JP6968041B2 - Conductive adhesive - Google Patents

Description

The present disclosure relates to conductive adhesives.

Conductive adhesives are often used in flexible printed wiring boards. For example, it is known to bond an electromagnetic wave shielding film having a shielding layer and a conductive adhesive layer to a flexible printed wiring board. In this case, the conductive adhesive firmly adheres the insulating film (coverlay) provided on the surface of the flexible printed wiring board and the shield layer, and is exposed from the opening provided in the insulating film. It is required to ensure good continuity with the ground circuit.

In recent years, heat resistance is also required for conductive adhesives, and various conductive adhesives in which a conductive filler is added to an epoxy resin having excellent heat resistance have been studied.

Further, with the miniaturization of electrical equipment, it is required to embed a conductive adhesive in a small opening to ensure conductivity. Therefore, it has been studied to improve the embedding property of the conductive adhesive by changing the resin composition of the conductive adhesive or adding various additives (see, for example, Patent Document 1). ).

International Publication No. 2014/010524

However, the factors that improve the implantability have not been sufficiently analyzed, and even if the implantability is improved in a specific composition, it is difficult to apply it if the composition is different. Conductive adhesives are required to have not only embedding properties but also heat resistance and adhesion as described above, and it is important to realize these characteristics in a well-balanced manner.

An object of the present disclosure is to make it possible to realize a conductive adhesive having excellent embedding property, heat resistance and adhesion.

One aspect of the conductive adhesive of the present disclosure is a press-processed conductive adhesive, which comprises a thermosetting resin, a conductive filler, and an organic phosphate, and the thermosetting resin is an epoxy. The conductive filler contains 50% by mass or more of the total solid content, and the organic phosphate contains a first polymer component having a group and a second polymer component having a functional group that reacts with an epoxy group. It is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the thermosetting resin, and has a heat absorption peak in the differential scanning calorific value analysis between the lower limit value and the upper limit value of the press processing temperature.

In one aspect of the conductive adhesive, the thermosetting resin can be a polyamide-modified epoxy resin or a polyurethane-modified epoxy resin.

In one aspect of the conductive adhesive, the press working temperature can be 150 ° C. or higher and 190 ° C. or lower, and the endothermic peak position can be 160 ° C. or higher and 180 ° C. or lower.

In one aspect of the conductive adhesive, the organic phosphate can be a phosphinic acid metal salt.

One aspect of the electromagnetic wave shielding film of the present disclosure includes a conductive adhesive layer made of the conductive adhesive of the present disclosure and an insulating protective layer.

The shielded printed wiring board of the present disclosure comprises a ground circuit, a printed wiring board having an insulating film having an opening for exposing the ground circuit, and an electromagnetic wave shielding film of the present disclosure, and the conductive adhesive layer has an opening. It is adhered to the insulating film so as to be conductive with the ground circuit in the portion.

According to the conductive adhesive of the present disclosure, embedding property, heat resistance and adhesion can be improved.

It is sectional drawing which shows an example of the electromagnetic wave shielding film. It is sectional drawing which shows the modification of the electromagnetic wave shielding film. It is sectional drawing which shows the shield printed wiring board. It is a figure which shows the measuring method of the connection resistance.

The conductive adhesive of the present embodiment contains a thermosetting resin, a conductive filler, and an organic phosphate. The thermosetting resin contains a first polymer component having an epoxy group and a second polymer component having a functional group that reacts with the epoxy group. The ratio of the conductive filler to the total solid content is 50% by mass or more. The amount of the organic phosphate is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the thermosetting resin. Further, it has an endothermic peak in the differential scanning calorimetry between the lower limit value and the upper limit value of the press working temperature.

<Organic phosphate>
In the present embodiment, the organic phosphate is preferably a polyphosphate and a phosphinic acid metal salt, and more preferably a phosphinic acid metal salt. As the phosphinic acid metal salt, an aluminum salt, a sodium salt, a potassium salt, a magnesium salt, a calcium salt and the like can be used, and among them, the aluminum salt is preferable. As the polyphosphate, melamine salt, methylamine salt, ethylamine salt, diethylamine salt, triethylamine salt, ethylenediamine salt, piperazine salt, pyridine salt, triazine salt, ammonium salt and the like can be used, and melamine salt is particularly preferable.

