JP6733721B2 - Electromagnetic wave shielding wiring circuit board and electronic equipment - Google Patents

Description

The present invention relates to an electromagnetic wave shield sheet suitable for being used by being joined to a part of a component that emits an electromagnetic wave. Further, the present invention relates to an electromagnetic wave shielding wired circuit board and an electronic device using the electromagnetic wave shielding sheet.

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

In Patent Document 1, a shield film, a shielded printed wiring board, and a shield film, which have good transmission characteristics, are well shielded from electric field waves, magnetic field waves and electromagnetic waves traveling from one surface side to the other surface side of the shield film. The following configurations are disclosed for the purpose of providing a method. That is, a shield film is disclosed, which comprises a conductive layer having a layer thickness of 0.5 to 12 μm and an anisotropic conductive adhesive layer in a laminated state. Then, it is described that, by the configuration, the electric field wave, the magnetic field wave, and the electromagnetic wave propagating from the one surface side to the other surface side can be well shielded.

International publication 2013/077108

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

FIG. 1 shows a schematic cross-sectional view of a shielded wiring board in which an electromagnetic wave shield sheet is attached to a printed wiring board. When the electromagnetic wave shield sheet 10 is attached, a capacitor component is added between the wiring 25 of the printed wiring board 20 and the conductive layer 2 of the electromagnetic wave shield sheet 10, as shown in FIG. There is also a problem that the transmission characteristics are deteriorated. That is, there is a problem that the electromagnetic wave shield sheet 10 affects the electrical characteristics of the shielded printed wiring board. Particularly in the case of a high frequency signal, signal reflection is likely to occur at the impedance mismatch point and noise is likely to occur, so that the problem of characteristic deterioration is serious.

If the transmission characteristics can be improved while securing the electromagnetic wave shielding property, further high 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 speed and frequency of signals, improvement of transmission characteristics is important for maintaining and improving performance characteristics.

Although the printed wiring board has been described above as an example, the same problem exists in a board having wiring and an electronic circuit.

The present invention has been made in view of the above background, and an object thereof is to have excellent bonding properties with components, while securing shielding properties for electromagnetic waves and the like, even when used for components for high frequency applications. An object of the present invention is to provide an electromagnetic wave shield sheet that can maintain good transmission characteristics.

As a result of intensive studies conducted by the present inventors in order to solve the above problems, they have found that the problems of the present invention can be solved in the following aspects, and have completed the present invention.

[1]: An electromagnetic wave shield sheet composed of a laminate, which shields at least a part of a component that emits an electromagnetic wave,
The laminate is
Placed on the component, an adhesive layer that is joined to the component by performing a joining 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
An electromagnetic wave shielding sheet in which the coating film (X) after thermocompression-bonding the binder component satisfies the following (i) and (ii).
(I) The relative permittivity 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.
[2]: The thermosetting resin (B) contains a carboxyl group-containing resin,
The electromagnetic wave shielding sheet according to [1], which contains an epoxy compound as the curable compound (C) and further contains at least one of an organometallic compound and an isocyanate compound.
[3]: The electromagnetic wave shield sheet according to [1] or [2], wherein the thickness of the adhesive layer after the bonding treatment is 3 to 50 μm.
[4]: The electromagnetic wave shield sheet according to any one of [1] to [3], wherein the adhesive layer further contains a conductive filler and exhibits anisotropic conductivity.
[5]: The electromagnetic shield sheet according to [4], wherein the conductive filler is selected from at least one of spherical particles and dendrite particles.
[6]: The binder component contains the (II),
In the coating film (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% [1 ] The electromagnetic wave shield sheet in any one of [5].
[7]: The binder component contains the (II),
The coating (Y) after thermosetting of the adhesive layer contains at least one group selected from a carboxyl group and a hydroxyl group,
When the carboxyl group is contained, the ratio of the number of carboxyl groups to the number of carbon atoms is in the range of 0.01 to 15%,
When the hydroxyl group is contained, the ratio of the number of hydroxyl groups to the number of carbon atoms is in the range of 0.5 to 20%,
The electromagnetic wave shield sheet according to any one of [1] to [6], wherein the total of the number of carboxyl groups and the number of hydroxyl groups with respect to the number of carbon atoms is 35% or less.
[8]: The electromagnetic wave shield sheet according to any one of [1] to [7], in which the curable compound (C) contains an organometallic compound.
[9] The electromagnetic wave shielding sheet according to any one of [1] to [8], wherein the conductive layer is a metal layer.

[10]: An electromagnetic wave shielding wired circuit board in which the electromagnetic wave shielding sheet according to any one of [1] to [9] is bonded onto the wired circuit board.

[11]: An electronic device to which the electromagnetic wave shielding sheet according to any one of [1] to [10] is joined.

According to the present invention, it is possible to provide an electromagnetic wave shield sheet which has excellent bondability with parts and which can maintain good transmission characteristics even when used for parts for high-frequency applications while ensuring shielding properties against electromagnetic waves and the like. It has an excellent effect.

FIG. 11 is a schematic cross-sectional view for explaining a capacitor component of a shielded wiring board according to a conventional 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 shield 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. FIG. 3 is a schematic plan view of a main surface side of printed wiring boards according to examples and comparative examples. FIG. 6 is a schematic plan view of the back surface side of a printed wiring board according to an example and a comparative example. It is a typical top view of the printed wiring board with an electromagnetic wave shield sheet concerning an example and a comparative example. FIG. 11 is a sectional view taken along line XI-XI of FIG. 10. FIG. 11 is a sectional view taken along the line XII-XII of FIG. 10.

Hereinafter, an example of an embodiment to which the present invention is applied will be described. It should be noted that the sizes and ratios of the respective members in the following drawings are for convenience of explanation and are not limited to these. Further, in the present specification, the description “arbitrary number A to arbitrary number B” includes the number A as a lower limit value and the number B as an upper limit value in the range. Further, the “sheet” in the present specification includes not only a “sheet” defined in JIS but also a “film”. Further, the numerical values specified in this specification are values obtained by the method disclosed in the embodiment or the example.

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

The electromagnetic wave shield sheet 10 may further include another layer. For example, a magnetic field cut may be made between the adhesive layer 1 and the conductive layer 2 and/or between the conductive layer 2 and the insulating layer 3 on the surface layer of the insulating layer 3 such as a film having scratch resistance, water vapor barrier property and oxygen barrier property. A reinforcing film or the like may be laminated.

