Electromagnetic wave shielding film and shielded printed wiring board

Abstract

Provided is an electromagnetic wave shielding film in which the adhesion between an adhesive layer and a metal foil is not easily damaged even when heated by reflow or the like. The present invention relates to an electromagnetic wave shielding film comprising an adhesive layer and a metal foil, the adhesive layer containing a resin, and the metal foil being laminated on the adhesive layer; the water vapor transmission rate of the metal foil is 0.40 g / (m < 2 > day) or more, and the moisture content of the adhesive layer is 1.00 wt% or less.

Description

Technical Field

[0001] The present invention relates to an electromagnetic wave shielding film and a shielding printed wiring board. Background Art

[0002] Conventionally, an electromagnetic shielding film is attached to a printed wiring board such as a flexible printed wiring board (FPC) to shield electromagnetic waves from the outside.

[0003] As an electromagnetic wave shielding film, a structure having an adhesive layer and a metal foil as a shielding layer is known. The electromagnetic wave shielding film is heated and pressed in a state where it is overlapped on a printed wiring board, so that the electromagnetic wave shielding film is bonded to the printed wiring board using the adhesive layer to produce a shielded printed wiring board. After the bonding, components are mounted on the shielded printed wiring board using solder reflow. In addition, the printed wiring board has a structure in which the printed pattern on the base film is covered by an insulating film.

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

[0005] Prior art literature

[0006] Patent Literature

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

[0008] When such an electromagnetic wave shielding film is disposed on a printed wiring board and then components are mounted by reflow or the like, the interlayer adhesion between the adhesive layer of the electromagnetic wave shielding film and the metal foil is destroyed, resulting in a problem of interlayer delamination.

[0009] The above-mentioned delamination is considered to occur due to the following mechanism.

[0010] Figure 3A and Figure 3B This is an explanatory diagram schematically showing a mechanism of interlayer delamination between an adhesive layer and a metal foil when a shielded printed wiring board is produced using a conventional electromagnetic wave shielding film.

[0011] like Figure 3A As shown, when manufacturing a shielded printed wiring board, the electromagnetic wave shielding film 510 on which the adhesive layer 520 and the metal foil 530 are sequentially laminated is heated by heat pressing or solder reflow.

[0012] Due to this heating, volatile components (mainly water) 560 are generated from the adhesive layer 520 and the like of the electromagnetic wave shielding film 510 , and are accumulated between the adhesive layer 520 and the metal foil 530 .

[0013] If intense heating such as reflow is performed for mounting components in this state, Figure 3B As shown, the volatile component 560 accumulated between the adhesive layer 520 and the metal foil 530 expands, thereby destroying the interlayer adhesion between the adhesive layer 520 and the metal foil 530, and interlayer delamination occurs.

[0014] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an electromagnetic wave shielding film in which the interlayer adhesion between the adhesive layer and the metal foil is not easily damaged even when heated by reflow or the like.

[0015] The present inventors have found that the accumulation of volatile components between the adhesive layer and the metal foil is due to the adhesive layer absorbing moisture in the air during storage of the electromagnetic wave shielding film. The above problem can be solved by reducing the hygroscopicity of the adhesive layer, thereby arriving at the present invention.

[0016] That is, the electromagnetic wave shielding film of the present invention is characterized in that it comprises an adhesive layer and a metal foil, wherein the adhesive layer contains a resin, and the metal foil is laminated on the adhesive layer; and the water vapor permeability of the metal foil is 0.40 g / (m 2 ·day) or more, the moisture content of the adhesive layer is 1.00 wt% or less.

[0017] In the electromagnetic wave shielding film of the present invention, if the water vapor permeability of the metal foil is 0.40 g / (m 2 ·day) or more, and the moisture content of the adhesive layer is in a low range of 1.00 wt % or less, the amount of volatile components generated when the electromagnetic shielding film is heated by reflow or the like is small. Therefore, the interlayer adhesion between the adhesive layer and the metal foil is not easily damaged.

