JP7405196B2 - Conductive adhesive composition, connection structure, and flexible wiring board with semiconductor light emitting device mounted - Google Patents

Description

The present invention relates to a conductive adhesive composition used for electrically connecting a flexible wiring board and an electronic component, a connected structure using the adhesive composition, and a flexible wiring board mounting a semiconductor light emitting element.

In recent years, flexible electronics and stretchable electronics, in which devices are manufactured using flexible and highly stretchable circuit boards, are expected to be a manufacturing technology for highly convenient and versatile devices such as wearable devices. In such fields, since a large mechanical load is applied to the circuit boards used, stretchable boards and circuit patterns having high stretchability and flexibility have been proposed (see Patent Documents 1 to 3).

However, when a device is fabricated by mounting electronic components on a flexible and stretchable circuit board, the electronic components themselves do not have stretch or flexibility, so when the device is used, the connections between the board and the electronic components The problem is that large distortions occur and the connections and electronic components are destroyed. Furthermore, stretchable substrates often employ thermoplastic organic base materials, and deformation of the substrate due to thermal history during electronic component mounting is also a major problem. Therefore, in this field, a connection method that can form a connection part with sufficient stretch resistance and bending resistance on a stretchable board, and that can minimize damage to the board when mounting electronic components. is required.

In order to mount electronic components onto a circuit board or the like, a connection method using lead-free solder such as Sn-Ag-Cu solder is widely known. However, Sn-Ag-Cu solder has a high connection temperature of 260°C, and when using a thermoplastic organic base material, which is seen as a promising circuit board for wearable devices, it is difficult to mount electronic components on the board. There is a problem in that the thermal history in the reflow process causes thermal contraction and deformation of the substrate, resulting in a significant decrease in flexibility and elasticity of the substrate.

Additionally, Sn--Bi solder, which has a melting point of 138.degree. C., is also used as a lead-free solder that can be connected at lower temperatures. However, although the Sn-Bi solder connection method can reduce damage to the board, the expansion, contraction and bending of the circuit board causes a huge amount of stress to be concentrated on the solder joints, causing the joints to break and resulting in poor continuity. There is.

In order to overcome these problems, a conductive adhesive in which metal particles such as silver powder are dispersed in a thermosetting resin and made into a paste has been proposed (see Patent Document 4). The thermosetting conductive adhesive can improve temperature cycle test resistance (TCT resistance) by using a thermosetting resin as a binder component.

Japanese Patent Application Publication No. 2014-162124 Japanese Patent Application Publication No. 2014-162125 Japanese Patent Application Publication No. 2015-079803 Japanese Patent Application Publication No. 2002-161259

However, since the conductivity development mechanism in the conductive adhesive described in Patent Document 4 is based on contact between metals, it is necessary to increase the content of conductive particles in order to ensure good conductivity. As a result, the adhesive force of the adhesive decreases as the binder component decreases, and when applied to flexible circuit boards that are used while repeatedly expanding, contracting and bending, the adhesive strength and conductivity decrease significantly. There is a tendency to put it away.

Therefore, the present invention has been made in view of the above circumstances, and is capable of forming a cured product having excellent adhesive strength and conductivity even after repeated expansion/contraction and bending, and is capable of connecting a flexible wiring board and an electronic component electrically. The present invention aims to provide a conductive adhesive composition used for electrical connection, a connection structure using the conductive adhesive composition, and a flexible wiring board mounting a semiconductor light emitting element.

The present invention relates to a conductive adhesive composition used for electrically connecting a flexible wiring board and an electronic component, comprising conductive particles containing a metal with a melting point of 200°C or less, a thermosetting resin, and a flux. A conductive adhesive composition is provided that includes an activator and a curing catalyst.

The flux activator may include a compound having a hydroxyl group and a carboxyl group. Further, the metal contained in the conductive particles may include at least one selected from the group consisting of bismuth, indium, tin, and zinc. Furthermore, the thermosetting resin may include an epoxy resin.

The conductive adhesive composition according to the present invention may be a paste composition having a viscosity of 5 to 400 Pa·s at 25°C.

The conductive adhesive composition according to the present invention may be used to electrically connect a connecting terminal arranged on a flexible wiring board and a connecting terminal arranged on an electronic component. The flexible wiring board may be composed of a flexible and stretchable base material.

The flexible wiring board may be composed of a base material containing at least one member selected from the group consisting of polyimide, polyethylene terephthalate, polycarbonate, polyethylene naphthalate, polyketone, polyetheretherketone, thermoplastic polyurethane elastomer, and cycloolefin polymer. .

The present invention also includes a flexible wiring board having a first connection terminal, an electronic component having a second connection terminal, and a connection portion disposed between the flexible wiring board and the electronic component, the connection portion comprising: Provided is a connected structure containing a cured product of the conductive adhesive composition according to the present invention, in which a first connecting terminal and a second connecting terminal are electrically connected.

The connection portion may have a connection structure including a metal portion containing a metal having a melting point of 200° C. or lower and a resin portion containing a thermosetting resin.

In the connection structure according to the present invention, when the connection structure is viewed in a cross section perpendicular to the upper surface of the second connection terminal, the metal part is in contact with the second connection terminal and the first connection terminal, and the resin part is in contact with the second connection terminal and the first connection terminal. It may have a connection structure existing around the metal part.

The area ratio of the metal part to the resin part may be 5:95 to 80:20. Further, a sealing member may be further provided around the resin portion.

The electronic component may include at least one selected from the group consisting of a semiconductor light emitting device, a capacitor, a Schottky barrier diode, and a driver integrated circuit.

The present invention further includes a flexible wiring board having a first connection terminal, a semiconductor light emitting element having a second connection terminal, and a connection part disposed between the flexible wiring board and the semiconductor light emitting element. provides a semiconductor light emitting device-mounted flexible wiring board, which contains a cured product of the conductive adhesive composition according to the present invention, and in which a first connection terminal and the second connection terminal are electrically connected. .

According to the present invention, it is possible to form a cured product having good adhesive strength and conductivity even after repeated expansion/contraction and bending. An adhesive composition can be provided. According to the present invention, there is provided a connection structure and a semiconductor light emitting element-mounted flexible wiring that includes a connection portion containing a cured product of the conductive adhesive composition and has excellent adhesive strength and conductivity even after repeated expansion, contraction and bending. A substrate can be provided.

In addition, the conductive adhesive composition according to the present invention can lower the mounting temperature (for example, reflow heating temperature) in the mounting process of a flexible wiring board and electronic components, thereby improving the flexibility and stretchability of the board. Connected structures such as flexible wiring boards mounted with electronic components can be manufactured without damaging the structure. Furthermore, since the conductive adhesive composition according to the present invention can form a connection part having a connection structure in which the metal part and the resin part are separated, the connection part is reinforced and has only bending resistance and stretch resistance. In addition, a connected structure having excellent TCT resistance can be produced.