INDUSTRIAL APPLICABILITY The electromagnetic wave shield sheet of the present invention is suitable for preventing radiated electromagnetic waves from components that emit electromagnetic waves (electric field waves and magnetic field waves) and for preventing malfunctions due to external magnetic fields and radio waves. Examples of the parts 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 metal layer and a layer containing a conductive filler in a binder resin. A known method can be used for the method of manufacturing the conductive layer. As the method for producing the metal layer, in addition to the method using a metal foil, vacuum deposition, sputtering, CVD method, MO (metal organic), plating or the like can be used. Among these, vacuum deposition or plating is preferable in consideration of mass productivity. The method for producing the layer in which the conductive filler is contained in the binder resin can be obtained, for example, by applying and drying a resin composition containing the conductive filler on the insulating film. The conductive layer 2 may be a single layer or a plurality of 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 still more preferable, from the viewpoints of shielding property, connection reliability, and cost. For copper, for example, it is preferable to use rolled copper foil or electrolytic copper foil, and it is more preferable to use electrolytic copper foil because the conductive layer can be made thinner. Further, 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, 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, more preferably 5 μm or less.

Suitable examples of the metal layer obtained by vacuum vapor deposition include aluminum, copper, silver and gold. Of these, copper and silver are more preferable. Further, preferable examples of the metal layer obtained by sputtering include aluminum, copper, silver, chromium, gold, iron, palladium, nickel, platinum, silver, zinc, indium oxide, and antimony-doped tin oxide. Of these, copper and silver are more preferable. The lower limit of the thickness of the metal layer obtained by vacuum vapor 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 formed by molding an insulating resin composition, and has a role of protecting the conductive layer and a role of ensuring the insulating property of the surface layer. The insulating resin composition preferably uses a thermoplastic resin or a thermosetting resin. The thermoplastic resin and the thermosetting resin are not particularly limited, but resins that can be exemplified in the adhesive layer described later can be preferably used. A resin film made of polyester, polycarbonate, polyimide, polyphenylene sulfide, or the like can be used for the insulating layer.

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

The thickness of the insulating layer may vary depending on the use, but it is preferably 2 to 10 μm. By adjusting the thickness to the above range, it becomes easy to balance various physical properties of the electromagnetic wave shield sheet.

[Adhesive Layer] The adhesive layer 1 is
(I) a thermoplastic resin (A), and (II) a thermosetting resin (B) and at least one of the curable compound (C) for the thermosetting resin (B), containing (I), ( The film (X) after thermocompression bonding of II) or the mixture of (I) and (II) satisfies the following (i) and (ii).
(I) The relative permittivity 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.
In addition, the thermosetting resin (B) includes all resins in which at least a part of the site that undergoes a curing reaction with the curable compound (C) is included.

The relative permittivity and dielectric loss tangent in the present specification refer to values obtained by the following method. That is, (I), (II) or a mixture of (I) and (II) was coated on a peeled polyester film and uniformly coated so that the film thickness after drying was 70 μm. It is dried to obtain a coating film. Then, the obtained coating films were laminated, vacuum-laminated, and heat-cured at 180° C. and 2.0 MPa for 1 hour. Then, the release films on both sides were peeled off to prepare a test piece for evaluation. The dielectric constant and dielectric loss tangent of this test piece at a measurement temperature of 23° C. and a measurement frequency of 1 GHz were obtained using a relative dielectric constant measuring device (cavity resonator type ADMS01Oc) manufactured by ATE.

The lower limit of the relative permittivity is more preferably 1 or more, further preferably 2 or more, and the upper limit is more preferably 3 or less, further preferably 2.8 or less. The dielectric loss tangent is preferably 0, but technically difficult. Therefore, 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, further preferably 0.01 or less.

As will be described later, in the adhesive layer of the present invention, the binder component may contain a conductive filler. When the conductive filler is contained, the values of the relative dielectric constant and the dielectric loss tangent become larger than those before the conductive filler is contained. However, the inventors of the present invention have made extensive studies and found that (I), (II) ) Alternatively, the coating (X) after thermocompression bonding the mixture of (I) and (II) satisfies the above (i) and (ii), which is surprising even when a conductive filler is added. It was found that the problems of the present invention can be solved. This is because by controlling the dielectric properties of (I), (II) or the mixture of (I) and (II) of the adhesive layer, the effect of increasing the shielding property in the conductive layer to which the conductive filler is added, and the binder It is considered that the problem of the present invention has been solved by the 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 permittivity 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, still more preferably 9 or less. The dielectric loss tangent after mixing the conductive filler in the adhesive layer is preferably 0, but it is technically difficult. Therefore, 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, further 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. Further, from the viewpoint of securing the adhesive force, it is preferably 3 μm or more, and more preferably 6 μm or more.

The curable compound (C) is preferably 0.2 part by mass or more, more preferably 1 part by mass or more, and 3 parts by mass or more with respect to 100 parts by mass of the thermosetting resin (B). More preferably. Further, it is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 20 parts by mass or less. By setting the curable compound (C) in the range of 0.2 to 50 parts by mass, the crosslink density can be made appropriate, and the hygroscopicity and the adhesiveness can be kept good. In addition, the elastic modulus of the cured product can be appropriately maintained and the folding endurance can be improved.

When joining the electromagnetic wave shield sheet to a component such as a printed wiring board, it is required to be a laminate capable of withstanding heating in a solder reflow furnace or the like. From this viewpoint, the 5% weight thermal decomposition temperature of the adhesive layer 1 is preferably 240° C. or higher, more preferably 260° C. or higher, and further 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 Examples thereof include polyamide-imide resin and the like. The thermoplastic resin (A) may be used alone or in combination of two or more.

Examples of the thermosetting resin (B) include 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 silicone resin can be exemplified. The thermosetting resin (B) may be used alone or in combination of two or more.

The curable compound (C) refers to all compounds that can contribute to curing with respect to the curable resin (B). The reaction site of the thermosetting resin (B) with the curable compound (C) is not limited, but examples thereof include a carboxyl group, a phenolic hydroxyl group, a (meth)acrylic group, an epoxy group, an oxetanyl group, an amino group, a hydroxyl group, and mercapto. Group, cyano group, isocyanate group, allyl group, vinyl group and the like. From the viewpoint of exhibiting good adhesiveness with the conductive layer 2 and the viewpoint of exhibiting adhesiveness with components such as a coverlay film (for example, a polyimide resin) of a printed wiring board, at least one hydroxyl group and at least one carboxyl group are included. The seed-containing curable resin (B) is preferred. The type of curable functional group in the curable resin (B) may 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, and β-hydroxyalkylamide group-containing compounds. Among these, epoxy compounds, organometallic compounds, aziridine compounds, and isocyanate compounds are preferable from the viewpoint of achieving both adhesiveness and heat resistance. The curable compound (C) may be used alone or in combination of two or more.

