JP6409760B2 - Method for manufacturing printed wiring board - Google Patents

Description

  The present invention relates to an electromagnetic wave shielding sheet for shielding electromagnetic waves used for printed wiring boards and the like.

In recent years, flexible and flexible flexible printed boards (hereinafter referred to as FPCs) have become indispensable in electronic devices such as mobile phones, video cameras, and notebook personal computers that are rapidly becoming smaller and thinner. Furthermore, as the performance of electronic devices increases, the signal wiring built-in is becoming narrower and higher in frequency, and countermeasures against electromagnetic noise are becoming increasingly important. For this reason, an FPC is generally incorporated with an electromagnetic shielding material that shields or absorbs electromagnetic noise generated from signal wiring.
The FPC is composed of a copper clad laminate (CCL) formed by etching and a cover coat material. The cover coat material is generally selected from cover lay film, photosensitive ink (solder resist), photosensitive film (photosensitive cover lay film), etc., and easy to handle, high durability, and high insulation reliability. Therefore, many coverlay films are used. A coverlay film is a material obtained by applying a thermosetting adhesive to an insulating substrate.
Therefore, for example, in Patent Document 1, a shield layer having a conductive adhesive layer, a metal thin film layer, or the like is bonded to the insulating layer of the FPC, and a metal thin film layer is attached to the ground wiring of the FPC via the conductive adhesive layer. An FPC having an electrically connected electromagnetic shielding function is disclosed.

  Patent Document 2 discloses an electromagnetic wave shield sheet having a conductive layer containing a thermosetting resin, a curing agent, conductive fine particles, and an ion scavenger.

  Conventionally, holes or the like have been formed in the coverlay film with a drill or the like in order to electrically connect the ground wiring and the shield layer. However, along with the narrowing of the signal wiring pitch, drills cannot be finely processed, and holes and the like have been formed by using a photosensitive coverlay film. Therefore, Patent Document 3 discloses an FPC using a photosensitive alkali development type solder resist as a cover coating material instead of a general polyimide cover lay film.

JP 2007-294996 A JP 2014-141628 A JP 2013-38235 A

However, when the cover coat layer is formed with a photosensitive alkali development type solder resist in this way, it has a single layer structure that does not have an insulating substrate as compared with the cover lay film, and includes contamination derived from the photolithography process. Therefore, the insulation reliability is low, and the FPC in which a conventional radio wave shield sheet is bonded to a cover coat layer formed of such a solder resist or a photosensitive cover lay film has a problem that the migration resistance is extremely deteriorated. It was.
Further, the FPC having the above configuration has a problem that the flexibility and the adhesive strength after the pressure cooker test (PCT test) are lowered.
Furthermore, there is a problem that the connection reliability between the electromagnetic wave shielding sheet and the signal wiring is lowered.

  The present invention aims to provide a printed wiring board with an electromagnetic wave shielding sheet having good migration resistance, connection reliability and flexibility even when it has a cover coat layer formed from a solder resist or a photosensitive cover lay film. And

  The electromagnetic wave shielding sheet of the present invention is for a printed wiring board comprising an electromagnetic wave shielding sheet, a cover coat layer formed from a solder resist or a photosensitive cover lay film, and a substrate having signal wiring and an insulating substrate. An electromagnetic wave shielding sheet comprising an insulating layer and a conductive layer, wherein the conductive layer contains a thermosetting resin, a curing agent, conductive fine particles, and an ion scavenger.

  According to the present invention described above, since the conductive layer of the electromagnetic wave shielding sheet contains an ion scavenger, the metal ions contained in the cover coat layer and the metal ions resulting from the conductive fine particles can be collected. Thereby, the printed wiring board incorporating the electromagnetic wave shielding sheet of the present invention has good migration resistance, adhesive strength, connection reliability, and good flexibility.

  The present invention can provide an electromagnetic wave shielding sheet and a printed wiring board that can produce a printed wiring board having good connection reliability and flexibility.

It is the conceptual diagram explaining the migration test. It is explanatory drawing of a connection reliability test.

  Before describing the present invention, terms will be defined. The wiring circuit includes a ground wiring and a signal wiring.

  The electromagnetic wave shielding sheet of the present invention is for a printed wiring board comprising an electromagnetic wave shielding sheet, a cover coat layer formed from a solder resist or a photosensitive cover lay film, and a substrate having signal wiring and an insulating substrate. An insulating layer and a conductive layer are provided, and the conductive layer includes a thermosetting resin, a curing agent, conductive fine particles, and an ion scavenger.

<Conductive layer>
The conductive layer of 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 is preferably a first embodiment of a conductive layer formed of a conductive adhesive and a second embodiment of a second embodiment having a metal layer and a conductive layer formed of a conductive adhesive. Employing the second aspect further improves the shielding effect. The conductive layer preferably has isotropic conductivity or anisotropic conductivity. Isotropic conductivity means conducting in the vertical direction (longitudinal direction) and the horizontal direction (plane direction) when the electromagnetic wave shielding sheet is placed horizontally. The anisotropic conduction means conducting in the vertical direction (longitudinal direction) when the electromagnetic wave shielding sheet is placed horizontally. Isotropic conductivity is obtained by a known method such as a method using flaky or dendritic conductive fine particles. The anisotropic conductivity can be obtained by a method using spherical or dendritic conductive fine particles. Note that isotropic conductivity is obtained when the conductive layer contains a large amount of dendritic conductive fine particles. Further, when the conductive layer contains a small amount of dendritic conductive fine particles, anisotropic conductivity can be obtained.

