Electromagnetic wave shielding film

Abstract

Provided is an electromagnetic wave shielding film in which expansion of a conductive adhesive layer due to heating does not readily occur, and which has sufficiently high solder fluidity resistance. The electromagnetic wave shielding film according to the present invention is characterized in that a protective layer, a metal layer, and a conductive adhesive layer are laminated in this order, and the conductive adhesive layer contains an epoxy resin having a weight average molecular weight Mw of 50,000 or more, a curing agent having a carboxyl group, a nitrogen-containing organic filler, a phosphorus-containing liquid flame retardant, and a conductive filler.

Description

Technical Field

[0001] This invention relates to electromagnetic wave shielding films. Background Technology

[0002] For a long time, methods have been employed such as attaching electromagnetic wave shielding films to printed circuit boards (FPCs) to shield electromagnetic waves from the outside.

[0003] As an electromagnetic wave shielding film, a known electromagnetic wave shielding film is formed by sequentially stacking a protective layer, a metal layer, and an adhesive layer. This electromagnetic wave shielding film is then overlapped onto a printed circuit board and heated and pressed in this state. Thus, the electromagnetic wave shielding film is bonded to the printed circuit board via the adhesive layer, allowing the fabrication of a shielded printed circuit board. Subsequently, components are mounted onto the shielded printed circuit board using reflow soldering. Furthermore, the printed pattern on the base film of the printed circuit board is covered by an insulating film.

[0004] As such an electromagnetic wave shielding film, Patent Document 1 discloses an electromagnetic wave shielding film that sequentially stacks an insulating resin layer, a shielding layer, and a conductive adhesive layer. The aforementioned insulating resin layer and the aforementioned conductive adhesive layer contain flame retardants containing phosphorus or nitrogen, and contain a specified amount of flame retardant containing phosphorus and flame retardant containing nitrogen.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2022-21641 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] During the hot pressing and reflow soldering processes in the fabrication of shielded printed circuit boards, a problem arises where the conductive adhesive layer of the electromagnetic wave shielding film expands when heated. This is believed to be due to the expansion and evaporation of gases generated by the conductive adhesive layer itself and moisture absorbed by it due to heat.

[0010] In addition, in the electromagnetic wave shielding film described in Patent Document 1, a flame retardant containing solid phosphorus is added to the adhesive layer as a flame retardant in order to improve the heat resistance of the conductive adhesive layer.

[0011] However, this type of electromagnetic wave shielding film has the problem of insufficient solder flowability.

[0012] This invention was made to solve the above-mentioned problems. The purpose of this invention is to provide an electromagnetic wave shielding film that is not prone to expansion of the conductive adhesive layer caused by heating and has sufficient solder fluidity.

[0013] Solution for solving the problem

[0014] The inventors have discovered that by including a phosphorus-containing liquid flame retardant in a conductive adhesive layer, solder flowability is improved.

[0015] That is, the electromagnetic wave shielding film of the present invention is characterized in that it is sequentially stacked with a protective layer, a metal layer and a conductive adhesive layer, wherein the conductive adhesive layer comprises: an epoxy resin with a weight average molecular weight Mw of 50,000 or more, a curing agent having carboxyl groups, a nitrogen-containing organic filler, a phosphorus-containing liquid flame retardant, and a conductive filler.

[0016] The electromagnetic wave shielding film of the present invention contains epoxy resin with a weight-average molecular weight (Mw) of 50,000 or more and a phosphorus-containing liquid flame retardant, thus it is not prone to expansion of the conductive adhesive layer caused by heating and has sufficient solder fluidity.

[0017] If the weight-average molecular weight (Mw) of the epoxy resin contained in the conductive adhesive layer is less than 50,000, the conductive adhesive layer will expand due to heating, and the solder fluidity will decrease.

[0018] It should be noted that if the conductive adhesive layer does not contain a curing agent with carboxyl groups, the solder flowability will be reduced.

