JP5861790B1 - Electromagnetic shielding sheet, electromagnetic shielding wiring circuit board, and electronic equipment - Google Patents

Abstract

Provided is an electromagnetic wave shielding sheet that is excellent in bondability with a part and can maintain good transmission characteristics even when used for a part for high frequency applications while ensuring shielding properties such as electromagnetic waves. An electromagnetic wave shielding sheet according to the present invention includes a laminate that shields at least a part of a component, and includes an adhesive layer, a conductive layer, an insulating layer, and a bonding layer that are bonded to the component by performing a bonding process. Is provided. The adhesive layer 1 includes, as a binder component, at least one of (I) a thermoplastic resin (A) and (II) a thermosetting resin (B) and a curable compound (C) for the thermosetting resin (B). In addition, the film after the thermocompression treatment of the binder component satisfies the following (i) and (ii) at a frequency of 1 GHz and 23 ° C. (I) The relative dielectric constant is in the range of 1 to 3, and (ii) the dielectric loss tangent is 0.0001 to 0.02. [Selection] Figure 3

Description

  The present invention relates to an electromagnetic wave shielding sheet suitable for joining to a part of a component that emits electromagnetic waves. The present invention also relates to an electromagnetic wave shielding wiring circuit board and an electronic device using the above-described electromagnetic wave shielding sheet.

  Various electronic devices such as portable terminals, PCs, servers, and the like incorporate a substrate such as a printed wiring board. These substrates are provided with an electromagnetic wave shield structure in order to prevent malfunction due to an external magnetic field or radio wave and to reduce unnecessary radiation from an electric signal (Patent Document 1).

  In Patent Document 1, production of a shield film, a shield printed wiring board, and a shield film that shields well an electric field wave, a magnetic field wave, and an electromagnetic wave traveling from one side of the shield film to the other side, and has good transmission characteristics. In order to provide a method, the following configuration is disclosed. That is, a shield film comprising a conductive layer having a layer thickness of 0.5 to 12 μm and an anisotropic conductive adhesive layer in a laminated state is disclosed. And it is described by the said structure that the electric field wave, magnetic field wave, and electromagnetic wave which advance from the one surface side of a shield film to the other surface side can be shielded favorably.

International Publication No. 2013/077108

  By the way, signal transmission speeds have increased dramatically due to recent progress in high-speed data communication technology. In order to perform high-speed transmission, characteristic impedance matching of the transmission path is important. This is because, if the incident wave is reflected and the signal wave is attenuated at the mismatch point between the output impedance of the sending circuit and the input impedance of the receiving circuit in the signal transmission path, distortion occurs and the characteristics deteriorate. . The phenomenon of reflection becomes particularly prominent when high-frequency or high-speed pulse signals are transmitted.

  FIG. 1 shows a schematic cross-sectional view of a shielding wiring board in which an electromagnetic wave shielding sheet is attached to a printed wiring board. When the electromagnetic shielding sheet 10 is pasted, as shown in the figure, a capacitor component is added between, for example, the wiring 25 of the printed wiring board 20 and the conductive layer 2 of the electromagnetic shielding sheet 10, and the characteristic impedance changes. There is also a problem that transmission characteristics deteriorate. That is, there is a problem that the electromagnetic wave shielding sheet 10 affects the electrical characteristics of the printed wiring board to be shielded. Particularly in the case of high-frequency signals, since signal reflection is likely to occur at impedance mismatch points and noise is easily generated, the problem of characteristic deterioration is serious.

  If the transmission characteristics can be improved while ensuring the electromagnetic shielding properties, further improvement in performance can be expected. It is also possible to increase the design margin of the internal electronic circuit and the like. With the recent increase in signal speed and frequency, the improvement of transmission characteristics has become important for maintaining and improving performance characteristics.

  In the above description, the printed wiring board has been described as an example. However, a similar problem exists in a board having wiring and electronic circuits.

  The present invention has been made in view of the above-mentioned background, and the object thereof is excellent in bondability with components, even when used for components for high frequency applications while ensuring shielding properties such as electromagnetic waves. An electromagnetic wave shielding sheet capable of maintaining good transmission characteristics is provided.

  As a result of extensive studies by the present inventors to solve the above-mentioned problems, the present inventors have found that the problems of the present invention can be solved in the following modes, and have completed the present invention.

An electromagnetic wave shielding sheet according to the present invention is an electromagnetic wave shielding sheet made of a laminate that shields at least a part of a component that emits electromagnetic waves, and the laminate is disposed on the component to perform a bonding process. Thus, an adhesive layer bonded to the component, a conductive layer laminated on the adhesive layer, and an insulating layer formed on the conductive layer are provided. And the said adhesive layer is as a binder component,
(I) a thermoplastic resin (A), and (II) a thermosetting resin (B) and a curable compound (C) for the thermosetting resin (B),
Including at least one of
The coating (X) after the thermocompression treatment of the binder component satisfies the following (i) and (ii).
(I) The relative dielectric constant is 1 to 3 at a frequency of 1 GHz and 23 ° C.
(Ii) The dielectric loss tangent is 0.0001 to 0.02 at a frequency of 1 GHz and 23 ° C.

  The electromagnetic wave shielding wired circuit board according to the present invention is obtained by bonding the electromagnetic wave shielding sheet of the above aspect on a wired circuit board.

  The electronic apparatus according to the present invention is obtained by bonding the electromagnetic wave shielding sheet of the above aspect.

  According to the present invention, it is possible to provide an electromagnetic wave shielding sheet that is excellent in bondability with components and can maintain good transmission characteristics even when used for components for high frequency applications while securing shielding properties such as electromagnetic waves. Excellent effect.

It is typical sectional drawing for demonstrating the capacitor component of the shielding wiring board which concerns on a prior art example. It is a typical cut section sectional view showing an example of an electromagnetic wave shield sheet concerning this embodiment. It is a typical cut section sectional view showing an example of an electromagnetic wave shielding wiring circuit board concerning this embodiment. It is a typical cut section sectional view showing an example of an electromagnetic wave shielding wiring circuit board concerning the 1st modification. It is a typical cut section sectional view showing an example of an electromagnetic wave shielding wiring circuit board concerning the 2nd modification. It is a typical cut section sectional view showing an example of an electromagnetic wave shielding wiring circuit board concerning the 3rd modification. It is a typical cut section sectional view showing an example of an electromagnetic wave shielding wiring circuit board concerning the 4th modification. It is a typical top view of the principal surface side of the printed wiring board concerning an Example and a comparative example. It is a typical top view of the back surface side of the printed wiring board which concerns on an Example and a comparative example. It is a typical top view of a printed wiring board with an electromagnetic wave shield sheet concerning an example and a comparative example. It is XI-XI cutting | disconnection part sectional drawing of FIG. It is XII-XII cutting part sectional drawing of FIG.

  Hereinafter, an example of an embodiment to which the present invention is applied will be described. In addition, the size and ratio of each member in the following drawings are for convenience of explanation, and are not limited to this. In the present specification, the description “any number A to any number B” includes the number A as a lower limit and the number B as an upper limit in the range. The “sheet” in this specification includes not only “sheet” defined in JIS but also “film”. Moreover, the numerical value specified in this specification is a value calculated | required by the method disclosed by embodiment or an Example.

  As shown in FIG. 2, the electromagnetic wave shielding sheet 10 according to the present invention includes a laminate in which an adhesive layer 1, a conductive layer 2, and an insulating layer 3 are laminated at least in this order. The electromagnetic wave shielding sheet 10 can be bonded to the component by arranging the adhesive layer 1 on the component (not shown) and performing a bonding process. The joining process is not limited as long as it can be joined, but heat treatment or thermocompression treatment is suitable. The insulating layer 3 plays a role of protecting the electromagnetic wave shielding sheet 10 and is arranged on the surface layer side from the conductive layer 2. The conductive layer 2 is a layer sandwiched between the insulating layer 3 and the adhesive layer 1 and mainly serves to shield electromagnetic waves. The printed wiring board plays a role of shielding electromagnetic noise generated from signal wiring or the like inside the component or shielding signals from the outside.

  The electromagnetic wave shielding sheet 10 may further include other layers. For example, the surface layer of the insulating layer 3 is cut with a magnetic field between another layer such as a scratch resistance, water vapor barrier property, oxygen barrier property film, or between the adhesive layer 1 and the conductive layer 2 and / or the conductive layer 2 and the insulating layer 3. A film to be reinforced may be laminated.

  The electromagnetic wave shielding sheet of the present invention is suitable for preventing radiation electromagnetic waves of components emitting electromagnetic waves (electric field waves and magnetic field waves) and preventing malfunctions due to external magnetic fields and radio waves. Examples of components include a hard disk, a cable, a printed wiring board, and the like built in a personal computer, a mobile device, a digital camera, or the like. It is also suitable for card readers and the like. Hereinafter, each layer will be described in detail.

