Electromagnetic wave shielding film and shielding printed circuit board

Abstract

Provided: An electromagnetic wave shielding film with high adhesion strength and excellent bending resistance of the shielding layer. The electromagnetic wave shielding film of the present invention is characterized by having an isotropic conductive adhesive layer, an insulating layer, and a metal layer sequentially stacked, wherein the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm.

Description

Technical Field

[0001] This invention relates to electromagnetic wave shielding films and shielded printed circuit boards. Background Technology

[0002] In mobile devices such as smartphones and tablets, shielded flexible printed circuit boards (hereinafter also referred to as "shielded printed circuit boards") with an adhered electromagnetic wave shielding film are used to shield against electromagnetic waves generated internally and those intruding from the outside. The shielding layer used in the electromagnetic wave shielding film can be formed by: a metal layer of a thin film formed by evaporation, sputtering, or plating; or a conductive paste with highly filled conductive fillers. If 5G and other technologies are formally expanded in the future, the advancement of high-capacity, high-frequency, and high-speed data transmission will further necessitate noise countermeasures for electronic devices.

[0003] As such an electromagnetic wave shielding film, Patent Document 1 discloses an electromagnetic wave shielding material (electromagnetic wave shielding film). The surface of the polymer film is formed by any method of sputtering, vapor deposition or plating, with one or more shielding layers having a thickness of 1 to 8 μm and selected from the group consisting of Ni, Fe, Co, Ti, Zn, Cr, Sn, Cu and alloys containing at least one of these metals. Between the surface of the polymer film and the shielding layer, there is one or more base layers formed by any method of sputtering or vapor deposition, with a thickness of less than 1 μm and selected from the group consisting of Ni, Co, Zn, Fe, Cu, Ti, Cr, oxides of these metals, nitrides of these metals and alloys containing at least one of these metals.

[0004] In addition, Patent Document 2 discloses an electromagnetic wave shielding film (electromagnetic wave shielding film), characterized in that it is an electromagnetic wave shielding film formed on a molded article made of any of ABS resin, PC and ABS / PC polymer alloy, wherein the electromagnetic wave shielding film is formed of a first layer of Cu and a second layer of Sn-Cr coating.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2004-128158

[0008] Patent Document 2: Japanese Patent No. 3826756 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] In the case of the aforementioned electromagnetic wave shielding film, multiple metal layers are stacked in a state of contact with each other. Therefore, the tightness between the shielding layers is not sufficient, and there is a problem that cracks can easily occur if the film is repeatedly bent.

[0011] This invention is made to solve the above-mentioned problems. The purpose of this invention is to provide an electromagnetic wave shielding film with high sealing strength and excellent bending resistance of the shielding layer.

[0012] Solution for solving the problem

[0013] That is, the electromagnetic wave shielding film of the present invention is characterized in that it is sequentially stacked with an isotropic conductive adhesive layer, an insulating layer and a metal layer, wherein the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm.

[0014] In the electromagnetic wave shielding film of the present invention, both the isotropic conductive adhesive layer and the metal layer have the effect of shielding electromagnetic waves.

[0015] In the electromagnetic wave shielding film of the present invention, an insulating layer is formed between the isotropic conductive adhesive layer and the metal layer. Therefore, the metal layer is not easily peeled off. In addition, even if the electromagnetic wave shielding film of the present invention is repeatedly bent, cracks are not easily generated in the metal layer.

[0016] In the electromagnetic wave shielding film of the present invention, the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm.

[0017] If the total thickness of the insulating layer and the metal layer is greater than 0.5μm and less than 20μm, the metal layer becomes difficult to peel off, and even if the electromagnetic wave shielding film is repeatedly bent, cracks are less likely to occur in the metal layer.

[0018] In the electromagnetic wave shielding film of the present invention, the thickness of the metal layer is preferably 0.1 to 8 μm.

[0019] If the thickness of the aforementioned metal layer is less than 0.1 μm, the strength of the metal layer becomes weaker and it becomes more easily damaged.

[0020] If the thickness of the aforementioned metal layer exceeds 8 μm, the flexibility of the metal layer decreases, and therefore, cracks become more likely to form in the metal layer when repeatedly bent.

[0021] In the electromagnetic wave shielding film of the present invention, the thickness of the insulating layer is preferably 0.5 to 10 μm.

[0022] If the thickness of the insulating layer is less than 0.5 μm, the amount of insulating layer becomes less, and therefore the metal layer becomes easier to peel off.

[0023] If the thickness of the insulating layer exceeds 10 μm, it becomes too thick, making it easier to apply stress to the metal layer when bending the electromagnetic wave shielding film. Consequently, repeated bending can easily cause cracks to form in the metal layer.

[0024] In the electromagnetic wave shielding film of the present invention, the metal layer preferably comprises at least one selected from the group consisting of copper, silver and aluminum.

[0025] These metals are inexpensive, and when metal layers are formed from these metals, they exhibit excellent electromagnetic shielding properties.

[0026] In the electromagnetic wave shielding film of the present invention, it is preferable that the metal layer has through holes.