[0019] In addition, if the conductive adhesive layer does not contain nitrogen-containing organic fillers, the solder flowability will be reduced.

[0020] In the electromagnetic wave shielding film of the present invention, the epoxy equivalent of the epoxy resin is preferably 7000 to 10000 g / eq.

[0021] If the epoxy equivalent of the epoxy resin is within the above range, the expansion of the conductive adhesive layer caused by heating is less likely to occur, and the fluidity of the solder becomes sufficiently high.

[0022] In the electromagnetic wave shielding film of the present invention, the epoxy resin preferably comprises at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin and bisphenol A / bisphenol F copolymer epoxy resin.

[0023] In addition, the epoxy resin described above preferably comprises a polymer having polymer units represented by the following general formula (1).

[0024] In addition, the epoxy resin described above may contain polymers represented by the following general formula (2).

[0025]

[0026] (In equation (1), R) 1 and R 2They are hydrogen or methyl, respectively, R 1 and R 2 They can be the same or different.

[0027]

[0028] (In equation (2), R) 1 R 2 R 3 and R 4 They are hydrogen or methyl, respectively, R 1 R 2 R 3 and R 4 They can be the same or different.

[0029] In the electromagnetic wave shielding film of the present invention, if the epoxy resin is of the type described above, the expansion of the conductive adhesive layer caused by heating is less likely to occur, and the solder fluidity is sufficiently increased.

[0030] In the electromagnetic wave shielding film of the present invention, the content of the epoxy resin is preferably 20 to 50 wt%.

[0031] If the epoxy resin content is within the above range, the solder fluidity will be significantly improved.

[0032] In the electromagnetic wave shielding film of the present invention, the content of the above-mentioned liquid flame retardant is preferably 10 to 19 wt%.

[0033] If the content of liquid flame retardant is less than 10 wt%, the conductive adhesive layer will not be able to achieve sufficient flame retardancy.

[0034] If the content of liquid flame retardant exceeds 19 wt%, the relative weight proportions of epoxy resin and conductive filler will decrease, making it difficult for the conductive adhesive layer to achieve sufficient adhesion or conductivity.

[0035] The effects of the invention

[0036] According to the present invention, an electromagnetic wave shielding film can be provided that is not prone to expansion of the conductive adhesive layer due to heating and has sufficiently high solder flowability. Attached Figure Description

[0037] Figure 1 A cross-sectional view of an example of the electromagnetic wave shielding film of the present invention is shown for illustrative purposes.

[0038] Figure 2 A cross-sectional view of an example of a shielded printed circuit board of the present invention using the electromagnetic wave shielding film of the present invention is shown for illustrative purposes.

[0039] Figure 3This is a schematic diagram of the method for determining the resistance value of an electromagnetic wave shielding film in a heat resistance test. Detailed Implementation

[0040] 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.

[0041] Figure 1 A cross-sectional view of an example of the electromagnetic wave shielding film of the present invention is shown for illustrative purposes.

[0042] Figure 1 The electromagnetic wave shielding film 10 shown is formed by sequentially stacking a protective layer 40, a metal layer 30, and a conductive adhesive layer 20.

[0043] In the electromagnetic wave shielding film 10, the conductive adhesive layer 20 comprises: an epoxy resin with a weight-average molecular weight Mw of 50,000 or more, a curing agent with carboxyl groups, a nitrogen-containing organic filler, a phosphorus-containing liquid flame retardant, and a conductive filler.

[0044] As described below, the electromagnetic wave shielding film 10 is overlapped onto the printed circuit board and then heated and pressed in this state. Thus, the electromagnetic wave shielding film 10 is bonded to the printed circuit board via an adhesive layer, forming a shielded printed circuit board. Subsequently, components are mounted onto the shielded printed circuit board using reflow soldering.

[0045] Even under such heating, the electromagnetic wave shielding film 10 does not easily cause the conductive adhesive layer to expand, and the solder has sufficient fluidity.