1 is a schematic cross-sectional view showing an embodiment of an electronic component-mounted flexible wiring board according to the present invention. 1 is a schematic cross-sectional view showing an embodiment of an electronic component-mounted flexible wiring board according to the present invention. 1 is a schematic cross-sectional view showing an embodiment of an electronic component-mounted flexible wiring board according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

<Conductive adhesive composition>
The conductive adhesive composition of the present embodiment contains (A) conductive particles containing a metal with a melting point of 200°C or less, (B) a thermosetting resin, (C) a flux activator, and (D) a curing catalyst. do. The conductive adhesive composition described above is used for electrically connecting a flexible wiring board and an electronic component.

((A) component: conductive particles)
(A) The conductive particles include a metal having a melting point of 200° C. or lower. When such conductive particles are used in a conductive adhesive composition, the conductive particles melt and agglomerate at a relatively low temperature (for example, 200°C or less), so the mounting temperature of electronic components on the board can be lowered. It is possible to form a connection portion with excellent conductivity without impairing the flexibility and stretchability of the substrate.

The above melting point means the melting point of (A) the one type of metal when the conductive particles contain one type of metal, and (A) the melting point of the one type of metal when the conductive particles include two or more metals. In the case of alloys, it means the melting point of the entire metal. That is, it can be said that (A) the conductive particles include a metal whose melting point as a whole is 200° C. or lower. (A) The melting point of the metal contained in the conductive particles is preferably 180°C or lower, more preferably 150°C or lower. (A) The lower limit of the melting point of the metal in the conductive particles is not particularly limited, but may be, for example, 100°C. The melting point can be measured, for example, by differential scanning calorimetry (DSC).

(A) The metal in the conductive particles is preferably composed of a metal other than lead from the viewpoint of reducing the burden on the environment. Examples of such metals include one metal selected from the group consisting of tin (Sn), bismuth (Bi), indium (In), and zinc (Zn), or an alloy consisting of two or more metals. . In addition, from the viewpoint of obtaining better connection reliability, the alloy may contain platinum (Pt), gold (Au), etc. within a range where the melting point of the metal as a whole in (A) conductive particles is 200°C or less. , silver (Ag), copper (Cu), nickel (Ni), palladium (Pd), aluminum (Al), and the like.

(A) The metals constituting the conductive particles include Sn42-Bi58 solder (melting point 138°C), Sn48-In52 solder (melting point 117°C), Sn42-Bi57-Ag1 solder (melting point 139°C), Sn90 -Ag2-Cu0.5-Bi7.5 solder (melting point 189°C), Sn89-Zn8-Bi3 solder (melting point 190°C), Sn91-Zn9 solder (melting point 197°C), etc. show clear solidification behavior after melting. Therefore, it is preferable. Solidification behavior refers to the fact that a metal cools and solidifies after being molten. Among these, it is preferable to use Sn42-Bi58 solder from the viewpoint of easy availability and excellent low-temperature connectivity. These can be used alone or in combination of two or more.

(A) The average particle diameter of the conductive particles is not particularly limited, but from the viewpoint of suppressing the increase in the viscosity of the conductive adhesive composition and obtaining better workability, it is preferably 0.1 μm or more, The thickness is more preferably 1 μm or more, and even more preferably 5 μm or more. (A) The average particle diameter of the conductive particles is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less, from the viewpoint of obtaining better printability and connection reliability. From this point of view, the average particle diameter of the conductive particles (A) is preferably 0.1 to 100 μm. Further, the average particle diameter of the conductive particles (A) is more preferably 1 to 50 μm from the viewpoint of obtaining better printability and workability of the conductive adhesive composition. Furthermore, the average particle diameter of the conductive particles (A) is more preferably 5 to 30 μm from the viewpoint of improving the storage stability of the conductive adhesive composition and the mounting reliability of the cured product. Here, the average particle diameter is determined by a laser diffraction/scattering method.

(A) The conductive particles are not limited to particles composed only of metals having a melting point of 200°C or lower, but may also include metals having a melting point higher than 200°C. In addition, (A) conductive particles are conductive particles in which the surface of particles made of a solid material other than metal, such as ceramics, silica, or resin material, is coated with a metal film made of a metal whose melting point is 200°C or less. It may also be a mixture of multiple types of conductive particles.

The content of (A) conductive particles in the conductive adhesive composition is determined based on the total amount of the conductive adhesive composition, from the viewpoint of obtaining even better conductivity of the cured product of the conductive adhesive composition. The content is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 45% by mass or more. The content of (A) conductive particles is determined from the viewpoints of suppressing the increase in viscosity of the conductive adhesive composition and obtaining better workability, and (A) conductivity in the conductive adhesive composition. From the viewpoint of suppressing a relative decrease in the content of components other than conductive particles (hereinafter also referred to as "adhesive components") and obtaining even better mounting reliability of the cured product, conductive adhesive compositions have been developed. It is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, based on the total amount. From this point of view, the content of (A) conductive particles is preferably 5 to 95% by mass. The content of the conductive particles (A) is more preferably 10 to 90% by mass from the viewpoint of further improving workability and conductivity, and 15 to 85% by mass from the viewpoint of further improving the mounting reliability of the cured product. Mass % is more preferred.

Note that (A) conductive particles may be used in combination with (a1) conductive particles made of a metal having a melting point higher than 200° C. (hereinafter also referred to as "(a1) conductive particles") to the extent that the effects of the present invention are not impaired. You may. Examples of metals with a melting point higher than 200°C include one metal selected from the group consisting of Pt, Au, Ag, Cu, Ni, Pd, Al, etc., or an alloy consisting of two or more metals, such as , Au powder, Ag powder, Cu powder, and Ag-plated Cu powder. As a commercial product, for example, "MA05K" (trade name, Hitachi Chemical Co., Ltd.), which is Ag-plated Cu powder, is available.

In addition, when (A) conductive particles and (a1) conductive particles are used together, the blending ratio of (A) conductive particles and (a1) conductive particles is 99:1 to 50:50 by mass ratio. It is preferably within the range of 99:1 to 60:40, and more preferably within the range of 99:1 to 60:40.

