JP2020021924A - Printed wiring board with electromagnetic wave shield sheet - Google Patents

Abstract

To provide a printed wiring board with an electromagnetic wave shield sheet excellent in thermocompression bonding resistance, migration resistance and flexibility while having high light blocking effect.SOLUTION: A printed wiring board with an electromagnetic wave shield sheet comprises an electromagnetic wave shield sheet, a cover coat layer, and a substrate with signal wiring and an insulating base material. The cover coat layer has a cured product of a resin layer formed from a thermosetting solder resist containing a colorant and a thermosetting resin. The cured product of the resin layer has a storage modulus at 85°C from 1.0E+06 to 1.0E+10 Pa.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printed wiring board with an electromagnetic wave shielding sheet, a method for manufacturing the same, and an electronic device including the same. The invention also relates to a thermosetting solder resist for forming a printed wiring board with an electromagnetic wave shielding sheet.

  2. Description of the Related Art In recent years, flexible and flexible flexible printed circuit boards (hereinafter, referred to as FPCs) have become indispensable for electronic devices such as mobile phones, video cameras, and notebook computers, which are rapidly becoming smaller and thinner. Further, as the pitch of the built-in signal wiring becomes narrower and higher in frequency as the performance of electronic devices becomes higher, measures against electromagnetic wave noise have become increasingly important. Therefore, it is common to incorporate an electromagnetic wave shielding material that shields or absorbs electromagnetic wave noise generated from signal wiring into the FPC.

  The FPC is composed of a copper clad laminate (CCL) having a circuit formed by an etching process and a cover coat layer. The formation of the cover coat layer is generally selected from a coverlay film, a thermosetting ink (thermosetting solder resist), a photosensitive ink (alkali developing solder resist or UV-curing solder resist), and the like. Coverlay films are often used because of their ease of handling, durability and insulation reliability.

  A coverlay film is a material in which a thermosetting adhesive is applied to an insulating base material. As a use form using such a coverlay film, Patent Document 1 discloses that a conductive layer is formed on a cover coat layer of an FPC. An electromagnetic wave in which a shield layer having a conductive adhesive layer, a metal thin film layer, and the like is bonded together, and a conductive adhesive layer is joined to a ground wiring through an opening of a cover coat layer of the FPC to electrically connect the metal thin film layer. An FPC having a shielding function is disclosed.

  With the increase in the density of FPCs accompanying the reduction in size and weight of electronic devices, a cover coat layer having a fine opening pattern has been required. Patent Literature 2 discloses an alkali developable resin, an epoxy resin, A resin composition and a dry film excellent in resolution and crack resistance by using a reaction initiator, a photopolymerizable monomer and a surface-treated inorganic filler have been proposed.

  The cover coat layer is also required to have high light-shielding properties from the viewpoint of information protection and visibility. Patent Document 3 discloses a compound having a carboxyl group and an ethylenically unsaturated group, urethane (meth) acrylate, Patent Document 4 discloses a black photosensitive composition and a dry film having excellent shielding properties and storage stability by using a polymerizable compound having an ethylenically unsaturated group other than the above, a photopolymerization initiator, and carbon black. A resin composition for a solder resist and a solder resist film having excellent insulation properties have been proposed by using, an inorganic filler, and a black pigment containing black titanium oxide.

JP 2007-294996 A JP-A-2006-177174 JP 2012-141605 A JP-A-2017-034213

However, the cover coat layer using a solder resist is often a single layer structure without an insulating base material compared to the coverlay film, and when the electromagnetic wave shielding sheet is laminated, the cover is applied due to heat and pressure at the time of lamination. The coat layer may flow, resulting in a decrease in thickness (heat-resistant pressure bonding property) or an extremely poor migration resistance. In addition, if the crosslink density is increased to improve the migration resistance and the hardness of the film is increased, cracks may occur at the time of bending (flexibility), making it difficult to achieve both migration resistance and flexibility. .
As described above, at present, there is no printed wiring board with an electromagnetic wave shielding sheet that has high heat-pressing resistance, migration resistance, and flexibility while having high light-shielding properties.

    Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the present invention can solve the above problems.

  That is, the present invention is a printed wiring board with an electromagnetic wave shielding sheet comprising an electromagnetic wave shielding sheet, a cover coat layer, and a substrate having signal wiring and an insulating substrate, wherein the cover coat layer is formed of a thermosetting resin. And a cured product of a resin layer formed from a thermosetting solder resist containing a colorant. The cured product of the resin layer has a storage elastic modulus at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa. The present invention relates to a printed wiring board provided with an electromagnetic wave shielding sheet.

  The present invention also relates to the printed wiring board with an electromagnetic wave shielding sheet, wherein the colorant is a black colorant.

  The present invention also relates to the printed wiring board with the electromagnetic wave shielding sheet, wherein the black colorant contains titanium black.

  The present invention also relates to the printed wiring board with an electromagnetic wave shielding sheet described above, which further contains hydrophobic silica fine particles.

  The present invention also relates to the printed wiring board with an electromagnetic wave shielding sheet, wherein the porosity of the cover coat layer is in the range of 0.1% to 10%.

  The present invention also relates to the printed wiring board with an electromagnetic wave shielding sheet, wherein the cover coat layer has an opening having an opening diameter of 0.05 to 1 mm.

  The present invention also relates to an electronic device provided with the printed wiring board with the electromagnetic wave shielding sheet.

  Further, the present invention provides a step of forming a signal wiring on an insulating substrate, a step of laminating a dry resist film on the signal wiring, a step of curing the dry resist film to form a cover coat layer having an opening, A method of manufacturing a printed wiring board with an electromagnetic wave shielding sheet, which is manufactured by laminating an electromagnetic wave shielding sheet on a cover coat layer and hot pressing, wherein the dry resist film comprises a thermosetting resin and a colorant. A printed wiring board with an electromagnetic wave shielding sheet, wherein the cured product of the resin layer has a storage elasticity at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa. And a method for producing the same.

Further, the present invention provides a step of forming a signal wiring on an insulating base material, a step of applying a thermosetting solder resist on the signal wiring to form a resin layer, and a step of curing the resin layer to form a cover coat layer having an opening. Forming an electromagnetic wave shielding sheet on the cover coat layer and hot pressing, wherein the thermosetting solder resist is heat-cured. Production of a printed wiring board with an electromagnetic wave shielding sheet having a resin layer containing a conductive resin and a coloring agent, wherein the cured product of the resin layer has a storage elastic modulus at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa. About the method.

Further, the present invention is a dry resist film for forming a printed wiring board with an electromagnetic wave shielding sheet according to any one of claims 1 to 6,
It has a resin layer formed from a thermosetting solder resist containing a thermosetting resin and a coloring agent. The cured product of the resin layer has a storage elastic modulus at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa. The present invention relates to a dry resist film characterized by the following.

  Further, the present invention relates to a thermosetting solder resist for forming a resin layer of the dry resist film, the thermosetting solder resist containing a thermosetting resin and a coloring agent.

  According to the present invention, it is possible to provide a printed wiring board with an electromagnetic wave shielding sheet, which has high light-shielding properties, and is excellent in heat compression resistance, migration resistance, and flexibility.