[0046] The mechanism by which this effect is achieved is not yet fully understood, but it is believed that phosphorus-containing liquid flame retardants are important.

[0047] The preferred configurations of the electromagnetic wave shielding film 10 will be described in detail below.

[0048] (Epoxy resin contained in the conductive adhesive layer)

[0049] The conductive adhesive layer 20 contains epoxy resin with a weight-average molecular weight (Mw) of 50,000 or more.

[0050] The weight-average molecular weight (Mw) of the epoxy resin is preferably 50,000 to 80,000, more preferably 50,000 to 70,000. If the weight-average molecular weight (Mw) of the epoxy resin contained in the conductive adhesive layer is less than 50,000, the conductive adhesive layer will expand due to heating, and the solder fluidity will decrease.

[0051] In the electromagnetic wave shielding film of the present invention, the epoxy equivalent of the epoxy resin is preferably 7,000 to 10,000 g / eq, more preferably 7,500 to 10,000 g / eq.

[0052] If the epoxy equivalent of the epoxy resin is within the above range, the expansion of the conductive adhesive layer caused by heating is less likely to occur, and the fluidity of the solder becomes sufficiently high.

[0053] It should be noted that in this specification, the "epoxy equivalent of epoxy resin" can be determined according to JIS K7236:2001.

[0054] The epoxy resin preferably comprises at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol A / bisphenol F copolymer epoxy resin. Bisphenol A / bisphenol F copolymer epoxy resin is preferred.

[0055] In addition, the epoxy resin described above preferably comprises a polymer having polymer units represented by the following general formula (1).

[0056] In addition, the epoxy resin described above may contain polymers represented by the following general formula (2).

[0057]

[0058] (In equation (1), R) 1 and R 2 They are hydrogen or methyl, respectively, R 1 and R 2 They can be the same or different.

[0059]

[0060] (In equation (2), R) 1 R 2 R 3 and R 4 They are hydrogen or methyl, respectively, R 1 R 2 R 3 and R 4 They can be the same or different.

[0061] When the epoxy resin in the electromagnetic wave shielding film 10 is of the type described above, the expansion of the conductive adhesive layer caused by heating is less likely to occur, and the fluidity of the solder is sufficiently increased.

[0062] In the electromagnetic wave shielding film 10, the epoxy resin content in the conductive adhesive layer 20 is preferably 20-50 wt%, more preferably 27-42 wt%.

[0063] If the epoxy resin content is within the above range, the solder fluidity will be significantly improved.

[0064] (The curing agent contained in the conductive adhesive layer)

[0065] As a carboxyl-containing curing agent contained in the conductive adhesive layer 20, there are no particular limitations as long as it can cure the epoxy resin. Examples include carboxyl-containing polyester modified urethane and carboxyl-containing polyolefin.

[0066] By using such a curing agent, the expansion of the conductive adhesive layer caused by heating is less likely to occur, and the fluidity of the solder is greatly improved.

[0067] In the electromagnetic wave shielding film 10, the content of the carboxyl-containing curing agent in the conductive adhesive layer 20 is preferably 5 to 25 wt%, more preferably 7 to 24 wt%.

[0068] If the epoxy resin content is within the above range, the solder fluidity will be significantly improved.

[0069] In addition to a curing agent with carboxyl groups, the electromagnetic wave shielding film 10 may also contain polyfunctional glycidyl amine, phenolic varnish resin, etc., as a curing agent.

[0070] If such a curing agent is included, the solder's fluidity becomes even higher.

[0071] (Nitrogen-containing organic fillers contained in the conductive adhesive layer)

[0072] Examples of nitrogen-containing organic fillers included in the conductive adhesive layer 20 include melamine cyanurate and polyurethane.

[0073] If the conductive adhesive layer 20 contains such organic filler, the solder flowability is further improved.