Among these organic phosphates, those having an endothermic peak in the differential scanning calorimetry between the lower limit and the upper limit of the press working temperature can be used. The temperature for press working is not particularly limited, but is preferably 150 ° C. or higher, more preferably 160 ° C. or higher, preferably 190 ° C. or higher, and more preferably 180 ° C. or lower from the viewpoint of productivity. Therefore, those having an endothermic peak in the differential scanning calorimetry in the temperature range are preferable. Among them, those having an endothermic peak in the temperature range of 160 ° C. or higher and 180 ° C. or lower are more preferable. Specifically, an aluminum salt of trisdiethylphosphinic acid having an endothermic peak near 170 ° C. can be used.

The temperature of the endothermic peak of the organic phosphate can be measured by the method shown in the examples.

By including such an organic phosphate, the embedding property of the conductive adhesive can be improved. Further, from the viewpoint of improving the embedding property and keeping the connection resistance low, the amount of the organic phosphate is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, preferably 10 parts by mass or more with respect to 100 parts by mass of the thermosetting resin. It is 50 parts by mass or less, more preferably 40 parts by mass or less. Further, by including the organic phosphate in such an amount, the effect of making the conductive adhesive flame-retardant can be obtained.

<Thermosetting resin>
In this embodiment, the thermosetting resin contains a first polymer component having an epoxy group. The first polymer component is not particularly limited as long as it is a polymer having two or more epoxy groups in one molecule, and for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin and the like. Bisphenol type epoxy resin; Spirocyclic epoxy resin; Naphthalene type epoxy resin: Biphenyl type epoxy resin; Terpen type epoxy resin, Tris (glycidyloxyphenyl) methane, Tetrakiss (glycidyloxyphenyl) ethane and other glycidyl ether type epoxy resins; Tetra Glycidylamine type epoxy resin such as glycidyldiaminodiphenylmethane; Tetrabrombisphenol A type epoxy resin; Cresol novolac type epoxy resin, phenol novolac type epoxy resin, α-naphthol novolac type epoxy resin, brominated phenol novolac type epoxy resin, etc. Epoxy resin; rubber-modified epoxy resin and the like can be used. These can be used alone or in combination of two or more. These epoxy resins may be solid or liquid at room temperature. Regarding the epoxy resin, "solid at room temperature" means that it is in a solvent-free state at 25 ° C. and has no fluidity, and "liquid at room temperature" has fluidity under the same conditions. It shall mean that it is in a state.

In the present embodiment, the second polymer component has two or more functional groups in one molecule that react with the epoxy group of the first polymer component. For example, it can be a polymer having a hydroxyl group, a carboxyl group, an epoxy group, an amino group and the like.

The second polymer component can be, for example, a urethane-modified polyester having a carboxyl group. The urethane-modified polyester is a polyester containing a urethane resin as a copolymer component. Urethane-modified polyester can be obtained by subjecting an acid component such as a polyvalent carboxylic acid or an anhydride thereof and a glycol component to polycondensation polymer to obtain a polyester, and then reacting the terminal hydroxyl group of the polyester with an isocyanate component. .. Further, a urethane-modified polyester can also be obtained by simultaneously reacting an acid component, a glycol component, and an isocyanate component.

The acid component is not particularly limited, but is, for example, terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 2,2'-diphenyl. Dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, adipic acid, azelaic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methyl-1 , 2-Cyclohexanedicarboxylic acid, dimer acid, trimellitic anhydride, pyromellitic anhydride, 5- (2,5-dioxotetrahydro-3-franyl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid An anhydride or the like can be used.

The glycol component is not particularly limited, and for example, ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanjiol, 1,3-butanjiol, and the like. 1,4-Butanjiol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentylglycol, diethyleneglycol, dipropylene glycol , 2,2,4-trimethyl-1,5-pentandiol, cyclohexanedimethanol, neopentyl hydroxypivalic acid ester, ethylene oxide adduct and propylene oxide adduct of bisphenol A, hydride bisphenol A ethylene oxide adduct and propylene oxide adduct, 1,9-nonanediol, 2-methyloctanediol, 1,10-decanediol, 2-butyl-2-ethyl-1,3-propanediol, tricyclo Dihydric alcohols such as decandimethanol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., and trivalent or higher polyhydric alcohols such as trimethylolpropane, trimethylolethane, pentaerythrete, etc. may be used if necessary. can.