FIG. 1 is a conceptual diagram illustrating a migration test.

  Hereinafter, an example of an embodiment to which the present invention is applied will be described. Note that the sizes and ratios of the respective members in the following drawings are for convenience of explanation, and are not limited thereto. 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 term “sheet” in this specification includes not only “sheet” defined in JIS but also “film”. The numerical values specified in the present specification are values obtained by the method disclosed in the embodiment or the example. In this specification, “parts” and “%” represent “parts by mass” and “% by mass”, respectively.

<Cover coat layer>
The cover coat layer is an insulating layer that covers the signal wiring of the wiring board and protects it from the external environment. The cover coat layer may be formed by curing a resin layer of a dry resist film, or after forming a resin layer by applying a thermosetting solder resist to a substrate having signal wiring and an insulating base material, It may be made by curing. In the description of the embodiment to which the present invention is applied, an example using a dry resist film will be described, but the present invention is not limited to this.

  The cured product of the resin layer in the cover coat layer has a storage elastic modulus at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa.

The porosity of the cover coat layer is preferably in the range of 0.1 to 10%. The “porosity” means the ratio (area ratio) of voids to the total area of the cross section in an arbitrary cross section.
When the cover coat layer has voids, the cover coat layer is easily deformed, and the flexibility is improved.
The porosity in the cover coat layer decreases as the filler content decreases, and increases as the filler content increases. The smaller the porosity in the cover coat layer, the better the migration resistance.

  The thickness of the cover coat layer is preferably from 5 to 100 μm, more preferably from 10 to 70 μm. By setting the thickness of the cover coat layer in the range of 5 to 100 μm, flexibility and migration resistance can be improved.

  The glass transition temperature (Tg) of the cover coat layer is preferably from 40C to 120C, more preferably from 50C to 100C. By setting the glass transition temperature (Tg) of the cover coat layer to 40 ° C. to 120 ° C., flexibility and migration resistance can be improved.

《Dry resist film》
The dry resist film of the present invention is a dry resist film for forming a printed wiring board with an electromagnetic wave shielding sheet, and is formed of a thermosetting resin and a thermosetting solder resist containing a colorant. With layers. The cured product of the resin layer has a storage elastic modulus at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa. As a result, a cover coat layer that can satisfy high light-shielding properties, heat-resistant pressure bonding properties, migration resistance, and flexibility can be obtained. A dry resist film often has a peelable sheet in addition to a resin layer.

<Storage modulus at 85 ° C.>
The cured product of the resin layer has a storage elastic modulus at 85 ° C. in the range of 1.0E + 06 to 1.0E + 10 Pa. Further, the lower limit value of the storage elastic modulus at 85 ° C. is preferably 1.0E + 07 Pa or more, and more preferably 4.0E + 07 Pa. The upper limit of the storage modulus at 85 ° C. is preferably 5.0E + 9Pa or less, more preferably 1.0E + 9Pa or less. Within this range, excellent migration resistance and flexibility can be imparted. Note that 1.0E + 06 to 1.0E + ¹⁰ Pa is synonymous with 1.0 × 10 ^{6 to} 1.0 × 10 ¹⁰ Pa and 0.001 to 10 GPa.

  For the cured product of the resin layer, for example, a thermosetting solder resist is applied to the release surface of a release sheet (polyethylene terephthalate (PET) film coated with a release agent) to form a dry resist film having a resin layer. Then, it can be obtained by heating and curing in a box oven at 140 to 180 ° C., and finally peeling off the peelable sheet.

<Thermosetting solder resist>
The thermosetting solder resist contains a thermosetting resin and a coloring agent.

(Thermosetting resin)
The thermosetting resin is a resin having a plurality of functional groups that can be used for a crosslinking reaction by heating. Examples of the functional group include a hydroxyl group, a carboxyl group, an amino group, an epoxy group, an oxetanyl group, an oxazoline group, an oxazine group, an aziridine group, a thiol group, and a silanol group. Among these, a hydroxyl group and a carboxyl group are preferable. . As the hydroxyl group, a phenolic hydroxyl group is also preferable.
The thermosetting resin having the above functional group, for example, acrylic resin, maleic acid resin, polybutadiene resin, polyester resin, melamine resin, polyurethane resin, polyurethane urea resin, epoxy resin, oxetane resin, phenoxy resin, polyimide resin, Examples include polyamide resin, polyamideimide resin, phenolic resin, alkyd resin, amino resin, polylactic acid resin, oxazoline resin, benzoxazine resin, silicone resin, and fluorine resin. Examples of the polyester resin include a condensation type polyester resin and an addition type polyester resin. Of these, polyester resins, polyurethane resins, polyurethane urea resins, phenoxy resins, and polyamide resins are preferred.

[Thermosetting agent]
The thermosetting agent forms a cover coat layer having excellent migration resistance and flexibility by crosslinking with the thermosetting resin. Examples of the thermosetting agent include known compounds such as an epoxy compound, an acid anhydride group-containing compound, an isocyanate compound, an aziridine compound, an amine compound, and a phenol compound. Of these, an isocyanate compound and an epoxy compound are preferable.

  The isocyanate compound is not particularly limited as long as it is a compound having an isocyanate group in the molecule, and is preferably a polyisocyanate compound such as a diisocyanate compound. Specifically, examples of the diisocyanate compound include an aromatic diisocyanate having 4 to 50 carbon atoms, an aliphatic diisocyanate, an araliphatic diisocyanate, and an alicyclic diisocyanate.

  Examples of the aromatic diisocyanate include 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6- Tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', 4 "-Triphenylmethane triisocyanate.

  Examples of the aliphatic diisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, , 4,4-trimethylhexamethylene diisocyanate.

  Examples of the aromatic aliphatic diisocyanate include ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene, , 4-tetramethylxylylene diisocyanate, 1,3-tetramethyl xylylene diisocyanate, and the like.

  Examples of the alicyclic diisocyanate include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate [also called isophorone diisocyanate], 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, and 1,4-cyclohexane diisocyanate. , Methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) Cyclohexane and the like can be mentioned.

As the isocyanate compound having one or three or more isocyanate groups in the molecule, specifically, as a monofunctional isocyanate having one isocyanate group in the molecule, (meth) acryloyloxyethyl isocyanate, 1,1 -Bis [(meth) acryloyloxymethyl] ethyl isocyanate, vinyl isocyanate, allyl isocyanate, (meth) acryloyl isocyanate, isopropenyl-α, α-dimethylbenzyl isocyanate and the like. Also, 1,6-diisocyanatohexane, isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, xylylene diisocyanate, tolylene 2,4-diisocyanate, toluene diisocyanate, 2,4-diisocyanate Toluene, hexamethylene diisocyanate, 4-methyl-m-phenylene diisocyanate, naphthylene diisocyanate, paraphenylene diisocyanate, tetramethyl xylylene diisocyanate, cyclohexyl methane diisocyanate, hydrogenated xylylene diisocyanate, cyclohexyl diisocyanate, tolidine diisocyanate, 2,2 2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate Compounds obtained by reacting a diisocyanate compound such as a diamine, m-tetramethylxylylene diisocyanate, p-tetramethyl xylylene diisocyanate, dimer acid diisocyanate, etc. with a hydroxyl, carboxyl, or amide group-containing vinyl monomer in an equimolar amount are also isocyanic acids. It can be used as an ester compound.