[0027] An electromagnetic wave shielding film is then mounted on a printed circuit board. At this point, the electromagnetic wave shielding film is thermally bonded. During this process, volatile components may sometimes be generated between the insulating layer and the metal layer.

[0028] Without through-holes in the metal layer, the volatile components expand due to heat, sometimes causing the metal layer to peel off from the insulating layer. However, if through-holes are formed in the metal layer, the volatile components can pass through the through-holes, thus preventing the metal layer from peeling off from the insulating layer.

[0029] In the electromagnetic wave shielding film of the present invention, the average opening area of ​​a single through-hole is preferably 10 to 80,000 μm. 2 .

[0030] If the opening area of ​​the through hole formed in the metal layer is within the above range, the bending resistance is sufficient and the accumulation of volatile components between the metal layer and the insulating layer can be prevented.

[0031] In the electromagnetic wave shielding film of the present invention, the aperture ratio of the through hole is preferably 0.05 to 30%.

[0032] If the aperture ratio of the through-hole formed in the metal layer is within the above range, the bending resistance is sufficient and the accumulation of volatile components between the metal layer and the insulating layer can be prevented.

[0033] The shielding printed circuit board of the present invention is characterized by comprising a printed circuit board and an electromagnetic wave shielding film. The printed circuit board is formed by a base film, a printed circuit including a grounding circuit disposed on the base film, and a cover layer covering the printed circuit. The electromagnetic wave shielding film is sequentially stacked with an isotropic conductive adhesive layer, an insulating layer, and a metal layer. The total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm. The electromagnetic wave shielding film is disposed on the printed circuit board in such a way that the isotropic conductive adhesive layer is in contact with the cover layer.

[0034] The shielded printed circuit board of the present invention includes an electromagnetic wave shielding film, wherein an isotropic conductive adhesive layer, an insulating layer, and a metal layer are sequentially stacked on the electromagnetic wave shielding film, and the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm. That is, the shielded printed circuit board of the present invention includes the electromagnetic wave shielding film of the present invention described above.

[0035] Therefore, in the shielding printed circuit board of the present invention, the metal layer is not easy to peel off, and even if the shielding printed circuit board is repeatedly bent, cracks are not easily generated in the metal layer.

[0036] In the shielded printed circuit board of the present invention, it is preferable to form an opening in the cover layer that exposes the grounding circuit, and the isotropic conductive adhesive layer is filled in the opening in such a way that the isotropic conductive adhesive layer contacts the grounding circuit.

[0037] In this type of shielded printed circuit board, the isotropic conductive adhesive layer is in full contact with and electrically connected to the grounding circuit. In the shielded printed circuit board of this invention, the isotropic conductive adhesive layer has the function of shielding electromagnetic waves; therefore, the electromagnetic wave shielding effect is improved.

[0038] In the shielded printed circuit board of the present invention, the aforementioned metal layer is electrically connected to an external ground.

[0039] In the shielded printed circuit board of the present invention, the metal layer has the function of shielding electromagnetic waves. Therefore, when the metal layer is electrically connected to the external ground, the electromagnetic wave shielding effect becomes higher.

[0040] The effects of the invention

[0041] In the electromagnetic wave shielding film of the present invention, an insulating layer is formed between the isotropic conductive adhesive layer and the metal layer. Therefore, the metal layer is not easily peeled off. In addition, even if the electromagnetic wave shielding film of the present invention is repeatedly bent, cracks are not easily generated in the metal layer.

[0042] Furthermore, in the electromagnetic wave shielding film of the present invention, the total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm.

[0043] If the total thickness of the insulating layer and the metal layer is greater than 0.5μm and less than 20μm, the metal layer becomes difficult to peel off, and even if the electromagnetic wave shielding film is repeatedly bent, cracks are less likely to occur in the metal layer. Attached Figure Description

[0044] Figure 1 A cross-sectional view illustrating an example of the electromagnetic wave shielding film of the present invention is shown for illustrative purposes.

[0045] Figure 2AThe following is a process diagram illustrating an example of the metal layer formation process in the method for manufacturing the electromagnetic wave shielding film of the present invention.

[0046] Figure 2B The following is a process diagram illustrating an example of the insulating layer formation process in the manufacturing method of the electromagnetic wave shielding film of the present invention.

[0047] Figure 2C The diagram illustrates an example of the isotropic conductive adhesive layer formation process in the manufacturing method of the electromagnetic wave shielding film of the present invention.

[0048] Figure 3 A cross-sectional view of an example of the shielded printed circuit board of the present invention is shown for illustrative purposes.

[0049] Figure 4A A cross-sectional view of another example of the shielded printed circuit board of the present invention is shown for illustrative purposes.

[0050] Figure 4B A cross-sectional view of another example of the shielded printed circuit board of the present invention is shown for illustrative purposes.

[0051] Figure 4C A cross-sectional view of another example of the shielded printed circuit board of the present invention is shown for illustrative purposes.

[0052] Figure 4D A cross-sectional view of another example of the shielded printed circuit board of the present invention is shown for illustrative purposes. Detailed Implementation

[0053] The electromagnetic wave shielding film of the present invention will now be described in detail. However, the present invention is not limited to the following embodiments, and can be appropriately modified and applied without changing the spirit of the invention.