The isocyanate component is not particularly limited, but is, for example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylenedi isocyanate, diphenylmethane diisocyanate, m-phenylenedi isocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, 3. , 3'-dimethoxy-4,4'-biphenylenediocyanate, 1,5-naphthalenediocyanate, 2,6-naphthalenediocyanate, 3,3'-dimethyl-4,4'-diisocyanate, 4,4'-diisocyanate diphenyl ether, 1,5-Xylylene diisocyanate, 1,3 diisocyanate methylcyclohexane, 1,4-diisocyanatemethylcyclohexane, isophorone diisocyanate and the like can be used.

Further, the second polymer component can be a carboxyl group-modified polyamide. The carboxyl group-modified polyamide resin is synthesized from an organic diisocyanate or diamine by a condensation reaction with a polyvalent carboxylic acid component such as a dicarboxylic acid, a tricarboxylic acid, or a tetracarboxylic acid dianhydride.

Examples of the above polyvalent carboxylic acid include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, decanedioic acid, dodecanedioic acid and dimer acid, isophthalic acid, terephthalic acid and phthalic acid. Aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, diphenylsulfonicdicarboxylic acid, oxydibenzoic acid, trimellitic acid, pyromellitic acid, diphenylsulfonetetracarboxylicdianehydride, benzophenone tetracarboxylicdianhydride and other aromaticcarboxylic acid anhydrides, etc. Can be mentioned. These can be used alone or in combination of two or more.

Examples of the above organic diisocyanate include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthalenedi isocyanate, and 3,3'-dimethyl-4,4'-. Aromatic diisocyanates such as diphenylmethane diisocyanate, p-phenylenediisocyanate, m-xylenediocyanate, m-tetramethylxylenediocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane Examples thereof include diisocyanate, transcyclohexane-1,4-diisocyanate, hydrogenated m-xylene diisocyanate, and aliphatic isocyanates such as lysine diisocyanate. These can be used alone or in combination of two or more.

A diamine can also be used instead of the above-mentioned organic diisocyanate. Examples of the diamine include phenylenediamine, diaminodiphenylpropane, diaminodiphenylmethane, benzidine, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, diaminodiphenyl ether and the like.

As the second polymer component, an acid anhydride-modified polyester, an epoxy resin, or the like can also be used.

When the first polymer component is an epoxy resin and the second polymer component is a urethane-modified polyester, the urethane-modified epoxy resin is obtained after the first polymer component and the second polymer component are reacted and cured. When the second polymer component is polyamide, a polyamide-modified epoxy resin can be obtained. The thermosetting resin containing the first polymer component and the second polymer component in the present disclosure contains an unreacted first polymer component and a second polymer component, and includes a non-cured resin. Further, a state in which the first polymer component and the second polymer component have completely reacted and no unreacted one remains is also included.

The first polymer component is not particularly limited, but the number average molecular weight is preferably 500 or more, more preferably 1000 or more, from the viewpoint of improving the bulk strength of the adhesive. Further, from the viewpoint of adhesion, the number average molecular weight is preferably 10,000 or less, more preferably 5000 or less.

The number average molecular weight (Mn) of the second polymer component is preferably 10,000 or more, preferably 50,000 or less, and more preferably 30,000 or less, from the viewpoint of further improving the embedding property. In addition, Mn can be a value in terms of styrene measured by gel permeation chromatography (GPC).

The mass ratio of the first polymer component to the second polymer component is preferably 1: 100 to 20: 100, more preferably 3: 100 to 15: 100. By setting the mass ratio of the first polymer component and the second polymer component in such a mass ratio, the adhesion can be improved.

The thermosetting resin can contain a curing agent that promotes the reaction between the first polymer component and the second polymer component. As the curing agent, an imidazole-based curing agent, a phenol-based curing agent, a cationic-based curing agent, or the like can be used. These can be used alone or in combination of two or more.