  The conductive layer can be formed using a conductive adhesive. The conductive adhesive includes a thermosetting resin, a curing agent, conductive fine particles, and an ion scavenger.

[Thermosetting resin]
A thermosetting resin is a resin having a plurality of functional groups capable of reacting with a curing agent. Functional groups include, for example, hydroxyl group, phenolic hydroxyl group, methoxymethyl group, carboxyl group, amino group, epoxy group, oxetanyl group, oxazoline group, oxazine group, aziridine group, thiol group, isocyanate group, blocked isocyanate group, blocked A carboxyl group, a silanol group, etc. are mentioned. Thermosetting resins include, for example, acrylic resins, maleic resins, polybutadiene resins, polyester resins, polyurethane resins, polyurethane urea resins, epoxy resins, oxetane resins, phenoxy resins, polyimide resins, polyamide resins, polyamideimide resins, phenolic resins. Known resins such as resins, alkyd resins, amino resins, polylactic acid resins, oxazoline resins, benzoxazine resins, silicone resins, and fluorine resins can be used. Among these, polyurethane resin, polyurethane urea resin, epoxy resin, phenoxy resin, polyimide resin, polyamide resin, and polyamideimide resin are preferable from the viewpoint of flexibility and insulation reliability.
Thermosetting resins can be used alone or in combination of two or more.

[Curing agent]
The curing agent has a plurality of functional groups that can react with the functional groups of the thermosetting resin. Examples of the curing 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.
A hardening | curing agent can be used individually or in combination with 2 or more types.

  It is preferable that 1-50 weight part is contained with respect to 100 weight part of thermosetting resins, as for a hardening | curing agent, 3-30 weight part is more preferable, and 3-20 weight part is further more preferable.

[Conductive fine particles]
The conductive fine particles have a function of imparting conductivity to the conductive layer. The conductive fine particles are preferably, for example, conductive metals such as gold, platinum, silver, copper and nickel, and alloys thereof, and conductive polymer fine particles, and silver is more preferable from the viewpoint of cost and conductivity.
In addition, composite fine particles having a coating layer in which a metal or a resin is used as a core and the surface of the core is covered, are preferable from the viewpoint of cost reduction. Here, the core is preferably selected appropriately from inexpensive nickel, silica, copper and alloys thereof, and resins. The coating layer may be a material that is more conductive than the core, and is preferably a conductive metal or a conductive polymer. Examples of the conductive metal include gold, platinum, silver, nickel, manganese, indium, and alloys thereof. Examples of the conductive polymer include polyaniline and polyacetylene. Among these, silver is preferable from the viewpoints of price and conductivity.

The shape of the conductive fine particles is not limited as long as desired conductivity is obtained. Specifically, for example, a spherical shape, a flake shape, a leaf shape, a dendritic shape, a plate shape, a needle shape, a rod shape, and a grape shape are preferable. Among these, a dendritic shape is more preferable from the viewpoint of improving connection reliability.
The conductive fine particles can be used alone or in combination of two or more.

The average particle diameter of the conductive fine particles is D50 average particle diameter, preferably 1 to 100 μm, more preferably 3 to 50 μm.
The D50 average particle size is determined by the laser diffraction / scattering particle size distribution analyzer LS13320.
This is a numerical value obtained by measuring conductive fine particles with a tornado dry powder sample module using (manufactured by Beckman Coulter), and a cumulative value in the cumulative particle size distribution is a particle size of 50%. The refractive index was set to 1.6.

  The conductive fine particles are preferably blended in an amount of 50 to 1500 parts by weight, more preferably 100 to 1000 parts by weight, with respect to 100 parts by weight of the thermosetting resin.

[Ion collector]
In the present invention, the ion collector has a function of collecting ions that adversely affect the properties of the electromagnetic wave shielding sheet.
The ion collector includes a cation collector, an anion collector, and both ion collectors. Among these, it is preferable to use a cation scavenger in terms of suppressing migration between the conductive adhesive layer of the electromagnetic wave shield sheet and the wiring circuit and improving connection reliability. Particularly preferred is an inorganic cation scavenger.

(Cation collector)
The cation collector has a function of collecting cations such as metal ions. When the conductive layer contains a cation scavenger, metal ions remaining in the cover coat layer and metal ions generated from the conductive fine particles are collected, and migration between the conductive layer and the signal wiring is suppressed. As the cation collector, there are an inorganic cation collector and an organic cation collector, and both can be used. Among these, an inorganic cation scavenger is preferable from the viewpoint of further improving migration resistance.