In the conductive adhesive composition of this embodiment, from the viewpoint of more effectively exhibiting the effects of the present invention, the blending ratio of components other than (A) conductive particles to (A) conductive particles (adhesive component: ( A) conductive particles) preferably have a solid content ratio (mass ratio) of 5:95 to 50:50 in the adhesive composition. Further, from the viewpoint of further superior adhesiveness, conductivity, and workability, the above-mentioned blending ratio is more preferably 10:90 to 30:70. When this blending ratio is 5:95 or more, the viscosity of the conductive adhesive composition is suppressed from increasing, resulting in better workability and improving the adhesive strength of the conductive adhesive composition. Sufficient amount can be secured. When the blending ratio is 50/50 or less, it is easy to ensure conductivity.

((B) component: thermosetting resin)
(B) The thermosetting resin has the function of adhering the adherend, and also acts as a binder component that binds the conductive particles in the conductive adhesive composition and the filler added as necessary to each other. Examples of such thermosetting resins include thermosetting organic polymer compounds such as epoxy resins, (meth)acrylic resins, maleimide resins, and cyanate resins, and precursors thereof. Here, (meth)acrylic resin refers to methacrylic resin and acrylic resin. Among these, compounds having a polymerizable carbon-carbon double bond, such as (meth)acrylic resins and maleimide resins, or epoxy resins are preferred. These thermosetting resins have excellent heat resistance and adhesive properties, and also have excellent workability because they can be handled in a liquid state by dissolving or dispersing them in an organic solvent as necessary. Furthermore, from the viewpoint of availability and connection reliability, it is more preferable to use epoxy resin. These thermosetting resins can be used alone or in combination of two or more.

As the epoxy resin, any known compound can be used without particular limitation as long as it has two or more epoxy groups in one molecule. Examples of such epoxy resins include epoxy resins derived from phenol compounds such as bisphenol A, bisphenol F, and bisphenol AD and epichlorohydridone.

As the epoxy resin, commercially available products can be used. Examples of epoxy resins include bisphenol A epoxy resins AER-X8501 (manufactured by Asahi Kasei Corporation, trade name), R-301 (manufactured by Mitsubishi Chemical Corporation, trade name), and YL-980 (manufactured by Mitsubishi Chemical Corporation, trade name). YDF-170 (manufactured by Toto Kasei Co., Ltd., trade name), which is a bisphenol F-type epoxy resin, YL-983 (manufactured by Mitsubishi Chemical Corporation, trade name), R- which is a bisphenol AD-type epoxy resin 1710 (manufactured by Mitsui Chemicals, Inc., trade name), N-730S (manufactured by DIC Corporation, trade name), which is a phenol novolak type epoxy resin (manufactured by DIC Corporation, trade name), Quatrex-2010 (manufactured by Dow Chemical Corporation, trade name), cresol novolak type Epoxy resins YDCN-702S (manufactured by Toto Kasei Co., Ltd., trade name), EOCN-100 (manufactured by Nippon Kayaku Co., Ltd., trade name), polyfunctional epoxy resins EPPN-501 (manufactured by Nippon Kayaku Co., Ltd., (trade name), TACTIX-742 (manufactured by Dow Chemical Co., Ltd., trade name), VG-3010 (manufactured by Mitsui Chemicals, Inc., trade name), 1032S (manufactured by Mitsubishi Chemical Corporation, trade name), epoxy with naphthalene skeleton resin HP-4032 (manufactured by DIC Corporation, trade name), alicyclic epoxy resins EHPE-3150, CEL-3000 (both manufactured by Daicel Corporation, trade name), DME-100 (made by Shin Nihon Rika Co., Ltd.) EX-216L (manufactured by Nagase ChemteX Co., Ltd., trade name), W-100 (manufactured by Shin Nippon Chemical Co., Ltd., trade name), an aliphatic epoxy resin, ELM, an amine-type epoxy resin -100 (manufactured by Sumitomo Chemical Co., Ltd., trade name), YH-434L (manufactured by Toto Kasei Co., Ltd., trade name), TETRAD-X, TETRAD-C (both manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name), 630, 630LSD (both manufactured by Mitsubishi Chemical Corporation, trade name), Denacol EX-201 (manufactured by Nagase ChemteX Co., Ltd., trade name), a resorcinol-type epoxy resin, and Denacol EX-211 (trade name, manufactured by Nagase ChemteX Co., Ltd.), a neopentyl glycol-type epoxy resin. Denacol EX-212 (manufactured by Nagase ChemteX Co., Ltd., trade name), a hexanediol type epoxy resin (manufactured by Chemtex Corporation, trade name), Denacol EX series (EX-810, 811, manufactured by ethylene propylene glycol type epoxy resin) , 850, 851, 821, 830, 832, 841, 861 (all manufactured by Nagase ChemteX Corporation, trade names)), epoxy resin E-XL-24, E-XL- represented by the following chemical formula (I) 3L (all manufactured by Mitsui Chemicals, Inc., trade names), and the like. Among these epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins and amine type epoxy resins are preferred from the viewpoint of having less ionic impurities and excellent reactivity. These epoxy resins can be used alone or in combination of two or more.

In formula (I), k represents an integer of 1 to 5.

When the conductive adhesive composition contains an epoxy resin as the thermosetting resin (B), it may further contain an epoxy compound having only one epoxy group in one molecule as a reactive diluent. Such epoxy compounds are available as commercial products. Examples of such epoxy compounds include PGE (manufactured by Nippon Kayaku Co., Ltd., trade name), PP-101 (manufactured by Toto Kasei Co., Ltd., trade name), ED-502, ED-509, ED-509S (manufactured by Toto Kasei Co., Ltd., trade name). ADEKA Co., Ltd., product name), YED-122 (Mitsubishi Chemical Co., Ltd., product name), KBM-403 (Shin-Etsu Chemical Co., Ltd., product name), TSL-8350, TSL-8355, TSL-9905 (all manufactured by Momentive Performance Materials Japan LLC, product names). These epoxy compounds can be used alone or in combination of two or more.

When a reactive diluent is blended into the adhesive composition, its blending ratio may be within a range that does not impede the effects of the present invention, and is preferably 0.1 to 30% by mass based on the total amount of the epoxy resin. preferable.

(B) The thermosetting resin may include (meth)acrylic resin. A (meth)acrylic resin is a polymer having a structural unit derived from a (meth)acrylate compound having a polymerizable carbon-carbon double bond. Here, "(meth)acrylate" refers to methacrylate and acrylate. Examples of such compounds include monoacrylate compounds, monomethacrylate compounds, diacrylate compounds, and dimethacrylate compounds.