Examples of imidazole-based curing agents include 2-phenyl-4,5-dihydroxymethylimidazole, 2-heptadecylimidazole, 2,4-diamino-6- (2'-undecylimidazolyl) ethyl-S-triazine, 1 -Cyanoethyl-2-phenylimidazole, 2-phenylimidazole, 5-cyano-2-phenylimidazole, 2,4-diamino-6- [2'methylimidazolyl- (1')]-ethyl-S-triazine isocyanuric acid addition Alkyl group on the imidazole ring, such as 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4,5-di (2-cyanoethoxy) methylimidazole, etc. , Ethylcyano group, hydroxyl group, compound to which azine and the like are added, and the like.

Examples of the phenol-based curing agent include novolak phenol, naphthol-based compounds and the like.

Examples of the cationic curing agent include an amine salt of boron trifluoride, an antimony trichloride-acetyl chloride complex, and a sulfonium salt having a phenethyl group or an allylic group.

The curing agent may not be added, but from the viewpoint of accelerating the reaction, it is preferably 0.3 parts by mass or more, more preferably 1 part by mass or more, and preferably 20 parts by mass with respect to 100 parts by mass of the first polymer component. By mass or less, more preferably 15 parts by mass or less.

<Conductive filler>
The conductive filler is not particularly limited, and for example, a metal filler, a metal-coated resin filler, a carbon filler, and a mixture thereof can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver coat copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. These metal powders can be produced by an electrolytic method, an atomizing method, a reducing method, or the like. Of these, any of silver powder, silver-coated copper powder and copper powder is preferable.

The conductive filler is not particularly limited, but from the viewpoint of contact between the fillers, the average particle size is preferably 1 μm or more, more preferably 3 μm or more, preferably 50 μm or less, and more preferably 40 μm or less. The shape of the conductive filler is not particularly limited and may be spherical, flake-shaped, dendritic, fibrous or the like, but is preferably dendritic from the viewpoint of obtaining a good connection resistance value.

The content of the conductive filler can be appropriately selected depending on the intended use, but in order to realize isotropic conductivity, the ratio to the total solid content is 50% by mass or more, preferably 60% by mass or more, preferably 60% by mass or more. It is 95% by mass or less, more preferably 90% by mass or less.

<Arbitrary ingredient>
To the conductive adhesive of the present embodiment, an antifoaming agent, an antioxidant, a viscosity modifier, a diluent, an antioxidant, a leveling agent, a coupling agent, a coloring agent, a flame retardant and the like are added as optional components. be able to.

The conductive adhesive of the present embodiment can be isotropically conductive. The conductive adhesive of the present disclosure can be used for an electromagnetic wave shielding film 101 having an insulating protective layer 112 and a conductive adhesive layer 111 as shown in FIG. In such an electromagnetic wave shielding film, the conductive adhesive layer 111 can function as a shield. As shown in FIG. 2, a shield layer 113 may be separately provided between the insulating protective layer 112 and the conductive adhesive layer 111.

The conductive adhesive layer 111 can be formed, for example, by applying the conductive adhesive of the present embodiment on the insulating protective layer 112 or the shield layer 113 formed on the insulating protective layer 112.

The thickness of the conductive adhesive layer 111 is preferably 1 μm to 50 μm from the viewpoint of controlling the embedding property.

If necessary, a peelable protective film may be attached to the surface of the conductive adhesive layer 111.

The insulating protective layer 112 has sufficient insulating properties and is not particularly limited as long as it can protect the conductive adhesive layer 111 and the shield layer 113 if necessary, but for example, a thermoplastic resin composition and a thermosetting resin composition. A substance, an active energy ray-curable composition, or the like can be used.

The thermoplastic resin composition is not particularly limited, but is limited to a styrene resin composition, a vinyl acetate resin composition, a polyester resin composition, a polyethylene resin composition, a polypropylene resin composition, an imide resin composition, and the like. Alternatively, an acrylic resin composition or the like can be used. The thermosetting resin composition is not particularly limited, but a phenol-based resin composition, an epoxy-based resin composition, a urethane-based resin composition, a melamine-based resin composition, an alkyd-based resin composition, or the like can be used. .. The active energy ray-curable composition is not particularly limited, and for example, a polymerizable compound having at least two (meth) acryloyloxy groups in the molecule can be used. The protective layer may be formed of a single material or may be formed of two or more kinds of materials.

