TWI757584B - conductive adhesive - Google Patents

Abstract

The subject of this invention is to implement|achieve the electroconductive adhesive which is excellent in embeddability, heat resistance, and adhesiveness.

The solution of the present invention is: a conductive adhesive for press processing, which contains a thermosetting resin, a conductive filler and an organic phosphate. A thermosetting resin contains the 1st polymer component which has an epoxy group, and the 2nd polymer component which has a functional group which reacts with an epoxy group. The ratio of the conductive filler to the total solid content is 50% by mass or more. 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 has an endothermic peak of differential scanning calorimetry between the lower limit value and the upper limit value of the pressing temperature.

Description

conductive adhesive

Field of Invention

The present disclosure relates to a conductive adhesive.

Background of the Invention

A conductive adhesive is often used in flexible printed wiring boards. For example, it is known that an electromagnetic wave shielding film having a shielding layer and a conductive adhesive layer is attached to a flexible printed wiring board. At this time, it is required for the conductive adhesive to firmly adhere to the insulating film (covering layer) and the shielding layer provided on the surface of the flexible printed wiring board, and at the same time to secure the ground exposed from the opening provided in the insulating film The circuit is well turned on.

In recent years, heat resistance is also required for conductive adhesives, and various conductive adhesives have been studied by adding conductive fillers to epoxy resins having excellent heat resistance.

In addition, with the miniaturization of electrical equipment, it is required to secure conductivity by inserting a conductive adhesive into minute openings. Therefore, studies have been made to improve the embeddability of the conductive adhesive by changing the resin composition of the conductive adhesive, adding various additives, and the like (for example, refer to Patent Document 1).

prior art literature

Patent Literature

Patent Document 1: International Publication No. 2014/010524

Summary of Invention

However, the main factors for the improvement of embeddedness have not been fully analyzed, and even if the embeddedness improves under a specific composition, it is difficult to apply as long as the composition is different. Therefore, the conductive adhesive is required not only for embedding properties, but also for the above-mentioned heat resistance and adhesion, and it is important to realize these properties in a well-balanced manner.

A subject of the present disclosure is to realize a conductive adhesive excellent in embeddability, heat resistance, and adhesion.

One aspect of the conductive adhesive of the present disclosure is a press-processable conductive adhesive, which contains a thermosetting resin, a conductive filler and an organic phosphate; the thermosetting resin includes a first polymer having an epoxy group a second polymer component having a functional group reactive with an epoxy group; the ratio of the conductive filler to the total solid content is 50% by mass or more; the organic phosphate is 5 parts by mass relative to 100 parts by mass of the thermosetting resin It is more than or equal to 40 parts by mass and has an endothermic peak of differential scanning calorimetry between the lower limit value and the upper limit value of the pressing temperature.

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

In one aspect of the conductive adhesive, the pressing temperature It is 150°C or more and 190°C or less, and the position of the endothermic peak can be set to 160°C or more and 180°C or less.

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 and an insulating protective layer composed of the conductive adhesive of the present disclosure.

The shielding printed wiring board of the present disclosure includes: a printed wiring board having a ground circuit and an insulating film, the insulating film having an opening for exposing the ground circuit; and the electromagnetic wave shielding film of the present disclosure; and the conductive adhesive layer is formed on the The opening portion is connected to the insulating film so as to conduct the ground circuit.

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

101: Electromagnetic wave shielding film

102: Printed wiring board

103: Shielded printed wiring board

111: Conductive adhesive layer

112: Insulation protective layer

113: Shielding layer

115: Ground circuit

121: insulating film

122: Base member

123: Adhesive layer

125: Ground circuit

126: Surface layer

128: Opening

205: Resistance Meter

a: Diameter of opening

FIG. 1 is a cross-sectional view showing an example of an electromagnetic wave shielding film.

FIG. 2 is a cross-sectional view showing a modification of the electromagnetic wave shielding film.

FIG. 3 is a cross-sectional view showing a shielded printed wiring board.

FIG. 4 is a diagram showing a method of measuring connection resistance.

Form for carrying out the invention

The conductive adhesive of this embodiment contains a thermosetting resin, a conductive filler, and an organic phosphate. The thermosetting resin contains the first epoxy group A polymer component and a second polymer component having a functional group reactive with an epoxy group. The ratio of the conductive filler to the total solid content is 50% by mass or more. 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. In addition, there is an endothermic peak of differential scanning calorimetry between the lower limit value and the upper limit value of the pressing temperature.