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, in particular, the adhesive layer contains a carboxyl group-containing resin as the thermosetting resin (B), an epoxy compound as the curable compound (C), and further contains at least one of an organometallic compound and an isocyanate compound. Those containing are preferable. The epoxy compound is preferably added in an amount of 0.5 to 10 times, more preferably 1 to 5 times, the epoxy equivalent of 1 equivalent of the carboxylic acid. Total curing agent equivalent of the organometallic compound and isocyanate sulfonate compound is preferably formulated in 0.1 to 5 times the carboxylic acid 1 equivalents, more preferably it is incorporated in a range from 0.5 to 3 times .. As described above, by using the curable compound (C), the number of unreacted functional groups after thermosetting can be suppressed, so that the dielectric constant and the dielectric loss tangent are further reduced.

As a suitable combination, a combination of a thermosetting resin (B) having a carboxyl group and a curable compound (C) containing an epoxy compound and an organometallic compound, or a thermosetting resin (B) having a phenolic hydroxyl group and a poly Examples thereof include a combination with a curable compound (C) having an isocyanate group and a combination of a thermoplastic resin (B) having an epoxy group and a curable compound (C) containing an organometallic compound.

The curable compound (C) can be used alone or in combination. Examples of preferable combinations when used in combination include an epoxy compound and an organometallic compound, and an epoxy compound, an aziridine compound and an organometallic compound. When they are used in combination, the crosslink 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.

The isocyanate compound, for example, tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethyl xylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, Polyisocyanate compounds such as polymethylene polyphenyl isocyanate and adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane, burettes and isocyanurates of these polyisocyanate compounds, and further known polyisocyanate compounds and known polyisocyanates. Examples thereof include adducts with ether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols 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'-. Tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N-diglycidylaniline, N,N-diglycidyltoluidine and the like can be mentioned.

Examples of the polycarbodiimide include carbodilite series manufactured by Nisshinbo Industries. Among them, carbodilite V-01, 03, 05, 07, 09 is preferable because it has excellent compatibility with an organic solvent.

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

The organometallic compound is a compound composed of a metal and an organic substance and reacts with a functional group of the curable resin (B) to form a crosslink. The type of the organometallic compound is not particularly limited, but examples thereof include an organoaluminum compound, an organotitanium compound, and an organozirconium compound. The bond between the metal and the organic substance may be a metal-oxygen bond and is not limited to the metal-carbon bond. In addition, the binding mode of the metal and the organic substance may be a chemical bond, a coordinate bond, or 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(ethylacetoacetate), alkylacetoacetate aluminum diisopropylate, aluminum monoacetylacetonate bis(ethylacetoacetate), aluminum tris(acetylacetate), Aluminum monoacetylacetate bis(ethylacetoacetate), aluminum di-n-butoxide monomethylacetoacetate, aluminum diisobutoxide monomethylacetoacetate, aluminum di-sec-butoxide monomethylacetoacetate, aluminum isopropylate, monosec-butoxyaluminum diisopropylate Rate, aluminum sec-butyrate, aluminum 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(ethylacetoacetate), Polytitanium acetyl acetylacetonate, tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetraoctyl titanate, tertiary amyl titanate, tetratertiary butyl titanate, tetrastearyl titanate, titanium isostearate, tri-n-butoxytitanium Examples thereof include monostearate, di-i-propoxytitanium distearate, titanium stearate, di-i-propoxytitanium diisostearate and (2-n-butoxycarbonylbenzoyloxy)tributoxytitanium.
The organic zirconium compound is preferably a zirconium chelate compound. Examples of the zirconium chelate compound include zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium monobutoxyacetylacetonate bis(ethylacetoacetate), zirconium dibutoxybis(ethylacetoacetate), zirconium tetraacetylacetonate, and normal. Examples thereof include propyl zirconate, normal butyl zirconate, zirconium stearate, zirconium octylate and the like. Among these, organic titanium compounds are preferable from the viewpoint 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), but from the viewpoint of heat resistance, the thermosetting resin (B) of (II) and It is preferable to use the curable compound (C).

In the adhesive layer containing the above (II), thermosetting of the adhesive layer from the viewpoint of providing an electromagnetic wave shield sheet capable of exhibiting better adhesive performance while maintaining good transmission characteristics even when used for parts for high frequency applications. It is preferable to use a coating film (Y) after that which 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) The coating (Y) after thermosetting of the adhesive layer contains at least one group selected from a carboxyl group and a hydroxyl group, and in the case of containing 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 hydroxyl groups, the ratio of the number of hydroxyl groups to the number of carbon atoms (hereinafter also referred to as [OH]) is in the range of 0.5 to 20%. Is. Here, the coating film (Y) after the thermosetting of the adhesive layer means a coating 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 further preferably 25% or less.

By using the coating film (Y) in the range of (a) above, the adhesiveness can be better maintained. 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 Examples below. 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, further 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, further preferably 15% or less.

By using the coating film (Y) in the above range (b), it is possible to reduce the water absorption while maintaining the adhesive strength of the adhesive layer, and to provide an adhesive layer having high moisture resistance.
The lower limit of [OH] is more preferably 0.7% or more, still more preferably 1% or more, and the upper limit is more preferably 18% or less, further preferably 15% or less. The lower limit of [COOH] is more preferably 0.05% or more, still more 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 achieved also in the in-plane direction. As a method of imparting conductivity, a mode in which an adhesive layer having isotropic conductivity is used is considered, but in the case of an isotropic conductive layer, when a high-frequency signal flows, a current flows in the horizontal direction between the signal circuit and the isotropic conductive layer. Therefore, it is preferable to use an adhesive layer having anisotropic conductivity, since this causes an 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 further preferably 7 μm or more, from the viewpoint of sufficiently ensuring anisotropy. On the other hand, from the viewpoint of compatibility with the thinness of the adhesive layer, it is preferably 30 μm or less, more preferably 20 μm or less, and further 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, 50% by mass or less in the solid content of the adhesive. It is more preferably 30% by mass or less. From the viewpoint of ensuring conductivity, the amount is preferably 1% by mass or more, and more preferably 10% by mass or more.

The average particle size is the D50 average particle size, and the D50 average particle size was measured using a laser diffraction/scattering particle size distribution analyzer LS13320 (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 means the ratio of the major axis and the minor axis of the particles of the conductive filler (major axis/minor axis). The aspect ratio is determined by measuring the major axis and minor axis of the 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 between the cut surfaces of the particles, and the minor axis is defined as the shortest distance in the direction perpendicular to the major axis.