The insulating protective layer 112 may be a laminated body having two or more layers having different physical properties such as material, hardness, and elastic modulus. For example, in the case of a laminate of an outer layer having a low hardness and an inner layer having a high hardness, the outer layer has a cushioning effect, so that the pressure applied to the shield layer 113 in the step of heating and pressurizing the electromagnetic wave shield film 101 onto the printed wiring substrate is relaxed. can. Therefore, it is possible to prevent the shield layer 113 from being destroyed by the step provided on the printed wiring board.

The insulating protective layer 112 includes a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, and a viscosity, if necessary. At least one of a modifier, an anti-blocking agent, and the like may be contained.

The thickness of the insulating protective layer 112 is not particularly limited and can be appropriately set as needed, but is preferably 1 μm or more, more preferably 4 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, and further. It can be preferably 5 μm or less. By setting the thickness of the insulating protective layer 112 to 1 μm or more, the conductive adhesive layer 111 and the shield layer 113 can be sufficiently protected. By setting the thickness of the insulating protective layer 112 to 20 μm or less, the flexibility of the electromagnetic wave shielding film 101 can be ensured, and it becomes easy to apply the electromagnetic wave shielding film 101 to a member that requires flexibility.

When the shield layer 113 is provided, the shield layer 113 can be formed of a metal foil, a vapor-deposited film, a conductive filler, or the like.

The metal foil is not particularly limited, but may be a foil made of any one of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc and the like, or an alloy containing two or more of them.

The thickness of the metal foil is not particularly limited, but is preferably 0.5 μm or more, and more preferably 1.0 μm or more. When the thickness of the metal foil is 0.5 μm or more, it is possible to suppress the attenuation of the high frequency signal when the high frequency signal of 10 MHz to 100 GHz is transmitted to the shield printed wiring board. The thickness of the metal foil is preferably 12 μm or less, more preferably 10 μm or less, still more preferably 7 μm or less. When the thickness of the metal layer is 12 μm or less, the raw material cost can be suppressed and the judgment elongation of the shield film becomes good.

The vapor deposition film is not particularly limited, but can be formed by vapor deposition of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc and the like. For the vapor deposition, an electrolytic plating method, an electroless plating method, a sputtering method, an electron beam vapor deposition method, a vacuum vapor deposition method, a chemical vapor deposition (CVD) method, a metal organic deposition (MOCVD) method, or the like can be used.

The vapor deposition film is not particularly limited, but can be formed by vapor deposition of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc and the like. For the vapor deposition, an electrolytic plating method, an electroless plating method, a sputtering method, an electron beam vapor deposition method, a vacuum vapor deposition method, a chemical vapor deposition (CVD) method, a metal organic deposition (MOCVD) method, or the like can be used.

The thickness of the thin-film film is not particularly limited, but is preferably 0.05 μm or more, and more preferably 0.1 μm or more. When the thickness of the metal vapor-deposited film is 0.05 μm or more, the electromagnetic wave shielding film has excellent characteristics of shielding electromagnetic waves in the shield-printed wiring substrate. The thickness of the metal vapor deposition film is preferably less than 0.5 μm, more preferably less than 0.3 μm. When the thickness of the metal vapor-deposited film is less than 0.5 μm, the bending resistance of the electromagnetic wave shielding film is excellent, and it is possible to prevent the shield layer from being destroyed by the step provided on the printed wiring board.

In the case of the conductive filler, the shield layer 113 can be formed by applying a solvent containing the conductive filler to the surface of the insulating protective layer 112 and drying it. As the conductive filler, a metal filler, a metal-coated resin filler, a carbon filler, or a mixture thereof can be used. As the metal filler, copper powder, silver powder, nickel powder, silver coat copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder and the like can be used. These metal powders can be produced by an electrolytic method, an atomizing method, or a reducing method. Examples of the shape of the metal powder include a spherical shape, a flake shape, a fibrous shape, and a dendritic shape.

In the present embodiment, the thickness of the shield layer 113 may be appropriately selected according to the required electromagnetic shielding effect and repeated bending / sliding resistance, but in the case of a metal foil, it is 12 μm from the viewpoint of ensuring breaking elongation. The following is preferable.

The electromagnetic wave shield film 101 of the present embodiment can be used for the shield printed wiring board 103 as shown in FIG. As shown in FIG. 3, the shield printed wiring board 103 has a printed wiring board 102 and an electromagnetic wave shielding film 101.