[0018] In the electromagnetic wave shielding film of the present invention, the water vapor permeability of the metal foil is preferably 0.40 g / (m 2 ·day)~11000g / (m 2 ·day), the water vapor permeability of the metal foil is more preferably 5.00 g / (m 2 ·day)~11000g / (m 2 ·day).

[0019] If the water vapor permeability of the metal foil is high, the water vapor generated by the moisture contained in the adhesive layer when heated by reflow or the like can be easily released to the outside through the metal foil. Therefore, the internal pressure of the space between the adhesive layer and the metal foil is not easy to increase, and the interlayer adhesion between the adhesive layer and the metal foil is less likely to be destroyed.

[0020] In the electromagnetic wave shielding film of the present invention, the adhesive layer preferably contains a low water-absorbing filler which is a material having a lower water absorption rate than the resin.

[0021] By making the adhesive layer contain a low water-absorbing filler, the amount of water contained in the adhesive layer can be reduced, and the interlayer adhesion between the adhesive layer and the metal foil is less likely to be destroyed.

[0022] In the electromagnetic wave shielding film of the present invention, the low water-absorbing filler is preferably melamine cyanurate or acrylic resin.

[0023] These materials have low water absorption rates and are suitable as materials for reducing the moisture content of the adhesive layer. In addition, since melamine cyanurate is also a material used as a flame retardant, it also contributes to improving the flame retardancy of the electromagnetic wave shielding film.

[0024] In the electromagnetic wave shielding film of the present invention, the weight ratio of the low water-absorbing filler in the adhesive layer is preferably 15% to 35% by weight. By increasing the ratio of the low water-absorbing filler, the moisture content of the adhesive layer can be reduced. On the other hand, if the ratio of the low water-absorbing filler is too high, the ratio of the resin that contributes to the adhesiveness becomes low, so the adhesiveness may be insufficient. From this point of view, the weight ratio of the low water-absorbing filler in the adhesive layer is preferably 15% to 35% by weight.

[0025] In the electromagnetic wave shielding film of the present invention, it is preferred that the moisture content of the adhesive layer is 0.75 wt % to 1.00 wt %, and the water vapor permeability of the metal foil is 5.00 g / (m 2 ·day)~100g / (m 2 ·day).

[0026] If the moisture content of the adhesive layer is within the above range, the moisture content of the adhesive layer is small. In addition, since the water vapor permeability of the metal foil is also high, the interlayer adhesion between the adhesive layer and the metal foil is not easily destroyed. In addition, in order to improve the water vapor permeability of the metal foil, the thickness of the metal foil may be reduced or an opening may be provided on the metal foil. However, if the thickness of the metal foil is too thin or the opening ratio is too high, the electromagnetic wave shielding properties may be reduced. From such a viewpoint, it is preferred to increase the water vapor permeability to a degree sufficient to prevent the destruction of the interlayer adhesion between the adhesive layer and the metal foil, and not to reduce the electromagnetic wave shielding properties.

[0027] In the electromagnetic wave shielding film of the present invention, the adhesive layer is preferably a conductive adhesive layer.

[0028] When the adhesive layer is a conductive adhesive layer, the shielding properties of the electromagnetic wave shielding film can be improved.

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

[0030] By forming the insulating layer, the metal foil and the adhesive layer can be protected. In addition, the presence of the insulating layer can prevent the metal foil from coming into contact with other conductive components.

[0031] The shielded printed wiring board of the present invention is characterized in that the above-mentioned electromagnetic wave shielding film is disposed on the printed wiring board.

[0032] The shield printed wiring board includes an electromagnetic wave shielding film, and the interlayer adhesion between the adhesive layer and the metal foil is not damaged even when heated by reflow or the like, so that the shield printed wiring board can be stably used as a shield printed wiring board.

[0033] According to the present invention, it is possible to provide an electromagnetic wave shielding film in which the interlayer adhesion between the adhesive layer and the metal foil is unlikely to be damaged even when heated by reflow or the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a cross-sectional view schematically showing an example of the electromagnetic shielding film of the present invention.

[0035] Figure 2 This is a cross-sectional view schematically showing an example of the shielded printed wiring board of the present invention using the electromagnetic wave shielding film of the present invention.