[0074] The content of nitrogen-containing organic filler in the conductive adhesive layer 20 is preferably 15-35 wt%, more preferably 25-35 wt%.

[0075] (Phosphorus-containing liquid flame retardant contained in the conductive adhesive layer)

[0076] Phosphorus-containing liquid flame retardants included in the conductive adhesive layer 20 are preferably phosphate esters. Examples of phosphate esters include bisphenol A bis(diphenyl phosphate), resorcinol bis(diphenyl phosphate), and mixed esters of phosphoric acid with [1,1'-biphenyl]-4,4'-diol and phenol. phenol)(CAS No.: 1003300-73-9), triethyl phosphate, tributyl phosphate, tri(2-ethylhexyl) phosphate, tributoxyethyl phosphate, tri(isopropylphenyl) phosphate, tricresyl phosphate, tributoxyethyl phosphate, tri(xylyl) phosphate, tri(2-ethylhexyl) phosphate, tolyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, tolyl 2,6-xylyl phosphate, tri(chloropropyl) phosphate, tri(dichloropropyl) phosphate, resorcinol bis[di(xylyl) phosphate], tolyl diphenyl phosphate, diphenyl(2-ethylhexyl) phosphate, etc.

[0077] These flame retardants can impart flame retardancy to conductive adhesive layers and significantly improve solder flowability.

[0078] It should be noted that in this specification, "liquid flame retardant" refers to a flame retardant that is liquid at 23°C.

[0079] In the electromagnetic wave shielding film of the present invention, the content of the above-mentioned liquid flame retardant is preferably 10-19 wt%, more preferably 10-13 wt%.

[0080] If the content of liquid flame retardant is less than 10 wt%, the conductive adhesive layer will not be able to achieve sufficient flame retardancy.

[0081] If the content of liquid flame retardant exceeds 19 wt%, the relative weight proportions of epoxy resin and conductive filler will decrease, making it difficult for the conductive adhesive layer to achieve sufficient adhesion or conductivity.

[0082] (Conductive filler contained in the conductive adhesive layer)

[0083] The conductive filler contained in the conductive adhesive layer 20 is not particularly limited, and can include metal particles, carbon nanotubes, carbon fibers, metal fibers, etc.

[0084] When the conductive filler is a metal particle, there is no particular limitation on the metal particle, which can be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder made by covering copper powder with silver, particles made by covering polymer particles with metal, glass microspheres, etc.

[0085] From an economic point of view, copper powder or silver-coated copper powder that can be obtained cheaply is preferred.

[0086] When the conductive filler is metal microparticles, there are no particular limitations on the shape of the conductive filler, and it can be appropriately selected from spherical, flat, scaly, dendritic, rod-shaped, fibrous, etc.

[0087] The content of conductive filler in the conductive adhesive layer 20 is preferably 5 to 40 wt%, more preferably 5 to 30 wt%.

[0088] If the content of conductive filler is less than 5 wt%, it is difficult to obtain sufficient conductivity.

[0089] If the content of conductive filler exceeds 40 wt%, the conductive adhesive layer will harden and its flexibility will easily decrease.

[0090] (Metal layer)

[0091] The material constituting the metal layer 30 is not particularly limited, but preferably includes at least one metal selected from the group consisting of copper, silver, gold, aluminum, nickel, tin, palladium, chromium, titanium, and zinc. Alternatively, the metal layer may comprise an alloy of at least two metals selected from the group consisting of these metals.

[0092] Metal foils made of these metals can effectively shield electromagnetic waves.

[0093] The metal layer 30 can be a rolled metal foil, a metal plating, or a metal vapor deposition layer.

[0094] The thickness of the metal layer 30 is preferably 0.1 to 10 μm, more preferably 0.5 to 6 μm.