[Conductive Layer] The conductive layer 2 is not particularly limited as long as it is a layer exhibiting conductivity in the layer, and examples thereof include a layer in which a conductive filler is contained in a metal layer and a binder resin. A well-known method can be used for the manufacturing method of a conductive layer. The method for producing the metal layer can be formed by vacuum deposition, sputtering, CVD, MO (metal organic), plating, etc., in addition to a method using a metal foil. Among these, vacuum deposition or plating is preferable in view of mass productivity. The manufacturing method of the layer in which the conductive filler is contained in the binder resin can be obtained, for example, by coating and drying a resin composition containing the conductive filler on the insulating film. The conductive layer 2 may be a single layer, or may be a stack of multiple layers of the same or different types.

  Suitable examples of the metal foil include aluminum, copper, silver, and gold. Copper, silver, and aluminum are more preferable, and copper is more preferable in terms of shielding properties, connection reliability, and cost. For example, it is preferable to use rolled copper foil or electrolytic copper foil, and copper is more preferable because the conductive layer can be made thinner. The metal foil may be formed by plating. The lower limit of the thickness of the metal foil is preferably 0.1 μm or more, and more preferably 0.5 μm or more. On the other hand, the upper limit of the thickness of the metal foil is preferably 10 μm or less, and more preferably 5 μm or less.

  Suitable examples of the metal layer obtained by vacuum deposition include aluminum, copper, silver, and gold. Of these, copper and silver are more preferable. Moreover, aluminum, copper, silver, chromium, gold, iron, palladium, nickel, platinum, silver, zinc, indium oxide, and antimony dope tin oxide can be illustrated as a suitable example of the metal layer obtained by sputtering. Of these, copper and silver are more preferable. The lower limit of the thickness of the metal layer obtained by vacuum deposition and sputtering is preferably 0.005 μm or more, more preferably 0.1 μm or more, and the upper limit is preferably 3 μm or less.

[Insulating layer] The insulating layer is an insulating sheet obtained by molding an insulating resin composition, and plays a role of protecting the conductive layer and ensuring insulation of the surface layer. The insulating resin composition is preferably a thermoplastic resin or a thermosetting resin. Although it does not specifically limit as a thermoplastic resin and a thermosetting resin, Resin which can be illustrated by the contact bonding layer mentioned later can be used suitably. Moreover, resin films, such as polyester, a polycarbonate, a polyimide, polyphenylene sulfide, can be used for an insulating layer.

  Insulating resin compositions include silane coupling agents, antioxidants, pigments, dyes, tackifying resins, plasticizers, UV absorbers, antifoaming agents, leveling regulators, fillers, flame retardants, etc. in addition to resins. Can be blended.

  The thickness of the insulating layer may vary depending on the application, but is preferably 2 to 10 μm. By setting the thickness, it becomes easy to balance various properties of the electromagnetic wave shielding sheet.

[Adhesive layer] The adhesive layer 1 is
(I) includes at least one of thermoplastic resin (A), and (II) thermosetting resin (B) and curable compound (C) for thermosetting resin (B), and (I), ( II) or a film (X) after thermocompression bonding of a mixture of (I) and (II) is used that satisfies the following (i) and (ii).
(I) The relative dielectric constant is 1 to 3 at a frequency of 1 GHz and 23 ° C.
(Ii) The dielectric loss tangent is 0.0001 to 0.02 at a frequency of 1 GHz and 23 ° C.
The thermosetting resin (B) includes all resins that contain at least part of the site that undergoes a curing reaction with the curable compound (C).

  In addition, the relative dielectric constant and dielectric loss tangent of this specification say the value calculated | required with the following method. That is, (I), (II) or a mixture of (I) and (II) is applied onto the peeled polyester film, and uniformly applied so that the film thickness after drying becomes 70 μm. Dry to obtain a coating film. And the obtained coating film was laminated | stacked and vacuum-laminated, and it heat-cured on 180 degreeC and 2.0 MPa conditions for 1 hour. Subsequently, the peeling film on both sides was peeled off to produce a test piece for evaluation. About this test piece, the relative dielectric constant and dielectric loss tangent in 23 degreeC of measurement temperature and the measurement frequency of 1 GHz were calculated | required using the relative dielectric constant measuring apparatus (cavity resonator type ADMS01Oc) by an EA company.

  The lower limit of the relative dielectric constant is more preferably 1 or more, further preferably 2 or more, and the upper limit is more preferably 3 or less, still more preferably 2.8 or less. The dielectric loss tangent is preferably 0 but technically difficult. From this viewpoint, the lower limit of the dielectric loss tangent is preferably 0.0001 or more. On the other hand, the upper limit is more preferably 0.02 or less, and still more preferably 0.01 or less.

  As will be described later, in the adhesive layer in the present invention, the binder component can contain a conductive filler. When the conductive filler is contained, the values of the dielectric constant and the dielectric loss tangent are larger than those before the conductive filler is contained. However, when the present inventors have repeatedly studied, (I), (II ) Or the coating (X) after thermocompression bonding of the mixture of (I) and (II) is surprising even when a conductive filler is added by satisfying the above (i) and (ii) It has been found that the problems of the present invention can be solved. This is because, by controlling the dielectric properties of the adhesive layer (I), (II) or a mixture of (I) and (II), the conductive layer to which the conductive filler is added has the effect of enhancing the shielding property, and the binder. It is considered that the problem of the present invention was solved by a synergistic effect with the low dielectric effect of the resin.

  In the case of an adhesive layer containing a conductive filler, that is, an adhesive layer exhibiting anisotropic conductivity, the lower limit of the relative dielectric constant after mixing the conductive filler in the adhesive layer is more preferably 1 or more, and 2 or more. More preferably, the upper limit is more preferably 10 or less, and even more preferably 9 or less. Further, the dielectric loss tangent after the conductive filler is mixed in the adhesive layer is preferably 0 but technically difficult. From this viewpoint, the lower limit of the dielectric loss tangent is preferably 0.0001 or more. On the other hand, the upper limit is more preferably 0.05 or less, and still more preferably 0.03 or less.

  When the electromagnetic wave shielding sheet is used for a flexible printed wiring board, the thickness of the adhesive layer 1 is preferably 50 μm or less and more preferably 20 μm or less from the viewpoint of ensuring flexibility. Moreover, from a viewpoint of ensuring adhesive force, it is preferable to set it as 3 micrometers or more, and it is more preferable to set it as 6 micrometers or more.

  The curable compound (C) is preferably 0.2 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the thermosetting resin (B), and 3 parts by mass or more. More preferably. Moreover, it is preferable that it is 50 mass parts or less, It is more preferable that it is 30 mass parts or less, It is still more preferable that it is 20 mass parts or less. By setting the curable compound (C) in the range of 0.2 to 50 parts by mass, the crosslinking density can be made appropriate, and the hygroscopicity and adhesiveness can be kept good. Moreover, the elasticity modulus of hardened | cured material can be kept appropriate and folding resistance can be made favorable.

  When joining an electromagnetic wave shielding sheet with components, such as a printed wiring board, it is calculated | required that it is a laminated body which can endure heating, such as a solder reflow furnace. From this viewpoint, the 5% weight pyrolysis temperature of the adhesive layer 1 is preferably 240 ° C. or higher, more preferably 260 ° C. or higher, and still more preferably 280 ° C. or higher.

  As the thermoplastic resin (A), polyamide resin, liquid crystal polymer resin, methacrylic resin, acrylic resin, polystyrene, polyester, polyurethane, polycarbonate, butadiene rubber, ester amide, isoprene rubber, cellulose, phenoxy resin, polyvinyl acetal resin, polyimide resin And polyamideimide resin. A thermoplastic resin (A) can be used individually by 1 type or in combination of multiple types.

  Thermosetting resin (B) includes acrylic resin, polyurethane resin, polyurethane urea resin, polyester resin, polyamide resin, polyamideimide resin, polyimide resin, polycarbonate resin, alicyclic olefin resin, polyphenylene ether resin, epoxy resin, phenoxy resin , Maleimide resin, polyimide benzoxazole resin, polybenzoxazole resin, polyesteramide resin, polyesterimide resin, vinyl ester resin, polyacetal resin, polyetherketone resin, polyetheretherketone resin, polyfumarate resin, benzoxazine resin, carbodiimide resin, Fluorine resin, polyolefin resin, and silicon resin can be exemplified. A thermosetting resin (B) can be used individually by 1 type or in combination of multiple types.

  The curable compound (C) refers to all compounds that can contribute to curing with respect to the curable resin (B). Although the reaction site of the thermosetting resin (B) with the curable compound (C) is not limited, for example, carboxyl group, phenolic hydroxyl group, (meth) acrylic group, epoxy group, oxetanyl group, amino group, hydroxyl group, mercapto Group, cyano group, isocyanate group, allyl group, vinyl group and the like. From the viewpoint of satisfactorily exhibiting adhesiveness with the conductive layer 2 and from the viewpoint of developing adhesiveness with a component, for example, a coverlay film (for example, polyimide resin) of a printed wiring board, at least one hydroxyl group and carboxyl group are present. A seed-containing curable resin (B) is preferred. The kind of the curable functional group in the curable resin (B) can be one or more.