The conductive filler is not particularly limited, but examples thereof include a metal filler, a carbon filler and a mixture thereof. Examples of the metal filler include metal powder such as silver, copper and nickel, alloy powder 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 coating rate of the metal powder on the surface is preferably 80% or more.

In the conductive filler, the coating layer for coating the core may cover at least a part of the core, but a higher coverage is preferable in order to obtain better conductive properties. From the viewpoint of maintaining good conductive properties, the average coverage of the coating layer is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. The average coverage in this specification refers to a value obtained by measuring powder by ESCA. Detailed conditions are AXIS-HS (Shimadzu/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 obtained from the peak areas of Ag3d:2 and Cu2P:1 under the conditions of 300 and the number of times of integration: 8, and the ratio of the mass concentration of silver was taken as the coverage.

Coating solution stability, that is, aggregation of fillers can be prevented, and when applying a conductive resin composition, from the viewpoint of effectively preventing the generation of streaks and unevenness on the coated surface, glass fiber, carbon filler, etc. The method of applying metal plating to the nucleus is preferable. These conductive fillers are used by being applied and dried in a state of being dispersed in a resin. The particle shape is not particularly limited as long as anisotropic conductivity can be secured. For example, a spherical shape, a dendritic shape (dendritic shape), a needle shape, a fibrous shape and the like can be exemplified. From the viewpoint of ensuring good anisotropic conductivity, spherical and dendritic (dendritic) particles are preferable.

In addition to the silane coupling agent, rust inhibitor, reducing agent, antioxidant, pigment, dye, tackifying resin, plasticizer, ultraviolet absorber, defoaming agent, the resin composition forming the adhesive layer , Leveling adjusters, fillers, flame retardants, etc. can be added.

The method for manufacturing the electromagnetic wave shield sheet 10 is not particularly limited, but as an example, the electromagnetic wave shield sheet 10 can be manufactured by the following manufacturing method. First, the composition of the adhesive layer 1 can be formed into a coating film on a release substrate by a known method. For example, after coating 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 produced by drying.

The thickness of the adhesive layer after being bonded to the component may vary depending on the application, but in order to obtain sufficient adhesiveness, when an anisotropic conductive adhesive layer further mixed with a conductive filler is used, it is preferable. In order to obtain anisotropic conductive characteristics, it is preferably 3 to 50 μm. The lower limit of the thickness of the adhesive layer 1 is more preferably 4 μm or more, further preferably 6 μm or more. The upper limit of the thickness of the adhesive layer 1 is more preferably 30 μm or less.

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

Next, an electromagnetic wave shielding wiring circuit board in which the electromagnetic wave shielding sheet of the present invention is bonded to the wiring circuit board will be described. FIG. 3 shows an example of a schematic explanatory view in which an electromagnetic wave shield sheet is joined to a printed wiring board. The electromagnetic wave shield sheet 10 is joined to the surface layer of the printed wiring board 20 which is a component. The printed wiring board 20 has 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 shield sheet 10 is attached to 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 the ground pattern 24 and the electromagnetic wave shielding sheet 1 are anisotropically conductive via the via 31 formed in the contact hole. The adhesive layer 1 having the property is electrically connected. It is suitable for a flexible printed circuit board or the like, since electrical connection can be achieved only by attaching the electromagnetic wave shield sheet 10 to the printed wiring board 20 and the manufacturing is simple.

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

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

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

FIG. 7 is a schematic sectional view of an electromagnetic wave shielding wired circuit board according to the fourth modification. In this example, by providing a ground via 41 penetrating from the surface layer of the insulating layer 3 to the ground pattern 24 and filling the ground paste 41 with the conductive paste 35, conduction between the electromagnetic wave shielding 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 permittivity of the cover lay of the flexible printed wiring board (hereinafter also referred to as FPC), d is the thickness of the FPC cover lay, and S is the conductive layer of the electromagnetic wave shielding sheet and the transmission circuit. The overlapping area of C, C is the capacitance. R is the conductor resistance (Ω/m), L is the inductance (H/m), G is the conductance (Ω/m) of the insulating layer (base material), f is the frequency, j is the imaginary number symbol, and Then, L and C become dominant. Since the characteristic impedance (Z ₀ ) generally decreases when a shield film is applied, it is necessary to increase the characteristic impedance Z ₀ for impedance matching. Here, the value of the capacitance C is expressed by Equation 2. By decreasing the value of the capacitance C, the value of the characteristic impedance (Z ₀ ) can be increased.
From Expression 2, in order to reduce the value of the capacitance C, a method of adjusting the width 25 (see FIG. 1) of the wiring 25, the thickness of the coverlay layer (insulating adhesive layer 22 + polyimide film 23) (see FIG. 1) And a method of lowering the relative dielectric constant of the coverlay layer. 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 thickening the coverlay layer is not desirable because it goes against the needs of lightness, thinness and shortness. In particular, a flexible printed wiring board or the like is not preferable because the flexibility is reduced. By using a material satisfying the above (i) as the adhesive layer, Dk of Formula 2 is lowered, and it is possible to thin the coverlay layer of the flexible printed board. The polyimide film 23 forming the coverlay layer is an example, and any protective layer having a function of protecting the circuit board may be used, and another material may be used.

If the adhesive layer is not sufficiently heat-cured when the electromagnetic wave shield sheet is thermocompression-bonded to the component, the adhesive layer may stick out from the side portion of the electromagnetic wave shield sheet, resulting in poor appearance. For this reason, it is required that there is no or little protrusion when the electromagnetic wave shield sheet is attached in the thermocompression bonding process.

According to the electromagnetic wave shielding sheet of the present invention, by using the adhesive layer satisfying the above (i) and (ii), it is possible to ensure good transmission even when it is used as a component for high frequency applications while securing the shielding property against electromagnetic waves and the like. The characteristics can be maintained. This is because by using an adhesive layer satisfying the above (i) and (ii), it is possible to suppress the phenomenon that the electric polarization of the dielectric material cannot follow the change of the electric field and part of the energy becomes heat. It is considered that this is possible, and as a result, the dielectric loss can be reduced. By satisfying the above (i), characteristic impedance matching can be improved. Further, by satisfying the above (i) and (ii), the transmission loss of the high frequency signal can be improved. Therefore, it can be suitably used in a wide frequency band. In particular, it is suitable for use as an electromagnetic wave shielding film for a signal transmission system that transmits a high frequency signal (10 MHz or more, preferably 1 GHz or more) in which impedance mismatch and transmission loss easily occur.