<Organophosphate>

鹽、吡啶鹽、三

鹽及銨鹽等，其中又以三聚氰胺鹽為佳。 In this embodiment, the organic phosphates are preferably polyphosphates and metal hypophosphorous acid salts, and more preferably metal hypophosphorous acid salts. As the metal hypophosphite salts, aluminum salts, sodium salts, potassium salts, magnesium salts, calcium salts, etc. can be used, and among them, aluminum salts are preferred. As the polyphosphate salts, melamine salts, methylamine salts, ethylamine salts, diethylamine salts, triethylamine salts, ethylenediamine salts, piperine

salt, pyridinium salt, tris

Salts and ammonium salts, etc., among which melamine salts are preferred.

Among these organic phosphates, those having an endothermic peak in differential scanning calorimetry analysis between the lower limit value and the upper limit value of the pressing temperature can be used. The press working temperature is not particularly limited, but from the viewpoint of productivity, it is preferably 150°C or higher, more preferably 160°C or higher, and preferably 190°C or lower, more preferably 180°C or lower. Therefore, those with endothermic peaks of differential scanning calorimetry in these temperature ranges are preferred. Among them, those having an endothermic peak in the temperature range of 160°C or higher and 180°C or lower are preferred. Specifically, it can be used for a tris (diethylphosphinic acid) aluminum salt having an endothermic peak around 170°C, or the like.

In addition, the temperature of the endothermic peak of the organic phosphate can be determined according to the method shown in the Examples.

The conductive connection can be made by containing the organic phosphate. The embeddedness of the agent is improved. In addition, from the viewpoint of improving the embeddability and maintaining low connection resistance, the amount of the organic phosphate is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and preferably 50 parts by mass relative to 100 parts by mass of the thermosetting resin. parts by mass or less, preferably 40 parts by mass or less. In addition, the effect of making the conductive adhesive flame retardant can also be obtained by containing the organic phosphate in the above amount.

<Thermosetting resin>

In this embodiment, a thermosetting resin contains the 1st polymer component which has 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, and bisphenol S type ring can be used. Bisphenol-type epoxy resins such as oxygen resins; Spiro-type epoxy resins; Naphthalene-type epoxy resins: Biphenyl-type epoxy resins; Terpene-type epoxy resins, ginseng (glycidoxyphenyl) methane, Glycidoxypropyl ether type epoxy resins such as (glycidoxyphenyl)ethane; glycidylamine type epoxy resins such as tetraglycidyldiaminodiphenylmethane; tetrabromobisphenol A type Epoxy resins; cresol novolac epoxy resins, phenol novolac epoxy resins, α-naphthol novolac epoxy resins, brominated phenol novolac epoxy resins and other novolac epoxy resins; and rubber modified epoxy resins resin, etc. These may be used individually by 1 type, and may use 2 or more types together. These epoxy resins can be solid or liquid at normal temperature. In addition, in the case of epoxy resins, "solid at room temperature" means that they have no fluidity at 25°C and no solvent; "liquid at room temperature" means that they have fluidity under the same conditions status.

In this embodiment, the 2nd polymer component has two or more functional groups which react with the epoxy group of a 1st polymer component in 1 molecule. For example, a polymer having a hydroxyl group, a carboxyl group, an epoxy group, an amine group, and the like can be used.

The second polymer component can be, for example, a urethane-modified polyester having a carboxyl group. The so-called urethane-modified polyester is a polyester containing a urethane resin as a copolymer component. The urethane-modified polyester can be obtained, for example, by polycondensing an acid component such as a polycarboxylic acid or an anhydride thereof and a diol component to obtain a polyester, and then reacting the terminal hydroxyl group of the polyester with an isocyanate component. Moreover, the urethane-modified polyester can also be obtained by simultaneously reacting an acid component, a diol component, and an isocyanate component.

The acid component is not particularly limited, and for example, terephthalic acid, isophthalic acid, phthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid can be used. Formic acid, 2,2'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic 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, Pyromelite anhydride, 5-(2,5-Dioxytetrahydro-3-furyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride, etc.