  The curable compound (C) is not particularly limited as long as it has two or more sites capable of reacting with the functional group of the thermosetting resin (B). Suitable curable compounds (C) include epoxy compounds, organometallic compounds (metal chelate compounds), acid anhydride group-containing compounds, isocyanate compounds, aziridine compounds, amine compounds, polyol compounds, melamine compounds, silane compounds, carbodiimide compounds. Examples thereof include compounds, phenol compounds, benzoxazine compounds, maleimide compounds, β-hydroxyalkylamide group-containing compounds. Among these, an epoxy compound, an organometallic compound, an aziridine compound, and an isocyanate compound are preferable from the viewpoint of achieving both adhesiveness and heat resistance. A curable compound (C) can be used individually by 1 type or in combination of multiple types.

  When the curable functional group of the thermosetting resin (B) is a hydroxyl group, the curable compound (C) is preferably an isocyanate compound, an epoxy compound, an aziridine compound, a carbodiimide compound, or an organometallic compound (metal chelate compound). When the curable functional group (B) is an amino group, the curable compound (C) is preferably an isocyanate compound, an epoxy compound, an aziridine compound, a carbodiimide compound, or an organometallic compound. Furthermore, when the curable functional group of the curable resin (B) is a carboxyl group, the curable compound (C) is preferably an epoxy compound or an organometallic compound.

  Among these, the adhesive layer includes, in particular, the thermosetting resin (B) containing a carboxyl group-containing resin, the curable compound (C), an epoxy compound, and at least one of an organometallic compound and an isocyanate compound. The inclusion is preferred. The epoxy compound is preferably blended with an epoxy equivalent of 0.5 to 10 times, more preferably 1 to 5 times, with respect to 1 equivalent of carboxylic acid. The total curing agent equivalent of the organometallic compound and the isocyanic compound is preferably 0.1 to 5 times, more preferably 0.5 to 3 times the equivalent of 1 equivalent of carboxylic acid. Since the number of unreacted functional groups after thermosetting can be suppressed by using the curable compound (C) as described above, the dielectric constant and dielectric loss tangent are further reduced.

  Suitable combinations include a combination of a thermosetting resin (B) having a carboxyl group and a curable compound (C) containing an epoxy compound and an organometallic compound, and a thermosetting resin (B) having a phenolic hydroxyl group and a poly The combination with the curable compound (C) which has an isocyanate group, the combination of the thermoplastic resin (B) which has an epoxy group, and the curable compound (C) containing an organometallic compound, etc. are mentioned.

  The curable compound (C) can be used alone or in combination. Preferred combinations when used in combination include an epoxy compound and an organometallic compound, an epoxy compound, an aziridine compound, and an organometallic compound. By using in combination, the crosslinking density can be increased, and the protrusion of the adhesive layer to the outside and the heat resistance at the time of thermocompression bonding can be effectively improved.

  Examples of the isocyanate compound include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, Polyisocyanate compounds such as polymethylene polyphenyl isocyanate, adducts of these polyisocyanate compounds and polyol compounds such as trimethylolpropane, burettes and isocyanurates of these polyisocyanate compounds, and these polyisocyanate compounds and known polyisocyanates. Ether polyol and polyester Polyols, acrylic polyols, polybutadiene polyols, adducts, etc. and polyisoprene polyol and the like.

  Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A / epichlorohydrin type epoxy resin, N, N, N ′, N′— Examples include tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N-diglycidylaniline, N, N-diglycidyltoluidine, and the like.

  Examples of the polycarbodiimide include a carbodilite series manufactured by Nisshinbo Co., Ltd. Among these, Carbodilite V-01, 03, 05, 07, 09 is preferable because of its excellent compatibility with organic solvents.

  Examples of the aziridine compound include 2,2'-bishydroxymethylbutanol tris [3- (1-aziridinyl) propionate], 4,4'-bis (ethyleneiminocarbonylamino) diphenylmethane, and the like.

  The said organometallic compound is a compound which consists of a metal and organic substance, and reacts with the functional group of curable resin (B), and forms bridge | crosslinking. Although the kind of organometallic compound is not specifically limited, An organic aluminum compound, an organic titanium compound, an organic zirconium compound, etc. are mentioned. The bond between the metal and the organic substance may be a metal-oxygen bond and is not limited to a metal-carbon bond. In addition, the bonding mode between the metal and the organic substance may be any of a chemical bond, a coordinate bond, and an ionic bond.

  The organoaluminum compound is preferably an aluminum chelate compound. Examples of the aluminum chelate compound include ethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum monoacetylacetonate bis (ethyl acetoacetate), aluminum tris (acetylacetate), Aluminum monoacetyl acetate bis (ethyl acetoacetate), aluminum di-n-butoxide monomethyl acetoacetate, aluminum diisobutoxide monomethyl acetoacetate, aluminum di-sec-butoxide monomethyl acetoacetate, aluminum isopropylate, mono sec-butoxy aluminum diisopropyl Rate, aluminum-sec-butylate, al Bromide ethylate, and the like.

The organic titanium compound is preferably a titanium chelate compound. Examples of the titanium chelate compound include titanium acetylacetonate, titanium tetraacetylacetonate, titanium ethyl acetoacetate, titanium octylene glycolate, titanium ethyl acetoacetate, titanium-1.3-propanedioxybis (ethyl acetoacetate), Polytitanium acetylacetylacetonate, tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetraoctyl titanate, dark amyl titanate, tetra tertiary butyl titanate, tetrastearyl titanate, titanium isostearate, tri-n-butoxy titanium Monostearate, di-i-propoxytitanium distearate, titanium stearate, di-i-propoxytitanium diisostearate Include (2-n-butoxycarbonyl benzoyloxy) tributoxy titanium.
The organic zirconium compound is preferably a zirconium chelate compound. Zirconium chelate compounds include, for example, zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium monobutoxyacetylacetonate bis (ethylacetoacetate), zirconium dibutoxybis (ethylacetoacetate), zirconium tetraacetylacetonate, normal Examples thereof include propyl zirconate, normal butyl zirconate, zirconium stearate, and zirconium octylate. Among these, an organic titanium compound is preferable from the viewpoints of thermosetting reactivity and heat resistance after curing.

  The resin used in the above (I) or (II) is not particularly limited as long as it satisfies the above (i) and (ii). From the viewpoint of heat resistance, the thermosetting resin (B) of (II) and It is preferable to use a curable compound (C).

  In the adhesive layer containing the above (II), the adhesive layer is thermally cured from the viewpoint of providing an electromagnetic wave shielding sheet that can exhibit better adhesive performance while maintaining good transmission characteristics even when used for high-frequency components. It is preferable to use a film (Y) that satisfies at least one of the following (a) and (b).

(A) The ratio of the number of nitrogen atoms to the number of carbon atoms (hereinafter also referred to as [N]) is 1 to 10%, and the ratio of the number of oxygen atoms to the number of carbon atoms (hereinafter also referred to as [O]). Is 3 to 20%.
(B) In the film (Y) after the thermosetting of the adhesive layer, it contains at least one group selected from a carboxyl group and a hydroxyl group, and when it contains a carboxyl group, the ratio of the number of carboxyl groups to the number of carbons (hereinafter, [COOH] is 0.01 to 15%, and when it contains a hydroxyl group, the ratio of the number of hydroxyl groups to the number of carbons (hereinafter also referred to as [OH]) is in the range of 0.5 to 20%. It is. Here, the film (Y) after thermosetting of the adhesive layer refers to a film (Y) in which the thermosetting resin (B) is sufficiently cured by the curable compound (C). However, the total of [COOH] and [OH] is preferably 35% or less, more preferably 30% or less, and even more preferably 25% or less.

  By using the coating film (Y) in the range of the above (a), the adhesiveness can be kept better. The above [N] and [O] are values obtained from the peak area of the 1S orbital spectrum by X-ray photoelectron spectroscopy (ESCA), and are obtained by the method described in the examples described later. The lower limit of [N] is more preferably 1.5% or more, further preferably 2% or more, and the upper limit is more preferably 8% or less, still more preferably 7% or less. Further, the lower limit of [O] is more preferably 3.5% or more, further preferably 4% or more, and the upper limit is more preferably 18% or less, still more preferably 15% or less.

By using the coating (Y) in the range of (b) above, it is possible to provide a highly moisture-resistant adhesive layer by reducing the water absorption rate while maintaining the adhesive strength of the adhesive layer.
The lower limit of [OH] is more preferably 0.7% or more, further preferably 1% or more, and the upper limit is more preferably 18% or less, further preferably 15% or less. Further, the lower limit of [COOH] is more preferably 0.05% or more, further preferably 0.1% or more, and the upper limit is more preferably 13% or less, still more preferably 10% or less.