[0054] Figure 1 A cross-sectional view illustrating an example of the electromagnetic wave shielding film of the present invention is shown for illustrative purposes.

[0055] Figure 1 The electromagnetic wave shielding film 10 shown contains an isotropic conductive adhesive layer 20, an insulating layer 30, and a metal layer 40 stacked sequentially.

[0056] In addition, in the electromagnetic wave shielding film 10, the total thickness of the insulating layer 30 and the metal layer 40 is more than 0.5 μm and less than 20 μm.

[0057] An electromagnetic wave shielding film 10 is disposed on a printed circuit board.

[0058] In the electromagnetic wave shielding film 10, both the isotropic conductive adhesive layer 20 and the metal layer 40 have the effect of shielding electromagnetic waves. Therefore, in the shielded printed circuit board equipped with the electromagnetic wave shielding film 10, electromagnetic waves can be shielded by the isotropic conductive adhesive layer 20 and the metal layer 40.

[0059] In the electromagnetic wave shielding film 10, an insulating layer 30 is formed between the isotropic conductive adhesive layer 20 and the metal layer 40. Therefore, the metal layer 40 is not easily peeled off. In addition, even if the electromagnetic wave shielding film 10 is repeatedly bent, cracks are not easily generated in the metal layer 40.

[0060] In the electromagnetic wave shielding film 10, the total thickness of the insulating layer 30 and the metal layer 40 is 0.5 μm or more and less than 20 μm. This thickness is preferably 1 to 12 μm.

[0061] If the total thickness of the insulating layer 30 and the metal layer 40 is greater than 0.5 μm and less than 20 μm, the metal layer 40 becomes difficult to peel off, and even if the electromagnetic wave shielding film 10 is repeatedly bent, cracks are less likely to occur in the metal layer 40.

[0062] The following describes the various components of the electromagnetic wave shielding film 10.

[0063] (Metal layer)

[0064] The material constituting the metal layer 40 is not particularly limited as long as it can shield electromagnetic waves, but preferably includes at least one material selected from the group consisting of copper, silver and aluminum.

[0065] These metals are inexpensive, therefore, when the metal layer 40 is formed from these metals, it exhibits excellent electromagnetic wave shielding.

[0066] As described above, in the electromagnetic wave shielding film 10, the thickness of the metal layer 40 is preferably 0.1 to 8 μm, more preferably 0.1 to 4 μm.

[0067] If the thickness of the aforementioned metal layer is less than 0.1 μm, the strength of the metal layer becomes weaker and it becomes more easily damaged.

[0068] If the thickness of the aforementioned metal layer exceeds 8 μm, the flexibility of the metal layer decreases, and therefore, cracks become more likely to form in the metal layer when repeatedly bent.

[0069] The metal layer 40 can be a vapor-deposited metal layer, a plated metal layer, or formed from rolled or electrolytic metal foil.

[0070] Preferably, a through hole is formed in the metal layer 40.

[0071] An electromagnetic wave shielding film 10 is disposed on a printed circuit board. At this time, the electromagnetic wave shielding film 10 is heat-pressed. During this process, volatile components may sometimes be generated between the insulating layer 30 and the metal layer 40.

[0072] If no through-holes are formed in the metal layer 40, the volatile components expand due to heat, and the metal layer 40 and the insulating layer 30 may sometimes peel off. However, if through-holes are formed in the metal layer 40, the volatile components can pass through the through-holes, thus preventing the metal layer 40 from peeling off from the insulating layer 30.

[0073] The shape of the through hole is not particularly limited; it can be a polygon such as a triangle or quadrilateral, or it can be a circle or an ellipse.

[0074] In the metal layer 40, the average opening area of ​​a single through hole is preferably 10 to 80,000 μm. 2 More preferably 10–8000 μm 2 .

[0075] If the opening area of ​​the through hole formed in the metal layer 40 is within the above range, the bending resistance is sufficient and the accumulation of volatile components between the metal layer 40 and the insulating layer 30 can be prevented.

[0076] In the metal layer 40, the aperture ratio of the through hole is preferably 0.05 to 30%, more preferably 0.1 to 10%.

[0077] If the aperture ratio of the through holes formed in the metal layer 40 is within the above range, the bending resistance is sufficient and the accumulation of volatile components between the metal layer 40 and the insulating layer 30 can be prevented.

[0078] In the metal layer 40, through holes can be arranged at equal intervals. When through holes are arranged at equal intervals, they are preferably arranged continuously in a constant pattern.

[0079] As an arrangement pattern for through holes, when viewed from above the metal layer 40, in a plane where equilateral triangles are continuously arranged in both directions, the center of the through hole may be located at the vertex of one of the equilateral triangles. Alternatively, when viewed from above the metal layer 40, in a plane where squares are continuously arranged in both directions, the center of the through hole may be located at the vertex of one of the squares. Furthermore, when viewed from above the metal layer 40, the center of the through hole may be located at the vertex of a regular hexagon.

[0080] (Insulating layer)

[0081] The material of the insulating layer 30 is not particularly limited as long as it can fully bond the metal layer 40; it can be a thermosetting resin composition or a thermoplastic resin composition.