[0036] Figure 3A This is an explanatory diagram schematically showing a mechanism of interlayer delamination between an adhesive layer and a metal foil when a shielded printed wiring board is produced using a conventional electromagnetic wave shielding film.

[0037] Figure 3B This is an explanatory diagram schematically showing a mechanism of interlayer delamination between an adhesive layer and a metal foil when a shielded printed wiring board is produced using a conventional electromagnetic wave shielding film. DETAILED DESCRIPTION

[0038] Hereinafter, the electromagnetic wave shielding film and the shielded printed wiring board 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 the gist of the present invention.

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

[0040] Figure 1 In the electromagnetic wave shielding film 10 shown, an adhesive layer 20 containing a resin, a metal foil 30 laminated on the adhesive layer 20 , and an insulating layer 40 further laminated on the metal foil 30 are laminated.

[0041] In the electromagnetic wave shielding film of the present invention, the adhesive layer contains a resin.

[0042] The material of the resin is not particularly limited, and thermoplastic resin compositions such as styrene resin compositions, vinyl acetate resin compositions, polyester resin compositions, polyethylene resin compositions, polypropylene resin compositions, imide resin compositions, amide resin compositions, and acrylic resin compositions; and thermosetting resin compositions such as phenolic resin compositions, epoxy resin compositions, polyurethane resin compositions, melamine resin compositions, and alkyd resin compositions can be used.

[0043] The resin material may be a single type or a combination of two or more types.

[0044] The moisture content of the adhesive layer is 1.00 wt % or less.

[0045] In the electromagnetic shielding film, when the moisture content of the adhesive layer is in the low range of 1.00 wt % or less, the amount of volatile components generated when the electromagnetic shielding film is heated by reflow or the like is small, so that the interlayer adhesion between the adhesive layer and the metal foil is less likely to be damaged.

[0046] Furthermore, from the viewpoint that the interlayer adhesion between the adhesive layer and the metal foil is less likely to be damaged if the amount of volatile components is further reduced, the moisture content of the adhesive layer is more preferably 0.90% by weight or less.

[0047] In addition, the moisture content of the adhesive layer is preferably 0.75% by weight or more. This is because even if the moisture content of the adhesive layer is less than 0.75% by weight, the interlayer adhesion between the adhesive layer and the metal foil is not easily damaged. In addition, in order to reduce the moisture content of the adhesive layer, a large amount of low water absorption filler described later needs to be added to the adhesive layer. However, if the amount of low water absorption filler added is too much, the resin component is insufficient, and the adhesive force of the adhesive layer may be insufficient.

[0048] The water content of the adhesive layer can be measured using a Karl Fischer titrator in accordance with JIS K 0068 (2001).

[0049] As a pretreatment, the adhesive layer was separated from the electromagnetic wave shielding film and treated at 23° C. and 60% humidity for 24 hours, and then the water content of the adhesive layer was measured.

[0050] The adhesive layer preferably contains a low water-absorbing filler, which is a material having a lower water absorption rate than the resin.

[0051] By making the adhesive layer contain a low water-absorbing filler, the amount of water contained in the adhesive layer can be reduced, and the interlayer adhesion between the adhesive layer and the metal foil is less likely to be destroyed.

[0052] Furthermore, the low water-absorbing filler preferably has a water absorption rate of 0.5% by weight or less.

[0053] The water absorption rate of the low water-absorbing filler can be measured by the Karl Fischer method in the same manner as the measurement of the water content of the adhesive layer.

[0054] The low water-absorbing filler is preferably an organic filler such as melamine cyanurate and acrylic resin.

[0055] Among them, the low water-absorbing filler is more preferably melamine cyanurate. Melamine cyanurate has a low water absorption rate and is suitable as a material for reducing the moisture content of the adhesive layer. In addition, since it is also a material used as a flame retardant, it helps to improve the flame retardancy of the electromagnetic wave shielding film.

[0056] In addition, the low water-absorbing filler may be an inorganic filler such as alumina. Among the inorganic fillers, an inorganic filler having a water absorption rate lower than that of the resin may be selected and used.