Examples of inorganic cation collectors include manganese compounds (hydrous manganese dioxide, etc.), antimony compounds (crystalline antimonic acid, hydrous antimony pentoxide, etc.), zirconium compounds (zirconium hydroxide, zirconium phosphate, zirconium molybdate, tungstic acid). Zirconium), silicate compounds (aluminosilicate, synthetic aluminosilicate, etc.), phosphate compounds (titanium phosphate, tin phosphate, etc.), cerium oxalate (III), ammonium molybdate, hexacyanoiron (III ) Cobalt (II) potassium, natural green sand, stabilized green sand, green sand having Mn ²⁺ type, and the like. Among these, antimony compounds and zirconium compounds have a high ability to collect cations, so that an electromagnetic wave shield sheet having high migration resistance can be easily obtained.
As the inorganic cation scavenger, known products such as IXE-100 and IXE-300 (manufactured by Toa Gosei Co., Ltd.) can be used.

Examples of the organic cation collector include pyrazole compounds such as 3,5-dimethylpyrazole and 3-methyl-5-pyrazolone. Examples of triazole compounds include 1,2,4-triazole, 4-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, benzotriazole, 1-hydroxybenzotriazole, and carboxybenzo. Triazole, 5-methylbenzotriazole, 5-aminobenzotriazole, 5-chlorobenzotriazole, 1- (hydroxymethyl) benzotriazole, 1-[(2-hexylamino) methyl] -benzotriazole, 1- (1,2 -Dicarboxyethyl) benzotriazole, N-benzotriazolymethylurea, 1- (2
, 3-Dicarboxypropyl) benzotriazole, 1- [N, N-bis (2-ethylhexyl) aminomethyl] triazole, 1- [N, N-bis (hydroxyethyl) aminomethyl] triazole, 1,2,3 -A benzotriazole sodium salt solution, tetrazole, 5-aminotetrazole, 5-methyltetrazole, 5-phenyltetrazole and the like. Examples of the thiazole compound include 2-mercaptobenzothiazole, sodium salt of 2-mercaptobenzothiazole, (2-benzothiazylthio) acetic acid, 3- (2-benzothiazylthio) propionic acid, benzothiazole, 2- Examples include benzothiazole acetonitrile, benzothiazole-6-carboxylic acid, and 2- (2-benzothiazolethio) ethanol. Examples of the crown ether compound include 12-crown-4, 15-crown-5, 18-crown-6, 21-crown-7, 24-crown-8, bistrene, cryptad, and dicyclohexano-18-crown-6. , Dibenzo-24-crown-8, cyclam (1,4,8,11-tetrazacyclate-tradicane), cyclodextrin and the like. Moreover, the dihydrazide compound which has a unit represented by following Chemical formula (1) is also preferable. Examples of the dihydrazide compound include N-salicyloyl-N′-aldehyde azine, N, N-dibenzal (oxal hydrazide), bis (2-phenoxypropionylhydrazine) isophthalic acid, [3- (N-salicyloyl) amino-1, 2,4-hydroxyphenyl) propionyl] hydrazine and the like. Among these, the compound represented by the chemical formula (2): decamethylenecarboxylic acid disalicyloyl hydrazide, and the compound represented by the chemical formula (3): N, N′-bis [3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionyl] hydrazine is preferred.

Chemical formula (1)

Chemical formula (2)

Chemical formula (3)

  As the organic cation collector, known products such as ADK STAB CDA-6 and CDA-10 (manufactured by ADEKA) can be used.

(Anion collector)
The electromagnetic wave shielding sheet of the present invention can also use an anion scavenger. Especially, it is preferable that an anion collector is further included in the cation collector. For example, when the conductive adhesive contains an epoxy compound as a curing agent, chloride ions derived from the raw material epichlorohydrin may remain in the conductive layer. In such a case, since the deterioration of the thermosetting resin due to the anion (chloride ion) can be suppressed by including the anion scavenger, the migration resistance, the adhesion force after PCT, and the bending resistance can be improved. .
Examples of the anion collector include bismuth compounds (hydrous bismuth oxide, hydrated bismuth nitrate, etc.), magnesium / aluminum composite oxides (magnesium aluminum hydrotalcite, etc.), phosphate compounds (lead hydroxide phosphate, etc.), etc. Is mentioned. Among these, the magnesium / aluminum composite oxide has a high ability to collect anions, and therefore can further improve the adhesive strength and bending resistance after PCT. The anion collector is preferably an inorganic cation collector from the viewpoint of further improving migration resistance, adhesion after PCT, and bending resistance.

  As the anion scavenger, known products such as IXE-500, IXE-530, IXE-550, IXE-700F, IXE-700D, and IXE-800 (manufactured by Toagosei Co., Ltd.) can be used.

(Both ion collector)
Both ion scavengers include a cation scavenger and an anion scavenger. Both ion collectors are, for example, a cation collector appropriately selected from the already described zirconium compounds, antimony compounds, phosphate compounds, and the like, and an anion collector appropriately selected from bismuth compounds, magnesium / aluminum compounds, etc. A mixture with is preferred.

  As the both ion scavengers, known products such as IXEPLAS-A1, IXEPLAS-A2, IXEPLAS-B1, IXE-600, IXE-633, IXE-6107, IXE-6136 (manufactured by Toa Gosei Co., Ltd.) can be used.

  The ion scavenger can be used alone or in combination of two or more.

  The ion scavenger is preferably blended in an amount of 0.1 to 20 parts by weight, more preferably 0.3 to 10 parts by weight with respect to 100 parts by weight of the thermosetting resin. By blending 0.1 to 20 parts by weight, it becomes easy to obtain an FPC with improved connection reliability and flexibility.