In addition, by combining a binder component satisfying the above (i) and (ii) with a conductive filler, not only the conduction with the component is simplified, but also the good adhesiveness is obtained and the transmission characteristics are improved. The 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 It is possible to widen the design margin of the wiring width w of the signal circuit and/or the thickness of the coverlay when matching the. Therefore, the yield can be improved and the production cost can be suppressed. Therefore, the productivity of the circuit can be improved.
INDUSTRIAL APPLICABILITY The electromagnetic wave shielding sheet of the present invention can be widely applied not only to a printed circuit board but also to a component or various electronic devices that emit or shield electromagnetic waves.

<<Example>>
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. In addition, "part" in the examples 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 Co., Ltd.)
R2 (polyester resin): Addition type polyester resin Acid value 19 [mgKOH/g] (manufactured by Toyochem Co., Ltd.)
R3 (urethane resin): Urethane urea resin Acid value 5 [mgKOH/g] (manufactured by Toyochem Co., Ltd.)
<Conductive filler>
F1 (silver-coated copper powder): “Dendritic particles using copper as core and silver as coating layer D50 average particle size=11.0 μm” (manufactured by Fukuda Metal Foil & Powder Co., Ltd.)
<Copper foil>
Electrolytic copper foil with carrier: “MT18SD-H (18 μm carrier copper foil and 3 μm electrolytic copper foil)” (manufactured by Mitsui Kinzoku Co., Ltd.)
<Curable compound>
H1 (tetraphenol ethane type epoxy curing agent): "jER1031S" (manufactured by Mitsubishi Chemical Corporation)
H2 (phenol novolac type epoxy curing agent): "jER152" (manufactured by Mitsubishi Chemical Corporation)
H3 (titanium chelate compound): "TC401" (manufactured by Matsumoto Fine Chemical Co., Ltd.)
H4 (aluminum chelate compound): "ALCH" (Kawaken Fine Chemical Co., Ltd.)
H5 (isocyanurate type blocked isocyanate): "BL3175" (manufactured by Sumika Bayer Urethane Co., Ltd.)
H6 (aziridine compound): "chemitite PZ-33" (manufactured by Nippon Shokubai Co., Ltd.)

<Production of electromagnetic wave shield sheet>
Example 1 100 parts of resin R1 (polyamide resin) and 50 parts of conductive filler F1 (silver-coated copper powder) were charged into a container, and a mixed solvent of toluene and isopropyl alcohol (toluene 100 was added so that the nonvolatile content concentration was 40%). 50 parts of isopropyl alcohol) was added to each part and mixed. Next, 15 parts of the curable compound H1 (tetraphenolethane type epoxy curing agent) and 3 parts of the curable compound H3 (titanium chelate compound) were added, and the mixture was stirred with a disper for 10 minutes to obtain a resin composition. Further, the obtained resin composition was coated on a peelable sheet using a bar coater so that the dry thickness was 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 (tetraphenolethane type epoxy curing agent) and 10 parts of curable compound H6 (aziridine compound) were added, and the mixture was stirred for 10 minutes with a disperser to produce an insulating resin. A composition was obtained. Next, the obtained insulating resin composition is applied onto a peelable sheet using a bar coater so that the dry thickness is 10 μm, and dried in an electric oven at 100° C. for 2 minutes to obtain an insulating layer. It was

After bonding the insulating layer to the electrolytic copper foil side of the carrier with an electrolytic copper foil, peeling off the carrier copper foil was laminated electrolytic copper foil on the insulating layer. Next, an adhesive layer was attached to the surface of the electrolytic copper foil to obtain an electromagnetic wave shield sheet composed of "peelable sheet/insulating layer/electrolytic copper foil/adhesive layer/peelable sheet". The electrolytic copper foil and the adhesive layer were attached to each other at a temperature of 90° C. and a pressure of 3 kgf/cm ² with a heat 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, the same procedure as in Example 1 was performed to obtain Examples 2 to 15 and Comparative Examples 1 to 1. The electromagnetic wave shield sheet of No. 5 was obtained.

(Film Thickness of Adhesive Layer) The film thickness of the electromagnetic wave shielding sheet is the thickness of the adhesive layer after being thermocompression bonded to the component, and was measured by the following method. First, the peelable sheet of the adhesive layer of the electromagnetic wave shield sheet was peeled off, and the exposed adhesive layer and the polyimide film (“Kapton 200EN” manufactured by Toray-Dupont Co., Ltd.) were bonded together and heat-pressed for 30 minutes at 2 MPa and 150° C. 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 Maltaux Co.) is dropped on a slide glass, and an electromagnetic wave shield sheet is adhered to the slide glass/electromagnetic wave shield. A laminate having a sheet/polyimide film structure was obtained. The obtained laminate was cut and processed by ion beam irradiation from the polyimide film side using a cross section polisher (SM-09010 manufactured by JEOL Ltd.) to obtain a measurement sample of the electromagnetic wave shield sheet after thermocompression bonding.

The thickness of the adhesive layer was measured from the enlarged image of the cross section of the obtained measurement sample using a laser microscope (VK-X100 manufactured by Keyence Corporation). 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 loss tangent]
Coating (X) of (I) thermoplastic resin (A) and (II) thermosetting resin (B) and curable compound (C) used for the adhesive layer (hereinafter, also simply referred to as "coating (X)") The relative permittivity and dielectric loss tangent containing at least one of the above were prepared by the following procedure.
<Measurement film of Example 1>
A container was charged with 100 parts of the resin R1, 15 parts of the curable compound H1 and 3 parts of the curable compound H3, and a non-volatile content was adjusted to 45% by adding a mixed solvent of 50 parts of isopropyl alcohol to 100 parts of toluene. .. Further, the solution was stirred with a disper for 10 minutes, and then vacuum defoaming treatment was performed to obtain a sample solution. The obtained sample solution was uniformly applied to a peelable sheet so that the dry thickness was 30 μm, and dried to obtain a pre-coated film.

<Coating films for measurement in Examples 2 to 15 and Comparative Examples 1 to 5>
Pre-coats of the adhesive layers of Examples 2 to 15 and Comparative Examples 1 to 5, respectively, were obtained in the same manner as in the measurement coating of Example 1 except that the raw materials and blending amounts shown in Table 1 were changed. ..

The above-mentioned coating (X) was used to determine the relative permittivity and dielectric loss tangent according to the following procedure in accordance with the Japan Electronic Circuits Association's flexible printed wiring board and flexible printed wiring board material-part 2 integrated standard-(JPCA-DG03). It was measured.
A plurality of layers of the coating (X) produced in the examples and the comparative examples are laminated so as to have a desired thickness, which is vacuum laminated and heat-cured at 180° C. and 2.0 MPa for 1 hour to form the coating (X). Got The coating (X) was cut into a size having a width of 3 mm and a length of 100 mm, the release sheets on both sides were peeled off, and a cured coating having a thickness of 80 μm was used as a test piece for evaluation. Three test pieces were set in the relative permittivity measuring device “ADMS01Oc” manufactured by ATE, and the relative permittivity and the dielectric loss tangent at a measuring temperature of 23° C. and a measuring frequency of 1 GHz were obtained by the cavity resonator method. It was The results are shown in Table 3.