[0057] Examples of the water absorption rate of the resin and the low water-absorbing filler which may be contained in the electromagnetic wave shielding film of the present invention are as follows.

[0058] Example of moisture absorption rate of resin

[0059] Epoxy resin 2.0 wt%

[0060] Unsaturated polyester resin 1.5 wt%

[0061] Examples of water absorption rates of low water-absorbent fillers

[0062] Melamine cyanurate 0.2 wt%

[0063] Acrylic resin 0.5 wt%

[0064] Alumina 0.004 wt%

[0065] The weight ratio of the low water-absorbing filler in the adhesive layer is preferably 15% by weight to 35% by weight.

[0066] By increasing the proportion of the low water absorption filler, the moisture content of the adhesive layer can be reduced. On the other hand, if the proportion of the low water absorption filler is too high, the proportion of the resin that contributes to the adhesiveness becomes low, so the adhesiveness may be insufficient. From this point of view, the weight proportion of the low water absorption filler in the adhesive layer is preferably 15% to 35% by weight.

[0067] The adhesive layer is preferably a conductive adhesive layer.

[0068] When the adhesive layer is a conductive adhesive layer, the shielding properties of the electromagnetic wave shielding film can be improved.

[0069] When the adhesive layer is a conductive adhesive layer, the adhesive layer preferably contains a conductive filler.

[0070] The conductive filler is not particularly limited, and may be metal fine particles, carbon nanotubes, carbon fibers, metal fibers, or the like.

[0071] When the conductive filler is metal particles, the metal particles are not particularly limited and may be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder obtained by silver-plating copper powder, particles obtained by coating polymer particles, glass beads, etc. with metal, etc.

[0072] Among them, copper powder or silver-coated copper powder, which is available at a low price, is preferred from the viewpoint of economic efficiency.

[0073] When the adhesive layer contains a conductive filler, the content of the conductive filler is preferably 5 to 900 parts by weight, more preferably 10 to 800 parts by weight, based on 100 parts by weight of the resin.

[0074] The thickness of the adhesive layer is preferably 5 to 50 μm, more preferably 5 to 30 μm.

[0075] If the thickness of the adhesive layer is less than 5 μm, the adhesiveness is reduced due to the thinness.

[0076] If the thickness of the adhesive layer exceeds 50 μm, the adhesive layer becomes thick and it becomes difficult to reduce the size of the electromagnetic wave shielding film.

[0077] The adhesive layer may contain, in addition to the resin, low water-absorbent filler, and conductive filler, a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, a defoamer, a leveling agent, a filler, a flame retardant, a viscosity modifier, and the like as needed.

[0078] In the electromagnetic wave shielding film of the present invention, a metal foil is laminated on the adhesive layer containing a resin.

[0079] The metal foil 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 foil may be composed of at least two alloys selected therefrom.

[0080] Metal foil composed of these metals can appropriately shield electromagnetic waves.

[0081] The water vapor permeability of the metal foil is 0.40g / (m 2 In addition, the water vapor permeability of the metal foil is preferably 0.40 g / (m 2 ·day)~11000g / (m 2 ·day), more preferably 5.00g / (m 2 ·day)~11000g / (m 2 ·day). In addition, the water vapor permeability of the metal foil is preferably 5.00 g / (m2 ·day) or more, more preferably 20.0g / (m 2 ·day) or more, more preferably 60.0g / (m 2 ·day) or more.

[0082] If the water vapor permeability of the metal foil is high, the water vapor generated by the moisture contained in the adhesive layer when heated by reflow or the like is easily released to the outside through the metal foil. Therefore, the internal pressure of the space between the adhesive layer and the metal foil is not easy to increase, and the interlayer adhesion between the adhesive layer and the metal foil is less likely to be destroyed.

[0083] In addition, the water vapor transmission rate can be 20000g / (m 2 ·day) or less, and can be 11000g / (m 2 ·day) or less, or 100g / (m 2 ·day) or less.

[0084] The water vapor transmission rate can be measured in accordance with JIS K 7129-4 (2019).