  The adhesive layer 1 can be an adhesive layer having anisotropic conductivity by containing a conductive filler. Here, anisotropic conductivity is a layer in which an electrically conductive state is ensured in the thickness direction, and is different from isotropic conductivity in which conduction is also achieved in the in-plane direction. As a method for imparting conductivity, an embodiment using an adhesive layer having isotropic conductivity is also conceivable. However, in the case of an isotropic conductive layer, when a high-frequency signal flows, a current flows in a horizontal direction between the signal circuit and the isotropic conductive layer. It is preferable to use an adhesive layer having anisotropic conductivity because of the increase in transmission loss.

  The average particle diameter of the conductive filler is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more from the viewpoint of sufficiently ensuring anisotropy. On the other hand, from the viewpoint of achieving compatibility with the thin adhesive layer, the thickness is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. The content of the conductive filler is preferably in the following range with respect to the total amount of the adhesive layer. That is, from the viewpoint of ensuring flexibility and adhesive strength, the content of the conductive filler is 50% by mass or less in the solid content. Preferably, it is more preferably 30% by mass or less. Moreover, from a viewpoint of ensuring electroconductivity, it is preferable to set it as 1 mass% or more, and it is more preferable to set it as 10 mass% or more.

  The average particle size is the D50 average particle size, and the D50 average particle size is measured using a laser diffraction / scattering method particle size distribution measuring device LS13320 (manufactured by Beckman Coulter, Inc.) with a tornado dry powder sample module. It is a numerical value obtained by measuring fine particles, and the cumulative value in the cumulative particle size distribution is a particle size of 50%. The refractive index was set to 1.6.

  The aspect ratio of the conductive filler is preferably 1 to 3. Here, the aspect ratio refers to the ratio of the major axis to the minor axis (major axis / minor axis) of the conductive filler particles. The aspect ratio is obtained by measuring the major axis and minor axis of particles appearing on the cut surface in the thickness direction of the adhesive layer using an electron microscope, and determining the ratio of major axis / minor axis. In the present application, the average value of the major axis / minor axis of 100 particles is defined as the aspect ratio. The major axis is a value that is the maximum distance of the cut surface of the particle, and the minor axis is defined as the shortest distance in the direction perpendicular to the major axis.

  Although a conductive filler is not specifically limited, A metal filler, a carbon filler, and mixtures thereof are mentioned. Examples of the metal filler include metal powders such as silver, copper, and nickel, alloy powders such as solder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. By containing silver, more excellent conductivity can be obtained. Of these, silver-coated copper powder is particularly preferable from the viewpoint of cost. The coverage of the coating layer with respect to the metal powder is preferably 80% or more with respect to the surface.

  In the conductive filler, the coating layer in the case of coating the core is only required to cover at least a part of the core, but in order to obtain more excellent conductive characteristics, a higher coverage is preferable. From the viewpoint of maintaining good conductive properties, the average coverage by the coating layer is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. In addition, the average coverage in this specification says the value calculated | required by the measurement of the powder by ESCA. Detailed conditions are: AXIS-HS (manufactured by Shimadzu Corporation / Kratos), X-ray source: Dual (Mg) 15 kV, 10 mA Pass energy 80 eV, Step: 0.1 eV / Step, Speed: 120 seconds / element, Dell: The mass concentration of silver and copper was determined from the peak areas of Ag3d: 2 and Cu2P: 1 under the conditions of 300 and the number of integrations: 8, and the ratio of the silver mass concentration was defined as the coverage.

  From the standpoint of effectively preventing streaks and unevenness on the coating surface when coating the conductive resin composition, that is, coating liquid stability, that is, preventing aggregation between fillers, glass fiber, carbon filler, etc. A method of performing metal plating on the core of this is preferable. These conductive fillers are used after being applied and dried in a state dispersed in a resin. The particle shape is not particularly limited as long as anisotropic conductivity can be secured. For example, spherical shape, dendritic shape (dendritic shape), needle shape, fibrous shape and the like can be exemplified. From the viewpoint of ensuring good anisotropic conductivity, spherical and dendritic (dendritic) particles are preferred.

  In addition to silane coupling agents, rust inhibitors, reducing agents, antioxidants, pigments, dyes, tackifying resins, plasticizers, UV absorbers, antifoaming agents as optional components for the resin composition forming the adhesive layer Leveling regulators, fillers, flame retardants, etc. can be blended.

  Although the manufacturing method of the electromagnetic wave shield sheet 10 is not specifically limited, As an example, it can produce with the following manufacturing methods. First, a coating film can be formed on the release substrate by a known method using the composition constituting the adhesive layer 1. For example, after applying the composition by comma coating, knife coating, die coating, lip coating, roll coating, curtain coating, bar coating, gravure printing, flexographic printing, dip coating, spray coating, spin coating, etc., usually at 40 to 150 ° C. It can be manufactured by drying.

  The thickness of the adhesive layer after joining to the component may vary depending on the application, but in order to obtain sufficient adhesiveness, it is good when the anisotropic conductive adhesive layer is further mixed with a conductive filler. In order to obtain anisotropic conductive characteristics, the thickness is preferably 3 to 50 μm. The lower limit of the thickness of the adhesive layer 1 is more preferably 4 μm or more, and further preferably 6 μm or more. Moreover, as for the upper limit of the thickness of the said contact bonding layer 1, it is more preferable that it is 30 micrometers or less.

  A known method can be used for laminating the adhesive layer, the conductive layer, and the insulating layer. For example, after forming an adhesive layer on a peelable sheet and laminating the adhesive layer on the electrolytic copper foil surface side of the electrolytic copper foil with copper carrier of the conductive layer, the copper carrier is peeled off. There is a method of laminating the surface from which the copper carrier has been peeled and an insulating layer separately formed on a peelable sheet. Also, there is a method in which an adhesive layer is formed on a peelable sheet, a conductive layer is formed on the surface thereof by electroless plating, and an insulating layer separately formed on the peelable sheet is laminated with the conductive layer. Can be mentioned.

  Next, an electromagnetic wave shielding wiring circuit board obtained by bonding the electromagnetic wave shielding sheet of the present invention to the wiring circuit board will be described. FIG. 3 shows an example of a schematic explanatory diagram in which an electromagnetic wave shielding sheet is bonded to a printed wiring board. The electromagnetic wave shielding sheet 10 is bonded to the surface layer of the printed wiring board 20 that is a component. The printed wiring board 20 includes a substrate 21 made of polyimide or the like, a wiring pattern 25, a ground pattern 24, an insulating adhesive layer 22 covering these, and a coverlay layer made of a polyimide film 23. The electromagnetic wave shielding sheet 10 is affixed on the printed wiring board 20 by a joining process such as thermocompression bonding. The printed wiring board 20 is provided with a contact hole penetrating from the surface of the polyimide film 23 to the surface of the ground pattern 24, and anisotropic conduction between the ground pattern 24 and the electromagnetic wave shielding sheet 1 through a via 31 formed in the contact hole. The adhesive layer 1 exhibiting electrical properties is electrically connected. Conductivity can be achieved only by attaching the electromagnetic wave shielding sheet 10 to the printed wiring board 20, and the manufacturing is simple, so that it is particularly suitable for a flexible printed circuit board or the like.

  FIG. 4 is a schematic cross-sectional view of an electromagnetic wave shielding wired circuit board according to a first modification. In this example, a bump 32 is provided on the main surface of the conductive layer 2 on the side of the adhesive layer 1 instead of the via 31, and this is electrically connected to the ground pattern 24. The bump 32 can be obtained, for example, by forming the conductive layer, placing the bump 32 on the conductive layer 2 corresponding to the ground pattern 24, and then forming the adhesive layer 1. According to this method, electrical connection between the ground pattern 24 and the conductive layer 2 can be achieved by performing the joining process of the electromagnetic wave shielding sheet 10 to the printed wiring board 20.

  FIG. 5 is a schematic cross-sectional view of an electromagnetic wave shielding wired circuit board according to a second modification. In this example, bumps 33 are formed in advance on the ground pattern 24 and can be electrically connected to the conductive layer 2 when bonded to the electromagnetic wave shielding sheet 10.

  FIG. 6 is a schematic cross-sectional view of an electromagnetic wave shielding wired circuit board according to a third modification. In this example, after the electromagnetic wave shielding sheet 10 and the printed wiring board 20 are joined, the conductive layer 2 is electrically connected from the surface layer side of the insulating layer 3 using an external grounding component.

  FIG. 7 is a schematic cross-sectional view of an electromagnetic wave shielding wired circuit board according to a fourth modification. In this example, a ground via 41 penetrating from the surface layer of the insulating layer 3 to the ground pattern 24 is provided, and the conductive paste 35 is filled therein, whereby conduction between the electromagnetic wave shield sheet 10 and the ground circuit can be achieved. . The conductive paste 35 exposed on the surface layer of the insulating layer 3 may be further grounded outside.