[0082] It should be noted that the electromagnetic wave shielding film 10 is heat-pressed when disposed on the printed circuit board. Whether a thermosetting resin composition or a thermoplastic resin composition is used as the insulating layer 30 is preferably determined according to the conditions under which the heat pressing is performed.

[0083] It should be noted that, from the viewpoint of heat resistance, the insulating layer 30 is preferably formed of a thermosetting resin composition.

[0084] Examples of thermoplastic resins included in thermoplastic resin compositions include polyurethane resins, polystyrene resins, vinyl acetate resins, polyester resins, polyolefin resins (such as polyethylene resins, polypropylene resin compositions, etc.), and acrylic resins.

[0085] The insulating layer 30 may be composed of only one of these resins or of two or more.

[0086] Examples of thermosetting resins included in thermosetting resin compositions include phenolic resins, epoxy resins, urethane resins, melamine resins, alkyd resins, and polyimide resins.

[0087] The insulating layer 30 may be composed of only one of these resins or of two or more.

[0088] The thickness of the insulating layer 30 is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.

[0089] If the thickness of the insulating layer is less than 0.5 μm, the amount of insulating layer becomes less, and therefore the metal layer becomes easier to peel off.

[0090] If the thickness of the insulating layer exceeds 10 μm, it is considered a thick insulating layer. Therefore, when the electromagnetic wave shielding film is bent, it becomes easier to apply stress to the metal layer. Consequently, repeated bending makes it easier for cracks to form in the metal layer.

[0091] (Isotropic conductive adhesive layer)

[0092] The isotropic conductive adhesive layer 20 is formed of conductive particles and a resin composition.

[0093] Examples of conductive particles include silver particles, copper particles, nickel particles, aluminum particles, and silver-plated copper particles.

[0094] These conductive particles have excellent conductivity, and therefore, the isotropic conductive adhesive layer 20 can be suitably imparted with conductivity.

[0095] These conductive particles can be contained in the isotropic conductive adhesive layer 20 as a single type, or in multiple types.

[0096] There is no particular limitation on the size of conductive particles, the average particle size (d) 50 The preferred size is 0.5–20 μm.

[0097] Average particle size (d) 50 If the particle size is above 0.5 μm, the conductive particles are well dispersed, which can suppress aggregation and make them less susceptible to oxidation.

[0098] Average particle size (d) 50 If it is below 20μm, the connection with the grounding circuit becomes good.

[0099] The weight ratio of conductive particles contained in the isotropic conductive adhesive layer 20 is preferably 40-80 wt%, more preferably 50-70 wt%.

[0100] If the weight ratio of conductive particles is less than 40 wt%, it becomes difficult to obtain isotropic conductivity.

[0101] If the weight ratio of conductive particles exceeds 80 wt%, the isotropic conductive adhesive layer becomes brittle, and the electromagnetic wave shielding film becomes easily damaged.

[0102] There are no particular limitations on the materials used in the resin composition. The following can be used: 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, and acrylic resin compositions; thermosetting resin compositions such as phenol-based resin compositions, epoxy-based resin compositions, urethane-based resin compositions, melamine-based resin compositions, and alkyd-based resin compositions.

[0103] Among them, epoxy resin compositions are preferred.

[0104] The adhesive resin composition may be made of one of these materials alone or in combination of two or more of them.

[0105] It should be noted that the isotropic conductive adhesive layer 20 may also include: flame retardants, flame retardant additives, curing accelerators, tackifiers, antioxidants, pigments, dyes, plasticizers, ultraviolet absorbers, defoamers, leveling agents, fillers, viscosity modifiers, etc.

[0106] The thickness of the isotropic conductive adhesive layer 20 is preferably 3 to 20 μm, more preferably 5 to 10 μm.

[0107] If the thickness of the isotropic conductive adhesive layer 20 is 3 μm or more, the cover layer provided on the printed circuit board will have better filling performance for the opening.

[0108] If the thickness of the isotropic conductive adhesive layer 20 is less than 20 μm, it can meet the requirements for thin-film electromagnetic wave shielding film.

[0109] In the electromagnetic wave shielding film 10, a protective layer can be further formed on the metal layer 40.

[0110] The protective layer prevents the metal layer 40 from being damaged by external impacts, etc.

[0111] It should be noted that a protective layer may not be formed in the electromagnetic wave shielding film of the present invention.

[0112] The material of the protective layer is not particularly limited as long as it is insulating and can protect the metal layer 40. It is preferably composed of thermoplastic resin composition, thermosetting resin composition, active energy radiation curable composition, etc.

[0113] The thermoplastic resin composition used as a protective layer is not particularly limited, and examples include styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, polyethylene-based resin compositions, polypropylene-based resin compositions, polyamide-based resin compositions, and acrylic resin compositions.

[0114] The thermosetting resin composition used as a protective layer is not particularly limited, and examples include phenolic resin compositions, epoxy resin compositions, urethane resin compositions, melamine resin compositions, alkyd resin compositions, and polyimide resin compositions.