  The average particle diameter of the ion scavenger is preferably from 0.1 to 10 μm, more preferably from 0.1 to 3 μm, still more preferably from 0.1 to 1 μm. By making the average particle diameter 0.1 to 10 μm, it becomes easy to obtain migration resistance. The average particle size is D50 average particle size.

  Conductive adhesives include silane coupling agents, rust inhibitors, reducing agents, antioxidants, pigments, dyes, tackifying resins, plasticizers, UV absorbers, antifoaming agents, leveling regulators as optional components. Fillers and flame retardants can be blended.

  The conductive adhesive can be obtained by mixing and stirring the materials described so far. For the stirring, for example, a known stirring device can be used for a disperse mat, a homogenizer or the like.

<Insulating layer>
The insulating layer can be formed using an insulating resin composition.
The insulating resin composition can contain the above-mentioned optional components as necessary for the thermosetting resin and the curing agent described in the conductive adhesive. The thermosetting resin and the curing agent used for the insulating layer and the conductive layer may be the same or different.

  The insulating resin composition can be obtained by the same method as that for the conductive adhesive.

<Electromagnetic wave shield sheet>
The electromagnetic wave shielding sheet of the present invention is for a printed wiring board comprising an electromagnetic wave shielding sheet, a cover coat layer formed from a solder resist or a photosensitive cover lay film, and a substrate having signal wiring and an insulating substrate. A conductive layer and an insulating layer are provided. Alternatively, a conductive layer, a metal layer, and an insulating layer are provided.

  A method for producing an electromagnetic wave shielding sheet will be described. First, a known method can be used for producing the conductive layer. For example, a method of forming a conductive layer by applying a conductive adhesive on a peelable sheet and drying, or extruding the conductive adhesive into a sheet using an extruder such as a T-die It can also be formed.

  Coating methods include, for example, gravure coating method, kiss coating method, die coating method, lip coating method, comma coating method, blade method, roll coating method, knife coating method, spray coating method, bar coating method, spin coating method, dip coating. A known coating method such as a method can be used. In coating, it is preferable to perform a drying step. In the drying step, for example, a known drying device such as a hot air dryer or an infrared heater can be used.

  1-100 micrometers is preferable, as for the thickness of a conductive layer, 3-50 micrometers is more preferable, and 4-15 micrometers is further more preferable. When the thickness is in the range of 1 to 100 μm, it becomes easy to balance the conductivity and other physical properties.

  As described above, a metal layer may be provided between the insulating layer and the conductive layer in addition to the conductive layer. A known method can be used for laminating the conductive layer and the metal layer. For example, the method forms a metal layer on a peelable sheet. Furthermore, a method of laminating a conductive layer separately formed on a peelable sheet with the metal layer can be used.

The metal layer is preferably a conductive metal foil such as aluminum, copper, silver, and gold. Copper, silver, and aluminum are more preferable, and copper is more preferable in terms of shielding properties, connection reliability, and cost. For example, rolled copper foil or electrolytic copper foil is preferably used as copper, and electrolytic copper is more preferable when the thickness of the metal layer is pursued. In the case of a metal foil, the thickness is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.
In addition to the metal foil, the metal may be formed by vacuum deposition, sputtering, CVD, MO (metal organic), plating, or the like. Among these, vacuum deposition is preferable in view of mass productivity. The thickness of the metal layer other than the metal foil is usually about 0.005 to 10 μm.

  The insulating layer can be formed by the same method as the conductive layer using the insulating resin composition. Alternatively, a film obtained by molding an insulating resin such as polyester, polycarbonate, polyimide, polyphenylene sulfide, or the like can be used.

  The thickness of the insulating layer is usually about 2 to 10 μm.

  The electromagnetic wave shielding sheet can be produced by bonding a conductive layer and an insulating layer, for example. As described above, a metal layer may be provided between the insulating layer and the conductive layer by a known method.

  In the electromagnetic wave shielding sheet, the thermosetting resin and the curing agent contained in the conductive layer exist in an uncured state, and a desired adhesive strength can be obtained by curing with a wiring board and thermocompression bonding. The uncured state includes a semi-cured state in which a part of the curing agent is cured.

  The peelable sheet is a sheet obtained by performing a known peeling treatment on a substrate such as paper or plastic.

  Note that the electromagnetic wave shielding sheet is generally stored in a state where a peelable sheet is attached to the conductive layer and the insulating layer in order to prevent adhesion of foreign matters.

  The electromagnetic wave shielding sheet can include other functional layers in addition to the conductive layer and the insulating layer. The other functional layer is a layer having functions such as hard coat property, water vapor barrier property, oxygen barrier property, thermal conductivity, low dielectric constant, high dielectric constant or heat resistance.

  The electromagnetic wave shielding sheet of the present invention can be used for various applications where electromagnetic waves need to be shielded. For example, flexible printed wiring boards can be used for rigid printed wiring boards, COFs, TABs, flexible connectors, liquid crystal displays, touch panels, and the like.

<Printed wiring board>
The printed wiring board of the present invention includes an electromagnetic wave shielding sheet, a cover coat layer formed from a solder resist or a photosensitive cover lay film, and a wiring board including a signal wiring and an insulating substrate.