ここで、Ｚ_０は特性インピーダンスであり、Ｄｋはフレキシブルプリント配線板（以下ＦＰＣともいう）のカバーレイの誘電率、ｄはＦＰＣのカバーレイの厚み、Ｓは電磁波シールドシートの導電層と伝送回路の重なっている面積、Ｃはキャパシタンスである。Ｒは導体抵抗値（Ω/ｍ）、Ｌはインダクタンス（Ｈ/ｍ）、Ｇは絶縁層（基材）のコンダクタンス（Ω/ｍ）、ｆは周波数、ｊは虚数記号であり、高周波数になるとＬとＣが支配的になる。一般的にシールドフィルムを被着すると特性インピーダンス（Ｚ_０）は低下するため、インピーダンス整合を取るために特性インピーダンスＺ_０を上げることが必要である。ここで、キャパシタンスＣの値は、式２により表される。キャパシタンスＣの値を小さくすることにより、特性インピーダンス（Ｚ_０）の値を上げることができる。
式２より、キャパシタンスＣの値を小さくするためには、配線２５幅ｗ（図１参照）を調整する方法、カバーレイ層（絶縁性接着剤層２２＋ポリイミドフィルム２３）（図１参照）の厚みを調整する方法、カバーレイ層の比誘電率を下げる方法が考えられる。しかしながら、回路幅を細線化する方法は生産効率が悪く、コストアップとなるため好ましくなく、カバーレイ層を厚膜化する方法は、軽薄短小化のニーズに逆行するため望ましくない。特に、フレキシブルプリント配線板等においては、フレキシブル性が低下するので好ましくない。接着層として、上記（ｉ）を満たす材料を用いたことで、式２のＤｋが下がり、フレキシブルプリント基板のカバーレイ層を薄くすることも可能となる。なお、カバーレイ層を構成するポリイミドフィルム２３は一例であり、回路基板を保護する機能を有する保護層であればよく、他の材料に変えてもよい。 By the way, the characteristic impedance (Z ₀ ) in the case of a high-frequency circuit is expressed by the following equations 1 and 2.

Here, Z ₀ is the characteristic impedance, Dk is the dielectric constant of the coverlay of the flexible printed wiring board (hereinafter also referred to as FPC), d is the thickness of the coverlay of the FPC, S is the conductive layer of the electromagnetic wave shield sheet and the transmission circuit The overlapping area, C, is the capacitance. R is a conductor resistance value (Ω / m), L is an inductance (H / m), G is a conductance (Ω / m) of an insulating layer (base material), f is a frequency, j is an imaginary symbol, Then, L and C become dominant. In general, when a shield film is attached, the characteristic impedance (Z ₀ ) decreases, so it is necessary to increase the characteristic impedance Z ₀ in order to achieve impedance matching. Here, the value of the capacitance C is expressed by Equation 2. By reducing the value of the capacitance C, the value of the characteristic impedance (Z ₀ ) can be increased.
From Equation 2, in order to reduce the value of the capacitance C, a method of adjusting the wiring 25 width w (see FIG. 1), the thickness of the coverlay layer (insulating adhesive layer 22 + polyimide film 23) (see FIG. 1). A method of adjusting the thickness and a method of reducing the relative dielectric constant of the coverlay layer are conceivable. However, the method of thinning the circuit width is not preferable because the production efficiency is low and the cost is increased, and the method of increasing the thickness of the coverlay layer is not desirable because it goes against the need for lightness and thinness. In particular, a flexible printed wiring board or the like is not preferable because flexibility is deteriorated. By using a material satisfying the above (i) as the adhesive layer, the Dk of Formula 2 is lowered, and the coverlay layer of the flexible printed board can be made thin. In addition, the polyimide film 23 which comprises a coverlay layer is an example, What is necessary is just a protective layer which has the function to protect a circuit board, and you may change into another material.

  When the electromagnetic wave shielding sheet is thermocompression bonded to a component, if the adhesive layer is not sufficiently cured, the adhesive layer may protrude from the side of the electromagnetic wave shielding sheet, resulting in poor appearance. For this reason, it is calculated | required that there is little or no protrusion property at the time of sticking an electromagnetic wave shield sheet | seat by a thermocompression bonding process.

  According to the electromagnetic wave shielding sheet according to the present invention, by using the adhesive layer satisfying the above (i) and (ii), good transmission can be achieved even when used for components for high frequency applications while ensuring shielding properties such as electromagnetic waves. The characteristics can be maintained. This is because the use of the adhesive layer satisfying the above (i) and (ii) suppresses the phenomenon that the electric polarization of the dielectric becomes unable to follow the change of the electric field and part of the energy becomes heat. As a result, it is considered that dielectric loss can be reduced. By satisfying the above (i), the characteristic impedance matching can be improved. Moreover, the transmission loss of a high frequency signal can be improved by satisfy | filling said (i) and (ii). For this reason, it can utilize suitably in a wide frequency band. In particular, it is suitable for use in an electromagnetic wave shielding film for a signal transmission system for transmitting a high-frequency (10 MHz or more, preferably 1 GHz or more) signal that easily causes impedance mismatching and transmission loss.

  Moreover, by combining the binder component satisfying the above (i) and (ii) and the conductive filler, not only simplification of conduction with the component but also improvement of transmission characteristics while drawing out good adhesiveness , Characteristic impedance can be reduced.

Also, by using (i) and an electromagnetic wave shielding sheet using a material satisfying the (ii), the formula (1), it is possible to lower the characteristic impedance Z ₀ of the formula (2), the characteristic impedance Z ₀ When matching these, the design margin of the wiring width w or / and the coverlay thickness of the signal circuit can be widened. For this reason, a yield can be improved and production cost can be held down. For this reason, the productivity of the circuit can be increased.
The electromagnetic wave shielding sheet of the present invention can be widely applied not only to a printed circuit board but also to components and various electronic devices that emit electromagnetic waves or need to be shielded.

<Example>
EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example. In the examples, “part” means “part by mass”, and “%” means “% by mass”.

First, the raw materials used in the examples are shown below.
<Resin>
R1 (polyamide resin): Thermosetting polyamide resin Acid value 20 [mgKOH / g] (manufactured by Toyochem)
R2 (polyester resin): addition-type polyester resin acid value 19 [mgKOH / g] (manufactured by Toyochem)
R3 (urethane resin): Urethane urea resin Acid value 5 [mgKOH / g] (manufactured by Toyochem)
<Conductive filler>
F1 (silver-coated copper powder): “Dendrite-like particles using copper as the core and silver as the coating layer D50 average particle diameter = 11.0 μm” (Fukuda Metal Foil Powder Industry Co., Ltd.)
<Copper foil>
Electrolytic copper foil with carrier: “MT18SD-H (18 μm carrier copper foil with 3 μm electrolytic copper foil)” (Mitsui Metals)
<Curable compound>
H1 (tetraphenol ethane type epoxy curing agent): “jER1031S” (Mitsubishi Chemical Corporation)
H2 (phenol novolac type epoxy curing agent): “jER152” (manufactured by Mitsubishi Chemical Corporation)
H3 (titanium chelate compound): “TC401” (Matsumoto Fine Chemical Co., Ltd.)
H4 (aluminum chelate compound): “ALCH” (manufactured by Kawaken Fine Chemical Co., Ltd.)
H5 (isocyanurate type blocked isocyanate): “BL3175” (manufactured by Sumika Bayer Urethane Co., Ltd.)
H6 (aziridine compound): “Chemite PZ-33” (manufactured by Nippon Shokubai Co., Ltd.)

<Production of electromagnetic shielding sheet>
[Example 1] 100 parts of resin R1 (polyamide resin) and 50 parts of conductive filler F1 (silver-coated copper powder) are charged in a container, and a mixed solvent of toluene and isopropyl alcohol (toluene 100 is used so that the nonvolatile content concentration becomes 40%. 50 parts of isopropyl alcohol) was added and mixed. Subsequently, 15 parts of curable compound H1 (tetraphenol ethane type epoxy curing agent) and 3 parts of curable compound H3 (titanium chelate compound) were added and stirred for 10 minutes with a disper to obtain a resin composition. Furthermore, the obtained resin composition was coated on a peelable sheet using a bar coater so as to have a dry thickness of 15 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain an adhesive layer. .

  Separately, 100 parts of resin R3 (urethane resin), 10 parts of curable compound H1 (tetraphenol ethane type epoxy curing agent) and 10 parts of curable compound H6 (aziridine compound) are added and stirred with a disper for 10 minutes to make an insulating resin. A composition was obtained. Next, the obtained insulating resin composition was coated on a peelable sheet using a bar coater so as to have a dry thickness of 10 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain an insulating layer. It was.