[0085] In order to increase the water vapor permeability of the metal foil, the thickness of the metal foil is preferably thin, and the thickness of the metal foil is preferably 6.0 μm or less, more preferably 5.0 μm or less, further preferably 4.0 μm or less, and further preferably 3.5 μm or less.

[0086] In addition, if the thickness of the metal foil is too thin, the strength of the metal foil becomes low. Therefore, the bending resistance may be reduced. In addition, since it is difficult to fully reflect and absorb electromagnetic waves, the electromagnetic wave shielding properties are easily reduced. Therefore, the thickness of the metal foil is preferably 1.0 μm or more, and more preferably 2.0 μm or more.

[0087] In order to increase the water vapor transmission rate, openings may be provided in the metal foil. The openings may be provided by laser processing, punching processing, or the like.

[0088] Thin metal foil can be obtained by etching the metal foil. For example, a rolled copper foil with a thickness of 6 μm can be etched to obtain a copper foil with a thickness of 0.5 μm to 5.0 μm. In addition, openings can be provided in the metal foil by adjusting the etching conditions.

[0089] In the electromagnetic wave shielding film of the present invention, it is preferred that the moisture content of the adhesive layer is 0.75 wt % to 1.00 wt %, the water vapor permeability of the metal foil is 5.00 g / (m 2 ·day)~100g / (m 2 ·day).

[0090] If the moisture content of the adhesive layer is within the above range, the moisture content of the adhesive layer is small. In addition, since the water vapor permeability of the metal foil is also high, the interlayer adhesion between the adhesive layer and the metal foil is not easily destroyed. In addition, in order to improve the water vapor permeability of the metal foil, the thickness of the metal foil can be reduced or an opening can be provided on the metal foil. However, if the thickness of the metal foil is too thin or the opening ratio is too high, the electromagnetic wave shielding properties may be reduced. From such a viewpoint, it is preferred to increase the water vapor permeability to a degree sufficient to prevent the destruction of the interlayer adhesion between the adhesive layer and the metal foil, and not to reduce the electromagnetic wave shielding properties.

[0091] In the electromagnetic wave shielding film of the present invention, it is preferred that an insulating layer is further laminated on the metal foil.

[0092] The insulating layer is not particularly limited as long as it has sufficient insulating properties and can protect the metal foil and the adhesive layer, and is preferably composed of, for example, a thermoplastic resin composition, a thermosetting resin composition, an active energy ray-curable composition, or the like.

[0093] The thermoplastic resin composition is not particularly limited, and examples thereof include styrene resin compositions, vinyl acetate resin compositions, polyester resin compositions, polyethylene resin compositions, polypropylene resin compositions, imide resin compositions, and acrylic resin compositions.

[0094] The thermosetting resin composition is not particularly limited, and examples thereof include phenolic resin compositions, epoxy resin compositions, polyurethane resin compositions, melamine resin compositions, and alkyd resin compositions.

[0095] The active energy ray-curable composition is not particularly limited, and examples thereof include polymerizable compounds having at least two (meth)acryloyloxy groups in a molecule.

[0096] The insulating layer may be composed of a single material or may be composed of two or more materials.

[0097] The insulating layer may further contain a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, a defoaming agent, a leveling agent, a filler, a flame retardant, a viscosity modifier, an anti-blocking agent, and the like as required.

[0098] The thickness of the insulating layer is not particularly limited and can be appropriately set as needed, but is preferably 1 to 15 μm, and more preferably 3 to 10 μm.

[0099] If the thickness of the insulating layer is less than 1 μm, it is difficult to sufficiently protect the metal foil and the adhesive layer because the insulating layer is too thin.

[0100] If the thickness of the insulating layer exceeds 15 μm, the electromagnetic wave shielding film is difficult to bend due to the excessive thickness, and the toughness of the insulating layer is reduced. Therefore, it is difficult to apply the insulating layer to parts that require bending resistance.

[0101] In addition, in the electromagnetic wave shielding film of the present invention, the insulating layer may be formed as necessary or may not be formed.

[0102] Next, the shielded printed wiring board of the present invention using the electromagnetic wave shielding film of the present invention will be described.