<Cover coat layer>
The cover coat layer is an insulating material that covers the signal wiring of the wiring board and protects it from the external environment. The cover coat layer in the printed wiring board of the present invention is composed of an ultraviolet curable solder resist and a photosensitive cover lay film. A photosensitive coverlay film is more preferable from the viewpoint of reducing the production cost of the printed wiring board.
By using a cover coat layer formed of such a solder resist or a photosensitive cover lay film, it is possible to form fine holes corresponding to a narrow pitch of signal wiring. Moreover, it is possible to prevent migration of metal ions derived from the cover coat layer by using an electromagnetic wave shielding sheet that includes a thermosetting resin, a curing agent, conductive fine particles, and an ion scavenger. it can. That is, the formation of holes using a photosensitive coverlay requires a photolithography process, so that metal ions (for example, sodium ions penetrate into the photosensitive coverlay from a developer (for example, an aqueous sodium hydroxide solution)). It is possible to suppress a decrease in connection reliability between the electromagnetic wave shielding sheet and the signal wiring due to migration of the metal ions.
It is also possible to prevent a decrease in connection reliability due to migration of metal ions (for example, silver ions) from conductive fine particles contained in the conductive layer of the electromagnetic wave shielding sheet.

As the solder resist and the photosensitive coverlay film, conventionally known ones can be used, and usually contain a thermosetting resin, a photosensitive resin, a monomer, a photoinitiator, a sensitizer and the like, and if necessary, a colorant including.
When the cover coat layer is formed from a photosensitive cover lay film, the photosensitive cover lay film is bonded to the signal wiring of the insulating base material by a vacuum laminator. Thereafter, the photosensitive cover lay film is irradiated with ultraviolet rays to be photocured, and then developed with an alkaline aqueous solution to wash away the unirradiated portion. After development, the photosensitive coverlay film is cured at 130 to 190 ° C. and cured to form a cover coat layer.
When using a solder resist, the solder resist is coated on the signal wiring and dried. Subsequent processes form a cover coat layer in the same procedure as the photosensitive cover lay film.

  The thickness of the cover coat layer is preferably 10 to 70 μm, and more preferably 20 to 50 μm. By setting the thickness of the cover coat layer in the range of 10 to 70 μm, the flexibility and migration resistance of the printed wiring board can be improved.

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

<Wiring board including signal wiring and insulating base>
The signal wiring includes a ground wiring for grounding and a wiring circuit for sending an electric signal to the electronic component, and is generally formed by etching a copper foil.
The insulating substrate is preferably a bendable plastic such as polyester, polycarbonate, polyimide, polyphenylene sulfide, and more preferably polyimide.

  In general, the thermocompression bonding between the electromagnetic wave shielding sheet and the wiring board is performed under conditions of 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 and the curing agent react by thermocompression bonding. In order to accelerate curing, post-curing may be performed at 150 to 190 ° C. for 30 to 90 minutes after thermocompression bonding. In addition, an electromagnetic wave shield sheet may be called an electromagnetic wave shield layer after thermocompression bonding.

  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.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited only to a following example. The following “parts” and “%” are values based on “parts by weight” and “% by weight”, respectively.

The raw materials used in the examples are shown below.
<Binder resin>
Urethane resin: (thermosetting resin acid value = 10 mgKOH / g, amine value = 0.1 mgKOH / g) Toyochem

<Conductive fine particles>
Conductive fine particles 1: (dendritic particles using copper for the core and silver for the coating layer D50 average particle diameter = 11.0 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd .: (copper for the core, coated) Spherical particles using silver for the layer D50 average particle diameter = 10.0 μm, manufactured by Fukuda Metal Foil Powder Co., Ltd. Conductive fine particles 3: (Flake particles using copper for the core and silver for the coating layer D50 average particle diameter = 10.0μm) Fukuda Metal Foil Powder Industry

<Curing agent>
Epoxy compound: “JER828” (bisphenol A type epoxy resin epoxy equivalent = 189 g / eq) manufactured by Mitsubishi Chemical Corporation Aziridine compound: “Chemite PZ-33” manufactured by Nippon Shokubai Co., Ltd.

<Cation collector>
IXE100: Zirconia-based inorganic cation scavenger, particle size 1 μm (manufactured by Toagosei Co., Ltd.)
IXE300: antimony inorganic cation scavenger, particle size 0.5 μm (manufactured by Toagosei Co., Ltd.)
CDA-6: Decamethylene carboxylic acid disalicyloyl hydrazide (manufactured by ADEKA)
CDA-10: N, N′-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine (manufactured by ADEKA)
<Anion collector>
IXE500: Bismuth inorganic anion scavenger, particle size 1.5 μm (manufactured by Toagosei Co., Ltd.)
IXE700F: Hydrotalcite-based inorganic anion scavenger, particle size 1.5 μm (manufactured by Toagosei Co., Ltd.)
<Both ion scavenger>
IXE PLUS-A1: Mixture of zirconia inorganic cation collector and hydrotalcite inorganic anion collector, particle size 0.5 μm (manufactured by Toagosei Co., Ltd.)