[Quantification of [N] and [O] of the adhesive layer after curing]
Measuring film of 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 were charged into the container. A pre-adhesion layer was obtained by the same method as in (1) and treated in an oven at 180° C. for 60 minutes to obtain a coating (Y) after thermosetting. ESCA analysis was performed on the surface of the obtained coating film (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.
Device: AXIS-HS (Shimadzu/Kratos)
Degree of vacuum 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/elemental Dell: 300, cumulative number of times: 5
Photoelectron take-off angle: 90 degrees with respect to sample surface Binding energy: C1s Main peak is 284.6 eV, shift correction C(1s) peak area: 280 to 296 eV
O(1s) peak area: 530 to 534 eV
N(1s) peak area: 395 to 405 eV
The peaks appearing in the above peak regions were drawn with a baseline by the linear method, and the ratio of the number of nitrogen atoms to the number of carbon atoms and the ratio of oxygen atoms were calculated from the atomic concentration "Atomic Conc" of each atom.
[N]=number of atoms of N(1s)/number of atoms of C(1s)×100
[O]=O(1s) atom number/C(1s) atom number×100
The above-mentioned measurement was performed at three places and at different places, and the average values were taken as [N] and [O] of the adhesive layer after curing.

[Quantification of residual functional group 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, a hydroxyl group or a carboxyl group cannot usually be identified by ESCA, which makes quantitative analysis difficult. However, by treating a fluorine reagent that selectively binds to a carboxylic acid or a hydroxyl group, only the carboxyl group or the hydroxyl group is modified with fluorine, and the functional group can be identified by ESCA. Further, since the fluorine bond has a high detection sensitivity of ESCA, it is possible to perform a highly sensitive quantitative analysis of functional groups on the surface. As a result of intensive studies by the present inventors, in the coating (Y), the ratio [COOH] of the number of carboxyl groups to the number of carbons is 0.01 to 15%, and the ratio [OH] of the number of hydroxyl groups to the number of carbons is 0.5. When it is in the range of up to 20%, good transmission characteristics can be maintained when the electromagnetic wave shielding sheet of the present invention is attached to a component for high frequency use such as a printed wiring board while maintaining high adhesiveness to the component. I found out.

A film (Y) obtained by the same method as above was cut into a width of 30 mm and a length of 30 mm, and the cut film was attached to a glass plate to prepare a sample. The vial was sealed, and the fluorine-modified reagent and the sample were subjected to a gas phase reaction in a non-contact state at 55° C. for 24 hours. After the gas phase reaction was completed, the sample was taken out of the reaction vessel and dried in a nitrogen stream to remove the residual reagent. The removal of the residual reagent was carried out by appropriately adjusting the temperature and time until the fluctuation of the N(1s) peak area disappeared.
The fluorine-modified sample was subjected to ESCA analysis under the same conditions as the above-mentioned quantification of [N] and [O] to quantify [OH] and [COOH] of the adhesive layer. Three measurement samples were prepared, and the average value of the calculated values was calculated.

<Method of measuring [OH]>
After performing 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 formula.
<Expression> [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 line baseline in the range of 280 to 296 eV. The peak area of F(1s) [F(1s)] is 682 to 695 eV. It was determined by drawing a linear 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 peculiar to the apparatus, and when AXIS-HS (Shimadzu/Kratos) is used, the sensitivity correction value peculiar to the apparatus is It was set to 3.6.

<Method of measuring [COOH]>
After carrying out the modification reaction of the carboxyl group 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] is represented by a value calculated by the following formula.
<Equation> [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 linear baseline in the range of 280 to 296 eV. The F(1s) peak area [F(1s)] is 682 to 695 eV. It was determined by drawing a straight baseline in the range. Further, similarly to the above, the reaction rate r was 1 and k was 3.6.

[Hygroscopicity] Hygroscopicity was evaluated based on the presence or absence of a change in the appearance of the adhesive layer after the electromagnetic wave shield sheet and the molten solder were brought into contact with each other. The sample having low hygroscopicity does not change in appearance, but the sample having 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 copper-plated laminated plate having a total thickness of 64 μm (gold plated 0.3 μm/nickel plated 1 μm/ The gold-plated surface of copper foil 18 μm/adhesive 20 μm/polyimide film 25 μm) was pressure-bonded under the conditions of 150° C., 2.0 MPa, 30 minutes, and heat-cured to obtain a laminate. The obtained laminated body was cut into a size of 10 mm in width and 65 mm in length to prepare a sample. The obtained sample was left for 72 hours in an atmosphere of 40° C. and 90% RH. After that, the polyimide film surface of the sample is placed on the molten solder at 250° C. for 1 minute, the sample is taken out, and the appearance is visually observed to check if there is any abnormality such as foaming, floating, or peeling of the adhesive layer. It evaluated by the standard.
Excellent: No change in appearance.
Good: Small bubbles are slightly observed.
Acceptable: Less than the above goodness, and unsuitable for the following.
Poor: Vigorous foaming and peeling are observed.

[Adhesive Strength] An electromagnetic wave shield sheet having a width of 25 mm and a length of 70 mm was prepared as a sample. The peelable sheet provided on the adhesive layer is peeled off, and a polyimide film (“Kapton 200EN” manufactured by Toray DuPont Co., Ltd.) having a thickness of 50 μm is pressure-bonded to the exposed adhesive layer under the conditions of 150° C., 2.0 MPa, and 30 minutes. , Heat cured. Then, the peelable sheet on the insulating layer side was peeled off for the purpose of reinforcing the sample for measuring the adhesive strength, and an adhesive sheet manufactured by Toyochem Co., Ltd. was used for the exposed insulating layer, and a polyimide film having a thickness of 50 μm was added at 150° C. and 1 MPa. Then, pressure-bonding was carried out under the condition of 30 minutes to obtain a laminate having a constitution of "polyimide film/adhesive sheet/electromagnetic wave shielding sheet/polyimide film". Using a tensile tester (manufactured by Shimadzu Corporation), this laminate was peeled off at a peeling speed of 50 mm/min and a peeling angle of 90° in an atmosphere of 23° C. and 50% RH, and an adhesive layer of an electromagnetic wave shielding sheet and a polyimide film were formed. The adhesive force was measured by peeling the interface of the. The evaluation criteria are as follows.
Excellent: 6 N/25 mm or more.
Good: 4 N/25 mm or more and less than 6 N/25 mm, practically no problem.
Poor: Less than 4 N/25 mm.