The diol component is not particularly limited, and for example, ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-Trimethyl-1,5-pentanediol, cyclohexanedimethanol, neopentyl hydroxytrimethyl acetate, ethylene oxide adduct of bisphenol A and propylene oxide Adducts, ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A, 1,9-nonanediol, 2- Methyloctanediol, 1,10-decanediol, 2-butyl-2-ethyl-1,3-propanediol, tricyclodecane dimethanol, polyethylene glycol, polypropylene glycol, polytetramethylene Diols and other diols; and trimethylolpropane, trimethylolethane, neopentylerythritol and other polyols of trihydric or higher can be used as required.

The isocyanate component is not particularly limited, and for example, 2,4-methylphenylene diisocyanate, 2,6-methylphenylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate can be used. Isocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 2,6- Naphthalene diisocyanate, 3,3'-dimethyl-4,4'-diisocyanate, 4,4'-diisocyanate diphenyl ether, 1,5-diisocyanate, 1,3 diisocyanate methyl Cyclohexane, 1,4-diisocyanate methylcyclohexane, isophorone diisocyanate, etc.

Also, the second polymer component may be a carboxyl group-modified polyamide. The carboxyl group-modified polyamide resin, for example, can be synthesized from polycarboxylic acid components such as dicarboxylic acid, tricarboxylic acid, and tetracarboxylic dianhydride, and organic diisocyanate or diamine by condensation reaction.

Examples of the above-mentioned polyvalent carboxylic acid include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, lipoic acid, sebacic acid, dodecanedioic acid, dimer acid, and isophthalic acid. Aromatic dicarboxylic acids such as formic acid, terephthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenyl dicarboxylic acid, oxydibenzoic acid, trimellitic acid, pyrometic acid, diphenyl Aromatic carboxylic acid anhydrides such as base tetracarboxylic dianhydride and diphenylketone tetracarboxylic dianhydride, etc. Moreover, these can be used individually or in combination of 2 or more types.

As said organic diisocyanate, 4, 4'- diphenylmethane diisocyanate, 2, 4- tolyl diisocyanate, 2, 6- tolyl diisocyanate, 1, 5- naphthalene diisocyanate are mentioned. , 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, m-xylene diisocyanate, m-tetramethylxylene diisocyanate and other aromatic diisocyanates, hexamethylene diisocyanate, etc. Methyl diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, trans-cyclohexane-1,4-diisocyanate Aliphatic isocyanates such as isocyanate, hydrogenated m-xylene diisocyanate, lysine diisocyanate, etc. These can be used alone or in combination of two or more.

In addition, a diamine may be used instead of the aforementioned organic diisocyanate. The diamines include: phenylenediamine, diaminodiphenylpropane, diaminodiphenylmethane, benzidine, 4,4'-diaminodiphenylene, 4,4'-diaminodiphenylene Phenyl sulfide (4,4'-diaminodiphenyl sulfide) and diaminodiphenyl ether, etc.

An acid anhydride-modified polyester, an epoxy resin, etc. can also be used as a 2nd polymer component.

When epoxy resin is used as the first polymer component and urethane modified polyester is used as the second polymer component, urethane can be obtained after the first polymer component and the second polymer component are reacted and cured. Ester modified epoxy resin. In addition, when polyamide is used as the second polymer component, a polyamide-modified epoxy resin can be obtained. In the thermosetting resin containing the first polymer component and the second polymer component of the present disclosure, the unreacted first polymer component and the second polymer component are contained, and the uncured resin is contained. Also, including the first A state in which the polymer component and the second polymer component are completely reacted and no unreacted material remains.

Although the first polymer component is not particularly limited, from the viewpoint of improving the overall strength of the adhesive, the number average molecular weight is preferably 500 or more, and more preferably 1,000 or more. Moreover, from the viewpoint of adhesiveness, the number average molecular weight is preferably 10,000 or less, more preferably 5,000 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 intercalation property. In addition, Mn may be a value measured by gel permeation chromatography (GPC) in terms of styrene.

The mass ratio of the first polymer component to the second polymer component is preferably 1:100~20:100, more preferably 3:100~15:100. Adhesion can be improved by making a 1st polymer component and a 2nd polymer component into the said mass ratio.

The thermosetting resin may incorporate 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 curing agent, or the like can be used. These may be used individually by 1 type, and may use 2 or more types together.