[0095] If the thickness of the metal layer is less than 0.1 μm, the metal layer is too thin, thus its strength is reduced. Consequently, its bending resistance decreases. Furthermore, it becomes difficult to adequately reflect and absorb electromagnetic waves, thus easily reducing its electromagnetic wave shielding properties.

[0096] If the thickness of the metal layer exceeds 10 μm, the flexibility tends to decrease. In addition, the overall thickness of the electromagnetic wave shielding film becomes more difficult to handle.

[0097] (protective layer)

[0098] The material of the protective layer 40 is not particularly limited, but it is preferably composed of a thermoplastic resin composition, a thermosetting resin composition, an active energy radiation curable composition, etc.

[0099] The thermoplastic resin composition described above 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, imide-based resin compositions, and acrylic-based resin compositions.

[0100] The thermosetting resin composition described above is not particularly limited, and may include at least one resin composition selected from the group consisting of epoxy resin compositions, urethane resin compositions, urethane urea resin compositions, styrene resin compositions, phenolic resin compositions, melamine resin compositions, acrylic resin compositions, and alkyd resin compositions.

[0101] The above-mentioned active energy ray curable composition is not particularly limited, and examples include polymeric compounds having at least two (meth)acryloyloxy groups in the molecule.

[0102] The protective layer 40 can be made of a single material or of two or more materials.

[0103] The protective layer 40 may contain curing accelerators, tackifiers, antioxidants, pigments, dyes, plasticizers, ultraviolet absorbers, defoamers, leveling agents, fillers, flame retardants, viscosity modifiers, anti-blocking agents, etc., as needed.

[0104] The thickness of the protective layer 40 is not particularly limited and can be set appropriately as needed, preferably 1 to 15 μm, more preferably 3 to 10 μm.

[0105] If the thickness of the protective layer is less than 1 μm, it becomes too thin to adequately protect the metal layer and the conductive adhesive layer.

[0106] If the thickness of the protective layer exceeds 15μm, it becomes too thick and difficult to bend; furthermore, the protective layer itself becomes easily damaged. Therefore, it becomes unsuitable for components requiring bending resistance.

[0107] Next, a shielded printed circuit board using the electromagnetic wave shielding film of the present invention will be described.

[0108] Figure 2 A cross-sectional view of an example of a shielded printed circuit board using the electromagnetic wave shielding film of the present invention is shown for illustrative purposes.

[0109] Figure 2 The shielded printed circuit board 1 shown consists of a printed circuit board 50 and an electromagnetic wave shielding film 10.

[0110] The printed circuit board 50 includes: a base film 51, a printed circuit 52 disposed on the base film 51, and a cover layer 53 disposed to cover the printed circuit 52.

[0111] In the printed circuit board 50, the printed circuit 52 includes a ground circuit 52a, and an opening 53a is formed on the cover layer 53 to expose the ground circuit 52a.

[0112] In the shielded printed circuit board 1, an electromagnetic wave shielding film 10 is disposed on the printed circuit board 50 in such a way that the cover layer 53 is in contact with the conductive adhesive layer 20.

[0113] In the shielded printed circuit board 1, the conductive adhesive layer 20 fills the opening 53a of the cover layer 53 and contacts the grounding circuit 52a. By adopting this configuration, the shielding characteristics of the electromagnetic wave shielding film 10 can be improved.

[0114] Furthermore, it is preferable that both the base film 51 and the cover layer 53 are made of engineering plastics. Examples of such resins include polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide amide, polyetherimide, and polyphenylene sulfide (PPS).

[0115] The printed circuit 52 can use common circuit materials such as copper.

[0116] The base film 51 and the printed circuit 52 can be bonded with an adhesive, or they can be bonded together in the same way as a so-called adhesive-free copper-clad laminate without using an adhesive. In addition, the cover layer 53 can be formed by laminating multiple flexible insulating films with an adhesive, or it can be formed by a series of methods such as coating, drying, exposure, development, and heat treatment of photosensitive insulating resin.

[0117] The following information is described in this manual.