[Example 1]
100 parts of binder resin and 450 parts of conductive fine particles 1 were charged into a container, and a mixed solvent of toluene: isopropyl alcohol (weight ratio = 2: 1) was added and mixed so that the nonvolatile content concentration was 40%. Next, 10 parts of an epoxy compound, 1.0 part of an aziridine compound and 2 parts of a cation scavenger (“IXE100” manufactured by Toa Gosei Co., Ltd.) were added and stirred with a disper for 10 minutes to prepare a conductive adhesive. Further, the obtained conductive adhesive was coated on a peelable sheet using a bar coater so as to have a dry thickness of 10 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain a conductive layer.

  Separately, 100 parts of a binder resin, 10 parts of an epoxy compound and 10 parts of an aziridine compound were added and stirred with a disper for 10 minutes to obtain an insulating resin composition. Next, the obtained insulating resin composition was coated on a peelable sheet using a bar coater so that the dry thickness was 10 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain an insulating layer. . Further, an electromagnetic wave shielding sheet was obtained by attaching an insulating layer to the conductive layer.

[Examples 2 to 17, Comparative Example 1]
Except that the composition of the conductive adhesive of Example 1 was changed as described in Tables 1 and 2, the electromagnetic wave shield sheets of Examples 2 to 17 and Comparative Example 1 were obtained by carrying out in the same manner as Example 1. It was.

[Example 18]
100 parts of binder resin and 50 parts of conductive fine particles 1 were charged into a container, and a mixed solvent of toluene: isopropyl alcohol (weight ratio = 2: 1) was added and mixed so that the nonvolatile content concentration was 40%. Next, 10 parts of an epoxy compound, 1.0 part of an aziridine compound and 2 parts of a cation scavenger (“IXEPLAS-A1” manufactured by Toa Gosei Co., Ltd.) were added and stirred with a disper for 10 minutes to prepare a conductive adhesive. Furthermore, the anisotropic conductive layer was obtained by applying the obtained conductive adhesive on the peelable sheet using a bar coater so as to have a dry thickness of 10 μm, and drying in an electric oven at 100 ° C. for 2 minutes. It was.

  Separately, 100 parts of a binder resin, 10 parts of an epoxy compound and 10 parts of an aziridine curing agent were added and stirred with a disper for 10 minutes to obtain an insulating resin composition. Next, the obtained insulating resin composition was coated on the surface of an electrolytic copper foil with a copper carrier having a thickness of 3 μm using a bar coater so as to have a dry thickness of 10 μm, and dried for 2 minutes in an electric oven at 100 ° C. Then, a slightly adhesive release sheet was laminated. Next, the copper carrier is peeled off, and an anisotropic conductive layer is laminated on the surface thereof, whereby an electromagnetic wave shield having a configuration of a slightly adhesive release sheet / insulating layer / metal layer (electrolytic copper foil) / anisotropic conductive layer / release sheet. A sheet was obtained.

[Example 19]
An electromagnetic wave shielding sheet of Example 19 was obtained in the same manner as in Example 18 except that the composition of the conductive adhesive of Example 18 was changed as described in Tables 1 and 2.

  The following physical properties of the obtained electromagnetic wave shielding sheet were evaluated. The results are shown in Tables 1 and 2.

<Migration test>
Epicoat 1031S (Mitsubishi Chemical Corporation) as a curing agent for 100 parts of a solid content of carboxyl group-containing photosensitive urethane resin (manufactured by Toyochem Co., Ltd .: acid value = 67 mg KOH / g, ethylenically unsaturated group equivalent = 765 g / eq) 10 parts, BL3175 (manufactured by Sumika Bayer Urethane Co., Ltd .: isocyanurate type block isocyanate), aluminum phosphinate EXOLITOP-935 (made by Clariant Japan Co., Ltd.) as a flame retardant 20 parts, copper phthalocyanine pigment LIONOL BLUE FG7350 (manufactured by Toyocolor Co., Ltd.) as a colorant; 1 part, Irgacure 907 (manufactured by Ciba Specialty Chemicals: 2-methyl-1- [4- ( Mechi Thio) phenyl] -2-morpholino-1-propane); 5 parts, DETX-S as a photosensitizer (manufactured by Nippon Kayaku Co., Ltd .: 2,4-diethylthioxanthone); The mixture was mixed and dispersed using a horizontal sand mill DYNO-MILL (manufactured by Shinmaru Enterprise Co., Ltd.) until the particle diameter by a grind gauge was less than 10 μm to obtain a photosensitive resin composition.

A polyethylene terephthalate (PET) film (S-12 thickness 12) was prepared so that the thickness after drying of the photosensitive resin composition obtained above using a doctor blade was 40 μm.
(μm manufactured by Toray DuPont) and dried at 100 ° C. for 5 minutes, and then cooled to room temperature to form a film. Furthermore, the obtained film was bonded to a peelable sheet made of a biaxially oriented polypropylene film (OPP film) to obtain a photosensitive coverlay film.
The glass transition temperature (Tg) after curing of the photosensitive coverlay film was 60 ° C.