  Examples of the polyfunctional isocyanate having three or more isocyanate groups in one molecule include aromatic polyisocyanate, aliphatic polyisocyanate such as lysine triisocyanate, araliphatic polyisocyanate, and alicyclic polyisocyanate. Examples include the above-mentioned trimethylolpropane adduct of diisocyanate, a buret body reacted with water, and a trimer having an isocyanurate ring. Among these, a trimethylolpropane adduct of diisocyanate and a trimer having an isocyanurate ring are preferable. Furthermore, by using a trimethylolpropane adduct of diisocyanate and a trimer having an isocyanurate ring in combination, migration resistance and flexibility can be improved.

The blocked isocyanate compound is an isocyanate compound in which an isocyanate group is protected by a blocking agent such as ε-caprolactam and MEK oxime. Specific examples include those in which the isocyanate group of the isocyanate compound is protected with a blocking agent such as ε-caprolactam, MEK oxime, cyclohexanone oxime, pyrazole, and phenol. Among these, MEK oxime is preferable. “MEK” is an abbreviation for “methyl ethyl ketone”.
Among these, the isocyanate compound is preferably a blocked isocyanate compound. It is preferable to use a blocked isocyanate compound because the sheet life is improved.

  The dissociation temperature of the blocking agent of the blocked isocyanate compound is preferably from 120 to 200 ° C, more preferably from 130 to 180 ° C. By setting the dissociation temperature of the blocking agent of the blocked isocyanate compound to 120 ° C. or higher, the thermosetting solder resist did not dissociate at the drying temperature when coated on the release sheet, and had excellent patterning properties. A dry resist film is obtained. By setting the dissociation temperature of the blocking agent to 200 ° C. or less, foaming in the cover coat layer can be suppressed during thermosetting when forming the cover coat layer.

  The blocked isocyanate compound preferably has an isocyanate equivalent of 200 to 400 g / eq and 500 to 900 g / eq in combination. Flexibility and migration resistance can be improved by using block isocyanates having different isocyanate equivalents in combination. The isocyanate equivalent referred to in the present invention is a value measured according to JIS K7301.

An epoxy compound used as a thermosetting agent is a compound having two or more epoxy groups in one molecule. The properties of the epoxy compound may be liquid or solid.
As the epoxy compound, for example, a glycidyl ether type epoxy compound, a glycidylamine type epoxy compound, a glycidyl ester type epoxy compound, a cyclic aliphatic (alicyclic type) epoxy compound and the like are preferable.

  The molecular weight of the epoxy compound is preferably from 100 to 2000, more preferably from 200 to 1500.

  Examples of the glycidyl ether type epoxy compound include bisphenol A type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, bisphenol AD type epoxy compound, cresol novolak type epoxy compound, phenol novolak type epoxy compound, α-naphthol novolak Epoxy compound, bisphenol A type novolak type epoxy compound, dicyclopentadiene type epoxy compound, tetrabromobisphenol A type epoxy compound, brominated phenol novolak type epoxy compound, tris (glycidyloxyphenyl) methane, tetrakis (glycidyloxyphenyl) ethane And the like.

  Examples of the glycidylamine type epoxy compound include tetraglycidyldiaminodiphenylmethane, triglycidylparaaminophenol, triglycidylmethaminophenol, and tetraglycidylmetaxylylenediamine.

  Examples of the glycidyl ester type epoxy compound include diglycidyl phthalate, diglycidyl hexahydrophthalate, diglycidyl tetrahydrophthalate, and the like.

Examples of the cycloaliphatic (alicyclic) epoxy compound include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate, bis (epoxycyclohexyl) adipate, and the like.
Among them, as the epoxy compound, bisphenol A type epoxy compound, cresol novolak type epoxy compound, phenol novolak type epoxy compound, tris (glycidyloxyphenyl) methane, and tetrakis (glycidyloxyphenyl) ethane are preferable. By using these epoxy compounds, migration resistance and flexibility are further improved.

[Colorant]
The dry resist film of the present invention contains a colorant in order to enhance the light-shielding property of the cover coat layer. Examples of the colorant include chromatic pigments and dyes such as black, red, green, blue, yellow, purple, cyan, and magenta. These may be used alone or may be used as a mixed colorant containing a plurality of them. A black colorant is preferable from the viewpoints of information protection and visibility, and a mixed colorant can obtain black by reducing and mixing a plurality of pigments.

  Examples of the black pigment include carbon black, Ketjen black, carbon nanotube (CNT), perylene black, titanium black, iron black, and aniline black. Among these, from the viewpoint of improving light-shielding properties and migration resistance, perylene black, titanium black, iron black and a mixed colorant are preferable, and perylene black and titanium black are more preferable. Particularly preferred is titanium black.

The colorant preferably has a specific gravity of 2 to 7 g / cm ³ , more preferably 4 to 6 g / cm ³ or more. When the specific gravity of the colorant is 2 to 7 g / cm ³ , the colorant contained therein is appropriately settled after the thermosetting solder resist is applied to the heavy release sheet. As a result, when a dry resist film is formed by drying, and the light-peelable sheet is attached, the concentration of the colorant is heavy on the heavy-peelable sheet surface and thin on the light-peelable sheet surface.
Since the dry resist film has the surface from which the light release sheet is peeled off and is attached to the signal circuit side to form a cover coat layer, if the colorant component on the signal circuit side can be reduced, the impurity component is reduced and migration resistance is reduced. Can be further improved.

The colorant preferably has an average primary particle diameter of 20 to 100 nm, and 30 to 90 nm.
Is more preferable, and 40 to 90 nm is further preferable. By using the coloring agent having the above average primary particle diameter, the cover coat layer formed from the dry resist film has more improved light-shielding properties and flexibility. When the particle shape of the colorant has an average aspect ratio (major axis length / minor axis length) of 1.5 or more, the average primary particle diameter is determined by averaging the major axis length.

  The colorant preferably has a powder resistance of 3 Ω · cm or more, more preferably 5 Ω · cm or more. By setting the powder resistance value of the colorant within the above range, the migration resistance is further improved. The powder resistance value is a resistance value when pressed at a pressing pressure of 2 MPa using a powder resistance measurement system MCP-PD51 and a resistivity meter MCP-T610 manufactured by Mitsubishi Chemical Analytech Co., Ltd.

The specific surface area of the colorant is 10 to 50 m ² / g are preferred, 15~40m ² / g is more preferable. By setting the specific surface area of the coloring agent in the above range, the patterning property is further improved.
The specific surface area can be determined by a BET method using BELSORP-miniII manufactured by Bell Japan Co., Ltd.

  The average primary particle diameter of the colorant can be determined from the average value of about 20 primary particles that can be observed from an image enlarged to about 50,000 to 1,000,000 times by a transmission electron microscope (TEM).

  The following pigments can be used as the mixed colorant. “CI” means a color index (CI).

  Red pigments and magenta pigments include, for example, C.I. I. Pigment Red 7, 14, 41, 48: 1, 48: 2, 48: 3, 48: 4, 57: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 122, 146, 168, 176, 177, 178, 184, 185, 187, 200, 202, 208, 210, 242, 246, 254, 255, 264, 270, 272 and 279.