[0115] The active energy ray curable composition used as a protective layer is not particularly limited, and examples include polymeric compounds having at least two (meth)acryloyloxy groups in the molecule.

[0116] The protective layer can be made of a single material or two or more materials.

[0117] The protective layer may contain curing accelerators, tackifiers, antioxidants, pigments, dyes, plasticizers, UV absorbers, defoamers, leveling agents, fillers, flame retardants, viscosity modifiers, anti-blocking agents, etc., as needed.

[0118] The thickness of the protective layer is not particularly limited and can be set appropriately as needed, preferably 1 to 15 μm, more preferably 3 to 10 μm.

[0119] Next, the method for manufacturing the electromagnetic wave shielding film of the present invention will be described.

[0120] In manufacturing the electromagnetic wave shielding film of the present invention, a metal layer formation process, an insulating layer formation process, and an isotropic conductive adhesive layer formation process are performed.

[0121] Figure 2A The following is a process diagram illustrating an example of the metal layer formation process in the method for manufacturing the electromagnetic wave shielding film of the present invention.

[0122] First, such as Figure 2A As shown, a peeling film 50 is prepared to form a metal layer 40 on it.

[0123] There are no particular limitations on the type of release film 50; previously used non-silicone release films, micro-adhesive films, etc., can be used.

[0124] There are no particular limitations on the method of forming the metal layer 40. It can be formed by rolling or electrolytic metal foil, by vapor deposition, or by plating.

[0125] Figure 2B The following is a process diagram illustrating an example of the insulating layer formation process in the manufacturing method of the electromagnetic wave shielding film of the present invention.

[0126] Next, as Figure 2B As shown, an insulating layer 30 is formed on the metal layer 40.

[0127] There are no particular limitations on the method for forming the insulating layer 30; for example, it can be applied using a bar coater.

[0128] Figure 2C The diagram illustrates an example of the isotropic conductive adhesive layer formation process in the manufacturing method of the electromagnetic wave shielding film of the present invention.

[0129] Next, as Figure 2C As shown, an isotropic conductive adhesive layer 20 is formed on the insulating layer 30.

[0130] There are no particular limitations on the method for forming the isotropic conductive adhesive layer 20; for example, it can be applied using a bar coater.

[0131] If the laminate manufactured through the above processes is reversed by 180°, it becomes Figure 1 The electromagnetic wave shielding film 10 shown.

[0132] It should be noted that the peeling film 50 can be peeled off during use.

[0133] Next, the shielded printed circuit board 1 equipped with the electromagnetic wave shielding film 10 will be described.

[0134] The shielded printed circuit board 1 is also an example of the shielded printed circuit board of the present invention.

[0135] Figure 3 A cross-sectional view of an example of the shielded printed circuit board of the present invention is shown for illustrative purposes.

[0136] Figure 3 The shielding printed circuit board 1 shown includes: a printed circuit board 60 formed of a base film 61, a printed circuit 62 including a grounding circuit 62a disposed on the base film 61 and a cover layer 63 covering the printed circuit 62; and an electromagnetic wave shielding film 10.

[0137] In the shielded printed circuit board 1, the electromagnetic wave shielding film 10 is disposed on the printed circuit board 60 in such a way that the isotropic conductive adhesive layer 20 contacts the cover layer 63.

[0138] The shielded printed circuit board 1 has an electromagnetic wave shielding film 10. Therefore, the metal layer 40 in the shielded printed circuit board 1 is not easy to peel off, and cracks are not easily generated in the metal layer 40 even if the shielded printed circuit board 1 is repeatedly bent.

[0139] in addition, Figure 3 In the shielded printed circuit board 1 shown, an opening 63a is formed in the cover layer 63 to expose the grounding circuit 62a.

[0140] In the opening 63a, the isotropic conductive adhesive layer 20 is filled in such a way that it contacts the grounding circuit 62a.

[0141] In this shielded printed circuit board 1, the isotropic conductive adhesive layer 20 is in full contact with and electrically connected to the grounding circuit 62a. In the shielded printed circuit board 1, the isotropic conductive adhesive layer 20 has the function of shielding electromagnetic waves, thus improving the electromagnetic wave shielding effect.

[0142] It should be noted that in the shielded printed circuit board of the present invention, the cover layer may not have an opening that exposes the grounding circuit.

[0143] In this case, the grounding circuit can be electrically connected to the isotropic conductive adhesive layer by conductive bumps and conductive pins.

[0144] In the shielded printed circuit board 1, the metal layer 40 is electrically connected to the external ground GND.

[0145] In the shielded printed circuit board 1, the metal layer 40 has the function of shielding electromagnetic waves. Therefore, if the metal layer 40 is electrically connected to the external ground GND, the electromagnetic wave shielding effect becomes higher.

[0146] There are no particular limitations on the method of electrically connecting the external ground GND to the metal layer 40. For example, conductive adhesives, conductive foams, conductive gaskets, etc., can be used to electrically connect the external ground GND to the metal layer 40.

[0147] Furthermore, in the shielded printed circuit board of the present invention, the case in which a protective layer is further formed on the metal layer of the electromagnetic wave shielding film is illustrated with reference to the accompanying drawings.