After the insulating layer was bonded to the electrolytic copper foil side of the electrolytic copper foil with carrier, the carrier copper foil was peeled off, and the electric field copper foil was laminated on the insulating layer. Next, the electromagnetic wave shielding sheet which consists of "peelable sheet / insulating layer / electrolytic copper foil / adhesive layer / peelable sheet" was obtained by bonding an adhesive layer on the electrolytic copper foil surface. The electrolytic copper foil and the adhesive layer were bonded at a temperature of 90 ° C. and a pressure of 3 kgf / cm ² with a thermal laminator.

[Examples 2 to 15, Comparative Examples 1 to 5]
Except for changing the composition of the adhesive layer of Example 1 and the thickness of the adhesive layer after thermocompression bonding as described in Table 1, Examples 2 to 15 and Comparative Examples 1 to 1 were carried out in the same manner as Example 1. 5 electromagnetic wave shield sheet was obtained.

(Film thickness of the adhesive layer) The film thickness of the electromagnetic wave shielding sheet is the thickness of the adhesive layer after thermocompression bonding to the component, and was measured by the following method. First, the peelable sheet of the adhesive layer of the electromagnetic wave shielding sheet was peeled off, and the exposed adhesive layer and a polyimide film (“Kapton 200EN” manufactured by Toray DuPont) were bonded together and thermocompression bonded under conditions of 2 MPa and 150 ° C. for 30 minutes. After cutting this into a size of about 5 mm in width and 5 mm in length, 0.05 g of epoxy resin (Petropoxy 154, manufactured by Marto) is dropped on the slide glass, and an electromagnetic wave shielding sheet is adhered to the glass slide / electromagnetic wave shield. A laminate having a sheet / polyimide film configuration was obtained. The obtained laminate was cut by ion beam irradiation from the polyimide film side using a cross section polisher (manufactured by JEOL Ltd., SM-09010) to obtain a measurement sample of the electromagnetic wave shield sheet after thermocompression bonding.

  The cross section of the obtained measurement sample was measured using a laser microscope (manufactured by Keyence Corporation, VK-X100), and the thickness of the adhesive layer was measured from the observed enlarged image. The magnification was 500 to 2000 times. Table 1 shows the thickness of the adhesive layer after coating and drying, and the thickness of the adhesive layer after thermocompression bonding.

[Relative permittivity and dissipation factor]
(I) Thermoplastic resin (A) and (II) Thermosetting resin (B) and curable compound (C) film (X) (hereinafter also simply referred to as “film (X)”) used for the adhesive layer A dielectric constant and a dielectric loss tangent including at least one of the following were prepared by the following procedure.
<Measurement film of Example 1>
A container was charged with 100 parts of resin R1, 15 parts of curable compound H1, and 3 parts of curable compound H3, and a mixed solvent containing 50 parts of isopropyl alcohol was added to 100 parts of toluene to make the nonvolatile content 45%. . Further, the solution was stirred with a disper for 10 minutes and then subjected to vacuum defoaming to obtain a sample solution. The obtained sample solution was uniformly applied to a peelable sheet so as to have a dry thickness of 30 μm and dried to obtain a pre-coating.

<Measurement Films of Examples 2 to 15 and Comparative Examples 1 to 5>
Except for changing to the raw materials and blending amounts shown in Table 1, pre-coating films for the adhesive layers of Examples 2 to 15 and Comparative Examples 1 to 5 were obtained in the same manner as the coating film for measurement of Example 1, respectively. .

The dielectric constant and dielectric loss tangent of the coating (X) are determined in accordance with the following procedure in accordance with the flexible printed wiring board and flexible printed wiring board material of the Japan Electronic Circuits Association -Part 2 Integrated Standard- (JPCA-DG03). It was measured.
A plurality of layers of the coating (X) prepared in the examples and comparative examples were laminated so as to have a desired thickness, and this was vacuum-laminated and thermally cured at 180 ° C. and 2.0 MPa for 1 hour to form the coating (X). Got. The film (X) was cut into a size of 3 mm in width and 100 mm in length, the release sheets on both sides were peeled off, and a cured film having a thickness of 80 μm was used as an evaluation test piece. Three test pieces are set in a relative dielectric constant measuring apparatus “ADMS01Oc” manufactured by AET Co., Ltd., and a relative dielectric constant and a dielectric loss tangent at a measurement temperature of 23 ° C. and a measurement frequency of 1 GHz are obtained by a cavity resonator method. It was. The results are shown in Table 3.

[Quantification of [N] and [O] of adhesive layer after curing]
Measurement film for relative permittivity and dielectric loss tangent, except that 100 parts of resin R1, 15 parts of curable compound H1, 3 parts of curable compound H3, and 50 parts of conductive filler are added to the container. The pre-adhesion layer was obtained by the same method as above, and the film (Y) after thermosetting was obtained by treating in an oven at 180 ° C. for 60 minutes. ESCA analysis was performed on the surface of the obtained coating (Y) under the following conditions, and [N] and [O] were measured from the number of nitrogen atoms, the number of carbon atoms, and the number of oxygen atoms. The measurement conditions are shown below.
Apparatus: AXIS-HS (manufactured by Shimadzu Corporation / Kratos)
Vacuum degree in sample chamber: 1 × 10 ⁻⁸ Torr or less X-ray source: Dual (Mg) 15 kV, 5 mA Pass energy 80 eV
Step: 0.1 eV / Step
Speed: 120 seconds / element Dell: 300, integration number: 5
Photoelectron extraction angle: 90 degrees with respect to sample surface Binding energy: C1s main peak is 284.6 eV and shift correction C (1 s) peak area: 280-296 eV
O (1 s) peak area: 530-534 eV
N (1 s) peak area: 395 to 405 eV
The base line was drawn for the peak that appeared in the peak region by the linear method, and the ratio of the number of nitrogen atoms to the number of carbon atoms and the ratio of the number of oxygen atoms were calculated from the atomic concentration “Atomic Conc” of each atom.
[N] = number of atoms of N (1 s) / number of atoms of C (1 s) × 100
[O] = number of atoms of O (1s) / number of atoms of C (1s) × 100
The above measurement was performed at three places and the place was changed, and the average value was defined as [N] and [O] of the adhesive layer after curing.

[Quantification of residual functional groups of adhesive layer after curing]
Next, [OH] and [COOH] were measured on the surface of the coating (Y) after curing of the adhesive layer. Since the resin is mainly composed of carbon, hydrogen, and oxygen atoms, hydroxyl groups and carboxyl groups cannot usually be identified by ESCA, and quantitative analysis is difficult. However, by treating a fluorine reagent that selectively binds to a carboxylic acid or a hydroxyl group, only the carboxyl group or hydroxyl group is modified with fluorine, and the functional group can be identified by ESCA. In addition, since fluorine bonds have high ESCA detection sensitivity, it is possible to perform a sensitive functional group quantitative analysis on the surface. As a result of extensive studies by the present inventors, the ratio (COOH) of the number of carboxyl groups to the number of carbons is 0.01 to 15% and the ratio of the number of hydroxyl groups to the number of carbons [OH] is 0.5. When the electromagnetic shielding sheet of the present invention is attached to a component for high-frequency applications such as a printed wiring board while maintaining high adhesion to the component by being in the range of ˜20%, good transmission characteristics can be maintained. I found out.

A film (Y) obtained by the same method as described above was cut into a width of 30 mm and a length of 30 mm and attached to a glass plate as a sample. The vial was sealed in a vial, and the fluorine modifying reagent and the sample were subjected to a gas phase reaction in a non-contact manner at 55 ° C. for 24 hours. After completion of the gas phase reaction, the sample was taken out of the reaction vessel and dried in a nitrogen stream to remove residual reagents. The residual reagent was removed by appropriately adjusting the temperature and time until there was no change in the N (1s) peak area.
The fluorine-modified sample was subjected to ESCA analysis under the same conditions as those described above for determining [N] and [O], and [OH] and [COOH] in the adhesive layer were determined. Three measurement samples were prepared, and the average value of the calculated values was obtained.

<Measurement method of [OH]>
After the gas phase modification reaction of the hydroxyl group with trifluoroacetic anhydride, the residual reagent was removed, and the ratio of the number of hydroxyl groups was calculated by ESCA measurement. The reaction formula and calculation formula are as follows.
R-OH + (CF ₃ CO) ₂ O → R-COOCF ₃ + CF ₃ OCOH
[OH] is represented by a value calculated by the following equation.
<Formula> [OH] = {[F (1s)] / (3k [C (1s)]-2 [F (1s)]) r} × 100 (%)

  [C (1s)] is the peak area of C (1s) and is obtained by drawing a straight base line in the range of 280 to 296 eV. The peak area [F (1s)] of F (1s) is 682 to 695 eV. It was obtained by drawing a straight baseline in the range of. The reaction rate r was 1. In addition, k is a sensitivity correction value of the F (1s) peak area with respect to the C (1s) peak area specific to the apparatus. When AXIS-HS (Shimadzu Corporation / Kratos) is used, the sensitivity correction value specific to the apparatus is 3.6.