Examples of monoacrylate compounds include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2- Ethylhexyl acrylate, nonyl acrylate, decyl acrylate, isodecyl acrylate, lauryl acrylate, tridecyl acrylate, hexadecyl acrylate, stearyl acrylate, isostearyl acrylate, cyclohexyl acrylate, isobornyl acrylate, diethylene glycol acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, methoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, dicyclopentenyloxyethyl acrylate, 2-phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, 2 -benzoyloxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, benzyl acrylate, 2-cyanoethyl acrylate, γ-acryloxyethyltrimethoxysilane, glycidyl acrylate, tetrahydrofurfuryl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, Examples include acryloxyethyl phosphate and acryloxyethyl phenyl acid phosphate.

Examples of monomethacrylate compounds include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2- Ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, hexadecyl methacrylate, stearyl methacrylate, isostearyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, diethylene glycol methacrylate, polyethylene glycol methacrylate, polypropylene glycol methacrylate, 2-Methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-butoxyethyl methacrylate, methoxydiethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, dicyclopentenyloxyethyl methacrylate, 2-phenoxyethyl methacrylate, phenoxydiethylene glycol methacrylate, phenoxypolyethylene glycol methacrylate, 2 -benzoyloxyethyl methacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, benzyl methacrylate, 2-cyanoethyl methacrylate, γ-methacryloxyethyltrimethoxysilane, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, Methacryloxyethyl phosphate and methacryloxyethyl phenyl acid phosphate are mentioned.

Examples of diacrylate compounds include ethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, 1,3-butanediol diacrylate, neo Pentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, bisphenol A, bisphenol F or bisphenol AD 1 mol and glycidyl acrylate 2 diacrylates of polyethylene oxide adducts of bisphenol A, bisphenol F or bisphenol AD, diacrylates of polypropylene oxide adducts of bisphenol A, bisphenol F or bisphenol AD, bis(acryloxypropyl)polydimethylsiloxane and Bis(acryloxypropyl)methylsiloxane-dimethylsiloxane copolymer may be mentioned.

Examples of dimethacrylate compounds include ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,3-butanediol dimethacrylate, neo Pentyl glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, bisphenol A, bisphenol F or bisphenol AD 1 mol and glycidyl methacrylate 2 Reaction products with moles, dimethacrylate of polyethylene oxide adducts of bisphenol A, bisphenol F or bisphenol AD, dimethacrylate of polypropylene oxide adducts of bisphenol A, bisphenol F or bisphenol AD, bis(methacryloxypropyl)polydimethylsiloxane and Bis(methacryloxypropyl)methylsiloxane-dimethylsiloxane copolymer may be mentioned.

These (meth)acrylate compounds can be used alone or in combination of two or more. (B) When the thermosetting resin contains a (meth)acrylic resin, the (meth)acrylate compound may be polymerized in advance and used, and the (meth)acrylate compound is combined with (A) conductive particles, (C) flux active Polymerization may be carried out at the same time as mixing with the agent and the like.

As the (meth)acrylic resin, commercially available products can be used. Examples of the (meth)acrylic resin include FINEDIC A-261 and FINEDIC A-229-30 (both trade names, manufactured by DIC Corporation).

(B) When the thermosetting resin contains a (meth)acrylic resin, the conductive adhesive composition preferably contains a radical polymerization initiator. As the radical polymerization initiator, commonly used ones can be used. Examples of the radical polymerization initiator include organic peroxides such as benzoyl peroxide and t-butylperoxy-2-ethylhexanoate, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. Can be mentioned. The radical polymerization initiator is preferably an organic peroxide from the viewpoint of effectively suppressing voids. Further, from the viewpoint of further improving the curability and viscosity stability of the adhesive component, the decomposition temperature of the organic peroxide is preferably 130°C to 200°C.

The blending ratio of the radical polymerization initiator is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass based on the total amount of the conductive adhesive composition. It is more preferable that it is expressed as % by mass.

The content of the thermosetting resin (B) in the conductive adhesive composition is preferably 1% by mass or more, and 5% by mass or more based on the total amount of the conductive adhesive composition, from the viewpoint of obtaining even better adhesive strength. % or more is more preferable, and even more preferably 10 mass % or more. (B) The content of the thermosetting resin is preferably 60% by mass or less, more preferably 40% by mass or less, based on the total amount of the conductive adhesive composition, from the viewpoint of easily ensuring sufficient conductivity. More preferably, it is 30% by mass or less. That is, the content of the thermosetting resin (B) in the conductive adhesive composition may be 1 to 60% by mass, or 5 to 40% by mass based on the total amount of the conductive adhesive composition. The content may be 10 to 30% by mass.

((C) component: flux activator)
(C) The flux activator exhibits the ability to remove the oxide film formed on the surface of the (A) conductive particles. By using such a flux activator, (A) the oxide film that obstructs the melting and aggregation of the conductive particles is removed. The flux activator (C) is not particularly limited as long as it does not inhibit the curing reaction of the thermosetting resin (B), and any known compound can be used.

Examples of the flux activator (C) include rosin resins, compounds having a carboxyl group, compounds having a hydroxyl group, and compounds having a hydroxyl group and a carboxyl group. Examples of the hydroxyl group include a phenolic hydroxyl group and an alcoholic hydroxyl group. Among these, compounds having a hydroxyl group and a carboxyl group are preferred because they exhibit good flux activity and exhibit reactivity with epoxy resins that can be used as (B) thermosetting resins. Acids are more preferred. Specifically, as the compound having a hydroxyl group and a carboxyl group, a compound represented by the following general formula (V) or tartaric acid is preferable.

In formula (V), R ⁵ represents an alkyl group having 1 to 5 carbon atoms, and is preferably a methyl group, ethyl group, or propyl group from the viewpoint of more effectively exhibiting good connection strength and connection reliability. In addition, n and m each independently represent an integer from 0 to 5, and from the viewpoint of more effectively achieving good connection strength and connection reliability, n is 0 and m is 1, or both n and m. is preferably 1.

Examples of the compound represented by the above general formula (V) include 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, and 2,2-bis(hydroxymethyl)pentane. Examples include acids.

(C) The content of the flux activator is determined from the viewpoint that when there is a large amount of surface oxide film at the connection part, the meltability of the metal is suppressed from decreasing and excellent conductivity is easily obtained. It is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, based on 100 parts by mass of the total amount of the particles. (C) The content of the flux activator is preferably 20 parts by mass or less, and 15 parts by mass or less, based on 100 parts by mass of the total amount of (A) conductive particles, from the viewpoint of easily obtaining excellent storage stability and printability. The amount is more preferably 1 part or less, and even more preferably 10 parts by mass or less. (C) The content of the flux activator is 0.5 to 20 parts by mass based on 100 parts by mass of the total amount of (A) conductive particles, from the viewpoint of more effectively obtaining good connection strength and connection reliability. Preferably, 0.5 to 15 parts by mass is more preferable. The content of the flux activator (C) is more preferably 1 to 10 parts by mass, particularly preferably 1 to 5 parts by mass, from the viewpoint of further excellent storage stability and conductivity.