The printed wiring board 102 has, for example, a printed circuit including a base member 122 and a ground circuit 125 provided on the base member 122. The insulating film 121 is adhered on the base member 122 by the adhesive layer 123. The insulating film 121 is provided with an opening that exposes the ground circuit 125. A surface layer 126 such as a gold plating layer can be provided on the exposed portion of the ground circuit 125. The printed wiring board 102 may be a flexible board or a rigid board.

Such a shield-printed wiring board 103 can be manufactured as follows. First, the printed wiring board 102 and the electromagnetic wave shielding film 101 are prepared.

Next, the electromagnetic wave shielding film 101 is arranged on the printed wiring board 102 so that the conductive adhesive layer 111 is located above the opening 128. Then, the electromagnetic wave shield film 101 and the printed wiring board 102 are sandwiched from above and below by two heating plates (not shown) heated to a predetermined temperature (for example, 120 ° C.), and a predetermined pressure (for example, 0.5 MPa) is sandwiched between them. ) For a short time (for example, 5 seconds). As a result, the electromagnetic wave shielding film 101 is temporarily fixed to the printed wiring board 102.

Subsequently, the temperature of the two heating plates is set to a predetermined press temperature (for example, 170 ° C.) higher than that at the time of the temporary fixing, and the pressure is applied at a predetermined pressure (for example, 3 MPa) for a predetermined time (for example, 30 minutes). As a result, the electromagnetic wave shielding film 101 can be fixed to the printed wiring board 102. The press temperature can be selected depending on the composition of the conductive adhesive, but is preferably 150 ° C. or higher, more preferably 160 ° C. or higher, from the viewpoint of thermal history of the printed wiring board, equipment configuration, operability, and the like. It is preferably 190 ° C. or lower, more preferably 180 ° C. or lower.

At this time, a part of the conductive adhesive layer 111 softened by heating flows into the opening 128 by pressurization. As a result, the shield layer 113 and the ground circuit 115 are connected. Since a sufficient amount of the conductive adhesive layer 111 is present between the shield layer 113 and the printed wiring board 102 in the opening 128, the electromagnetic wave shielding film 101 and the printed wiring board 102 have sufficient strength. Be glued. Further, since the conductive adhesive layer 111 has high embedding property, connection stability can be ensured even if it is exposed to a high temperature during reflow in the component mounting process.

After this, a solder reflow process for component mounting is performed. In the reflow process, the electromagnetic wave shielding film 101 and the printed wiring board 102 are exposed to a high temperature of about 260 ° C. The components to be mounted are not particularly limited, and examples thereof include chip components such as resistors and capacitors in addition to connectors and integrated circuits.

Since the conductive adhesive of the present embodiment has high embedding property, even when the diameter a of the opening 128 is as small as 1 mm or less, the conductive adhesive can be sufficiently embedded in the opening 128, and the electromagnetic wave shielding film 101 and the electromagnetic wave shielding film 101 can be sufficiently embedded. Good connection with the ground circuit 125 can be ensured.

From the viewpoint of firmly adhering the electromagnetic wave shielding film 101, the peel strength between the conductive adhesive layer 111 and the insulating film 121 is preferably high, specifically preferably 11 N / cm or more, and more preferably 13 N / cm. Above, more preferably 15 N / cm or more.

The base member 122 may be, for example, a resin film or the like, and specifically, a film made of a resin such as polypropylene, cross-linked polyethylene, polyester, polybenzoimidazole, polyimide, polyimideamide, polyetherimide, or polyphenylene sulfide. be able to.

The insulating film 121 is not particularly limited, but can be formed of, for example, a resin such as polyethylene terephthalate, polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimideamide, polyetherimide, or polyphenylene sulfide. The thickness of the insulating film 121 is not particularly limited, but can be about 10 μm to 30 μm.

The printed circuit including the ground circuit 125 can be, for example, a copper wiring pattern formed on the base member 122. The surface layer 126 is not limited to the gold-plated layer, but may be a layer made of copper, nickel, silver, tin, or the like. The surface layer 126 may be provided as needed, and the surface layer 126 may not be provided.