[0118] This disclosure (1) is an electromagnetic wave shielding film, characterized in that a protective layer, a metal layer and a conductive adhesive layer are sequentially stacked, wherein the conductive adhesive layer comprises: an epoxy resin with a weight average molecular weight Mw of 50,000 or more, a curing agent having carboxyl groups, a nitrogen-containing organic filler, a phosphorus-containing liquid flame retardant, and a conductive filler.

[0119] This disclosure (2) is the electromagnetic wave shielding film described in this disclosure (1), wherein the epoxy equivalent of the epoxy resin is 7000 to 10000 g / eq.

[0120] This disclosure (3) is the electromagnetic wave shielding film described in disclosure (1) or (2), wherein the epoxy resin comprises at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin and bisphenol A / bisphenol F copolymer epoxy resin.

[0121] This disclosure (4) is an electromagnetic wave shielding film as described in any one of disclosures (1) to (3), wherein the epoxy resin comprises a polymer having polymer units represented by the following general formula (1).

[0122]

[0123] (In equation (1), R) 1 and R 2 They are hydrogen or methyl, respectively, R 1 and R 2 They can be the same or different.

[0124] This disclosure (5) is an electromagnetic wave shielding film as described in any one of disclosures (1) to (4), wherein the epoxy resin comprises a polymer represented by the following general formula (2).

[0125]

[0126] (In equation (2), R) 1 R 2 R 3 and R 4 They are hydrogen or methyl, respectively, R 1 R 2 R 3 and R 4 They can be the same or different.

[0127] This disclosure (6) is the electromagnetic wave shielding film of any one of disclosures (1) to (5), wherein the content of the epoxy resin is 20 to 50 wt%.

[0128] This disclosure (7) is the electromagnetic wave shielding film described in any one of disclosures (1) to (6), wherein the content of the liquid flame retardant is 10 to 19 wt%.

[0129] Example

[0130] The following describes embodiments of the invention in more detail, but the invention is not limited to these embodiments.

[0131] Examples 1 through 7 and Comparative Examples 1 through 6

[0132] Mix the materials shown in Table 1 to prepare a conductive adhesive composition.

[0133] It should be noted that the numbers in Table 1 are in "wt%".

[0134] The materials in Table 1 are as follows.

[0135] Epoxy Resin 1: Bisphenol A / Bisphenol F copolymer epoxy resin, weight average molecular weight Mw: 60000, epoxy equivalent: 8800 g / eq

[0136] Epoxy Resin 2: Bisphenol A type epoxy resin, weight average molecular weight Mw: 470, epoxy equivalent: 250 g / eq

[0137] Epoxy Resin 3: Bisphenol A type epoxy resin, weight average molecular weight Mw: 45000, epoxy equivalent: 7300 g / eq

[0138] Epoxy Resin 4: Epoxy resin, weight-average molecular weight Mw: 35000, epoxy equivalent: 12500 g / eq

[0139] Curing agent 1: Polyester-modified urethane with carboxyl groups, acid value: 20 mg KOH / g

[0140] Curing agent 2: Multifunctional glycidyl amine, epoxy equivalent 100g / eq

[0141] Hardener 3: Imidazole (curing initiation temperature 90℃)

[0142] Hardener 4: Imidazole (curing initiation temperature 130℃)

[0143] Nitrogen-containing organic fillers: melamine cyanurate

[0144] Liquid flame retardants containing phosphorus: Phosphate esters (Bisphenol A bis(diphenyl phosphate))

[0145] Conductive filler: 7% silver-plated atomized copper powder

[0146] [Table 1]

[0147]

[0148] Prepare a protective layer made of epoxy resin with a thickness of 5μm.

[0149] Next, electroplating is performed to form a copper layer with a thickness of 2.0 μm on the protective layer.

[0150] Then, the prepared conductive adhesive compositions are coated onto the copper layer to a thickness of 20 μm to manufacture the electromagnetic wave shielding films.