  Green pigments include, for example, C.I. I. Pigment Green 1, 2, 4, 7, 8, 10, 13, 14, 15, 17, 18, 19, 26, 36, 45, 48, 50, 51, 54, 55, and 58, and the like.

  Blue pigments and cyan pigments include, for example, C.I. I. Pigment Blue 1, 1: 2, 9, 14, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, 19, 25, 27, 28, 29, 33, 35, 36, 56, 56: 1, 60, 61, 61: 1, 62, 63, 66, 67, 68, 71, 72, 73, 74, 75, 76, 78, 79 and the like.

  Yellow pigments include, for example, C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 10, 12, 13, 14, 15, 16, 17, 18, 24, 31, 32, 34, 35, 35: 1, 36, 36: 1, 37, 37: 1, 40, 42, 43, 53, 55, 60, 61, 62, 63, 65, 73, 74, 77, 81, 83, 93, 94, 95, 97, 98, 100, 101, 104, 106, 108, 109, 110, 113, 114, 115, 116, 117, 118, 119, 120, 123, 126, 127, 128, 129, 138, 139, 147, 150, 151, 152, 153, 154, 155, 156, 161, 162, 164, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 179, 180, 181, 82,184,185,187,188,193,194,198,199,213 and 214, and the like.

  Examples of the purple pigment include C.I. I. Pigment Violet 1, 1: 1, 2: 2: 2, 3: 1, 3: 3, 5, 5: 1, 14, 15, 16, 19, 23, 25, 27, 29, 31, 32, 37, 39, 42, 44, 47, 49 and 50.

  The coloring agent preferably contains 0.5 to 40% by mass, more preferably 1 to 30% by mass, based on 100% by mass of the dry resist film. By containing the coloring agent in an amount of 0.5 to 40% by mass, it is easy to achieve both high light-shielding properties and resistance to a migration test.

[Inorganic filler]
The thermosetting solder resist of the present invention preferably further contains an inorganic filler. By including the inorganic filler, the heat-resistant pressure bonding property is further improved. Examples of the inorganic filler include silica, alumina, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium carbonate, titanium oxide, zinc oxide, antimony trioxide, magnesium oxide, talc, montmorolinite, kaolin, and bentonite. Compounds. Among these, hydrophobic silica fine particles obtained by reacting a silanol group on the silica surface with a halogenated silane are preferable from the viewpoint of increasing not only the heat-resistant compression resistance but also the hydrophobicity of the film and further improving the migration resistance. .

BET specific surface area of the inorganic filler, 50 to 300 m ² / g are preferred. When the content is within the above range, the inorganic filler is uniformly dispersed in the dry resist film, and the heat-resistant pressure-bonding property is improved.

  The average particle diameter (average particle diameter D50) of the inorganic filler is preferably from 0.01 to 10 μm, and more preferably from 0.05 to 8 μm. When the average particle diameter of the inorganic filler is 0.01 to 10 μm, the heat-resistant pressure-bonding property can be further improved.

  The content of the inorganic filler is preferably 0.5 to 40% by mass based on 100% by mass of the solid content of the thermosetting solder resist. That is, it is preferably 0.5 to 40% by mass based on 100% by mass of the resin layer of the dry resist film. More preferably, it is 1 to 30% by mass. If it is 0.5% by mass or more, migration resistance is improved. When the content is 40% by mass or less, the heat-resistant pressure bonding property is improved.

Thermosetting solder resists can be used as necessary, including monomers, solvents, silane coupling agents, ion scavengers, antioxidants, tackifier resins, plasticizers, ultraviolet absorbers, defoamers, leveling regulators, and fillers. , Flame retardants and the like.
A thermosetting solder resist can be produced by adding a solvent to a thermosetting resin and a colorant as needed, and mixing and stirring. For the stirring, a known stirring device such as a disper mat or a homogenizer can be used.

<Production method of dry resist film>
The dry resist film of the present invention has a resin layer obtained by applying and drying a thermosetting solder resist. Further, in order to protect the resin layer, it is common to attach a light-peelable sheet to form a laminated structure of a heavy-peelable sheet / resin layer / light-peelable sheet. Is sometimes referred to as a dry resist film with a heavy release sheet. The dry resist film of the present invention may further have a cushion layer, an adhesive layer, a light absorbing layer, an intermediate layer such as a gas barrier layer, and the like.

The resin layer of the dry resist film is formed on the release surface of the heavy release sheet by, for example, knife coating, die coating, lip coating, roll coating, curtain coating, bar coating, gravure coating, flexo coating, dip coating, spray coating, or spin coating. It can be formed by coating a liquid thermosetting solder resist dissolved and dispersed in a solvent by a method such as coating, and then drying the solvent at a temperature of usually 40 to 120 ° C.

  The release sheet is a film in which a release agent is coated on one or both sides of a polyethylene terephthalate film or an OPP film, and is a member to be laminated to protect the dry resist film. By forming the resin layer as a dry resist film sandwiched between both sides of a release sheet having different release properties, the light release release sheet can be released first, and the handling becomes easy. Further, by using the light-peelable sheet on the side of the resin layer where the colorant component is small, the colorant component on the signal circuit side of the resin layer is reduced, and the impurity resistance is reduced and the migration resistance can be further improved.

  The thickness of the resin layer of the dry resist film is preferably from 5 to 100 μm, more preferably from 10 to 70 μm.

《Printed circuit board》
Subsequently, the printed wiring board with the electromagnetic wave shielding sheet of the present invention will be described. The printed wiring board of the present invention includes an electromagnetic wave shielding sheet, a cover coat layer, and a substrate having signal wiring and an insulating base material.

<Electromagnetic wave shield sheet>
The electromagnetic wave shielding sheet includes a conductive layer and an insulating layer.
[Conductive layer]
The conductive layer in the electromagnetic wave shielding sheet is a layer that shields noise such as electromagnetic waves and is mainly attached to the cover coat layer of the FPC. The conductive layer has two modes, a first mode of a conductive layer formed from a conductive adhesive and a second mode having a metal layer and a conductive layer formed from a conductive adhesive. The conductive adhesive layer is made of a conductive metal such as gold, platinum, silver, copper, and nickel, and conductive fine particles made of an alloy thereof, and a thermosetting solder resist that forms the dry resist film. The conductive resin composition obtained by mixing a conductive resin and a curing agent is formed into a coating film. As the metal layer, for example, a conductive metal vapor-deposited film such as aluminum, copper, silver, or gold having a thickness of 0.005 to 10 μm, a metal foil, or the like is used.

[Insulating layer]
The insulating layer can be formed using an insulating resin composition. The insulating resin composition can be formed by coating the insulating resin composition containing a thermosetting resin and a thermosetting agent in the same manner as the conductive adhesive. Further, a film obtained by molding an insulating resin such as polyester, polycarbonate, polyimide, and polyphenylene sulfide can also be used.

The electromagnetic wave shielding sheet has a thermosetting resin and a thermosetting agent contained in the conductive layer in an uncured state, and can be cured by a hot press together with the cover coat layer to obtain a desired adhesive strength. The uncured state includes a semi-cured state in which a part of the thermosetting agent is cured.