The conductive adhesive of the present embodiment is excellent in embedding property and adhesiveness, and exhibits a particularly excellent effect in attaching the electromagnetic wave shielding film 101 to the printed wiring board 102. However, it is also useful in other applications where conductive adhesives are used. For example, it can be used as an adhesive layer in a conductive reinforcing plate.

Hereinafter, the conductive adhesive of the present disclosure will be described in more detail with reference to Examples. The following examples are exemplary and are not intended to limit the invention.

<Making an electromagnetic wave shield film>
An epoxy resin was coated on the release film with a thickness of 6 μm and dried to form a protective layer. Next, the predetermined material was mixed and stirred using a planetary stirring / defoaming device to prepare conductive adhesive compositions of Examples 1 to 3 and Comparative Examples 1 to 4 having the compositions shown in Table 1. ..

Next, a paste-like conductive adhesive composition was applied onto the protective layer and dried at 100 ° C. for 3 minutes to prepare an electromagnetic wave shielding film.

<Measurement of endothermic peak>
The position of the endothermic peak of the organic phosphate was measured using a differential scanning calorimetry device (DSC3500SA, manufactured by NETZSCH). The measurement conditions were a temperature range of 0 ° C. to 300 ° C., a heating rate of 10 ° C./min, and a nitrogen atmosphere.

<Adhesion with polyimide>
The adhesion between the polyimide and the conductive adhesive was measured by a 180 ° peel test. Specifically, the conductive adhesive layer side of the electromagnetic wave shielding film is attached to a polyimide film (manufactured by Toray DuPont, Kapton 100EN (registered trademark)) under the conditions of temperature: 170 ° C., time: 3 minutes, and pressure of 2 MPa. I pasted it. Next, a bonding film (manufactured by Arisawa Mfg. Co., Ltd.) was bonded to the protective layer side of the electromagnetic wave shielding film under the conditions of temperature: 120 ° C., time: 5 seconds, and pressure 0.5 MPa. Next, a polyimide film (manufactured by Toray DuPont, Kapton 100EN (registered trademark)) was laminated on the bonding film to prepare a laminate for evaluation. Then, the laminate of the polyimide film / bonding film / shield film was peeled off from the polyimide film at 50 mm / min. Table 1 shows the average value with the number of tests set to n = 5.

<Manufacturing of shield printed wiring board>
Next, the electromagnetic wave shield film produced in each Example and Comparative Example and the printed wiring board are adhered to each other using a press machine under the conditions of temperature: 170 ° C., time: 3 minutes, pressure: 2 to 3 MPa, and shielded. A printed wiring board was produced.

As a printed wiring board, as shown in FIG. 3, a copper foil pattern 125 simulating a ground circuit is formed on a base member 122 made of a polyimide film, and an insulating adhesive layer 123 and an insulating adhesive layer 123 are formed on the copper foil pattern 125. A coverlay (insulating film) 121 made of a polyimide film was formed. A gold-plated layer was provided as the surface layer 126 on the surface of the copper foil pattern 125. The coverlay 121 was formed with an opening simulating a ground connection portion having a diameter a of 0.8 mm.

<Measurement of connection resistance value>
Using the shielded printed wiring board produced in each Example and Comparative Example, as shown in FIG. 4, the electric resistance value between two copper foil patterns 125 provided with a surface layer 126 which is a gold plating layer on the surface. Was measured with a resistance meter 205, and the connection resistance between the copper foil pattern 125 and the electromagnetic wave shielding film 101 was evaluated.

(Example 1)
A solid epoxy resin (NC-3000, Nippon Kayaku Co., Ltd.) was used as the first polymer component. A polyamide resin (carboxyl group-modified polyamide resin having an acid value of 15 mgKOH / g (number average molecular weight: 2000, Tg: 30 ° C.) was used as the second polymer component. The mass ratio of the first polymer component to the second polymer component. As a curing agent, 2-phenyl-1H-imidazole-4,5-dimethanol (2PHZPW, manufactured by Shikoku Kasei Kogyo) was added in an amount of 6 n parts by mass based on 100 parts by mass of the resin component.

The organic phosphate, trisdiethylphosphinate aluminum salts (OP935, clear manufactured cement Japan) having a heat absorption peak by differential scanning calorimetry to 170 ° C. was used to 10 parts by mass with respect to 100 parts by weight of the resin component.

