JP2002226807A - Adhesive for connecting circuit, method for connecting circuit by using the same, and connecting structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive for connecting circuits, capable of connecting the circuits well even by using a double layered FPC made of a polyimide, and further to provide a method for connecting the circuits by using the adhesive, and a connecting structure. SOLUTION: This adhesive for connecting the circuits, capable of electrically connecting electrodes in the pressurized direction by placing the adhesive between boards having the mutually facing circuit electrodes, and pressurizing the mutually facing circuit electrodes, has the first adhesive layer and the second adhesive layer regulated so that the modulus E1 of the cured product of the first adhesive layer at 50 deg.C may be higher than the modulus E2 of the cured product of the second adhesive layer at 50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit connection adhesive, a circuit connection method using the same, and a connection structure obtained by the method.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display and a TCP or F
An anisotropic conductive adhesive in which conductive particles are dispersed in an adhesive is used for the connection between the PC and the TCP and the connection between the FPC and the printed wiring board. In recent years, even when a semiconductor silicon chip is mounted on a substrate, so-called flip chip mounting, in which the semiconductor silicon chip is directly mounted on the substrate face down instead of conventional wire bonding, has been performed. Application of a water-soluble adhesive has been started (JP-A-59-120436 and JP-A-60-120436).
191228, JP-A-1-251787, JP-A-7
-90237).

[0003]

However, in the conventional anisotropic conductive adhesive, since the physical properties of the anisotropic conductive adhesive are different from those of the adherend, thermal stress and residual stress are generated during thermocompression bonding. I do. In recent years, as electronic devices have become smaller and thinner, the density of circuits has been increasing, and the gap between electrodes and the width of electrodes have become extremely narrow. For this reason, there has been a demand for a reduction in displacement during connection. Specifically, studies have been made using a so-called two-layer FPC in which a polyimide resin is directly applied to a copper foil to produce or electrically form a circuit in the polyimide resin. However, when a conventional anisotropic conductive adhesive is used, there have been problems such as insufficient bonding strength and insufficient electrical characteristics. The present invention uses a circuit connection adhesive which can be connected well even by using a so-called two-layer FPC in which a polyimide resin is directly applied to a copper foil or a circuit is formed electrically on the polyimide resin, and using the same. A circuit connection method and a connection structure are provided.

[0004]

According to the present invention, there is provided (1) a method of interposing a substrate having opposing circuit electrodes, and pressing the substrate having opposing circuit electrodes to electrically connect the electrodes in the pressing direction. The adhesive has a first adhesive layer and a second adhesive layer, and the cured product of the first adhesive layer has an elastic modulus El at 50 ° C. of the second adhesive layer. A circuit connection adhesive characterized by having a higher elastic modulus E2 at 50 ° C. of a cured product of the adhesive layer. Here, the elastic modulus is a storage elastic modulus, which was measured using a dynamic viscoelasticity measuring device (Solid Analyzer RSA-II, manufactured by Rheometric Scientific) at a heating rate of 5 ° C./min, 1 Hz. (2) The range of E1 / E2 = 1.1 to 50 obtained from the elastic modulus El of the cured product of the first adhesive layer at 50 ° C. and the elastic modulus E2 of the cured product of the second adhesive layer at 50 ° C. The adhesive for circuit connection according to the above (1), wherein (3) The adhesive for circuit connection according to (1) or (2), wherein at least one of the first adhesive layer and the second adhesive layer contains conductive particles. (4) The thickness ratio of the first adhesive layer and the second adhesive layer is the second adhesive layer.
Thickness of adhesive layer / thickness of first adhesive layer = 0.3 to 3.0
The adhesive for circuit connection according to any one of the above (1) to (3). Further, the present invention provides (5) a substrate having opposing circuit electrodes by interposing the adhesive for circuit connection according to any one of (1) to (4) between substrates having opposing circuit electrodes. And electrically connecting the electrodes in the pressing direction by arranging the first adhesive layer on the side of the substrate having the opposite circuit electrode having the smaller coefficient of thermal expansion. Circuit connection method.
Further, the present invention provides (6) a substrate having opposing circuit electrodes by interposing the circuit-connecting adhesive according to any of (1) to (4) between substrates having opposing circuit electrodes. A connection structure in which electrodes are electrically connected to each other in a pressure direction by pressing the first adhesive layer and the second adhesive layer.
The cured product of the first adhesive layer having an adhesive layer has an elastic modulus El at 50 ° C. of the cured product of the second adhesive layer.
This is a connection structure in which the first adhesive layer is higher than 2, and the first adhesive layer is arranged and connected to the substrate having the smaller thermal expansion coefficient among the substrates having the circuit electrodes facing each other. (7) A connection structure, wherein the height of one of the circuit electrodes facing each other in (6) is 5 to 14 μm.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When a circuit connection method according to the present invention is used, no floating or peeling off from a substrate occurs even after various reliability tests such as a moisture resistance test and a thermal cycle test. In particular, the characteristics of a so-called two-layer FPC in which a polyimide resin is applied directly to a copper foil or a circuit is formed electrically on the polyimide resin can be remarkably improved. The adhesive for circuit connection according to the present invention is used for a circuit connection that is interposed between substrates having opposing circuit electrodes and presses the substrate having opposing circuit electrodes to electrically connect the electrodes in the pressing direction. An adhesive, wherein the adhesive has a first adhesive layer and a second adhesive layer, and the cured product of the first adhesive layer has an elastic modulus El at 50 ° C. of the cured product of the second adhesive layer. A circuit connection adhesive characterized by having a higher elastic modulus E2 at 50 ° C. than the elastic modulus El at 50 ° C. of the cured product of the first adhesive layer and the cured product of the second adhesive layer. It is desirable that E1 / E2 = 1.1 to 50 in the range obtained from the elastic modulus E2 at 50 ° C. The ratio of the thickness of the first adhesive layer to the thickness of the second adhesive layer can be used in the range of the thickness of the second adhesive layer / the thickness of the first adhesive layer = 0.3 to 3.0. is there. When at least one of the first adhesive layer and the second adhesive layer contains conductive particles, connection reliability is improved.