((D) component: curing catalyst)
(D) The curing catalyst has the effect of accelerating the curing of the (B) thermosetting resin. (D) As the curing catalyst, an imidazole compound is preferable from the viewpoints of curability at a desired curing temperature, length of pot life, heat resistance of the obtained cured product, etc. Among these, imidazole curing agents for epoxy resins are more preferred. Commercially available imidazole compounds include, for example, 2P4MHZ-PW (2-phenyl-4-methyl-5-hydroxymethylimidazole), 2PHZ-PW (2-phenyl-4,5-dihydroxymethylimidazole), and C11Z-CN ( 1-cyanoethyl-2-undecylimidazole), 2E4MZ-CN (1-cyanoethyl-2-ethyl-4-methylimidazole), 2PZ-CN (1-cyanoethyl-2-phenylimidazole), 2MZ-A (2,4 -diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine), 2E4MZ-A (2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-( 1')]-ethyl-s-triazine) and 2MAOK-PW (2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct) (both (manufactured by Shikoku Kasei Kogyo Co., Ltd., product name). These curing catalysts can be used alone or in combination of two or more.

(D) The content of the curing catalyst is preferably 0.01 parts by mass or more, and 0.1 parts by mass or more, based on 100 parts by mass of the (B) thermosetting resin, from the viewpoint of easily obtaining excellent curability. is more preferable. The content of the curing catalyst is preferably 90 parts by mass or less, more preferably 50 parts by mass or less, from the viewpoint of suppressing the increase in viscosity and easily obtaining excellent workability when handling the conductive adhesive composition. preferable. That is, the content of the curing catalyst (D) may be 0.01 to 90 parts by mass, or may be 0.1 to 50 parts by mass, based on 100 parts by mass of the (B) thermosetting resin. .

(Other ingredients)
In addition to the above-mentioned components, the conductive adhesive composition of the present embodiment may optionally contain a flexibility agent for stress relaxation, additives (diluent, adhesive force improver) to improve workability. , a wettability improver, and an antifoaming agent). Further, in addition to these components, various additives may be contained within a range that does not impede the effects of the present invention.

As the flexibilizing agent, for example, liquid polybutadiene (manufactured by Ube Industries, Ltd., product name "CTBN-1300x31", "CTBN-1300x9", manufactured by Nippon Soda Co., Ltd., product name "NISSO-PB-C-" 2000''). When a flexibilizing agent is contained, the content of the flexibilizing agent is preferably 0.1 to 500 parts by mass based on 100 parts by mass of the (B) thermosetting resin.

A diluent can be added to the conductive adhesive composition of the present embodiment, if necessary, in order to improve the workability during production of the paste composition and the application workability during use. Examples of such diluents include organic solvents with relatively high boiling points such as butyl carbitol, butyl cellosolve, carbitol, butyl cellosolve acetate, carbitol acetate, dipropylene glycol monomethyl ether, ethylene glycol diethyl ether, and α-terpineol. preferable. When these diluents are contained, the content of the diluents is preferably 0.1 to 30% by mass based on the total amount of the conductive adhesive composition.

The conductive adhesive composition of this embodiment may contain a coupling agent such as a silane coupling agent or a titanium coupling agent as an adhesive force improver. Examples of the silane coupling agent include KBM-573 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.). Further, the conductive adhesive composition of this embodiment may contain a wettability improver such as an anionic surfactant and a fluorine surfactant. Furthermore, the conductive adhesive composition of this embodiment may contain silicone oil or the like as an antifoaming agent. The above adhesive force improver, wettability improver, and antifoaming agent can each be used singly or in combination of two or more types. When these additives are contained, the content of each additive is preferably 0.1 to 10% by mass based on the total amount of the conductive adhesive composition.

The conductive adhesive composition of this embodiment may contain a filler. Examples of the filler include polymer particles such as acrylic rubber and polystyrene, and inorganic particles such as diamond, boron nitride, aluminum nitride, alumina, and silica. These fillers can be used alone or in combination of two or more.

The conductive adhesive composition of this embodiment may further contain a curing agent in order to adjust the curing speed of the (B) thermosetting resin (for example, epoxy resin).

The curing agent is not particularly limited as long as it is a conventionally used curing agent, and commercially available curing agents are available. Commercially available curing agents include, for example, phenol novolac resin H-1 (manufactured by Meiwa Kasei Co., Ltd., trade name), VR-9300 (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name), and phenol aralkyl resin XL. -225 (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name), MTPC, which is a p-cresol novolac resin represented by the following general formula (II) (manufactured by Honshu Chemical Industry Co., Ltd., trade name), allylated phenol novolac resin AL-VR-9300 (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name), which is a phenolic resin represented by the following general formula (III), PP-700-300 (manufactured by Nippon Petrochemical Co., Ltd., trade name) etc.

In formula (II), R ¹ each independently represents a monovalent hydrocarbon group, preferably a methyl group or an allyl group, and q represents an integer of 1 to 5.

In formula (III), R ² each independently represents an alkyl group, preferably a methyl group or an ethyl group, R ³ represents a hydrogen atom or a monovalent hydrocarbon group, and p represents an integer of 2 to 4. show.

As the curing agent, those conventionally used as curing agents such as dicyandiamide can be used, and commercially available products are available. Commercially available products include, for example, ADH, PDH, and SDH, which are dibasic acid dihydrazides represented by the following general formula (IV) (all trade names, manufactured by Nippon Finechem Co., Ltd.), and reaction products of epoxy resins and amine compounds. Novacure (manufactured by Asahi Kasei Corporation, trade name), which is a microcapsule type curing agent consisting of: These curing agents can be used alone or in combination of two or more.

In formula (IV), R ⁴ represents a divalent aromatic group or a linear or branched alkylene group having 1 to 12 carbon atoms, preferably an m-phenylene group or a p-phenylene group.

From the viewpoint of storage stability and curing time, it is preferable that the curing agent is not substantially contained in the conductive adhesive composition. "Substantially not containing" means that the content is 0.05% by mass or less based on the total amount of the conductive adhesive composition.

In this embodiment, each of the above-mentioned components may be combined with any of those exemplified.

The conductive adhesive composition of this embodiment is a paste-like composition in which each of the above-mentioned components is uniformly dispersed by mixing, dissolving, dissolving, kneading, or dispersing the above-mentioned components at once or in multiple steps. obtained as. When obtaining a paste-like composition, heating may be performed as necessary. Examples of the dispersing device and dissolving device include a known stirrer, a sieve, a three-roll mill, and a planetary mixer.

