figure 2 The shielded printed circuit board 1 shown includes a printed circuit board 50 and an electromagnetic wave shielding film 10.

[0122] The printed circuit board 50 includes: a base film 51, a printed circuit 52 disposed on the base film 51, and a covering layer 53 disposed so as to cover the printed circuit 52.

[0123] In the printed circuit board 50, the printed circuit 52 includes a ground circuit 52a, and an opening 53a for exposing the ground circuit 52a is formed in the covering layer 53.

[0124] In the shielded printed circuit board 1, the electromagnetic wave shielding film 10 is disposed on the printed circuit board 50 in such a manner that the covering layer 53 is in contact with the conductive adhesive layer 20.

[0125] In the shielded printed circuit board 1, the conductive adhesive layer 20 fills the opening 53a of the covering layer 53 and contacts the ground circuit 52a. By forming such a configuration, the shielding characteristics of the electromagnetic wave shielding film 10 can be improved.

[0126] Examples

[0127] Hereinafter, examples for more specifically explaining the present invention are shown, but the present invention is not limited to these examples.

[0128] (Example 1)

[0129] As the insulating layer, an insulating layer made of epoxy resin with a thickness of 5 μm was prepared.

[0130] Next, electroplating was performed on this insulating layer to form a copper layer with a thickness of 2.0 μm. It should be noted that this copper layer functions as a shielding layer.

[0131] Next, a polyester-based thermosetting resin as a resin and silver powder (particle size D 50 : 10.8 μm) were mixed so that the conductive filler accounted for 20% by weight of the total amount of the conductive adhesive, and the conductive adhesive of Example 1 was produced. Table 1 shows parameters such as the specific surface area of the conductive filler used and the conductivity of the produced conductive adhesive.

[0132] Next, this conductive adhesive was coated on the shielding layer to a thickness of 20 μm to manufacture the electromagnetic wave shielding film of Example 1.

[0133] [Table 1]

[0134]

[0135] (Examples 2) to (Examples 6) and (Comparative Examples 1) to (Comparative Example 9)

[0136] As the conductive filler, the substances shown in Table 1 were used, and the ratio of the conductive filler was changed. Except for this, electromagnetic wave shielding films of Examples 2 to 6 and Comparative Examples 1 to 9 were produced in the same manner as in Example 1.

[0137] (Evaluation of the presence or absence of delamination between layers)

[0138] The electromagnetic wave shielding films of each example and each comparative example were attached to a printed circuit board by hot pressing. Then, after leaving this printed circuit board in a thermo-hygrostat at 30 °C and 60% RH for 1 day, it was exposed to the temperature conditions during reflow soldering, and the presence or absence of delamination between layers was evaluated. Note that, as the temperature conditions during reflow soldering, a temperature of up to 260 °C was set. In addition, regarding the presence or absence of delamination between layers, the printed circuit board with the shielding film attached was floated 3 times in a solder bath, and the presence or absence of swelling was visually observed and evaluated. Here, those in which no swelling occurred in the shielding film were marked as "◎", those in which swelling occurred only in a part of the shielding film were marked as "〇", and those in which swelling clearly occurred on the entire surface of the shielding film were marked as "×". The results are shown in Table 1.

[0139] (Evaluation of adhesive strength)

[0140] Using the electromagnetic wave shielding films of each example and each comparative example, the adhesive strength was evaluated according to the following steps.

[0141] Figure 4A FIG. is a schematic cross-sectional view of a sample used in the adhesive strength evaluation test.

[0142] As shown in Figure 4A , first, each electromagnetic wave shielding film 10 having an insulating layer 40, a shielding layer 30, and a conductive adhesive layer 20 laminated in this order was pressed against the polyimide film substrate side of a copper-clad laminate (polyimide film substrate / adhesive layer / chemically gold-plated copper foil) as a base material 61 under the conditions of 2 MPa, 170 °C, 10 sec, and 180 sec. Next, the electromagnetic wave shielding film 10 attached to the base material 61 was pressed against the bonding film 62b side of a reinforcing film 62 (polyimide film substrate 62a / bonding film 62b) under the conditions of 3 MPa, 170 °C, and 3 minutes. Thereafter, these laminates were heated at 150 °C for 60 minutes for post-curing. Finally, the reinforcing film 62 of these laminates was attached to the double-sided tape 63b side of a fixing plate 63 (glass epoxy substrate 63a / double-sided tape 63b), and a sample 60 with a width of 10 mm was prepared.

[0143] Figure 4B It is a cross-sectional view of a sample in an evaluation test of adhesive strength shown schematically.

[0144] Then, while the sample 60 is fixed as Figure 4B shown, the base material 61 is stretched under the conditions of a stretching speed of 50 mm / minute and a stretching angle of 180°, thereby peeling off the base material 61 and the electromagnetic wave shielding film 10, and the average peeling force at this time is measured. The evaluation test was carried out 5 times. The results are shown in Table 1.

[0145] It should be noted that the evaluation criteria are as follows. When the average peeling force is 4 N / 10 mm or more, this electromagnetic wave shielding film is suitable for practical use. When the average peeling force is less than 4 N / 10 mm, this electromagnetic wave shielding film is not suitable for practical use.

[0146] ◎: The average peeling force is 5 N / 10 mm or more

[0147] 〇: The average peeling force is 4 N / 10 mm or more and less than 5 N / 10 mm

[0148] ×: The average peeling force is less than 4 N / 10 mm

[0149] As shown in Table 1, it is clear that almost no interlayer peeling occurred in the electromagnetic wave shielding films of the respective examples.

[0150] Explanation of reference numerals

[0151] 1 Shielded printed circuit board

[0152] 10, 510 Electromagnetic wave shielding film

[0153] 20 Conductive adhesive layer

[0154] 30, 530 Shielding layer

[0155] 40, 540 Insulating layer

[0156] 50 Printed circuit board

[0157] 51 Base film

[0158] 52 Printed circuit

[0159] 52a Grounding circuit

[0160] 53 Cover layer

[0161] 53a Opening

[0162] 60 Sample

[0163] 61 Base material

[0164] 62 Reinforced film

[0165] 62a Polyimide film substrate

[0166] 62b Bonding film

[0167] 63 Fixed plate

[0168] 63a Glass epoxy substrate

[0169] 63b Double-sided tape

[0170] 520 Adhesive layer

[0171] 560 Volatile components

Claims

1. An electromagnetic wave shielding film, characterized in that, It has a conductive adhesive layer and a shielding layer laminated on the conductive adhesive layer, wherein the conductive adhesive layer contains 50 wt% or less of a conductive filler, The specific surface area of the conductive filler is 0.9 m 2 / g or less.

2. The electromagnetic wave shielding film according to claim 1, wherein, The tapped density of the conductive filler is 1 g / cm 3 or more.

3. The electromagnetic wave shielding film according to claim 1 or 2, wherein, and an insulating layer is further laminated on the shielding layer.

4. A method for manufacturing an electromagnetic wave shielding film, characterized in that, It includes the following steps: a step of mixing a conductive filler and a resin to prepare a conductive adhesive containing 50 wt% or less of the conductive filler; and a step of coating the conductive adhesive on the shielding layer to form a conductive adhesive layer. The specific surface area of the conductive filler is 0.9 m 2 / g or less.

5. The manufacturing method of the electromagnetic wave shielding film according to claim 4, wherein, The tapped density of the conductive filler is 1 g / cm 3 or more.

Images