<Measuring method of [COOH]>
After the carboxyl group modification reaction was performed with a mixed solution of trifluoroethanol, pyridine, and dicyclohexylcarbodiimide, the residual reagent was removed, and the ratio of the carboxyl group was calculated by ESCA measurement. The reaction formula and calculation formula are as follows.
R-COOH + CF ₃ CH ₂ -OH C ₆ H ₁₁ -NCN-C ₆ H ₁₁ / C ₅ H ₅ N → R-COOCH ₂ CF ₃ + C ₆ H ₁₁ NCONC ₆ H ₁₁

[COOH] was represented by a value calculated by the following equation.
<Formula> [COOH] = {[F (1s)] / (3k [C (1s)]-(2 [F (1s)]) r} × 100 (%)

  [C (1s)] is the peak area of C (1s) and is obtained by drawing a straight base line in the range of 280 to 296 eV. The F (1s) peak area [F (1s)] is 682 to 695 eV. Obtained by drawing a straight baseline over the range. Similarly to the above, the reaction rate r was 1 and k was 3.6.

[Hygroscopicity] Hygroscopicity was evaluated based on whether or not the appearance of the adhesive layer was changed after contacting the electromagnetic wave shielding sheet and the molten solder. The sample with low hygroscopicity does not change the appearance, but the sample with high hygroscopicity causes foaming or peeling.
First, the peelable sheet of the adhesive layer of the electromagnetic wave shield sheet having a width of 25 mm and a length of 70 mm was peeled off, and the exposed adhesive layer and a total of 64 μm gold-plated copper-clad laminate (gold plating 0.3 μm / nickel plating 1 μm / A gold-plated surface of copper foil (18 μm / adhesive 20 μm / polyimide film 25 μm) was pressure-bonded under conditions of 150 ° C. and 2.0 MPa for 30 minutes, and thermally cured to obtain a laminate. The obtained laminate was cut into a size of 10 mm width and 65 mm length to prepare a sample. The obtained sample was left for 72 hours in an atmosphere of 40 ° C. and 90% RH. After that, float on the molten solder at 250 ° C. for 1 minute with the polyimide film surface of the sample facing down, then take out the sample and visually observe its appearance to check for abnormalities such as foaming, floating, and peeling of the adhesive layer. The standard was evaluated.
Excellent: No change in appearance.
Good: Small foaming is slightly observed.
Acceptable: Less than the above-mentioned good, the following inappropriate exceeding.
Poor: Severe foaming or peeling is observed.

[Adhesive Strength] An electromagnetic wave shielding sheet was prepared to have a width of 25 mm and a length of 70 mm to prepare a sample. The peelable sheet provided on the adhesive layer is peeled off, and a 50 μm-thick polyimide film (“Kapton 200EN” manufactured by Toray DuPont) is pressure-bonded to the exposed adhesive layer at 150 ° C., 2.0 MPa for 30 minutes. And heat cured. Next, the peelable sheet on the insulating layer side is peeled off for the purpose of reinforcing the sample for measuring the adhesive force, and a polyimide film having a thickness of 50 μm is applied to the exposed insulating layer using a Toyochem adhesive sheet at 150 ° C., 1 MPa. The laminated body of the structure of "a polyimide film / adhesive sheet / electromagnetic wave shield sheet / polyimide film" was obtained by crimping | bonding on conditions for 30 minutes. Using this tensile body, a tensile tester (manufactured by Shimadzu Corp.) and an atmosphere of 23 ° C. and 50% RH, a peeling speed of 50 mm / min, a peeling angle of 90 °, an electromagnetic wave shielding sheet conductive layer, a polyimide film, The adhesive force was measured by peeling the interface. The evaluation criteria are as follows.
Excellent: 6N / 25mm or more.
Good: 4N / 25mm or more and less than 6N / 25mm, no problem in practical use.
Poor: Less than 4N / 25mm.

[Excessiveness]
The protrusion property was evaluated by the following samples. An electromagnetic wave shielding sheet having a width of 50 mm and a length of 50 mm was prepared, and a through-hole having a diameter of 5 mm was formed in the center portion with a drilling machine. Next, the peelable sheet of the adhesive layer was peeled off, and the adhesive layer and a polyimide film (“Kapton 200EN” manufactured by Toray DuPont) were heat-pressed under conditions of 150 ° C., 2 MPa, and 30 minutes. After cooling to room temperature, the hole portion of the electromagnetic shielding sheet was observed with a magnifying glass, and the length of the adhesive layer protruding inside the hole was measured. For the length of protrusion, the most protruding part was selected. The evaluation criteria are as follows.
Excellent: The protruding length is less than 0.1 mm.
Good: The protruding length is 0.2 mm or more and less than 2.0, and there is no practical problem.
Poor: The protruding length is 2 mm or more.

[Folding resistance]
The folding resistance of the electromagnetic shielding sheet was evaluated by an MIT test according to JIS C6471. First, an electromagnetic wave shielding sheet was prepared with a width of 15 mm and a length of 120 mm. Separately, as an adherend to which an electromagnetic shielding film is attached, based on a two-layer CCL obtained by laminating a polyimide film (thickness 12.5 μm “Kapton 50EN” manufactured by Toray DuPont) and copper foil (thickness 18 μm), A wiring is formed in a shape based on JIS C6471, and a coverlay “CISV1215 (manufactured by Nikkan Kogyo)” composed of a polyimide film with a thickness of 12.5 μm and a thermosetting adhesive with a thickness of 15 μm is bonded to the cover. A coat layer was formed. Furthermore, the sample was obtained by pressure-bonding the conductive layer exposed by peeling off the peelable sheet on the conductive layer side of the electromagnetic wave shielding sheet to the cover coat layer at 150 ° C. for 30 minutes at 2.0 MPa. The folding resistance of the obtained sample was measured using a MIT test machine under the conditions of a temperature of 25 ° C. and a humidity of 50% under the conditions of a curvature radius of 0.38 mm, a load of 500 g, and a speed of 180 times / minute. In the evaluation, bending was performed 3000 times and the number of bending until the wiring was disconnected was measured. The evaluation criteria are as follows.
Excellent: Even when the number of flexing was 3000 times, the wire was not broken.
Good: The number of bendings until disconnection is 2500 times or more and less than 3000 times, and there is no practical problem.
Poor: Disconnected less than 2500 times.

[Appropriate evaluation for high frequency applications]
The suitability for high frequency applications was evaluated using the following measurement samples.
FIG. 8 is a schematic plan view on the main surface side of a flexible printed wiring board (hereinafter also referred to as a printed wiring board) 7 having a coplanar structure used for measurement, and FIG. 9 is a schematic plan view on the back surface side. First, double-sided CCL “R-F775” (manufactured by Panasonic Corporation) in which a rolled copper foil having a thickness of 12 μm was laminated on both sides of a polyimide film 50 having a thickness of 50 μm was prepared. And six through holes 51 (diameter 0.1 mm) were provided in the vicinity of the four rectangular corner portions. In the drawing, for convenience of illustration, only two through holes 51 are shown at each corner. Next, after performing an electroless plating process, an electroplating process was performed to form a 10 μm copper plating film 52, and conduction between both main surfaces was ensured through the through holes 51. Thereafter, as shown in FIG. 8, two signal wirings 53 having a length of 10 cm are formed on the main surface of the polyimide film 50, and a ground wiring 54 parallel to the signal wirings 53 and the ground wiring 54 are extended outside thereof. The ground pattern 55 formed in the region including the through hole 51 in the lateral direction of the polyimide film 50 was formed.

  Thereafter, the copper foil formed on the back surface of the polyimide film 50 was etched to obtain a back surface side ground pattern 56 as shown in FIG. 9 at a position corresponding to the ground pattern 55. The inspection specification of the appearance and tolerance of the circuit was the JPCA standard (JPCA-DG02). Next, on the main surface side of the polyimide film 50, a coverlay 57 “CISV1215 (manufactured by Nikkan Kogyo Co., Ltd.) composed of a polyimide film 57a (thickness 12.5 μm) and an insulating adhesive layer 57b (thickness 15 μm). Is pasted (see FIG. 8). In FIG. 8, the coverlay 57 is shown in a perspective view so that the structure of the signal wiring 53 and the like can be understood. Thereafter, nickel plating (not shown) was performed on the copper foil pattern exposed from the coverlay 57, and then gold plating (not shown) was performed.