The migration test will be described with reference to FIG. As shown in the plan view of FIG. 1A by etching a laminate of a 16 μm thick copper foil and a 25 μm thick polyimide film, line / space = 0.050 mm / 0.050 mm on the polyimide film 1. The cathode electrode comb signal wiring 2 having the cathode electrode connection point 2 'and the anode electrode comb signal wiring 3 having the anode electrode connection point 3' were formed. Next, the OPP film is peeled off from the photosensitive cover lay film, and as shown in the plan view of FIG. 1 (2), the cathode electrode comb signal wiring 2 and the anode electrode comb signal wiring 3 are covered, and the cathode electrode connection point The photosensitive coverlay film was laminated in such a size that the vicinity of 2 ′ and the vicinity of the anode electrode connection point 3 ′ were exposed, and the photosensitive coverlay film was bonded to the laminate by vacuum lamination. The vacuum lamination conditions were a heating temperature of 60 ° C., a vacuum time of 60 seconds, a vacuum ultimate pressure of 2 hPa, a pressure of 0.4 MPa, and a pressurization time of 60 seconds. Further, a PET sheet having a thickness of 120 μm was stacked on the photosensitive coverlay film of the laminate, and exposed for 5 minutes from above using a mercury short arc amplifier (5 kW). Subsequently, the PET mylar sheet was peeled off, and developed with a developing machine for 40 seconds (developer: sodium carbonate aqueous solution with a concentration of 1%, liquid temperature 30 ° C., spray pressure 0.2 MPa). After development, the photosensitive coverlay film is 1 in a hot air dryer at 150 ° C.
A wiring board with a cover coat layer 4 was obtained by time-curing (post-cure).
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 onto the cover coat layer 4 so that a sample laminated as shown in the plan view of FIG. Obtained. In the obtained sample, the conductive layer 5b is electrically connected to the comb signal wiring 2 for the cathode electrode as described in the AA ′ sectional view of the sample shown in FIG.

The obtained sample was hot-pressed under the conditions of 150 ° C., 2.0 MPa, and 30 min to cure the thermosetting resin. Next, the anode was connected to the anode electrode connection point 3 ′ and the cathode electrode was connected to the cathode electrode connection point 2 ′ in an atmosphere of 85 ° C. to 85% RH (relative humidity). Application was continued for 500 hours. And the change of the resistance value until 1000 hours passed was measured continuously. The “leak touch” described below means that there is a dielectric breakdown due to a short circuit, the resistance decreases instantaneously, and a current flows. If there is no leak touch, insulation does not decrease. The evaluation criteria are as follows.

A: Resistance value after 500 hours is 1 × 10 ⁸ Ω or more and no leak touch. Good ○: Resistance value after 500 hours is 1 × 10 ⁷ Ω or more and no leak touch. Good Δ: Resistance value after 500 hours is 1 × 10 ⁷ Ω or more, and there is one leak touch. There is no problem in practical use.
×: Resistance value after 500 hours is less than 1 × 10 ⁷ Ω, and there are two or more leak touches.
Not practical.

<Flexibility>
Flexibility after the pressure cooker test (PCT) was measured by MIT test for folding resistance according to JIS C6471.
An electromagnetic wave shielding sheet was prepared with a width of 15 mm and a length of 120 mm. In addition, the adherend to which the electromagnetic wave shielding film is attached is formed in a shape based on JIS C6471, based on a two-layer CCL in which a polyimide film (thickness 12.5 μm) and a copper foil (thickness 18 μm) are laminated. did. Next, a cover coat layer was formed by pasting a photosensitive coverlay film on the wiring in the same manner as in the migration test, post-curing after exposure and development. Furthermore, the sample was obtained by pressure-bonding the conductive layer exposed by peeling the peelable sheet on the conductive layer side of the electromagnetic wave shielding sheet to the cover coat layer at 150 ° C. for 30 minutes at 2.0 MPa. The obtained sample was subjected to a PCT test (conditions: 121 ° C., 100% RH, 2 atmospheres, 24 hours). With respect to the sample after the PCT test, bending resistance was measured using an MIT tester under conditions of a curvature radius of 0.38 mm, a load of 500 g, and a speed of 180 times / min in an atmosphere of a temperature of 25 ° C. and a humidity of 50%. In the evaluation, the number of bending until the wiring was broken after 3000 times of bending was measured. The evaluation criteria are as follows.

○: No disconnection after 3000 times. Good.
Δ: 2500 times or more and less than 3000 times before disconnection No problem in practical use.
X: Disconnected in less than 2500 times. Not practical.

<Adhesive strength>
The adhesive strength after PCT was measured as follows.
The obtained electromagnetic wave shielding sheet was prepared to have a width of 25 mm and a length of 70 mm and used as a sample. The peelable sheet of the conductive layer is peeled off from the sample, and a polyimide film (“Kapton 200EN” manufactured by Toray DuPont Co., Ltd.) having a thickness of 50 μm is pressure-bonded to the exposed conductive layer under conditions of 150 ° C., 2.0 MPa, 30 min, and thermosetting. I let you. The sample after thermosetting was subjected to PCT (conditions: 121 ° C., 100% RH, 2 atm, 24 hours). The sample was then reinforced in order to measure the adhesive strength stably. Specifically, the peelable sheet on the insulating layer side of the sample is peeled off, and the exposed insulating layer, a thermosetting adhesive sheet (manufactured by Toyochem Co., Ltd.), and a polyimide film having a thickness of 50 μm are stacked, and 150 ° C., 1 MPa, 30 min. A laminate of “polyimide film / electromagnetic wave shield sheet / thermosetting adhesive sheet / polyimide film” was obtained by thermocompression bonding under the above conditions. Using this tensile tester (manufactured by Shimadzu Corp.), the conductive layer of the electromagnetic wave shielding sheet and the polyimide film were peeled at a peel rate of 50 mm / min and a peel angle of 90 ° in an atmosphere of 23 ° C.-50% RH. The peel strength was measured by peeling the interface. The evaluation criteria are as follows.