The viscosity at 25° C. of the conductive adhesive composition of the present embodiment is preferably 5 to 400 Pa·s, more preferably 50 to 300 Pa·s, and 100 to 400 Pa·s, from the viewpoint of paste applicability. More preferably, it is 200 Pa·s. The viscosity can be measured using, for example, a B-type viscometer manufactured by Hideko Seiki Co., Ltd.

The conductive adhesive composition of the present embodiment described above has good adhesive strength and conductivity, and is a cured product that can maintain both good adhesive strength and conductivity even after repeated expansion/contraction and bending. can be formed. In addition, the conductive adhesive composition of the present embodiment can lower the mounting temperature in the process of mounting the flexible wiring board and electronic components, so it is possible to reduce the mounting temperature of the electronic components without impairing the flexibility and stretchability of the substrate. A connection structure such as a mounted flexible wiring board can be obtained. Furthermore, since the adhesive composition according to the present embodiment can form a connection part having a connection structure in which the metal part and the resin part are separated, the connection part is reinforced and has only bending resistance and stretch resistance. Therefore, a connected structure having excellent TCT resistance can be obtained. The conductive adhesive composition can be used in a stretchable device composed of a flexible wiring board and an electronic component, which is in a bent or stretched shape.

<Connection structure>
The connection structure of this embodiment includes a flexible wiring board having a first connection terminal, an electronic component having a second connection terminal, and a connection portion disposed between the flexible wiring board and the electronic component, This is a connected structure in which a connecting portion contains a cured product of the conductive adhesive composition of the present embodiment, and a first connecting terminal and a second connecting terminal are electrically connected.

The flexible wiring board is preferably made of a base material that is flexible and stretchable. Examples of flexible and stretchable base materials include polyimide, polyethylene terephthalate (PET), polycarbonate, polyethylene naphthalate (PEN), polyketone, polyetheretherketone, thermoplastic polyurethane elastomer (TPU), and cycloolefin polymer. can be mentioned. Among these, from the viewpoint of dimensional stability after wiring processing, thermoplastic polyurethane elastomers, polyethylene terephthalate and polyethylene naphthalate are preferred, and thermoplastic polyurethane elastomers are more preferred.

There are no particular limitations on the electronic components, and known electronic components can be used. Specific examples thereof include semiconductor light emitting devices, capacitors, Schottky barrier diodes, driver integrated circuits (driver ICs), and the like. Examples of the semiconductor light emitting device include an LED-SMD package, an LED flip chip, and an LED-CSP.

The connecting portion contains the cured product of the conductive adhesive composition of the present embodiment, and is made of a metal portion containing a metal with a melting point of 200°C or less and a resin portion containing a thermosetting resin. It is possible to adopt an embodiment having a connection structure consisting of: The metal part preferably contains a metal derived from the conductive particles (A) containing a metal having a melting point of 200° C. or less as a main component, and the resin part contains a resin derived from an adhesive component such as a thermosetting resin. It is preferable to use it as the main component. In the connection structure according to the present embodiment, when viewed in a cross section perpendicular to the upper surface of the second connection terminal of the electronic component, the metal portion is connected to the second connection terminal of the electronic component and the first connection of the flexible wiring board. The resin portion may be in contact with the terminal and may be present around the metal portion.

The area ratio between the metal part and the resin part (metal part: resin part) in the connection part is 5:95 to 80:20 from the viewpoint of maintaining better adhesive strength and conductivity even after repeated bending and expansion/contraction. The ratio is preferably 10:90 to 90:10, and even more preferably 30:70 to 70:30. The above area ratio can be determined by observing the cross section of the connection portion. Further, a sealing member may be further provided around the resin portion.

The connected structure of this embodiment can be obtained by bonding an electronic component and a flexible wiring board using the conductive adhesive composition. For example, first, a conductive adhesive composition is applied onto the connection terminals of the flexible wiring board by a dispensing method, a screen printing method, a stamping method, or the like. Next, the electronic component is laminated on the flexible wiring board so that the connection terminal of the electronic component and the connection terminal of the flexible wiring board are in contact with each other via the conductive adhesive composition. Thereafter, the conductive adhesive composition is heated and cured using a heating device such as an oven or a reflow oven, and the flexible wiring board and the electronic component are electrically connected through the cured product of the conductive adhesive composition. (hereinafter, this connected structure is also referred to as "electronic component mounted flexible wiring board").

Examples of the electronic component-mounted flexible wiring board include a semiconductor light-emitting element-mounted flexible wiring board. The semiconductor light emitting element mounted flexible wiring board includes a flexible wiring board having a first connection terminal, a semiconductor light emitting element having a second connection terminal, and a connecting portion disposed between the flexible wiring board and the semiconductor light emitting element. An embodiment may be adopted in which the connecting portion contains a cured product of the conductive adhesive composition, and the first connecting terminal and the second connecting terminal are electrically connected.

Next, the connected structure of this embodiment will be explained using FIGS. 1 to 3. However, the dimensional ratios in the drawings are not limited to the ratios shown. FIG. 1 is a schematic cross-sectional view showing one embodiment of a flexible wiring board mounted with electronic components. As shown in FIG. 1, the electronic component mounting flexible wiring board 1 includes a board connection terminal 7 (first connection terminal) formed on the flexible wiring board 5, and an electronic component connection terminal 6 formed on the electronic component 4. (second connection terminal) are joined to each other by the connection portion 8 and are electrically connected to each other. The connecting portion 8 includes a cured product obtained by curing the conductive adhesive composition described above. Further, the connecting portion 8 is composed of a metal portion 8a and a resin portion 8b.

The electronic component-mounted flexible wiring board according to this embodiment is not limited to the structure shown in FIG. 1, but may have the structure shown in FIG. 2 or 3, for example. FIG. 2 is a schematic cross-sectional view showing another embodiment of the electronic component-mounted flexible wiring board. The electronic component mounted flexible wiring board 2 shown in FIG. terminals) are electrically connected by a connecting portion 8 containing a cured product obtained by curing the conductive adhesive composition of this embodiment. Further, the connecting portion 8 is composed of a metal portion 8a and a resin portion 8b.

Moreover, FIG. 3 is a schematic cross-sectional view showing still another embodiment of the electronic component-mounted flexible wiring board. The electronic component mounted flexible wiring board 3 shown in FIG. 3 has a structure in which the flexible wiring board 5 and the electronic component 4 are connected by combining the conductive adhesive composition of this embodiment and solder. In the electronic component mounting flexible wiring board 3, an electronic component connection terminal 6 is formed on the electronic component 4, and further, a solder ball 10 is formed on the electronic component connection terminal 6. The solder balls 10 and the board connection terminals 7 formed on the flexible wiring board 5 are electrically connected by a connection part 8 containing a cured product obtained by curing the conductive adhesive composition of this embodiment. Thus, an electronic component mounting flexible wiring board 3 is formed. Further, the connecting portion 8 is composed of a metal portion 8a and a resin portion 8b.