<Cover coat layer>
The cover coat layer is an insulating layer that covers the signal wiring of the wiring board and protects it from the external environment. The cover coat layer may be formed by curing a resin layer of a dry resist film, or after forming a resin layer by applying a thermosetting solder resist to a substrate having signal wiring and an insulating base material, It may be made by curing.

  The cured product of the resin layer in the cover coat layer has a storage elastic modulus at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa.

The porosity of the cover coat layer is preferably in the range of 0.1 to 10%. The “porosity” means the ratio (area ratio) of voids to the total area of the cross section in an arbitrary cross section.
When the cover coat layer has voids, the cover coat layer is easily deformed, and the flexibility is improved.
The porosity in the cover coat layer decreases as the filler content decreases, and increases as the filler content increases. The smaller the porosity in the cover coat layer, the better the migration resistance.

  The thickness of the cover coat layer is preferably from 5 to 100 μm, more preferably from 10 to 70 μm. By setting the thickness of the cover coat layer in the range of 5 to 100 μm, flexibility and migration resistance can be improved.

  The glass transition temperature (Tg) of the cover coat layer is preferably from 40C to 120C, more preferably from 50C to 100C. By setting the glass transition temperature (Tg) of the cover coat layer to 40 ° C. to 120 ° C., flexibility and migration resistance can be improved.

<Substrate>
The substrate has a signal wiring and an insulating base.

  Examples of the signal wiring include a ground wiring for grounding and a wiring circuit for sending an electric signal to an electronic component. The wiring is generally formed by etching a copper foil.

  The insulating base material is preferably a flexible plastic such as polyester, polycarbonate, polyimide, polyphenylene sulfide, or liquid crystal polymer, and more preferably polyimide.

<Production method of printed wiring board with electromagnetic wave shield>
A method for manufacturing a printed wiring board with an electromagnetic wave shielding sheet according to the present invention will be described. The printed wiring board with an electromagnetic wave shielding sheet of the present invention includes a step of forming signal wiring on an insulating base material (step A), a step of laminating a dry resist film on the signal wiring (step B), and a resin layer of the dry resist film. To form a cover coat layer by heat curing (Step C), and a step of laminating an electromagnetic wave shielding sheet on the cover coat layer and hot pressing (Step D). Hereinafter, each step will be specifically described.

(Step A; signal wiring forming step)
First, ground wiring for grounding by etching a copper foil on an insulating substrate and signal wiring including a wiring circuit for sending an electric signal to an electronic component are formed.

(Step B: Dry resist film laminating step)
Next, the light release sheet of the dry resist film sandwiched between the heavy release sheet and the light release sheet on both sides is peeled off, and the exposed resin layer surface is bonded by a laminator so as to cover the signal wiring on the insulating substrate.

(Step C: cover coat layer forming step)
After heating at 150 ° C. to 180 ° C. for 1 minute to 2 hours and thermosetting, the heavy release sheet is peeled off to form a cover coat layer. At that time, if necessary, a press at a pressure of about 1 to 3 MPa can be used in combination. The step of forming the opening may be performed before or after the dry resist film is attached to the substrate, or after the formation of the heat-cured cover coat layer, but it is easy to maintain the shape when the opening is formed. From the viewpoint of size reduction, it is more preferable after heat curing.
Examples of a method for forming an opening on a ground wiring or at a necessary position include die cutting, router processing, and laser processing. From the viewpoint of reducing the size of the opening, router processing and laser processing are preferable. By setting the opening diameter to 0.05 to 1 mm, for example, the ground wiring area can be significantly reduced, so that the FPC can be shortened.

(Step D; hot press step)
Next, an electromagnetic wave shielding sheet punched into a predetermined size is laminated on a part or the entire surface of the cover coat layer, and is temporarily attached. Thereafter, the conductive layer of the electromagnetic wave shielding sheet is thermally cured and bonded by hot pressing. At this time, the conductive adhesive layer flows into the opening of the cover coat layer formed on the ground wiring and hardens, so that the conductive adhesive layer is electrically connected to the ground, so that the shielding property is further improved.

  The heat pressing of the electromagnetic wave shielding sheet and the wiring board is generally performed at a temperature of about 150 to 190 ° C., a pressure of about 1 to 3 MPa, and a time of about 1 to 60 minutes. The thermosetting resin reacts with the curing agent by hot pressing. In addition, post-curing may be performed at 150 to 190 ° C. for 30 to 90 minutes after hot pressing in order to promote curing. The electromagnetic wave shielding sheet may be referred to as an electromagnetic wave shielding layer after hot pressing.

  The printed wiring board of the present invention is preferably provided in an electronic device such as a notebook PC, a mobile phone, a smartphone, and a tablet terminal, in addition to a liquid crystal display and a touch panel.

  Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to only the following Examples. The method for synthesizing the thermosetting resin used in the examples is shown below.

[Thermosetting resin 1]
In a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, an inlet tube, and a thermometer, a polycarbonate diol (UM90 (3/1): 1,4-cyclohexanedimethanol / 1, manufactured by Ube Industries, Ltd.) was added. 274.8 parts of 6-hexanediol = 3/1 copolymerized polycarbonate diol), 39.2 parts of isophorone diisocyanate, and 300 parts of toluene as a solvent are charged, and the mixture is heated to 60 ° C. while stirring under a nitrogen stream, and uniformly dissolved. I let it. Subsequently, 0.1 part of dibutyltin dilaurate was charged into the flask, heated to 110 ° C., and reacted for 3 hours. Then, after cooling to 40 ° C., 37.6 parts of tetrahydrophthalic anhydride (Likacid TH: manufactured by Shin Nippon Rika Co., Ltd.) was added, and the temperature was raised to 110 ° C. and reacted for 4 hours. Subsequently, after cooling to 40 ° C., 39.6 parts of a polycyclic aromatic epoxy resin (“YX8800” manufactured by Mitsubishi Chemical Corporation) and 4 parts of triphenylphosphine as a catalyst were added, the temperature was raised to 110 ° C., and the reaction was carried out for 8 hours. I let it. After cooling to 40 ° C., 32.5 parts of tetrahydrophthalic anhydride was added and reacted at 110 ° C. for 3 hours. After cooling to 40 ° C., the solid content was adjusted to 60% with toluene to obtain a carboxyl group-containing modified urethane ester resin (A) solution. The weight average molecular weight of the carboxyl group-containing modified urethane ester resin (A) was 39,000, and the acid value of the resin solids was 31.3 mgKOH / g.