[0103] Figure 2 This is a cross-sectional view schematically showing an example of the shielded printed wiring board of the present invention using the electromagnetic wave shielding film of the present invention.

[0104] Figure 2 The shielded printed wiring board 1 shown is constituted by a printed wiring board 50 and an electromagnetic wave shielding film 10 .

[0105] The printed wiring board 50 includes a base film 51 , a printed circuit 52 arranged on the base film 51 , and a cover layer 53 arranged so as to cover the printed circuit 52 .

[0106] In the printed wiring board 50 , the printed circuit 52 includes a ground circuit 52 a , and an opening 53 a for exposing the ground circuit 52 a is formed in the cover layer 53 .

[0107] In the shield printed wiring board 1 , the electromagnetic wave shielding film 10 is arranged on the printed wiring board 50 so that the cover layer 53 and the adhesive layer 20 are in contact with each other.

[0108] In the shielded printed wiring board 1, the adhesive layer 20 fills the opening 53a of the cover layer 53 and contacts the ground circuit 52a. With such a configuration, the shielding property of the electromagnetic wave shielding film 10 can be improved.

[0109] The following matters are disclosed in this specification.

[0110] The present disclosure (1) is an electromagnetic wave shielding film, characterized in that it comprises an adhesive layer and a metal foil, wherein the adhesive layer contains a resin, and the metal foil is laminated on the adhesive layer; the water vapor permeability of the metal foil is 0.40 g / (m 2 ·day) or more, the moisture content of the adhesive layer is 1.00 wt% or less.

[0111] The present disclosure (2) is the electromagnetic wave shielding film according to the present disclosure (1), wherein the water vapor permeability of the metal foil is 0.40 g / (m 2 ·day)~11000g / (m 2 ·day).

[0112] The present disclosure (3) is the electromagnetic wave shielding film according to the present disclosure (2), wherein the water vapor permeability of the metal foil is 5.00 g / (m 2 ·day)~11000g / (m 2 ·day).

[0113] The present disclosure (4) is the electromagnetic wave shielding film according to any one of the present disclosures (1) to (3), wherein the adhesive layer contains a low water-absorbing filler having a lower water absorption rate than the resin.

[0114] The present disclosure (5) is the electromagnetic wave shielding film according to the present disclosure (4), wherein the low water-absorbing filler is melamine cyanurate or acrylic resin.

[0115] The present disclosure (6) is the electromagnetic wave shielding film according to the present disclosure (4) or (5), wherein the weight ratio of the low water-absorbing filler in the adhesive layer is 15% by weight to 35% by weight.

[0116] The present disclosure (7) is an electromagnetic wave shielding film according to any one of the present disclosures (1) to (6), wherein the moisture content of the adhesive layer is 0.75 wt% to 1.00 wt%, and the water vapor permeability of the metal foil is 5.00 g / (m 2 ·day)~100g / (m 2 ·day).

[0117] This disclosure (8) is the electromagnetic wave shielding film according to any one of this disclosure (1) to (7), wherein the adhesive layer is a conductive adhesive layer.

[0118] This disclosure (9) is the electromagnetic wave shielding film according to any one of this disclosure (1) to (8), wherein an insulating layer is further laminated on the metal foil.

[0119] The present disclosure (10) is a shielded printed wiring board, characterized in that the electromagnetic wave shielding film according to any one of the present disclosures (1) to (9) is arranged on the printed wiring board.

[0120] Example

[0121] Hereinafter, although the Example which demonstrates this invention more concretely is shown, this invention is not limited to these Examples.

[0122] A conductive adhesive is prepared by mixing a polyester-based thermosetting resin as a resin, a silver-coated copper powder as a conductive filler, and melamine cyanurate particles as a low water-absorbing filler.

[0123] Various conductive adhesives were prepared by changing the ratio of the resin to the low water-absorbing filler as shown in Table 1. The prepared conductive adhesives are designated as (A-1) to (A-10).

[0124] [Determination of water content]

[0125] The water content of the conductive adhesives (A-1) to (A-10) was measured using a Karl Fischer titrator according to the method described in the present specification.