等之化合物等，諸如：2-苯基-4,5-二羥基甲基咪唑、2-十七基咪唑、2,4-二胺基-6-(2'-十一基咪唑基)乙基-S-三

、1-氰乙基-2-苯基咪唑、2-苯基咪唑、5-氰基-2-苯基咪唑、2,4-二胺基-6-[2'甲基咪唑基-(1')]-乙基-S-三

異三聚氰酸加成物、2-苯基 咪唑異三聚氰酸加成物、2-甲基咪唑異三聚氰酸加成物、1-氰乙基-2-苯基-4,5-二(2-氰乙氧基)甲基咪唑等。 Examples of imidazole-based curing agents include an alkyl group, an ethyl cyano group, a hydroxyl group, an acridine group added to an imidazole ring.

and other compounds, such as: 2-phenyl-4,5-dihydroxymethylimidazole, 2-heptadecylimidazole, 2,4-diamino-6-(2'-undecylimidazolyl)ethyl base-s-three

, 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole, 5-cyano-2-phenylimidazole, 2,4-diamino-6-[2'methylimidazolyl-(1 ')]-ethyl-S-tri

Isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4, 5-bis(2-cyanoethoxy)methylimidazole, etc.

As an example of a phenol type hardening|curing agent, a novolac, a naphthol type compound, etc. are mentioned.

Examples of the cationic curing agent include amine salts of boron trifluoride, antimony pentachloride-acetyl chloride complexes, and permalium salts having a phenethyl group or an allyl group.

Although the curing agent may not be blended, from the viewpoint of accelerating the reaction, the amount of the curing agent is preferably 0.3 parts by mass or more, more preferably 1 part by mass or more, and preferably 20 parts by mass relative to 100 parts by mass of the first polymer component Below, it is preferable that it is 15 mass parts or less.

<Conductive filler>

The conductive filler is not particularly limited, and for example, metal fillers, metal-coated resin fillers, carbon fillers, and mixtures thereof can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder, and the like. These metal powders can be produced by an electrolysis method, an atomization method, a reduction method, or the like. Among them, any one of silver powder, silver-coated copper powder and copper powder is preferable.

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

The content of the conductive filler can be appropriately selected according to the application, but in order to achieve isotropic conductivity, the ratio of the content of the conductive filler to the total solid content is 50% by mass or more, preferably 60% by mass or more, and preferably 50% by mass or more. 95 mass % or less, preferably 90 mass % or less.

<optional ingredient>

In the conductive adhesive of the present embodiment, a defoaming agent, an antioxidant, a viscosity modifier, a diluent, an anti-settling agent, a leveling agent, a coupling agent, a coloring agent, a flame retardant and the like can be added as optional components.

The conductive adhesive of this embodiment can be made isotropically conductive. The conductive adhesive of the present disclosure can be used for the electromagnetic wave shielding film 101 having the insulating protective layer 112 and the conductive adhesive layer 111 as shown in FIG. 1 . Such an electromagnetic wave shielding film can make the conductive adhesive layer 111 function as a shield. In addition, as shown in FIG. 2 , a shielding layer 113 may be additionally provided between the insulating protective layer 112 and the conductive adhesive layer 111 .

The conductive adhesive layer 111 can be formed by, for example, coating the conductive adhesive of this embodiment on the insulating protective layer 112 or the shielding layer 113 formed on the insulating protective layer 112 .

From the viewpoint of controlling the embeddability, the thickness of the conductive adhesive layer 111 is preferably set to 1 μm to 50 μm.

In addition, a peelable protective film can be attached to the surface of the conductive adhesive layer 111 as required.

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

The thermoplastic resin composition is not particularly limited, and a styrene-based resin composition, a vinyl acetate-based resin composition, a polyester-based resin composition, a polyethylene-based resin composition, a polypropylene-based resin composition, and an imide can be used. resin composition or acrylic resin composition, etc. The thermosetting resin composition is not particularly limited, and a phenol-based resin composition, an epoxy-based resin composition, a urethane-based resin composition, a melamine-based resin composition, or an alkyd-based resin composition can be used. Although it does not specifically limit as an active energy ray curable composition, For example, the polymeric compound etc. which have at least 2 (meth)acryloyloxy groups in a molecule|numerator can be used. The protective layer may be formed of a single material, or may be formed of two or more materials.

The insulating protective layer 112 may be a laminate of two or more layers having different physical properties such as material, hardness, or modulus of elasticity. For example, as long as it is a laminate of an outer layer with low hardness and an inner layer with high hardness, since the outer layer has a buffering effect, the application of the shielding layer 113 to the shielding layer 113 can be alleviated during the step of heating and pressing the electromagnetic wave shielding film 101 to the printed wiring board. pressure. Therefore, the shielding layer 113 can be suppressed from being damaged due to the difference in height provided on the printed wiring board.