[0151] Solder flow test

[0152] After baking the copper-clad laminate (polyimide film substrate / adhesive layer / copper foil or electroless gold-plated copper foil) at 135°C for 60 minutes, the electromagnetic wave shielding films of each embodiment and each comparative example were hot-pressed onto the polyimide film substrate side of the copper-clad laminate at 170°C, 3MPa for 30 minutes to produce a test laminate.

[0153] Next, the experimental laminate was baked at 135°C for 60 minutes.

[0154] Next, the test laminate was passed twice through an atmospheric reflow oven at a maximum set temperature of 267°C.

[0155] Next, for the test laminates, test laminates in their initial state and test laminates placed in a constant temperature and humidity bath and left to stand for a specified time (24 hours, 48 ​​hours, 72 hours) at 30°C and 60%Rh.

[0156] Next, the experimental laminate was floated in a solder bath (temperature: 288°C) with the electromagnetic wave shielding film side facing upwards. The floating conditions in the solder bath were 10 seconds × 3 times.

[0157] Then, the test laminate was removed from the solder bath and observed from the electromagnetic wave shielding film side to observe whether the electromagnetic wave shielding film expanded and to evaluate the solder flowability.

[0158] The evaluation criteria are shown below. The results are presented in Table 1.

[0159] A: Even after being left to stand in a constant temperature and humidity bath for 72 hours, no expansion of the electromagnetic wave shielding film was observed.

[0160] B: The expansion of the electromagnetic wave shielding film was observed after standing in a constant temperature and humidity bath for 48 hours.

[0161] C: The expansion of the electromagnetic wave shielding film was observed when the film was left to stand in a constant temperature and humidity bath for 24 hours.

[0162] D: The expansion of the electromagnetic wave shielding film was observed in the initial state.

[0163] [Heat Resistance Test]

[0164] Figure 3 This is a schematic diagram of the method for determining the resistance value of an electromagnetic wave shielding film in a heat resistance test.

[0165] Figure 3 The electromagnetic wave shielding film 110 in the figure schematically illustrates the electromagnetic wave shielding films of various embodiments and comparative examples.

[0166] The electromagnetic wave shielding film 110 is formed by sequentially stacking a protective layer 140, a metal layer 130, and a conductive adhesive layer 120.

[0167] In addition, in the heat resistance test, a model substrate 150 is prepared, which includes: a base film 151, a plurality of measurement printed circuits 152 formed on the base film 151, and a cover layer 153 covering the measurement printed circuits 152, wherein an opening 153a is formed on the cover layer 153 to expose the measurement printed circuits 152.

[0168] It should be noted that the opening 153a is a circle with a diameter of 1 mm.

[0169] In heat resistance tests, such as Figure 3 As shown, the electromagnetic wave shielding film 110 is disposed on the model substrate 150 in such a way that the conductive adhesive layer 120 of the electromagnetic wave shielding film 110 contacts the printed circuit 152 for measurement. After being pressurized / heated at 170°C, 3MPa for 3 minutes, it is cured at 150°C for 1 hour (after cure), thereby attaching the electromagnetic wave shielding film 110 to the model substrate 150.

[0170] The resistance between the measuring printed circuit 152 of the model substrate 150, to which the electromagnetic wave shielding film 110 is adhered, was measured using a ohmmeter 160 after being left to stand at 60°C for 3 days. This resistance value was taken as the "initial resistance value". The results are shown in Table 1.

[0171] The reflow solderability of a model substrate 150 with an electromagnetic wave shielding film 110 adhered to it after being left to stand at 60°C for 3 days was evaluated. As a reflow soldering condition, lead-free solder was assumed, and a temperature profile was set for exposing the shielding film in the shielded printed circuit board to 265°C for 10 seconds. The resistance between the printed circuit boards 152 was measured using a ohmmeter 160 after a total of 5 reflow soldering cycles under these conditions. This resistance value was taken as the "resistance value after 5 reflow soldering cycles".