The electronic component-mounted flexible wiring boards 1 to 3 shown in FIGS. 1 to 3 are cured products in which the connection terminals on the substrate and the connection terminals on the electronic component are obtained by curing the conductive adhesive composition of the present embodiment, respectively. They have a structure in which they are joined to each other and electrically connected by a connecting portion including. The connecting portion is composed of a metal portion 8a and a resin portion 8b, and the metal portion 8a is reinforced by the resin portion 8b. Here, in conventional flexible wiring boards mounted with electronic components in which the connecting parts are made only of metal parts, when a bending test and an expansion/contraction test are performed, the board deforms significantly, causing direct distortion to the connecting parts and electronic components. This may cause damage to the connections and electronic components. In the flexible wiring board with electronic components in which the connection part of this embodiment is composed of a metal part and a resin part, the metal part is reinforced by the resin part, so even if the board deforms significantly, the deformation of the board will not be caused by the resin part. It is possible to hold the connection part in place and maintain the rigid state of the connection part.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Further, the present invention can be modified in various ways without departing from the gist thereof. For example, other substrates or electronic components may be further mounted on the substrate in the connected structure shown in FIGS. 1 to 3.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

<Preparation of conductive adhesive composition>
[Example 1]
16.0 parts by mass of YL980 (bisphenol F type epoxy resin, manufactured by Mitsubishi Chemical Corporation, trade name), which is a thermosetting resin, and 2P4MHZ-PW (imidazole compound, manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name), which is a curing catalyst. ) and 2.7 parts by mass of BHPA (2,2-bis(hydroxymethyl)propionic acid), which is a flux activator, were mixed and passed through three rolls three times to prepare an adhesive component. did.

Next, 80 parts by mass of Sn42-Bi58 solder (average particle size 20 μm, manufactured by Mitsui Kinzoku Co., Ltd., melting point 138°C), which is conductive particles, was added to 20 parts by mass of the above adhesive component, and a planetary mixer was added. A conductive adhesive composition was obtained by performing a defoaming treatment for 10 minutes at 500 Pa or less.

[Examples 2 to 8, Comparative Examples 1 to 7]
Conductive adhesive compositions of Examples 2 to 8 and Comparative Examples 1 to 7 were obtained in the same manner as in Example 1 except that the compositions and amounts shown in Tables 1 and 2 below were used. Moreover, the unit of the amount of each component in the table is parts by mass.

Details of each component in the table are as follows.
YL980: Bisphenol F-type epoxy resin, manufactured by Mitsubishi Chemical Corporation, trade name 2P4MHZ-PW: Imidazole compound, manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name BHPA: 2,2-bis(hydroxymethyl)propionic acid BHBA: 2,2 -Sn42-Bi58 bis(hydroxymethyl)butanoate solder: average particle size 20 μm, manufactured by Mitsui Kinzoku Co., Ltd., melting point 138°C
Sn42-Bi57-Ag1 solder: average particle size 20 μm, manufactured by Mitsui Kinzoku Co., Ltd., melting point 139°C
Sn96.5-Ag3-Cu0.5 solder: average particle size 20 μm, manufactured by Mitsui Kinzoku Co., Ltd., melting point 217°C
Ag paste: manufactured by Fujikura Kasei Co., Ltd., curing temperature 150°C
Sn42-Bi58 cream solder: Senju Metal Industry Co., Ltd., melting point 138°C
Sn96.5-Ag3-Cu0.5 cream solder: Senju Metal Industry Co., Ltd., melting point 219°C

<Characteristics evaluation>
The characteristics of the conductive adhesive compositions obtained in the above Examples and Comparative Examples were evaluated by the following method. The results are summarized in Tables 1 and 2 below.

TPU (thermoplastic polyurethane elastomer) having flexibility and stretchability was used as the base material of the flexible wiring board used for evaluation of TCT resistance, bending resistance, and stretch resistance.

(1) Adhesiveness (adhesive strength)
Approximately 0.5 mg of the conductive adhesive composition was applied onto a silver-plated copper plate, and a rectangular flat tin-plated copper plate measuring 2 mm in length x 2 mm in width x 0.25 mm in thickness was crimped onto the test piece. Obtained. Thereafter, the test pieces of Examples 1 to 8 and Comparative Examples 1 to 6 were subjected to a heat history at 150° C. for 10 minutes. The test piece of Comparative Example 7 was subjected to a heat history of 260° C. for 10 minutes. Next, the shear strength at 25°C was measured for the test pieces of Examples 1 to 8 and Comparative Examples 1 to 7 using a bond tester (manufactured by DAGE, model number: 2400) at a shear speed of 500 μm/sec and a clearance of 100 μm. did.

(2) Conductivity (volume resistivity)
Two strip-shaped gold-plated copper plates measuring 1 mm in width x 50 mm in length x 0.03 mm in thickness are pasted together in a cross shape orthogonally to each other via the adhesive composition to form an adhesive layer (orthogonal portion). A test piece was obtained with dimensions of 1 mm width x 1 mm length x 0.03 mm thickness. Subsequently, the same heat history as in the adhesive evaluation described in (1) above was applied to the test piece. Thereafter, the volume resistivity of the test piece in the thickness direction was measured using a four-terminal method.

(3) TCT resistance A rectangular flat TPU board measuring 100 mm in length x 50 mm in width x 1.0 mm in thickness and provided with a 1.7 mm x 1.4 mm copper foil land was prepared. Next, an adhesive composition was printed on the copper foil land using a metal mask (thickness 100 μm, opening size 1.0 mm x 1.6 mm), and a chip resistor (3.2 mm x 1.6 mm, MCR manufactured by ROHM Co., Ltd.) was printed. ). This component-mounted board was subjected to the same thermal history as in the adhesive evaluation described in (1) above to obtain a test board for TCT resistance evaluation. This test board was tested using a thermal shock tester, TSE-11-A manufactured by ESPEC Co., Ltd. (1 cycle: held at -55°C for 30 minutes, heated to 125°C for 5 minutes, held at 125°C for 30 minutes, -55°C). ℃) and measured the connection resistance. For evaluation of TCT resistance, the number of cycles showing a resistance change rate within ±10% with respect to the initial resistance value was used as an index.