[0126] [Measurement of Adhesion]

[0127] Each of the conductive adhesives (A-1) to (A-10) was applied onto a copper foil having a thickness of 2 μm to have a thickness of 5 μm, thereby producing an electromagnetic wave shielding film.

[0128] A peel test using the adhesive tape and adhesive sheet test method specified in STM D3330 was performed. Specifically, each electromagnetic wave shielding film cut into 125 mm in length and 25 mm in width was attached to a test plate made of a stainless steel material, and the electromagnetic wave shielding film was peeled off from the test plate in a 180° direction using a tensile testing machine, and the tensile force at this time was measured to evaluate the adhesion. The results are shown in Table 1.

[0129]

[0130] Conductive adhesives (A-4) to (A-10) having a moisture content of 1.00 wt % or less are conductive adhesives for obtaining the electromagnetic wave shielding film of the present invention.

[0131] In addition, regarding the adhesion, in the region where the amount of the low water-absorbing filler is 0 to 20% by weight, the adhesion tends to be improved when the amount of the low water-absorbing filler is large. It can be inferred that since a high-polarity material, namely melamine cyanurate, is used as the low water-absorbing filler, the cohesive force with the resin and the conductive filler in the adhesive layer becomes high, and the adhesion is improved. If the amount of the low water-absorbing filler is greater than 20% by weight, the amount of the resin becomes less, so it can be seen that the adhesion tends to decrease. In particular, if the amount of the low water-absorbing filler is 40% by weight or more, it can be seen that the adhesion tends to be greatly reduced.

[0132] [Measurement of water vapor transmission rate of copper foil]

[0133] The water vapor transmission rates of copper foils having thicknesses of 8.0 μm, 7.0 μm, 6.0 μm, 5.0 μm, 4.0 μm, 3.0 μm, 2.0 μm, 1.0 μm, and 0.5 μm were measured according to the method described in this specification.

[0134] Next, the conductive adhesives (A-1) to (A-10) were applied onto the copper foil to have a thickness of 5 μm to produce an electromagnetic wave shielding film.

[0135] [Measurement of shielding properties]

[0136] The shielding properties of each electromagnetic wave shielding film were measured at a frequency of 10 GHz by a coaxial tube method.

[0137] In the measurement based on the coaxial tube method, the attenuation of electromagnetic waves due to each electromagnetic wave shielding film was measured using a coaxial tube type shielding effectiveness measurement system of KEYCOM Corporation under the conditions of temperature 25°C and relative humidity 30-50% in accordance with ASTM D4935.

[0138] Table 2 shows the measurement results.

[0139] The shielding property is related to the thickness of the copper foil. When the copper foil of the same thickness is used, the shielding property is the same regardless of the type of conductive adhesive. Therefore, in Table 2, the shielding property [dB] is shown below the "Copper Foil" column. The higher the value, the better the shielding property.

[0140] When the thickness of the copper foil is 3.0 μm or more, the shielding property exceeds 100 dB.

[0141] [Evaluation of the presence or absence of interlayer peeling]

[0142] Each electromagnetic wave shielding film is arranged on a printed wiring board by hot pressing to obtain a shielded printed wiring board. Next, the shielded printed wiring board is placed in a constant temperature and humidity chamber at 30°C and 60% RH for 1 day, and then exposed to the temperature conditions during solder reflow to evaluate whether there is interlayer peeling. It should be noted that the temperature conditions during solder reflow are set to a maximum temperature of 288°C. In addition, the presence or absence of interlayer peeling is evaluated by floating the shielded printed wiring board in the solder tank 3 times and visually observing whether there is expansion. Here, the case where the area of ​​the expanded region is less than 1% of the area of ​​the shielding film is evaluated as "○", the case where the area of ​​the expanded region is more than 1% and less than 10% is evaluated as "△", and the case where the expanded area is more than 10% is evaluated as "×". The results are shown in Table 2.

[0143]

[0144] According to Table 2, when the conductive adhesives (A-1) to (A-3) having a moisture content of more than 1.00 wt % were used, the interlayer peeling test results were "×", and the interlayer adhesion between the adhesive layer and the metal foil was destroyed in a wide range.