  FIG. 10 is a schematic plan view of the printed wiring board 8 with an electromagnetic wave shield in which an electromagnetic wave shielding sheet is attached to the main surface side of the printed wiring board 7. 11 is a cross-sectional view taken along the line XI-XI of FIG. 10, and FIG. 12 is a cross-sectional view taken along the line XII-XII of FIG. In FIG. 10, for convenience of explanation, the electromagnetic wave shielding sheet 61 is shown in a perspective view. Two electromagnetic shielding sheets 61 and 62 were prepared, and a release treatment sheet (not shown) provided on the adhesive layer 71 of the electromagnetic shielding sheets 61 and 62 was peeled off. Then, the printed wiring board 7 is sandwiched with the respective adhesive layers 71 of the electromagnetic wave shielding sheets 61 and 62 inside, and the printed wiring board 8 with the electromagnetic wave shielding sheet is bonded by pressure bonding under conditions of 150 ° C. and 2.0 MPa for 30 minutes. Got. As the electromagnetic wave shielding sheets 61 and 62, a sheet in which an adhesive layer 71, a conductive layer 72, and an insulating layer 73 are laminated in this order was used.

  As shown in FIG. 10, the electromagnetic wave shielding sheet 61 provided on the main surface side of the printed wiring board 7 is provided with two openings 60. From each opening 60, the protruding portion 58 extending from the two ground patterns 55 and the ends of the two signal wirings 53 are exposed. A spectrum analyzer is connected to the exposed ground pattern 55 and the signal wiring 53 to perform a test. On the back surface side of the printed wiring board 7, an electromagnetic wave shielding sheet 62 having substantially the same shape as the electromagnetic wave shielding sheet 61 and not provided with an opening is provided in a region overlapping with the printed wiring board 7. Using a network analyzer E5071C (manufactured by Agilent Japan), a signal in the range of 1 MHz to 20 GHz was sent to the signal wiring 53, and the characteristic impedance and transmission loss of the printed wiring board 8 with the electromagnetic wave shielding sheet were measured. In Examples 1 to 15 and Comparative Examples 1 to 4, the L / S (line / space) of the signal circuit is 30/100 μm, and the characteristic impedance obtained from the equation (1) is in the range of 100 mΩ ± 5 mΩ. The thickness of the adhesive layer between the coverlay and the shield sheet was adjusted as appropriate. On the other hand, in Comparative Example 5, the wiring width of the signal circuit was adjusted so that the total thickness of the adhesive layer of the coverlay and the shield sheet was 50.5 μm and the characteristic impedance was in the range of 100 mΩ ± 5 mΩ. In Examples 1 to 15 and Comparative Examples 1 to 5, the width of the ground wiring 54 was 100 μm, and the distance between the ground wiring 54 and the signal wiring 53 was 1 mm.

(Thickness of cover lay and adhesive layer) After cutting the printed wiring board 8 with an electromagnetic wave shield to a size of about 5 mm in width and 5 mm in length, an epoxy resin (Petropoxy 154, manufactured by Marto Co., Ltd.) is put on the slide glass by 0.0. 05 g was dropped and the printed wiring board 8 with the electromagnetic wave shield and the slide glass were adhered to obtain a laminate of the slide glass / printed wiring board 8 with the electromagnetic wave shield. The obtained laminate was cut by ion beam irradiation from the printed wiring board 8 side using a cross section polisher (manufactured by JEOL Ltd., SM-09010) to obtain a measurement sample of the printed wiring board 8 with an electromagnetic wave shield. .

Using a laser microscope (VK-X100, manufactured by Keyence Co., Ltd.), the cross section of the obtained measurement sample is observed at the position indicated by the arrow T in FIG. 12 (position where no circuit is formed). The thickness of the adhesive layer 71, the polyimide film 57a, and the insulating adhesive layer 57b (hereinafter, the total thickness of the coverlay and the adhesive layer is defined as the thickness of the FPC in this specification) was measured. The FPC thickness was measured at a magnification of 500 to 2000, and evaluated as follows. The results are shown in Table 3.
Excellent: The total thickness of the adhesive layer of the coverlay and the electromagnetic wave shielding sheet is less than 48.5 μm.
Good: The total thickness of the adhesive layer of the coverlay and the electromagnetic wave shielding sheet is 48.5 μm or more and less than 52.5 μm.
Poor: The total thickness of the adhesive layer of the coverlay and the electromagnetic wave shielding sheet is 52.5 μm or more.

[Transmission loss] The transmission loss in a high-frequency signal was evaluated by measuring the transmission loss at 10 GHz and 20 GHz. The evaluation criteria were as follows. The obtained results are shown in Table 3.
[10GHz]
Excellent: Less than 4.5 dB Good: 4.5 dB or more, less than 5.0 dB Poor: 5.0 dB or more [20 GHz]
Excellent: Less than 7 dB Good: 7 dB or more, Less than 7.5 dB Poor: 7.5 dB or more

  By using a material satisfying the above (i) and (ii) as the adhesive layer, as shown in Table 3, it is found that the transmission loss in the high frequency signal can be effectively suppressed without narrowing the L / S of the circuit. It was. Example 14 using an adhesive layer that does not contain a conductive filler, ie, does not exhibit conductivity, not only can effectively suppress transmission loss, but also includes the same thermosetting resin and curing agent as in Example 14 as a binder. Also in Examples 12 and 13 in which a conductive filler was added to this as a component, the results were obtained that transmission characteristics in high frequency applications can be improved (transmission loss can be effectively suppressed). Although the compositions of Comparative Example 2 and Comparative Example 5 are the same, in Comparative Example 5 where the thickness of the FPC is 50.5 μm as in the example, it is necessary to narrow L / S, and as a result, productivity is increased. It will decline.

DESCRIPTION OF SYMBOLS 1,71 Adhesive layer 2,72 Conductive layer 3,73 Insulating layer 7 Printed wiring board 8 Printed wiring board 10, 61,62 with electromagnetic wave shield Electromagnetic wave shielding sheet 20 Printed wiring board (component)
21 Substrate 22, 57b Insulating adhesive layer 23, 57a Polyimide film 24 Ground pattern 25 Wiring pattern 31 Via 32, 33 Bump 34 External ground 35 Conductive paste 41 Ground via 50 Polyimide film 51 Through hole 52 Copper plating film 53 Signal wiring 54 Ground wiring 55 Ground pattern 56 Back side ground pattern 57 Coverlay 58 Protrusion 60 Opening 61, 62 Electromagnetic wave shield sheet

Claims (10)

An electromagnetic wave shielding sheet comprising a laminate that shields at least a part of a component that emits electromagnetic waves,
The laminate is
An adhesive layer disposed on the component and bonded to the component by performing a bonding process;
A conductive layer laminated on the adhesive layer;
An insulating layer formed on the conductive layer,
The adhesive layer as a binder component,
(I) a thermoplastic resin (A), and (II) a thermosetting resin (B) and a curable compound (C) for the thermosetting resin (B),
Including at least one of
The adhesive layer further contains a conductive filler, exhibits anisotropic conductivity,
An electromagnetic wave shielding sheet in which the coating (X) after the thermocompression treatment of the binder component satisfies the following (i) and (ii).
(I) The relative dielectric constant is 1 to 3 at a frequency of 1 GHz and 23 ° C.
(Ii) The dielectric loss tangent is 0.0001 to 0.02 at a frequency of 1 GHz and 23 ° C. The thermosetting resin (B) includes a carboxyl group-containing resin,
The electromagnetic wave shielding sheet according to claim 1, comprising an epoxy compound as the curable compound (C), and further comprising at least one of an organometallic compound and an isocyanate compound.   The electromagnetic wave shield sheet according to claim 1 or 2, wherein a thickness of the adhesive layer after the joining treatment is 3 to 50 µm. The electromagnetic wave shielding sheet according to any one of claims 1 to 3, wherein the conductive filler is selected from at least one of spherical particles and dendrite particles. The binder component includes the (II),
In the coating (Y) after thermosetting of the adhesive layer, the ratio of the number of nitrogen atoms to the number of carbon atoms is 1 to 10%, and the ratio of the number of oxygen atoms to the number of carbon atoms is 3 to 20%. The electromagnetic wave shield sheet of any one of 1-4 . The binder component includes the (II),
The film (Y) after the thermosetting of the adhesive layer includes at least one group selected from a carboxyl group and a hydroxyl group,
When the carboxyl group is included, the ratio of the carboxyl group number to the carbon number is in the range of 0.01 to 15%,
When the hydroxyl group is included, the ratio of the hydroxyl number to the carbon number is in the range of 0.5 to 20%,
Electromagnetic wave shielding sheet according to any one of claims 1 to 5 Total of carboxyl groups and the number of hydroxyl groups is less than 35% relative to the number of carbon atoms. The electromagnetic wave shielding sheet according to any one of claims 1 to 6 , wherein the curable compound (C) contains an organometallic compound. The conductive layer, an electromagnetic wave shielding sheet according to any one of claims 1 to 7 which is a metallic layer. The electromagnetic wave shielding wiring circuit board by which the electromagnetic wave shielding sheet of any one of Claims 1-8 was joined on the wiring circuit board. The electronic device with which the electromagnetic wave shielding sheet of any one of Claims 1-8 was joined.

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