The insulating protective layer 112 may contain hardening accelerators, tackifiers, antioxidants, pigments, dyes, plasticizers, ultraviolet absorbers, defoaming agents, leveling agents, fillers, flame retardants, and viscosity adjusters as required. At least one of an anti-caking agent and an anti-caking agent.

The thickness of the insulating protective layer 112 is not particularly limited, and can be appropriately set according to requirements, but it is preferably set to 1 μm or more, preferably 4 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, and more preferably 5 μm or less. By setting the thickness of the insulating protective layer 112 to be 1 μm or more, the conductive adhesive layer 111 and the shielding layer 113 can be sufficiently protected. By setting the thickness of the insulating protective layer 112 to be 20 μm or less, the flexibility of the electromagnetic wave shielding film 101 can be ensured, and the electromagnetic wave shielding film 101 can be easily applied to a member requiring flexibility.

When the shielding layer 113 is provided, the shielding layer 113 can be formed by metal foil, vapor deposition film, conductive filler, or the like.

The metal foil is not particularly limited, and may be a foil made of any one of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc, 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, more preferably 1.0 μm or more. If the thickness of the metal foil is 0.5μm or more, the attenuation of the high-frequency signal can be suppressed when the high-frequency signal of 10MHz to 100GHz is transmitted to the shielded printed wiring board. In addition, the thickness of the metal foil is preferably 12 μm or less, more preferably 10 μm or less, and more preferably 7 μm or less. When the thickness of the metal layer is 12 μm or less, the cost of raw materials can be suppressed, and the elongation at break of the shielding film can be improved.

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

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

The thickness of the vapor-deposited film is not particularly limited, but is preferably 0.05 μm or more, 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 in the shielding printed wiring board has excellent properties of shielding electromagnetic waves. In addition, 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 vapor-deposited metal film is less than 0.5 μm, the electromagnetic wave shielding film is excellent in the deflection resistance, and the shielding layer can be suppressed from being damaged due to the level difference provided on the printed wiring board.

In the case of the conductive filler, the shielding layer 113 can be formed by applying a solvent mixed with the conductive filler on the surface of the insulating protective layer 112 and drying it. As the conductive filler, metal fillers, metal-coated resin fillers, carbon fillers, and mixtures thereof can be used. As the metal filler, copper powder, silver powder, nickel powder, silver-coated 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 electrolysis method, an atomization method, and a reduction method. The shape of the metal powder includes spherical shape, platelet shape, fibrous shape, and dendritic shape.

In the present embodiment, the thickness of the shielding layer 113 can be appropriately selected according to the required electromagnetic shielding effect and repeated deflection/sliding resistance, but in the case of metal foil, it is preferable from the viewpoint of ensuring the breaking elongation. It is set to 12 micrometers or less.

The electromagnetic wave shielding film 101 of this embodiment can be used for shielding the printed wiring board 103 as shown in FIG. 3 . As shown in Figure 3, the shield printed configuration The wire substrate 103 includes the printed wiring substrate 102 and the electromagnetic wave shielding film 101 .

The printed wiring board 102 , for example, has a base member 122 and a printed circuit, and the printed circuit is provided on the base member 122 and includes a ground circuit 125 . An insulating film 121 is adhered to the base member 122 through the adhesive layer 123 . In addition, an opening for exposing the ground circuit 125 is provided in the insulating film 121 . A surface layer 126 such as a gold plating layer can be provided on the exposed portion of the ground circuit 125 . In addition, the printed wiring board 102 may be a flexible board or a rigid board.

Such a shielded 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 positioned on the opening portion 128 . Then, the electromagnetic wave shielding 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 shorted by a predetermined pressure (for example, 0.5 MPa). time (eg 5 seconds) to press. Thereby, the electromagnetic wave shielding film 101 is temporarily fixed on the printed wiring board 102 .