As the conductive filler, a dendrite-like silver-coated copper powder having an average particle size of 6 μm and a silver coverage of 8% by mass was used. The conductive filler was 150 parts by mass (60% by mass as a ratio to the total solid content) with respect to 100 parts by mass of the resin component.

When the hole diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance was 350 mΩ / hole, and the peel strength with respect to polyimide was 19 N / cm.

(Example 2)
The same procedure as in Example 1 was carried out except that the amount of the organic phosphate was 20 parts by mass with respect to 100 parts by mass of the resin component.

When the hole diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance was 375 mΩ / 1 hole, and the peel strength with respect to the polyimide was 21 N / cm.

(Example 3)
The second polymer component was a polyurethane-modified polyester resin, and the mass ratio of the first polymer component to the second polymer component was 10: 100. Further, the amount of the organic phosphate was 30 parts by mass with respect to 100 parts by mass of the resin component. Other conditions were the same as in Example 1.

When the hole diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance was 385 mΩ / 1 hole, and the peel strength with respect to the polyimide was 16 N / cm.

(Comparative Example 1)
The procedure was the same as in Example 1 except that no organic phosphate was added. When the hole diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance was 500 mΩ / 1 hole, and the peel strength with respect to the polyimide was 17 N / cm.

(Comparative Example 2)
The second polymer component was a polyurethane-modified polyester resin, and the mass ratio of the first polymer component to the second polymer component was 10: 100. In addition, no organic phosphate was added. Other conditions were the same as in Example 1.

When the hole diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance exceeded 1000 mΩ / 1 hole and could not be measured. The peel strength with respect to polyimide was 15 N / cm.

(Comparative Example 3)
The same procedure as in Example 1 was carried out except that 20 parts by mass of melamine cyanurate (MC-6000, manufactured by Nissan Chemical Industries, Ltd.) was added to 100 parts by mass of the resin component instead of the organic phosphate. When the hole diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance was 350 mΩ / hole, and the peel strength with respect to polyimide was 10 N / cm.

(Comparative Example 4)
The same procedure as in Example 1 was carried out except that the amount of the organic phosphate was 50 parts by mass with respect to 100 parts by mass of the resin component.

When the hole diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance exceeded 1000 mΩ / 1 hole and could not be measured. The peel strength with respect to polyimide was 11 N / cm.

Table 1 summarizes the results of each Example and Comparative Example.

The conductive adhesive of the present disclosure is excellent in embedding property, heat resistance and adhesiveness, and is useful in applications such as an electromagnetic wave shielding film.

101 Electromagnetic wave shield film 102 Printed wiring board 103 Shielded printed wiring board 111 Conductive adhesive layer 112 Insulation protection layer 113 Shield layer 115 Ground circuit 121 Insulation film 122 Base member 123 Adhesive layer 125 Ground circuit 126 Surface layer 128 Opening

Claims (4)

It is a conductive adhesive that is pressed.
Contains thermosetting resin, conductive filler, and organic phosphate.
The thermosetting resin contains a first polymer component having an epoxy group and a second polymer component having a functional group that reacts with the epoxy group.
The conductive filler has a ratio of 50% by mass or more with respect to the total solid content.
The organic phosphate is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the thermosetting resin, and differential scanning calorimetry is performed between the lower limit value and the upper limit value of the press working temperature. have a heat absorption peak in,
The thermosetting resin is a polyamide-modified epoxy resin or a polyurethane-modified epoxy resin, and is
The organic phosphate is a conductive adhesive which is a metal salt of phosphinic acid. The conductive adhesive according to claim 1 , wherein the press working temperature is 150 ° C. or higher and 190 ° C. or lower, and the position of the endothermic peak is 160 ° C. or higher and 180 ° C. or lower. The conductive adhesive layer made of the conductive adhesive according to claim 1 or 2.
An electromagnetic wave shielding film with an insulating protective layer. A printed wiring board having a ground circuit and an insulating film having an opening that exposes the ground circuit.
The electromagnetic wave shielding film according to claim 3 is provided.
A shield-printed wiring board in which the conductive adhesive layer is adhered to the insulating film so as to be conductive to the ground circuit at the opening.

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