[Thermosetting resin 2]
A polyester polyol (P-2041, manufactured by Kuraray Co., Ltd., 3-methyl-1,5-pentanediol / 1,4) was placed in a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, an inlet tube, and a thermometer. 407.3 parts of cyclohexanedicarboxylic acid copolymerized polyester polyol (mass average molecular weight of about 2000), 26.1 parts of isophorone diisocyanate, and 300 parts of toluene as a solvent, and the mixture was heated to 60 ° C. while stirring under a nitrogen stream. Uniformly dissolved. Subsequently, 0.1 part of dibutyltin dilaurate was charged into the flask, heated to 110 ° C., and reacted for 3 hours. Then, after cooling to 40 ° C., 16.5 parts of succinic anhydride (SA: manufactured by Shin Nihon Rika Co., Ltd.) was added, the temperature was raised to 110 ° C., and the reaction was carried out for 4 hours. Subsequently, after cooling to 40 ° C., 29.3 parts of bisphenol A type epoxy resin (“YD-8125” manufactured by Nippon Steel Chemical Co., Ltd.) and 4 parts of triphenylphosphine as a catalyst were added, and the temperature was raised to 110 ° C. For 8 hours. After cooling to 40 ° C., 21.6 parts of tetrahydrophthalic anhydride was added and reacted at 110 ° C. for 3 hours. After cooling to 40 ° C., the solid content was adjusted to 60% with toluene to obtain a carboxyl group-containing modified urethane ester resin (A) solution. The obtained carboxyl group-containing modified urethane ester resin (A) had a mass average molecular weight of 520,000 and an acid value of resin solids of 17.9 mgKOH / g.

[Thermosetting resin 3]
In a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, an inlet tube, and a thermometer, 80.1 parts of bisphenol F, 58.9 parts of a biphenyl type epoxy resin (“YX4000H” manufactured by Mitsubishi Chemical Corporation), polyethylene glycol 123.8 parts of epoxy resin ("EX830" manufactured by Nagase ChemteX Corporation), 130 parts of toluene, 2 parts of triphenylphosphine and 2 parts of N, N-dimethylbenzylamine as a catalyst were charged and stirred under a nitrogen stream. The temperature was raised to 110 ° C. while reacting for 8 hours. After cooling to room temperature, 24.2 parts of tetrahydrophthalic anhydride and 150 parts of MEK were added and reacted at 80 ° C. for 3 hours to obtain a carboxyl group-containing phenoxy resin solution. The weight average molecular weight was 21,000 and the acid value was 32 mgKOH / g.

[Surface treatment flame retardant]
To 800 ml of an ethanol solution (concentration: 0.4%) of tetraethyl orthosilicate (hereinafter also referred to as TEOS), 10 g of aluminum phosphinate having a D95 particle diameter of 5 μm determined by the method described later was added, and the pH was adjusted with concentrated NH ₃ water. After adjusting to 12, the mixture was stirred for 3 hours, filtered, and washed with ethanol to obtain a surface-treated flame retardant having silica adhered to the surface of aluminum phosphinate.
The amount of silica adhering to the surface was determined by ICP emission spectroscopy described later, and it was 0.01 parts by mass with respect to 100 parts by mass of aluminum phosphinate.

<Method for measuring D95 particle size>
D95 indicates a particle size when the volume integrated value of 95% is included in the particle size distribution of the flame retardant. The particle size of the flame retardant was measured using Microtrac MT3000EX (manufactured by Nikkiso Co., Ltd.). A flame retardant was dispersed while stirring a 1% aqueous solution of sodium dodecylbenzenesulfonate to prepare a measurement sample. The measurement was performed by inputting the refractive index of water and the refractive index of the flame retardant, and adjusting the sample concentration so that the measurement time was 20 seconds and the Signal Level was within the green range.

Table 1 shows the physical property values of the coloring agents 1 to 4.
Thermoplastic resin 1: Styrene-isoprene-styrene block copolymer (SIS), “QTC3520” Thermoplastic resin 2: Nippon Zeon Co., Ltd. Liquid crystal polymer, “E4008” Sumitomo Chemical Co., Ltd. Thermosetting agent 1: Epoxy resin, “JER828” (Bisphenol A type epoxy resin epoxy equivalent = 189 g / eq) Mitsubishi Chemical Corporation thermosetting agent 2: epoxy resin, "JER1031S" (polyfunctional epoxy resin epoxy equivalent = 200 g / eq) Mitsubishi Chemical Corporation thermosetting agent 3 : Epoxy resin, "Denacol EX212" (bifunctional epoxy resin, epoxy equivalent = 151 g / eq), manufactured by Nagase ChemteX Corp. Inorganic filler: hydrophobic silica "" AEROSIL R812 (primary average particle diameter: 7 nm) "Nippon Aerosil Co., Ltd. Surface treatment flame retardant: TEOS surface treatment produced above Aluminum phosphinate (D95
= 5 μm)

<Preparation of electromagnetic wave shielding sheet>
100 parts of the thermosetting resin 1, 550 parts of conductive fine particles (dendritic particles D50 using copper for the core and silver for the coating layer, average particle size D1 = 11.0 μm, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) 15 parts of "Denacol EX212" (bifunctional epoxy compound, epoxy equivalent = 151 g / eq, manufactured by Nagase ChemteX Corporation) as a curing agent and 2.0 parts of "Chemiteit PZ-33" (aziridine compound, manufactured by Nippon Shokubai Co., Ltd.) A conductive resin composition was obtained by charging the mixture in a container, adding a mixed solvent of toluene: isopropyl alcohol (mass ratio 2: 1) so as to have a nonvolatile content of 40% by mass, and stirring with a disper for 10 minutes. Next, the conductive resin composition was applied on a peelable sheet using a bar coater so that the dry thickness became 10 μm, and further dried in an electric oven at 100 ° C. for 2 minutes to obtain a conductive layer. .
Separately, 100 parts of the thermosetting resin 1, 15 parts of "Denacol EX212" (epoxy equivalent of bifunctional epoxy compound = 151 g / eq, manufactured by Nagase ChemteX Corp.) as a thermosetting agent, and "chemitite PZ-33" (aziridine) Compound, manufactured by Nippon Shokubai Co., Ltd.) into a container, and a mixed solvent of toluene: isopropyl alcohol (mass ratio 2: 1) was added thereto so that the nonvolatile content became 40% by mass, followed by stirring with a disper for 10 minutes. An insulating resin composition was obtained. This insulating resin composition was applied to a peelable sheet using a bar coater so that the dry thickness became 15 μm, and further dried in an electric oven at 100 ° C. for 3 minutes to obtain an insulating layer. Further, an electromagnetic wave shielding sheet was obtained by laminating the conductive layer and the insulating layer with a laminator.

[Example 1]
100 parts of the thermosetting resin 1, 10 parts of the flame retardant, 1.5 parts of the hydrophobic silica, and 3 parts of the black colorant 1 are charged into a container, and methyl ethyl ketone: methyl polyglycol is adjusted to have a solid content of 50%. A mixed solvent of 1: 1 (mass ratio) was added and mixed so as to be uniform. This was dispersed using a horizontal sand mill DYNO-MILL (manufactured by Shinmaru Enterprise Co., Ltd.) until the particle diameter by a grind gauge became less than 10 μm. Next, 10 parts of the thermosetting resin 1 was added to 100 parts of the thermosetting resin 1 of the dispersion coating liquid, and the mixture was mixed uniformly to obtain a thermosetting solder resist.

  The obtained thermosetting solder resist is coated with a 25 μm-thick heavy release sheet (polyethylene terephthalate (PET) film coated with a heavy release agent) so that the thickness after drying with a doctor blade is 45 μm. ), And then dried at 100 ° C. for 5 minutes, and then cooled to room temperature to form a resin layer. Further, the obtained resin layer is bonded to a light-peelable sheet (polyethylene terephthalate (PET) film coated with a light-release agent) having a thickness of 75 μm, whereby the resin sandwiched between the heavy-peelable sheet and the light-peelable sheet is bonded. A dry resist film having a layer was obtained.