Then, the temperature of the two heating plates is set to a predetermined pressing temperature (eg, 170° C.) higher than that of the temporary fixing, and pressurized with a predetermined pressure (eg, 3 MPa) for a predetermined time (eg, 30 minutes). Thereby, the electromagnetic wave shielding film 101 can be fixed on the printed wiring board 102 . In addition, the pressing temperature can be selected according to the composition of the conductive adhesive, but is preferably 150°C or higher from the viewpoints of the thermal history of the printed wiring board, the structure and operability of the equipment, etc. It is preferably 160°C or higher, more preferably 190°C or lower, and 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 pressing. Thereby, the shielding layer 113 and the ground circuit 115 are connected. In the opening 128, since a sufficient amount of the conductive adhesive layer 111 exists between the shielding layer 113 and the printed wiring board 102, the electromagnetic wave shielding film 101 and the printed wiring board 102 are bonded with sufficient strength. In addition, since the conductive adhesive layer 111 has high embeddability, connection stability can be ensured even when exposed to high temperatures during reflow during the component mounting step.

Afterwards, a reflow step for mounting the components is performed. In the reflow step, the electromagnetic wave shielding film 101 and the printed wiring board 102 are exposed to a high temperature of about 260°C. The parts to be mounted are not particularly limited, and other than connectors and integrated circuits, chip parts such as resistors and capacitors can also be used.

Since the conductive adhesive of this embodiment has high embeddability, even when the diameter a of the opening portion 128 is as small as 1 mm or less, it can be sufficiently embedded in the opening portion 128, and the electromagnetic wave shielding film 101 and the grounding circuit can be secured. 125 for a good connection.

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

The base member 122 can be, for example, a resin film, etc., specifically, can be made of polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide, polyether Resin such as imide or polyphenylene sulfide formed membrane.

The insulating film 121 is not particularly limited, and for example, polyethylene terephthalate, polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide, and polyetherimide can be used. Resins such as imine and polyphenylene sulfide are formed. The thickness of the insulating film 121 is not particularly limited, but can be set to about 10 μm to 30 μm.

The printed circuit including the ground circuit 125 may be, for example, a copper wiring pattern or the like formed on the base member 122 . The surface layer 126 is not limited to a gold-plated layer, and can also be a layer composed of copper, nickel, silver, and tin. In addition, the surface layer 126 only needs to be provided as required, and the structure without the surface layer 126 can also be made.

The conductive adhesive of this embodiment has excellent embeddability and adhesion, and exhibits particularly excellent effects when the electromagnetic wave shielding film 101 is pasted to the printed wiring board 102 . However, it is also useful for other uses to which the conductive adhesive can be applied. For example, it can be used as an adhesive layer in a conductive reinforcing plate.

Example

Hereinafter, the use examples of the conductive adhesive of the present disclosure will be described in more detail. The following embodiments are examples, not intended to limit the present invention.

<Production of Electromagnetic Wave Shielding Film>

A 6-micrometer-thick epoxy resin was apply|coated to a mold release film, and it dried to form a protective layer. Next, a planetary stirring/defoaming device was used to mix and stir the predetermined materials to obtain Examples 1 to 3 and Comparative Examples 1 to 4 with the compositions shown in Table 1. The conductive adhesive composition.

Next, a paste-like conductive adhesive composition was applied on the protective layer, and dried at 100° C. for 3 minutes, thereby producing 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 calorimeter (DSC3500SA, manufactured by NETZSCH). The measurement conditions were temperature range: 0°C to 300°C, temperature increase rate: 10°C/min, and nitrogen atmosphere.

<Adhesion to 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 was bonded to a polyimide film (manufactured by DU PONT-TORAY CO., LTD., Kapton 100EN (registered trademark)) at a temperature of 170° C. , Time: 3 minutes, paste under the conditions of pressure 2MPa. Next, under the conditions of temperature: 120° C., time: 5 seconds, and pressure of 0.5 MPa, an adhesive film (manufactured by Arisawa Manufacturing Co., Ltd.) was attached to the protective layer side of the electromagnetic wave shielding film. Next, a polyimide film (Kapton 100EN (registered trademark) manufactured by DU PONT-TORAY CO., LTD.) was bonded to the adhesive film to obtain a laminate for evaluation. Then, the laminate of the polyimide film/adhesive film/barrier film was peeled off from the polyimide film at 50 mm/min. The average value of the number of tests is n=5 is shown in Table 1.

<Production of Shielded Printed Wiring Board>

Next, use a press at temperature: 170°C, time: 3 minutes, pressure: The electromagnetic wave shielding films and printed wiring boards obtained in the respective Examples and Comparative Examples were followed under the conditions of 2 to 3 MPa to obtain a shielded printed wiring board.