[0148] Figures 4A to 4D A cross-sectional view of another example of the shielded printed circuit board of the present invention is shown for illustrative purposes.

[0149] Figure 4A The shielded printed circuit board 1A shown includes: a printed circuit board 60 formed of a base film 61, a printed circuit 62 including a grounding circuit 62a disposed on the base film 61 and a cover layer 63 covering the printed circuit 62; and an electromagnetic wave shielding film 11.

[0150] In the electromagnetic wave shielding film 11, an isotropic conductive adhesive layer 20, an insulating layer 30, a metal layer 40 and a protective layer 70 are stacked in sequence.

[0151] In the shielded printed circuit board 1A, the electromagnetic wave shielding film 11 is disposed on the printed circuit board 60 in such a way that the isotropic conductive adhesive layer 20 contacts the cover layer 63.

[0152] The shielded printed circuit board 1A includes a grounding member 80A, which has a further flat conductive external connection member 81 located on the protective layer 70 of the electromagnetic wave shielding film 11, and a conductive protrusion 82 protruding from one side of the conductive external connection member 81.

[0153] The conductive protrusion 82 penetrates the protective layer 70 and contacts the metal layer 40, and the conductive external connecting member 81 is electrically connected to the external ground GND.

[0154] That is, in the shielded printed circuit board 1A, the grounding component 80A then connects the metal layer 40 to the external ground GND.

[0155] The conductive external connection member 81 and conductive protrusion 82 of the grounding member 80A only need to be conductive and can be made of any material, such as copper, silver, aluminum, etc.

[0156] In the grounding member 80A, the conductive external connection member 81 and the conductive protrusion 82 can be connected by solder or welding. Alternatively, the conductive protrusion 82 can be formed by etching, and the conductive external connection member 81 and the conductive protrusion 82 can be integrated.

[0157] Figure 4B The shielded printed circuit board 1B shown includes: a printed circuit board 60 formed of a base film 61, a printed circuit 62 including a grounding circuit 62a disposed on the base film 61 and a cover layer 63 covering the printed circuit 62; and an electromagnetic wave shielding film 11.

[0158] In the electromagnetic wave shielding film 11, an isotropic conductive adhesive layer 20, an insulating layer 30, a metal layer 40 and a protective layer 70 are stacked in sequence.

[0159] In the shielded printed circuit board 1B, the electromagnetic wave shielding film 11 is disposed on the printed circuit board 60 in such a way that the isotropic conductive adhesive layer 20 contacts the cover layer 63.

[0160] The shielded printed circuit board 1B includes a grounding member 80B, which has a further flat conductive external connection member 81 located on the protective layer 70 of the electromagnetic wave shielding film 11, and conductive particles 83 disposed on one side of the conductive external connection member 81.

[0161] The conductive particles 83 penetrate the protective layer 70 and contact the metal layer 40, and the conductive external connecting component 81 is electrically connected to the external ground GND.

[0162] That is, in the shielded printed circuit board 1B, the metal layer 40 is connected to the external ground GND by means of the grounding member 80B.

[0163] The external connection member 81 of the grounding member 80B only needs to be conductive and can be made of any material, such as copper, silver, aluminum, etc.

[0164] In addition, the conductive particles 83 of the grounding component 80B only need to be conductive and can be made of any material, such as copper, silver, aluminum, etc.

[0165] In the grounding component 80B, the conductive particles 83 are bonded to the conductive external connection component 81 by a conductive adhesive.

[0166] Figure 4C The shielded printed circuit board 1C shown includes: a printed circuit board 60 formed of a base film 61, a printed circuit 62 including a grounding circuit 62a disposed on the base film 61 and a cover layer 63 covering the printed circuit 62; and an electromagnetic wave shielding film 11.

[0167] In the electromagnetic wave shielding film 11, an isotropic conductive adhesive layer 20, an insulating layer 30, a metal layer 40 and a protective layer 70 are stacked in sequence.

[0168] In the shielded printed circuit board 1C, the electromagnetic wave shielding film 11 is disposed on the printed circuit board 60 in such a way that the isotropic conductive adhesive layer 20 contacts the cover layer 63.

[0169] The shielded printed circuit board 1C includes a grounding member 80C formed by a further conductive external connection member 84 located on the protective layer 70 of the electromagnetic wave shielding film 11.

[0170] The conductive external connecting member 84 is a shape formed by bending a flat plate multiple times, and has a protruding convex part 84a.

[0171] The protrusion 84a penetrates the protective layer 70 and contacts the metal layer 40, and the conductive external connecting member 84 is electrically connected to the external ground GND.

[0172] That is, in the shielded printed circuit board 1C, the metal layer 40 is connected to the external ground GND by means of the grounding component 80C.

[0173] The external connection component 84 of the grounding component 80C only needs to be conductive and can be made of any material, such as copper, nickel, silver, aluminum, etc.

[0174] Figure 4D The shielded printed circuit board 1D shown includes: a printed circuit board 60 formed of a base film 61, a printed circuit 62 including a grounding circuit 62a disposed on the base film 61 and a cover layer 63 covering the printed circuit 62; and an electromagnetic wave shielding film 12.