(4) Flexibility A rectangular flat TPU board measuring 200 mm in length x 20 mm in width x 1.0 mm in thickness and provided with a 1.7 mm x 1.4 mm copper foil land was prepared. Next, an adhesive composition was printed on the copper foil land using a metal mask (thickness 100 μm, opening size 1.0 mm x 1.6 mm), and a chip resistor (3.2 mm x 1.6 mm, MCR manufactured by ROHM Co., Ltd.) was printed. ). This component-mounted board was subjected to the same thermal history as in the adhesive evaluation described in (1) above to obtain a test board for evaluation of bending resistance. This test board was bent into a U-shape using a U-shaped folding tester (Yuasa System Equipment Co., Ltd., DLDMLH-FU) with the bending radius set to 2.0 mm so that the component mounting section was on the inside. Both ends of the board were attached to a sliding plate and a fixed plate, and in a test atmosphere of 23°C, the sliding plate was slid left and right with a stroke of 50 mm and a sliding speed of 100 times/min, and the test board was repeatedly bent a predetermined number of times. The resistance value of the component mounting area was measured when the For evaluation of bending resistance, the number of sliding operations at the time when the initial resistance value increased by 10% was defined as the bending resistance life.

(5) Stretching Resistance A rectangular flat TPU board measuring 200 mm in length x 20 mm in width x 1.0 mm in thickness and provided with a 1.7 mm x 1.4 mm copper foil land was prepared. Next, an adhesive composition was printed on the copper foil land using a metal mask (thickness 100 μm, opening size 1.0 mm x 1.6 mm), and a chip resistor (3.2 mm x 1.6 mm, MCR manufactured by ROHM Co., Ltd.) was printed. ). This component-mounted board was subjected to the same heat history as in the adhesive evaluation described in (1) above to obtain a test board for evaluation of stretch resistance. This test board was repeatedly fixed at both ends to a stretching tester (manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd., DC-210) so that it was in the most shrunk state, and the test board was stretched by 30% when pulled in a test atmosphere of 23°C. The resistance value was measured when the material was repeatedly expanded and contracted a predetermined number of times at 100 times/min. For evaluation of stretch resistance, the number of stretches at which the initial resistance value increased by 10% was defined as the stretch life.

Examples 1 to 8 all showed good adhesive strength, volume resistivity, TCT resistance, bending resistance, and stretch resistance.

It was confirmed that in Comparative Examples 1 and 3, the metal particles did not aggregate and there was a problem in connectivity. Although Comparative Examples 2, 4, and 6 had good metal bonding, it was confirmed that they were inferior in TCT resistance, bending resistance, and stretch resistance compared to Examples 1 to 8. It was confirmed that Comparative Example 5 was inferior to Examples 1 to 8 in terms of adhesive strength, volume resistivity, TCT resistance, bending resistance, and stretching resistance. Comparative Example 7 showed good connection strength and volume resistivity, but regarding TCT resistance, bending resistance, and stretch resistance, the TPU substrate was greatly deformed when heated and connected at 260°C. Measurement was not possible because the connection part was damaged.

DESCRIPTION OF SYMBOLS 1, 2, 3... Electronic component mounted flexible wiring board, 4... Electronic component, 5... Flexible wiring board, 6... Electronic component connection terminal, 7... Board connection terminal, 8... Connection part, 8a... Metal part, 8b... Resin part, 9...lead, 10...solder ball.

Claims (13)

A conductive adhesive composition used for electrically connecting a flexible wiring board and an electronic component, the composition comprising:
Contains conductive particles containing a metal with a melting point of 200°C or less, a thermosetting resin, a flux activator and a curing catalyst,
The conductive particles include Sn42-Bi58 solder, Sn48-In52 solder, Sn42-Bi57-Ag1 solder, Sn90-Ag2-Cu0.5-Bi7.5 solder, Sn89-Zn8-Bi3 solder, and Sn91-Zn9 solder. Containing at least one species selected from the group,
the flux activator comprises 2,2-bis(hydroxymethyl)propionic acid,
The thermosetting resin contains at least one epoxy resin selected from the group consisting of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol AD epoxy resin, and amine epoxy resin,
A conductive adhesive composition , wherein the curing catalyst contains an imidazole compound . The conductive adhesive composition according to claim 1 , which is a paste composition having a viscosity of 5 to 400 Pa·s at 25°C. The conductive adhesive composition according to claim 1 or 2 , which is used for electrically connecting connection terminals arranged on the flexible wiring board and connection terminals arranged on the electronic component. The conductive adhesive composition according to any one of claims 1 to 3 , wherein the flexible wiring board is composed of a flexible and stretchable base material. The flexible wiring board is composed of a base material containing at least one selected from the group consisting of polyimide, polyethylene terephthalate, polycarbonate, polyethylene naphthalate, polyketone, polyetheretherketone, thermoplastic polyurethane elastomer, and cycloolefin polymer. The conductive adhesive composition according to any one of claims 1 to 4 . a flexible wiring board having a first connection terminal;
an electronic component having a second connection terminal;
a connecting portion disposed between the flexible wiring board and the electronic component;
The connecting portion contains a cured product of the conductive adhesive composition according to any one of claims 1 to 5 , and the first connecting terminal and the second connecting terminal are electrically connected. A connection structure. The connected structure according to claim 6 , wherein the connecting portion has a connecting structure consisting of a metal portion containing a metal having a melting point of 200° C. or lower and a resin portion containing a thermosetting resin. When the connection structure is viewed in a cross section perpendicular to the upper surface of the second connection terminal, the metal part is in contact with the second connection terminal and the first connection terminal, and the resin part is in contact with the metal part. 8. The connection structure according to claim 7 , comprising a connection structure existing around the periphery of the connection structure. The connected structure according to claim 7 or 8 , wherein the area ratio of the metal part to the resin part is 5:95 to 80:20. The connection structure according to any one of claims 7 to 9 , further comprising a sealing member around the resin part. The flexible wiring board is composed of a base material containing at least one selected from the group consisting of polyimide, polyethylene terephthalate, polycarbonate, polyethylene naphthalate, polyketone, polyetheretherketone, thermoplastic polyurethane elastomer, and cycloolefin polymer. The connection structure according to any one of claims 6 to 10 . The connected structure according to any one of claims 6 to 11 , wherein the electronic component includes at least one selected from the group consisting of a semiconductor light emitting device, a capacitor, a Schottky barrier diode, and a driver integrated circuit. a flexible wiring board having a first connection terminal;
a semiconductor light emitting element having a second connection terminal;
a connection portion disposed between the flexible wiring board and the semiconductor light emitting element,
The connecting portion contains a cured product of the conductive adhesive composition according to any one of claims 1 to 5 , and the first connecting terminal and the second connecting terminal are electrically connected. A flexible wiring board equipped with semiconductor light emitting elements.

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