[Protrusion]
The squeeze-out property was evaluated by the following samples. An electromagnetic wave shield 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 with a hole punching machine. Then, the peelable sheet of the adhesive layer was peeled off, and the adhesive layer and the polyimide film (“Kapton 200EN” manufactured by Toray-Dupont Co., Ltd.) were heated and pressed under the conditions of 150° C., 2 MPa, and 30 minutes. After cooling to room temperature, the hole portion of the electromagnetic wave shield sheet was observed with a magnifying glass, and the length of the adhesive layer protruding inside the hole was measured. For the protruding length, the most protruding portion 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 endurance]
The folding resistance of the electromagnetic wave shield sheet was evaluated by a MIT test in accordance with JIS C6471. First, an electromagnetic wave shield sheet was prepared with a size of 15 mm in width and 120 mm in length. Separately, as an adherend to which the electromagnetic wave shielding film is attached, based on a two-layer CCL in which a polyimide film (thickness 12.5 μm “Kapton 50EN” manufactured by Toray DuPont) and a copper foil (thickness 18 μm) are laminated, Wiring is formed in a shape based on JIS C6471, and a cover lay "CISV1215 (manufactured by Nikkan Kogyo Co., Ltd.)" composed of a 12.5 μm thick polyimide film and a 15 μm thick thermosetting adhesive is attached to cover. A coat layer was formed. Furthermore, a sample was obtained by peeling the peelable sheet on the conductive layer side of the electromagnetic wave shield sheet and exposing the exposed conductive layer to the cover coat layer under the conditions of 150° C., 30 minutes and 2.0 MPa. Folding endurance of the obtained sample was measured using an MIT tester under the conditions of a temperature of 25° C. and a humidity of 50%, a radius of curvature of 0.38 mm, a load of 500 g, and a speed of 180 times/min. For evaluation, bending was performed 3000 times, and the number of times of bending until the wiring was broken was measured. The evaluation criteria are as follows.
Excellent: No breakage occurred even after bending 3000 times.
Good: The number of bends before disconnection is 2500 or more and less than 3000, and there is no practical problem.
Poor: Broken after less than 2500 times.

[Appropriate evaluation for high frequency applications]
The suitability for high frequency use was evaluated using the following measurement samples.
FIG. 8 shows a schematic plan view of 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 shows a schematic plan view of the back surface side. First, a double-sided CCL “R-F775” (manufactured by Panasonic Corporation) in which rolled copper foil with a thickness of 12 μm was laminated on both sides of a polyimide film 50 with a thickness of 50 μm was prepared. Then, six through holes 51 (diameter 0.1 mm) were provided in the vicinity of each of the four rectangular corners. In the figure, for convenience of illustration, only two through holes 51 are shown at each corner. Next, after performing electroless plating, electrolytic plating was performed to form a copper plating film 52 of 10 μm, and electrical continuity between both main surfaces was secured via the through hole 51. After that, as shown in FIG. 8, two signal wirings 53 having a length of 10 cm are provided on the main surface of the polyimide film 50, and a ground wiring 54 parallel to the signal wiring 53 and a ground wiring 54 extending outside the signal wiring 53. The polyimide film 50 was formed with a ground pattern 55 formed in a region including the through hole 51 in the lateral direction.

Then, 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 appearance of the circuit and the inspection specification of the tolerance are set to the JPCA standard (JPCA-DG02). Next, on the main surface side of the polyimide film 50, a cover lay 57 "CISV1215 (manufactured by Nikkan Kogyo Co., Ltd.)" including a polyimide film 57a (thickness 12.5 μm) and an insulating adhesive layer 57b (thickness 15 μm) Was attached (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 seen. Then, the copper foil pattern exposed from the coverlay 57 was nickel-plated (not shown), and then gold-plated (not shown).

FIG. 10 shows a schematic plan view of a 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. Further, FIG. 11 shows a sectional view taken along the line XI-XI of FIG. 10, and FIG. 12 shows a sectional view taken along the line XII-XII of FIG. In FIG. 10, for convenience of explanation, the electromagnetic wave shield sheet 61 is shown in a perspective view. Two electromagnetic wave shield sheets 61 and 62 were prepared, and the release treatment sheet (not shown) provided on the adhesive layer 71 of the electromagnetic wave shield 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 shield sheets 61 and 62 inside, and pressure-bonded under the conditions of 150° C., 2.0 MPa, and 30 minutes to obtain the printed wiring board 8 with the electromagnetic wave shield sheet. Got As the electromagnetic wave shield sheets 61 and 62, sheets in which an adhesive layer 71, a conductive layer 72 and an insulating layer 73 were laminated in this order were used.

The electromagnetic wave shielding sheet 61 provided on the main surface side of the printed wiring board 7 has two openings 60 as shown in FIG. From the respective openings 60, the protrusions 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 these exposed ground pattern 55 and signal wiring 53, and a test is performed. On the back side of the printed wiring board 7, an electromagnetic wave shield sheet 62 having substantially the same shape as the electromagnetic wave shield sheet 61 and having no 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 an electromagnetic wave shield 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 within the range of 100 mΩ±5 mΩ. As described above, the thicknesses of the coverlay and the adhesive layer of the shield sheet were appropriately adjusted. On the other hand, in Comparative Example 5, the total thickness of the adhesive layers of the coverlay and the shield sheet was 50.5 μm, and the wiring width of the signal circuit was adjusted so that the characteristic impedance was within 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 Coverlay and Adhesive Layer) After cutting the printed wiring board 8 with an electromagnetic wave shield into a size with a width of about 5 mm and a length of about 5 mm, an epoxy resin (Petropoxy 154, manufactured by Maltaux Co.) was applied on a slide glass to a size of 0. 05 g was dropped and the printed wiring board 8 with an electromagnetic wave shield and the slide glass were adhered to each other to obtain a laminate of slide glass/printed wiring board 8 with an electromagnetic wave shield. The obtained laminate was cut and processed by ion beam irradiation from the printed wiring board 8 side using a cross section polisher (SM-09010 manufactured by JEOL Ltd.) to obtain a measurement sample of the printed wiring board 8 with an electromagnetic wave shield. ..