[0175] In the electromagnetic wave shielding film 12, an isotropic conductive adhesive layer 20, an insulating layer 30, a metal layer 40 and a protective layer 70 are stacked in sequence.

[0176] In the shielded printed circuit board 1D, the electromagnetic wave shielding film 12 is disposed on the printed circuit board 60 in such a way that the isotropic conductive adhesive layer 20 contacts the cover layer 63.

[0177] In the shielded printed circuit board 1D, an opening 71a is formed in the protective layer 71 of the electromagnetic wave shielding film 12, exposing the metal layer 40.

[0178] Furthermore, the metal layer 40 is electrically connected to the external ground GND through the opening 71a.

[0179] It should be noted that in the shielded printed circuit board 1D, the opening 71a of the protective layer 71 is filled with a conductive adhesive, which allows the metal layer 40 to be connected to the external ground GND.

[0180] The materials of the base film 61 and the cover layer 63 are not particularly limited, but are preferably formed of engineering plastics.

[0181] Examples of such engineering plastics include polyethylene terephthalate, polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide amide, polyetherimide, polyphenylene sulfide, and other resins.

[0182] Furthermore, within these engineering plastics, a polyphenylene sulfide film is preferred when flame retardancy is required, while a polyimide film is preferred when heat resistance is required. It should be noted that the thickness of the base film 61 is preferably 10–40 μm. Additionally, the thickness of the cover layer 63 is preferably 20–50 μm.

[0183] The printed circuit 62 and the grounding circuit 62a are not particularly limited and can be formed by etching the conductive material, etc.

[0184] Examples of conductive materials include copper, nickel, silver, and gold.

[0185] As a method for manufacturing the shielded printed circuit board 1, the following method can be cited: prepare a printed circuit board 60 and an electromagnetic wave shielding film 10, and place the electromagnetic wave shielding film 10 on the printed circuit board 60. More specifically, the following method can be cited: heat-press the electromagnetic wave shielding film 10 onto the printed circuit board 60 in such a way that the isotropic conductive adhesive layer 20 contacts the cover layer 63.

[0186] There are no particular limitations on the conditions for hot pressing, but conditions such as 150-200°C, 2-5 MPa, and 1-60 minutes can be cited.

[0187] By performing the above-mentioned hot pressing, the isotropic conductive adhesive layer 20 fills the opening 63a.

[0188] As a result, the grounding circuit 62a is electrically connected to the isotropic conductive adhesive layer 20. This improves the electromagnetic wave shielding effect.

[0189] Example

[0190] The following are embodiments that illustrate the invention in more detail, but the invention is not limited to these embodiments.

[0191] (Example 1)

[0192] (Metal layer formation process)

[0193] Silver (Ag) is vapor deposited onto the surface of a release film containing a non-silicon-based release agent to form a metal layer with a thickness of 0.1 μm.

[0194] (Insulation layer formation process)

[0195] An epoxy resin is coated onto the metal layer to form an insulating layer with a thickness of 1.0 μm.

[0196] (Isotropic conductive adhesive layer formation process)

[0197] Prepare an isotropic conductive adhesive comprising 60 wt% conductive particles formed from silver-coated copper powder and 40 wt% epoxy resin.

[0198] The isotropic conductive adhesive layer is coated onto the insulating layer to form an isotropic conductive adhesive layer with a thickness of 15 μm.

[0199] The electromagnetic wave shielding film of Example 1 was produced through the above processes.

[0200] (Examples 2-13) and (Comparative Examples 1-6)

[0201] As shown in Table 1, the material and thickness of the metal layer and the thickness of the insulating layer were changed. Otherwise, the electromagnetic wave shielding films of Examples 2 to 13 and Comparative Examples 1 to 3 were made in the same manner as in Example 1.

[0202] In addition, as shown in Table 1, the material and thickness of the metal layer were changed, and no insulating layer was provided. Otherwise, the electromagnetic wave shielding films of Comparative Examples 4 to 6 were made in the same manner as in Example 1.

[0203] [Table 1]

[0204]

[0205] (MIT Experiment)

[0206] The bending resistance of the electromagnetic wave shielding films of each embodiment and each comparative example after the peeling film was removed was determined using the following method.

[0207] Electromagnetic wave shielding films were placed on a 50 μm thick polyimide film using an isotropic conductive adhesive layer, and then bonded by hot pressing (170°C, 3 MPa, 30 minutes). Afterwards, the films were cut to a size of 130 mm × 15 mm, and the release film was peeled off to form test pieces. The flexural resistance of each test piece was determined using an MIT flexural fatigue testing machine (Yasuda Seiki Co., Ltd., No. 307MIT type flexural fatigue testing machine) based on the method specified in JISP8115:2001.

[0208] The test conditions are as follows.

[0209] Bending fixture front end radius (R): 0.38mm

[0210] Bending angle: ±135°

[0211] Bending speed: 175 cpm

[0212] Load: 500gf

[0213] Detection method: The built-in power supply device detects the open circuit in the shielding film.

[0214] The evaluation criteria for the MIT experiment are as follows. The results are shown in Table 1.