The lightly releasable sheet of the obtained dry resist film was peeled off, and the exposed resin layer surface was placed on the signal wiring side of the insulating substrate on which the signal wiring was formed, and a vacuum laminator (Nichigo Morton's small pressurized vacuum laminator V-130) was used. And pasted together. The vacuum lamination conditions were a heating temperature of 60 ° C., a vacuum time of 60 seconds, an ultimate vacuum pressure of 2 hPa, a pressure of 0.4 MPa, and a pressure time of 60 seconds. Next, the heavy release sheet is peeled off and thermally cured in a box oven at 160 ° C. for 1 hour, and thereafter, using a CO ₂ laser beam machine (manufactured by Hitachi Via Mechanics), a cover having an opening with an opening diameter of 0.5 mm. A wiring board with a coat layer 4 was obtained.

  Further, the conductive layer side of the obtained electromagnetic wave shielding sheet and the cover coat layer 4 are bonded to each other, and the thermosetting resin is cured by hot pressing at 150 ° C., 2.0 MPa, for 30 minutes. A printed wiring board was obtained.

[Examples 2 to 12, Comparative Example 1]
Dry resist films of Examples 2 to 12 and Comparative Example 1 were obtained in the same manner as in Example 1 except that the composition of the thermosetting solder resist was changed as described in Table 2. In the table, unless otherwise specified, numerical values indicate parts, and blank columns indicate that no compounding was performed.

Example 13
100 parts of the thermosetting resin 1, 10 parts of the flame retardant, 1.5 parts of the hydrophobic silica, and 3 parts of the black colorant 1 were charged into a container, preliminarily mixed, and kneaded sufficiently with a three-roll mill. Next, 10 parts of the thermosetting agent 1 is added to 100 parts of the thermosetting resin 1 of the dispersion coating liquid, and cellosolve acetate is further added as a solvent so as to have a solid content of 70%, and mixed with a small planetary mixer. Thus, a thermosetting solder resist was obtained.

  The obtained thermosetting solder resist was uniformly coated on the same place where the dry film was bonded by a screen printing method using a polyester screen plate having a mesh size selected so that the film thickness after drying was 45 μm. Thereafter, drying was performed at 80 ° C. for 30 minutes in a hot air oven to form a resin layer. Thereafter, adjustment was performed under the same conditions as for the dry resist film to obtain a wiring board with a cover coat layer 4 having an opening having an opening diameter of 0.5 mm and a printed wiring board with an electromagnetic wave shielding sheet.

[Comparative Example 2]
A dry resist film in which the thermoplastic resin 2 was formed into a thickness of 45 μm using an injection molding machine was obtained.

The obtained dry resist film is adhered to the signal wiring side of the insulating base material on which the signal wiring is formed, and then the opening having an opening diameter of 0.5 mm is formed using a CO ₂ laser processing machine (manufactured by Hitachi Via Mechanics). A wiring board with a cover coat layer 4 having a portion was obtained. The bonding conditions were a heating temperature of 300 ° C., a pressure of 4.0 MPa, and a pressing time of 10 minutes.

  Further, the conductive layer side of the obtained electromagnetic wave shielding sheet and the cover coat layer 4 were bonded together and hot-pressed at 150 ° C. and 2.0 MPa for 30 minutes to obtain a printed wiring board with an electromagnetic wave shielding sheet.

The following physical properties were evaluated for the dry resist film, the wiring board with the cover coat layer, and the printed wiring board with the electromagnetic wave shielding sheet obtained by the methods described in the above Examples and Comparative Examples.
<Storage modulus, glass transition temperature (Tg)>
The storage elastic modulus and Tg of the cured product of the resin layer of the dry resist film were determined by the following methods. Two dry resist films were prepared and bonded together under the conditions for preparing the wiring board with the cover coat layer 4 described in Examples and Comparative Examples. Only the cured product of the resin layer of the dry resist film was cut into a size of 5 mm width × 30 mm length to obtain a measurement sample. Next, using a dynamic elastic modulus measurement device DVA-200 (manufactured by IT Measurement Control Co., Ltd.), the deformation mode is “tensile”, the frequency is 10 Hz, the heating rate is 10 ° C./min, and the measurement temperature range is −30. The measurement was performed under the conditions of 〜300 ° C., and the storage elastic modulus and Tg at 85 ° C. were obtained.

<Migration test>
The migration test will be described with reference to FIG. As shown in the plan view of FIG. 1 (1), a laminate of a copper foil having a thickness of 12 μm and a polyimide film having a thickness of 25 μm was etched to form a line / space on the polyimide film 1 of 0.05 mm / 0.05 mm. Then, a comb-shaped signal wire 2 for a cathode provided with a cathode electrode connection point 2 'and a comb-shaped signal wire 3 for an anode electrode provided with an anode electrode connection point 3' were formed.
Next, as shown in the plan view of FIG. 1 (2), the comb-shaped signal wiring 2 for the cathode electrode and the comb-shaped signal wiring 3 for the anode electrode are covered, and the vicinity of the cathode electrode connection point 2 ′ and the vicinity of the anode electrode connection point 3 ′. The resin layer surface of the dry resist film was overlapped to such an extent that it was exposed, and a wiring board with a cover coat layer 4 was obtained under the conditions for preparing the wiring board with a cover coat layer 4 described in Examples and Comparative Examples.
Further, the peelable sheet was peeled off from the conductive layer side of the obtained electromagnetic wave shielding sheet, and the exposed conductive layer surface was bonded on the cover coat layer 4 to laminate a sample as shown in the plan view of FIG. Obtained. In the obtained sample, the conductive layer 5b is electrically connected to the comb-shaped signal wiring 2 for the cathode electrode as described in the AA 'cross-sectional view of the sample shown in FIG.

The thermosetting resin was cured by hot-pressing the obtained sample under the conditions of 150 ° C., 2.0 MPa, and 30 minutes. Next, the sample was placed in an atmosphere of 85 ° C.-85% RH (relative humidity), an anode electrode was connected to the anode electrode connection point 3 ′, a cathode electrode was connected to the cathode electrode connection point 2 ′, and a voltage of 50 V was applied. The application was continued for 500 hours. Then, the change of the resistance value until 500 hours passed was continuously measured. Note that “leak touch” described below means that there is dielectric breakdown due to a short circuit, and the resistance instantaneously decreases and current flows. If there is no leak touch, the insulation does not decrease. The evaluation criteria are as follows.

◎: The resistance value after 500 hours has passed is 1 × 10 ⁷ Ω or more, and there is no leak touch. Very good ：: The resistance value after 500 hours passed was 1 × 10 ⁷ Ω or more, and there was one leak touch. Good: The resistance value after 500 hours passed was 1 × 10 ⁷ Ω or more, and there were two leak touches. No problem in practical use.
×: The resistance value after 500 hours has passed is less than 1 × 10 ⁷ Ω, or
The resistance value after 500 hours has passed is 1 × 10 ⁷ Ω or more, and there are three or more leak touches. Not practical.