[0172] It should be noted that this heating cycle simulates the reflow soldering process of mounting electronic components after the electromagnetic wave shielding film is attached to the printed circuit board. The results are shown in Table 1.

[0173] In addition, the electromagnetic wave shielding films were observed after a total of 5 reflow soldering processes to confirm whether the electromagnetic wave shielding film disposed at the opening 153a had expanded. The results are shown in Table 1.

[0174] [Adhesion Test]

[0175] Under conditions of 2 MPa, 170°C, 10 sec, and 180 sec, the electromagnetic wave shielding films of each embodiment and each comparative example were pressed onto the polyimide film substrate side of a copper-clad laminate (polyimide film substrate / adhesive layer / chemically gold-plated copper foil). Next, each electromagnetic wave shielding film adhered to the copper-clad laminate was hot-pressed onto the bonding film side of a reinforcing film (a film on which a bonding film is laminated on a polyimide film substrate) at 3 MPa, 170°C, and 3 minutes to create a laminate. Then, these laminates were heated at 150°C for 60 minutes for post-curing. Next, the reinforcing film of these laminates was adhered to a fixing plate using double-sided tape to prepare sample laminates.

[0176] Then, with the sample laminate fixed, the copper-clad laminate was stretched at a stretching speed of 50 mm / min and a stretching angle of 180°, thereby peeling off the copper-clad laminate and each electromagnetic wave shielding film, and the average peel force was measured. Five evaluation tests were conducted. The results are shown in Table 1.

[0177] As shown in Table 1, the electromagnetic wave shielding films of each embodiment are not prone to expansion of the conductive adhesive layer due to heating, and have sufficiently high solder fluidity.

[0178] Explanation of reference numerals in the attached figures

[0179] 1. Shielded Printed Circuit Board

[0180] 10, 110 Electromagnetic wave shielding film

[0181] 20, 120 conductive adhesive layers

[0182] 30, 130 metal layers

[0183] 40, 140 protective layers

[0184] 50 Printed Circuit Boards

[0185] 51, 151 base film

[0186] 52. Printed Circuit Boards

[0187] 52a Grounding circuit

[0188] 53, 153 Covering Layer

[0189] 53a, 153a opening

[0190] 150 model base plate

[0191] 152 Printed Circuit for Measurement

[0192] 160 ohmmeter.

Claims

1. An electromagnetic wave shielding film, characterized in that, It consists of a protective layer, a metal layer, and a conductive adhesive layer, layered sequentially. The conductive adhesive layer comprises: Epoxy resins with a weight-average molecular weight (Mw) of 50,000 or higher Curing agents with carboxyl groups Nitrogen-containing organic fillers Liquid flame retardants containing phosphorus, and Conductive filler.

2. The electromagnetic wave shielding film according to claim 1, wherein, The epoxy equivalent of the epoxy resin is 7000-10000 g / eq.

3. The electromagnetic wave shielding film according to claim 1 or 2, wherein, The epoxy resin comprises at least one selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol A / bisphenol F copolymer epoxy resin.

4. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein, The epoxy resin comprises a polymer having polymer units represented by the following general formula (1), In equation (1), R 1 and R 2 They are hydrogen or methyl, respectively, R 1 and R 2 They can be the same or different.

5. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein, The epoxy resin comprises a polymer represented by the following general formula (2). In equation (2), R 1 R 2 R 3 and R 4 They are hydrogen or methyl, respectively, R 1 R 2 R 3 and R 4 They can be the same or different.

6. The electromagnetic wave shielding film according to any one of claims 1 to 5, wherein, The epoxy resin content is 20-50 wt%.

7. The electromagnetic wave shielding film according to any one of claims 1 to 6, wherein, The content of the liquid flame retardant is 10-19 wt%.

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