The cross section of the obtained measurement sample was observed using an enlarged image of a laser microscope (VK-X100 manufactured by Keyence Corp.) at a position indicated by an arrow T in FIG. 12 (a position where a circuit is not formed). The thicknesses 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 the present specification) were measured. The FPC thickness was measured at a magnification of 500 to 2000 times and evaluated as follows. The results are shown in Table 3.
Excellent: The total thickness of the adhesive layers of the cover lay and the electromagnetic wave shielding sheet is less than 48.5 μm.
Good: The total thickness of the adhesive layers of the cover lay 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 layers of the cover lay 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 are as follows. The results obtained are shown in Table 3.
[10 GHz]
Excellent: less than 4.5 dB Good: less than 4.5 dB, less than 5.0 dB Poor: more than 5.0 dB [20 GHz]
Excellent: Less than 7 dB Good: 7 dB or more, less than 7.5 dB Poor: 7.5 dB or more

As shown in Table 3, it was found that by using a material satisfying the above (i) and (ii) as the adhesive layer, the transmission loss in the high frequency signal can be effectively suppressed without narrowing the L/S of the circuit. It was Example 14 not containing a conductive filler, that is, using an adhesive layer having no conductivity can effectively suppress the transmission loss, and also uses the same thermosetting resin and curing agent as Example 14 as a binder. Also in Examples 12 and 13 in which a conductive filler was added to this as a component, the result was obtained that the transmission characteristics in high frequency applications could be improved (transmission loss could be effectively suppressed). Although the compositions of Comparative Example 2 and Comparative Example 5 are the same, in Comparative Example 5 in which the thickness of the FPC was 50.5 μm as in the case of Example, it was necessary to reduce L/S, and as a result, the productivity was reduced. Will fall.

1, 71 Adhesive layer 2, 72 Conductive layer 3, 73 Insulating layer 7 Printed wiring board 8 Printed wiring board with electromagnetic wave shield 10, 61, 62 Electromagnetic wave shield 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 Projection 60 Openings 61, 62 Electromagnetic Wave Shield Sheet

Claims (11)

A printed circuit board comprising a substrate on which a wiring pattern is formed, and a coverlay layer formed on the wiring pattern,
An electromagnetic wave shield sheet which is joined to the coverlay layer by thermocompression bonding and shields at least a part of electromagnetic waves emitted from the printed circuit board;
The electromagnetic wave shield sheet is a sheet obtained by thermocompression bonding an electromagnetic wave shield sheet composed of the following laminated body,
The laminate is
An adhesive layer that is joined to the coverlay layer (provided that it does not exhibit conductivity ),
A conductive layer laminated on the adhesive layer,
An insulating layer formed on the conductive layer,
The adhesive layer contains a thermosetting resin (B) and a curable compound (C) for the thermosetting resin (B) as a binder component,
The curable compound (C) is contained in an amount of 0.2 to 50 parts by mass with respect to 100 parts by mass of the thermosetting resin (B),
The coating (X) after thermocompression-bonding the binder component satisfies the following (i) and (ii),
In the coating film (Y) after thermosetting of the adhesive layer, an electromagnetic wave shield having a ratio of the number of nitrogen atoms to the number of carbon atoms of 1 to 10% and a ratio of the number of oxygen atoms to the number of carbon atoms of 3 to 20%. Printed circuit board.
(I) The relative permittivity 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. As the curable compound (C),
The electromagnetic wave shielding wired circuit board according to claim 1, wherein the epoxy compound and the organometallic compound are used together, or the epoxy compound, the organometallic compound and the aziridine compound are used together. The thermosetting resin (B) contains a carboxyl group-containing resin,
The electromagnetic wave shielding wired circuit board according to claim 1, which contains an epoxy compound as the curable compound (C), and further contains at least one of an organometallic compound and an isocyanate compound. The electromagnetic wave shielding wired circuit board according to claim 1, wherein the thickness of the adhesive layer after the thermocompression bonding is 3 to 50 μm. The coating (Y) after thermosetting of the adhesive layer contains at least one group selected from a carboxyl group and a hydroxyl group,
When the carboxyl group is contained, the ratio of the number of carboxyl groups to the number of carbon atoms is in the range of 0.01 to 15%,
When the hydroxyl group is contained, the ratio of the number of hydroxyl groups to the number of carbon atoms is in the range of 0.5 to 20%,
Electromagnetic shielding wiring circuit board according to any one of claims 1-4 total carboxyl groups and the number of hydroxyl groups is less than 35% relative to the number of carbon atoms. The conductive layer, the electromagnetic wave shielding wiring circuit board according to any one of claims 1 to 5 which is a metal layer. As a hygroscopic test of the electromagnetic shielding sheet,
The laminate is 25 mm in width and 70 mm in length, and the laminate and the copper clad laminate are thermocompression bonded under the conditions of 150° C., 2.0 MPa, and 30 minutes so as to be bonded via the adhesive layer. A sample was obtained, and the sample was cut into a size of 10 mm in width and 65 mm in length, and then left in an atmosphere of 40° C. and 90% RH for 72 hours so that the surface of the copper clad laminate contacted the molten solder at 250° C. When visually observing the appearance of the adhesive layer after floating for 1 minute,
Electromagnetic shielding wiring circuit board according to peeling and foaming was not observed any one of claims 1-6. A sample prepared by preparing the laminate having a width of 25 mm and a length of 70 mm and thermocompressing the adhesive layer of the laminate and a polyimide film having a thickness of 50 μm under the conditions of 150° C., 1 MPa, and 30 minutes The adhesive force when the interface between the adhesive layer and the polyimide film is peeled off is 4 N/25 mm or more at a peeling speed of 50 mm/min and a peeling angle of 90° in an atmosphere of 50°C and 50% RH. 7 electromagnetic shielding wiring circuit board according to any one of. The thickness of the adhesive layer before thermocompression bonding is 15 μm, and after forming a through hole having a diameter of 5 mm in the laminate, the adhesive layer of the laminate and the polyimide film are formed under the conditions of 150° C., 2 MPa, and 30 minutes. in samples cooled to room temperature thermocompression bonding, electromagnetic shielding wiring circuit board according to any one of the through holes of claims 1-8 protrusion amount of the adhesive layer to the inside is less than 2.0mm .. A sample prepared by preparing the laminate having a width of 15 mm and a length of 120 mm and thermocompressing the adhesive layer and the polyimide film of the laminate under the conditions of 150° C., 2 MPa, and 30 minutes to room temperature, According to JIS C6471, when the folding endurance was measured using a MIT tester under the conditions of a radius of curvature of 0.38 mm, a load of 500 g, and a speed of 180 times/min, the number of bendings until the break was 2500 times or more. An electromagnetic wave shielding wired circuit board according to any one of claims 1 to 10 . Electronic equipment electromagnetic shielding wiring circuit board according is mounted to any one of claims 1-10.

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