[0145] Even if the moisture content of the conductive adhesive is 1.00 wt % or less, when the water vapor permeability of the copper foil is less than 0.40 g / (m 2 ·day), the result of the interlayer peeling test was also "×", indicating that the interlayer adhesion between the adhesive layer and the metal foil was destroyed in a wide range.

[0146] On the other hand, when copper foil is used, the water vapor permeability is 0.40 g / (m 2 ·day) or more and the moisture content of the conductive adhesive is less than 1.00 wt% for conductive adhesives (A-4) to (A-10), the result of the interlayer peeling test is "△" or "○", which prevents the interlayer adhesion between the adhesive layer and the metal foil from being destroyed. In particular, when the moisture content of the conductive adhesive is less than 0.89 wt% for conductive adhesives (A-5) to (A-10), the result of the interlayer peeling test is "○". In addition, when the moisture content of the conductive adhesive is 0.92 wt% for conductive adhesive (A-4), by using a conductive adhesive with a water vapor permeability of 5.46 g / (m 2 The result of the interlayer peeling test of the copper foil having a thickness of 100 mm / s and a thickness of 100 mm / s (day) or more was "○".

[0147] In addition, regarding the shielding property, the thicker the copper foil is, the better it is.

[0148] When the moisture content of the adhesive is less than 1.00 wt %, an electromagnetic wave shielding film can be formed in which the interlayer adhesion between the adhesive layer and the metal foil is not easily broken even when heated by reflow or the like.

[0149] In addition, considering the shielding property and adhesion as other properties, it is preferable that the moisture content of the adhesive layer is 0.75 wt % to 1.00 wt % and the water vapor permeability of the metal foil is 5.00 g / (m 2 ·day)~100g / (m 2 day).

[0150] Explanation of symbols

[0151] 1 Shielded printed wiring board

[0152] 10. 510 electromagnetic wave shielding film

[0153] 20, 520 adhesive layer

[0154] 30, 530 metal foil

[0155] 40, 540 insulation layer

[0156] 50 Printed wiring board

[0157] 51 basement membrane

[0158] 52 Printed Circuit

[0159] 52a grounding circuit

[0160] 53 Overlay

[0161] 53a Opening

[0162] 560 Volatile ingredients

Claims

1. An electromagnetic wave shielding film comprising an adhesive layer and a metal foil, The adhesive layer contains a resin, The metal foil layer is stacked on the adhesive layer; The water vapor permeability of the metal foil is 0.40 g / (m 2 ·day) or above, The adhesive layer has a moisture content of 1.00 wt % or less.

2. The electromagnetic wave shielding film according to claim 1, wherein The water vapor permeability of the metal foil is 0.40 g / (m 2 ·day)~11000g / (m 2 ·day).

3. The electromagnetic wave shielding film according to claim 2, wherein The water vapor permeability of the metal foil is 5.00 g / (m 2 ·day)~11000g / (m 2 ·day).

4. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein The adhesive layer contains a material having a lower water absorption rate than the resin, that is, a low water absorption filler.

5. The electromagnetic wave shielding film according to claim 4, wherein The low water-absorbent filler is melamine cyanurate or acrylic resin.

6. The electromagnetic wave shielding film according to claim 4 or 5, wherein The weight ratio of the low water-absorbent filler in the adhesive layer is 15 wt % to 35 wt %.

7. The electromagnetic wave shielding film according to any one of claims 1 to 6, wherein The moisture content of the adhesive layer is 0.75 wt% to 1.00 wt%, and the water vapor permeability of the metal foil is 5.00 g / (m 2 ·day)~100g / (m 2 ·day).

8. The electromagnetic wave shielding film according to any one of claims 1 to 7, wherein The adhesive layer is a conductive adhesive layer.

9. The electromagnetic wave shielding film according to any one of claims 1 to 8, wherein An insulating layer is further laminated on the metal foil.

10. A shielded printed wiring board, characterized in that: The electromagnetic wave shielding film according to any one of claims 1 to 9 is disposed on a printed wiring board.

Images