<Heat resistant crimp resistance>
The light release sheet of the dry resist film with the heavy release sheet was peeled off, and vacuum-laminated with a polyimide film ("Kapton 200EN" manufactured by Du Pont-Toray Co., Ltd.). Thereafter, a polyimide film with a cover coat layer (sample a) was prepared in the same procedure as in the migration test. Next, an electromagnetic wave shielding sheet was attached to the surface of the cover coat layer of the sample a in the same procedure as in the migration test, and hot-pressed to produce a laminate (sample b) composed of an electromagnetic wave shielding film / cover coat layer / polyimide film.
Samples a and b were each cut from the polyimide film side by ion beam irradiation using a cross section polisher (SM-09010, manufactured by JEOL Ltd.) to form a cross section of the cover coat layer. Using a laser microscope VK-X100 (manufactured by Keyence Corporation) and VK-H1XV (manufactured by Keyence Corporation) as an observation application, the thicknesses of the cover coat layers of the samples a and b were measured, and the rate of change of the thickness was determined from the following equation. Was.

Thickness change rate = 100− (cover coat layer thickness of sample b / cover coat layer thickness of sample a × 100)

The heat resistance and pressure resistance were evaluated according to the following evaluation criteria by the thickness change rate.
A: Less than 2%. Good.
：: 2% or more and less than 4%.
Δ: 4% or more and less than 5%. No problem in practical use.
X: 5% or more. Not practical.

<Flexibility>
The light release sheet of the dry resist film with the heavy release sheet was peeled off and vacuum-laminated on a circuit board having a line / space of 0.05 mm / 0.05 mm. Thereafter, a circuit board with a cover coat layer was formed in the same procedure as in the migration test.
The circuit board with the cover coat layer is bent 180 degrees so that the cover coat layer is on the outside, and a 500 g weight is placed on the bent portion for 5 seconds. Then, the bent portion is returned to the original flat state, and 500 g is returned again. Was placed for 5 seconds, and this was folded once. Whether or not cracks occurred in the cover coat layer was observed with a microscope "VHX-900" manufactured by KEYENCE CORPORATION, and the number of times of bending without cracks was evaluated.
The number of times of bending until a crack occurred in the bent portion where a load of 500 g was applied was counted. The evaluation criteria are as follows.

：: 5 times or more. Very good.
：: 3 or more and less than 5 times. Good: 2 times or more and less than 3 times. No problem in practical use.
X: Less than 2 times. Not practical.

<Light shielding>
The optical density was measured by a Macbeth densitometer (GRETAGD200-II) after peeling the light release sheet of the dry resist film with the heavy release sheet, and the optical density (OD) at a film thickness of 45 μm was obtained. The evaluation criteria are as follows.

：: 1.5 or more. Good.
〇: 1 or more and less than 1.5. No problem in practical use.
×: less than 1. Not practical.

<Void ratio>
The light release sheet of the dry resist film with the heavy release sheet was peeled off, and vacuum-laminated with a polyimide film ("Kapton 200EN" manufactured by Du Pont-Toray Co., Ltd.). Thereafter, a laminate (sample b) composed of an electromagnetic wave shielding film / cover coat layer / polyimide film was prepared in the same procedure as in the evaluation of the heat-resistant pressure resistance. A cross section of the obtained sample b was cut out, and an enlarged image (SEM image: 3000 times) of the cross section was obtained. From this enlarged image, a secondary image was created in which the area filled with resin or filler was painted white and the area where voids were observed was painted black. This secondary image was subjected to binarized image processing using software, and the ratio of the area of the void portion to the area of the observation visual field was calculated.

A: 0.1% or more and less than 3%.
：: 3% or more and less than 5%.
Δ: 5% or more and 10% or less.
X: Over 10%.

  From the evaluation results, it was confirmed that the connection reliability was improved in the circuit to which the electromagnetic wave shielding sheet was attached by improving the ion migration resistance.

DESCRIPTION OF SYMBOLS 1 Polyimide film 2 Comb-shaped signal wiring 2 'for cathode electrode Cathode electrode connection point 3 Comb-shaped signal wiring 3' for anode electrode Anode electrode connection point 4 Cover coat layer 5 Electromagnetic wave shielding sheet 5a Insulation layer 5b Conductive layer

Claims (11)

An electromagnetic wave shielding sheet, a cover coat layer, a printed wiring board with an electromagnetic wave shielding sheet comprising a substrate having signal wiring and an insulating base material,
The cover coat layer has a cured product of a resin layer formed of a thermosetting resin and a thermosetting solder resist containing a colorant,
A printed wiring board with an electromagnetic wave shielding sheet, wherein the cured product of the resin layer has a storage elastic modulus at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa.   The printed wiring board with an electromagnetic wave shielding sheet according to claim 1, wherein the coloring agent is a black coloring agent.   The printed wiring board with an electromagnetic wave shielding sheet according to claim 1, wherein the black colorant includes titanium black.   The printed wiring board with an electromagnetic wave shielding sheet according to any one of claims 1 to 3, further comprising hydrophobic silica fine particles.   The printed wiring board with an electromagnetic wave shielding sheet according to any one of claims 1 to 4, wherein the porosity of the cover coat layer is in the range of 0.1% to 10%.   The printed wiring board with an electromagnetic wave shielding sheet according to any one of claims 1 to 5, wherein the cover coat layer has an opening having an opening diameter of 0.05 to 1 mm.   An electronic device comprising the printed wiring board with the electromagnetic wave shielding sheet according to claim 1. Forming a signal wiring on the insulating base material, laminating a dry resist film on the signal wiring, curing the dry resist film to form a cover coat layer having openings, and applying an electromagnetic wave on the cover coat layer. A method of manufacturing a printed wiring board with an electromagnetic wave shield sheet, which is manufactured by laminating the shield sheets and hot pressing,
The dry resist film has a resin layer formed of a thermosetting solder resist containing a thermosetting resin and a coloring agent, and the cured product of the resin layer has a storage elastic modulus at 85 ° C. of 1 0.0E + 06 to 1.0E + 10 Pa, a method for manufacturing a printed wiring board with an electromagnetic wave shielding sheet. Forming a signal wiring on the insulating base material, applying a thermosetting solder resist on the signal wiring to form a resin layer, curing the resin layer to form a cover coat layer having openings, Laminating the electromagnetic wave shielding sheet on the cover coat layer, a step of hot pressing, a method of manufacturing a printed wiring board with an electromagnetic wave shielding sheet to be manufactured by,
The thermosetting solder resist has a resin layer containing a thermosetting resin and a coloring agent, and the cured product of the resin layer has a storage elastic modulus at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa. Of manufacturing a printed wiring board with an electromagnetic wave shielding sheet. A dry resist film for forming a printed wiring board with an electromagnetic wave shielding sheet according to any one of claims 1 to 6,
Thermosetting resin, having a resin layer formed from a thermosetting solder resist containing a coloring agent,
A dry resist film, wherein the cured product of the resin layer has a storage elastic modulus at 85 ° C. of 1.0E + 06 to 1.0E + 10 Pa. A thermosetting solder resist for forming a resin layer of a dry resist film according to claim 10, wherein the thermosetting solder resist contains a thermosetting resin and a coloring agent.