[0215] 〇: When the number of bends exceeds 1000, an open circuit in the metal layer is confirmed.

[0216] △: When the number of bends is more than 300 but less than 999, an open circuit in the metal layer is confirmed.

[0217] ×: When the number of bends is less than 300, an open circuit in the metal layer is confirmed.

[0218] (Seam strength test)

[0219] The adhesion strength of the electromagnetic wave shielding films of each embodiment and each comparative example after the peeling film was removed was determined using the following method.

[0220] Electromagnetic wave shielding films were placed on the polyimide film by contacting an isotropic conductive adhesive layer with a 25μm thick polyimide film, and then heat-pressed at a temperature of 170℃ for 30 minutes and a pressure of 3MPa.

[0221] The metal layer side of the electromagnetic wave shielding film is fixed with double-sided tape. At room temperature, the polyimide film is peeled off at a tensile speed of 50 mm / min and a peel angle of 180°. The peel strength during peeling is measured, and the average of the maximum and minimum values ​​is taken as the adhesion strength.

[0222] The evaluation criteria for the seal strength test are as follows. The results are shown in Table 1.

[0223] 〇: Metal layer peeling under tensile force above 4.0 N / cm.

[0224] △: Metal layer peeling under tensile force above 3.0 N / cm and below 4.0 N / cm.

[0225] ×: Metal layer peeling under tensile force below 3.0 N / cm.

[0226] As shown in Table 1, the electromagnetic wave shielding films of Examples 1 to 13, which contain an insulating layer between the isotropic conductive adhesive layer and the metal layer, and whose total thickness of the insulating layer and the metal layer is 0.5 μm or more and less than 20 μm, showed good performance in both the MIT test and the adhesion strength test.

[0227] On the other hand, it was determined that in the electromagnetic wave shielding films of Comparative Examples 1 to 3, where the total thickness of the insulating layer and the metal layer exceeded 20 μm, the MIT test was not good, and cracks easily entered the metal layer when repeatedly bent.

[0228] In addition, it was determined that in the electromagnetic wave shielding films of Comparative Examples 4 to 6, which do not have an insulating layer between the isotropic conductive adhesive layer and the metal layer, the adhesion strength test was not good and the metal layer was easy to peel off.

[0229] Explanation of reference numerals in the attached figures

[0230] 1. Shielded printed circuit boards, 1A, 1B, 1C, 1D

[0231] 10, 11, 12 Electromagnetic wave shielding films

[0232] 20 layers of isotropic conductive adhesive

[0233] 30 Insulation layer

[0234] 40 metal layers

[0235] 50 Peel off the film

[0236] 60 Printed Circuit Boards

[0237] 61 Basic Thin Films

[0238] 62 Printed Circuits

[0239] 62a Grounding circuit

[0240] 63 Covering layer

[0241] 63a Opening

[0242] 70, 71 Protective layers

[0243] 71a Opening

[0244] 80A, 80B, 80C grounding components

[0245] 81, 84 Conductive external connection components

[0246] 82 Conductive protrusions

[0247] 83 Conductive particles

[0248] 84a convex part

[0249] GND External Ground

Claims

1. An electromagnetic wave shielding film, characterized in that, Layered sequentially are: an isotropic conductive adhesive layer, Insulation layer, and Metal layer, The total thickness of the insulating layer and the metal layer is greater than 0.5 μm and less than 20 μm.

2. The electromagnetic wave shielding film according to claim 1, wherein, The thickness of the metal layer is 0.1–8 μm.

3. The electromagnetic wave shielding film according to claim 1 or 2, wherein, The thickness of the insulating layer is 0.5–10 μm.

4. The electromagnetic wave shielding film according to claim 1 or 2, wherein, The metal layer comprises at least one element selected from the group consisting of copper, silver, and aluminum.

5. The electromagnetic wave shielding film according to claim 1 or 2, wherein, Through holes are formed in the metal layer.

6. The electromagnetic wave shielding film according to claim 5, wherein, The average opening area of ​​one of the through holes is 10–80,000 μm. 2 .

7. The electromagnetic wave shielding film according to claim 5, wherein, The aperture ratio of the through hole is 0.05% to 30%.

8. A shielded printed circuit board, characterized in that, It features a printed circuit board and an electromagnetic wave shielding film. The printed circuit board is formed from a base film, a printed circuit containing a grounding circuit disposed on the base film, and a cover layer covering the printed circuit; and, The electromagnetic wave shielding film is sequentially stacked with an isotropic conductive adhesive layer, an insulating layer, and a metal layer. The total thickness of the insulating layer and the metal layer is greater than 0.5 μm and less than 20 μm. The electromagnetic wave shielding film is disposed on the printed circuit board in such a way that the isotropic conductive adhesive layer is in contact with the cover layer.

9. The shielded printed circuit board according to claim 8, wherein, An opening is formed in the covering layer to expose the grounding circuit. The isotropic conductive adhesive layer is filled in the opening in such a way that it contacts the grounding circuit.

10. The shielded printed circuit board according to claim 8 or 9, wherein, The metal layer is electrically connected to an external ground.

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