In addition, as the 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 copper foil pattern 125 is formed thereon. The adhesive layer 123 and the cover layer (insulating film) 121 made of a polyimide film are adhered. A gold-plated layer is provided on the surface of the copper foil pattern 125 as the surface layer 126 . In addition, the cover layer 121 is formed with an opening part simulating a ground connection part with a diameter a of 0.8 mm.

<Measurement of connection resistance value>

Using the shielded printed wiring boards prepared in the respective Examples and Comparative Examples, and as shown in FIG. 4 , the resistance value between the two copper foil patterns 125 of the surface layer 126 provided with the gold-plated layer was measured with a resistance meter 205 . The connection resistance between the copper foil pattern 125 and the electromagnetic wave shielding film 101 was evaluated.

(Example 1)

As the first polymer component, a solid epoxy resin (NC-3000, Nippon Kayaku Co., Ltd.) was used. As the second polymer component, a polyamide resin (carboxy-modified polyamide resin with an acid value of 15 mgKOH/g (number average molecular weight: 2000, Tg: 30° C.)) was used. The mass ratio of the first polymer component and the second polymer component was set to 10:100. Furthermore, 6n parts by mass of 2-phenyl-1H-imidazole-4,5-dimethanol (2PHZPW, manufactured by Shikoku Chemical Industry Co., Ltd.) was added as a curing agent with respect to 100 parts by mass of the resin component.

As the organophosphate system, aluminum bis-diethyl hypophosphite having an endothermic peak obtained by differential scanning calorimetry at 170°C (OP935, Clariant (Japan) K.K. product), and was made into 10 mass parts with respect to 100 mass parts of resin components.

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

When the pore diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance was 350 mΩ/1 pore, and the peel strength to polyimide was 19 N/cm.

(Example 2)

The same procedure as in Example 1 was performed except that the organic phosphate was set to 20 parts by mass relative to 100 parts by mass of the resin component.

When the pore diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance was 375 mΩ/1 pore, and the peel strength to 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 and the second polymer component was 10:100. In addition, the organic phosphate was set to 30 parts by mass with respect to 100 parts by mass of the resin component. Other conditions are the same as in Example 1.

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

(Comparative Example 1)

Except that no organic phosphate is added, the rest is the same as in Example 1. When the pore diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance was 500 mΩ/1 pore, and the peel strength to 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 and the second polymer component was 10:100. In addition, no organic phosphate was added. Other conditions are the same as in Example 1.

When the pore 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 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 Corporation) substituted with an organic phosphate was added with respect to 100 parts by mass of the resin component. When the pore diameter of the obtained conductive adhesive was 0.8 mmφ, the connection resistance was 350 mΩ/1 pore, and the peel strength to polyimide was 10 N/cm.

(Comparative Example 4)

The same procedure as in Example 1 was performed except that the organic phosphate was set to 50 parts by mass relative to 100 parts by mass of the resin component.

When the pore 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 to polyimide was 11 N/cm.

The results of the respective Examples and Comparative Examples are collectively shown in Table 1.

[Table 1]

industrial availability

The conductive adhesive of the present disclosure has excellent embeddability, heat resistance, and adhesion, and is useful for applications such as electromagnetic wave shielding films.

Claims (4)

A conductive adhesive, which can be pressed and processed, is characterized in that it contains a thermosetting resin, a conductive filler and an organic phosphate; the thermosetting resin comprises a first polymer component having an epoxy group and a The second polymer component of the functional group of the radical reaction; the ratio of the conductive filler to the total solid content is 50% by mass or more; the organic phosphate is 5 parts by mass or more and 40 parts by mass relative to 100 parts by mass of the thermosetting resin Parts by mass or less, and there is an endothermic peak of differential scanning calorimetry analysis between the lower limit value and the upper limit value of the aforementioned pressing temperature; the aforementioned thermosetting resin is polyamide modified epoxy resin or polyurethane Modified epoxy resin; the aforementioned organic phosphate is a hypophosphite metal salt. 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. An electromagnetic wave shielding film comprising: a conductive adhesive layer composed of the conductive adhesive as claimed in claim 1 or 2; and an insulating protective layer. A shielded printed wiring board, comprising: a printed wiring board having a ground circuit and an insulating film, the insulating film having an opening exposing the ground circuit; and the electromagnetic wave shielding film of claim 3; In addition, the conductive adhesive layer is bonded to the insulating film so as to conduct the ground circuit in the opening.

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