○: 6 N / 25 mm or more. Good.
Δ: 4 N / 25 mm or more and less than 6 N / 25 mm. There is no problem in practical use.
X: Less than 4N / 25mm. Not practical.

<Connection reliability>
An electromagnetic wave shielding sheet having a width of 20 mm and a length of 50 mm was prepared as Sample 15. 2A, the peelable sheet is peeled off from the electromagnetic wave shielding sheet 15, and the exposed conductive layer 15b is electrically connected to a separately prepared flexible printed wiring board (polyimide film 11 having a thickness of 25 μm). 18 μm thick copper foil circuit 12A and copper foil circuit 12B that are not connected to each other are formed, and formed on the copper foil circuit 12A using a photosensitive coverlay film in the same manner as the migration test, Pressure bonding to a wiring board on which a cover coat layer 13 having a through hole 14 having a thickness of 37.5 μm and a diameter of 1.6 mm is laminated under conditions of 150 ° C., 2 MPa, 30 min, and curing the conductive layer 15b and the insulating layer 15a. A sample was obtained. Next, after removing the peelable sheet on the insulating layer 15a side of the sample and leaving it in an oven at 85 ° C. and 85% for 500 hours, the connection reliability between 12A and 12B shown in the plan view of FIG. Evaluation was made by measuring the resistance value using a BSP probe of “Lorestar GP” manufactured by Mitsubishi Chemical. 2 (2) is a cross-sectional view taken along the line DD ′ of FIG. 2 (1), and FIG. 2 (3) is a cross-sectional view taken along the line CC ′ of FIG. 2 (1). Similarly, FIG. 2 (5) is a DD ′ sectional view of FIG. 2 (4), and FIG. 2 (6) is a CC ′ sectional view of FIG. 2 (4). The evaluation criteria for connection reliability are as follows.

○: Resistance value is less than 300 mΩ.
Δ: Resistance value of 300 mΩ or more and less than 700 mΩ There is no practical problem.
×: Resistance value of 700 mΩ or more

From the results in Table 1, Examples 1 to 19 obtained results with favorable migration resistance, flexibility after PCT, adhesive strength, and connection reliability. Among these, when an inorganic cation scavenger is added, the migration resistance is more excellent. This is because the migration resistance was further improved by collecting metal cations such as sodium ions derived from the developer (for example, sodium hydroxide aqueous solution) in the photolithographic process of the photosensitive coverlay film. It is done.
Further, as shown in Examples 8 and 9, when an inorganic cation collector and an inorganic anion collector were used in combination, not only migration resistance but also flexibility and adhesive strength were obtained. Yes. This is thought to be because the flexibility of the conductive adhesive layer and the adhesive strength after PCT were further improved by collecting the chloride ions derived from the epoxy compound with the anion collector.

DESCRIPTION OF SYMBOLS 1 Polyimide film 2 Comb signal wiring 2 'for cathode electrodes Cathode electrode connection point 3 Comb signal wiring 3' for anode electrodes Anode electrode connection point 4 Cover coat layer 5 Electromagnetic wave shielding sheet 5a Insulating layer 5b Conductive layer 11 Polyimide films 12A and 12B Copper Foil circuit 13 Cover film 14 Through hole 15a Insulating layer 15b Conductive layer

Claims (5)

On a substrate having signal wiring and an insulating base material,
Coating with alkali-developing UV curable solder resist and drying,
A step of photocuring with ultraviolet light, developing, and forming a cover coat layer;
A step of heat-pressing an electromagnetic wave shielding sheet on the cover coat layer;
With
The electromagnetic wave shielding sheet has an insulating layer and a conductive layer,
The said conductive layer is a manufacturing method of the printed wiring board containing a thermosetting resin, a hardening | curing agent, electroconductive fine particles, and an ion scavenger. On a substrate having signal wiring and an insulating base material,
Laminate an alkali development type photosensitive coverlay,
A step of photocuring with ultraviolet light, developing, and forming a cover coat layer;
A step of heat-pressing an electromagnetic wave shielding sheet on the cover coat layer;
With
The electromagnetic wave shielding sheet has an insulating layer and a conductive layer,
The said conductive layer is a manufacturing method of the printed wiring board containing a thermosetting resin, a hardening | curing agent, electroconductive fine particles, and an ion scavenger. The method for producing a printed wiring board according to claim 1 or 2, wherein 0.1 to 20 parts by weight of the ion scavenger is included with respect to 100 parts by weight of the thermosetting resin. The said electromagnetic wave shield sheet has an insulating layer, a metal layer, and the conductive layer formed from a conductive adhesive, The manufacture of the printed wiring board of any one of Claims 1-3 characterized by the above-mentioned. Method. The method for producing a printed wiring board according to claim 1, wherein the ion collector is a cation collector.