The first adhesive layer or the second adhesive layer used in the present invention may be made of thermoplastic resin such as acrylic rubber, styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, or the like. Epoxy resin,
A thermosetting resin such as a (meth) acrylic resin, a maleimide resin, a citraconic imide resin, a nadiimide resin, and a phenol resin is used, but it is preferable to use a thermosetting resin in terms of heat resistance and reliability.

As the (meth) acrylic resin, methyl (meth) acrylate, ethyl (meth) acrylate,
Isopropyl (meth) acrylate, isobutyl (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylene glycol tetra (meth) acrylate, 2-hydroxy-1 , 3-Diacryloxypropane, 2,2-bis [4- (acryloxymethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy) phenyl] propane, dicyclopentenyl (meth)
Acrylate tricyclodecanyl (meth) acrylate, tris (acryloxyethyl) isocyanurate,
There are urethane (meth) acrylates and the like, and these may be used alone or in combination of two or more. If necessary, a radical polymerization inhibitor such as hydroquinone or methyl ether hydroquinone may be used as long as the curability is not impaired.

Further, when a radical polymerizable substance having a phosphate ester structure is used, the adhesive strength to an inorganic substance such as a metal can be improved. The amount of the radical polymerizable substance having a phosphate ester structure is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight. The radical polymerizable substance having a phosphate ester structure is obtained as a reaction product of phosphoric anhydride and 2-hydroxyethyl (meth) acrylate. Specifically, there are mono (2-methacryloyloxyethyl) acid phosphate, di (2-methacryloyloxyethyl) acid phosphate and the like, and these may be used alone or in combination.

The maleimide resin is a resin having at least one maleimide group in the molecule, for example, phenylmaleimide, 1-methyl-2,4-bismaleimidebenzene, N, N'-m-phenylenebis Maleimide, N,
N'-p-phenylenebismaleimide, N, N'-4,4-biphenylenebismaleimide, N, N'-4,4- (3,3-dimethylbiphenylene) bismaleimide, N, N'-4,4 −
(3,3-dimethyldiphenylmethane) bismaleimide,
N, N'-4,4- (3,3-diethyldiphenylmethane) bismaleimide, N, N'-4,4-diphenylmethanebismaleimide, N, N'-4,4-diphenylpropanebismaleimide, N, N '-4,4-diphenylether bismaleimide, N, N'-4,4-diphenylsulfonebismaleimide, 2,2-bis (4- (4-maleimidophenoxy) phenyl) propane, 2,2-bis (3- s-butyl-3,4-
(4-maleimidophenoxy) phenyl) propane, 1,
1-bis (4- (4-maleimidophenoxy) phenyl)
Decane, 4,4'-cyclohexylidene-bis (1- (4-
Maleimidophenoxy) phenoxy) -2-cyclohexylbenzene, 2,2-bis (4- (4-maleimidophenoxy) phenyl) hexafluoropropane, etc.
They may be used alone or in combination of two or more.

The citraconic imide resin is a resin having at least one citraconic imide group in the molecule, for example, phenylcitraconic imide, 1-methyl-
2,4-biscitraconimide benzene, N, N'-m-phenylenebiscitraconimide, N, N'-p-phenylenebiscitraconimide, N, N'-4,4-biphenylenebiscitraconimide, N, N '-4,4- (3,3-dimethylbiphenylene) biscitraconimide, N, N'-4,4
-(3,3-dimethyldiphenylmethane) biscitraconimide, N, N'-4,4- (3,3-diethyldiphenylmethane) biscitraconimide, N, N'-4,4-diphenylmethanebiscitraconimide, N, N'-4,4-diphenylpropanebiscitraconimide, N, N'-4,4-diphenyletherbiscitraconimide, N, N'-4,4
-Diphenylsulfonebiscitraconimide, 2,2-bis (4- (4-citraconimidophenoxy) phenyl)
Propane, 2,2-bis (3-s-butyl-3,4- (4-citraconimidophenoxy) phenyl) propane, 1,1
-Bis (4- (4-citraconimidophenoxy) phenyl) decane, 4,4'-cyclohexylidene-bis (1-
(4-citraconimidophenoxy) phenoxy) -2-
There are cyclohexylbenzene, 2,2-bis (4- (4-citraconimidophenoxy) phenyl) hexafluoropropane and the like, and these may be used alone or as a mixture of two or more.

The nadimide resin has at least one nadimide group in the molecule, for example, phenylnadimide, 1-methyl-2,4-bisnadimide benzene, N, N'-m-phenylene Bisnadiimide, N,
N'-p-phenylenebisnadimide, N, N'-4,4-biphenylenebisnadimide, N, N'-4,4- (3,3-dimethylbiphenylene) bisnadimide, N, N'-4,4-
(3,3-dimethyldiphenylmethane) bisnadiimide,
N, N'-4,4- (3,3-diethyldiphenylmethane) bisnadimide, N, N'-4,4-diphenylmethanebisnadimide, N, N'-4,4-diphenylpropanebisnadimide, N, N ' -4,4-diphenyletherbisnadimide, N, N'-4,4-diphenylsulfonebisnadimide, 2,2-bis (4- (4-nadiimidophenoxy) phenyl) propane, 2,2-bis (3- s-butyl-3,4-
(4-nadiimidophenoxy) phenyl) propane, 1,
1-bis (4- (4-nadiimidophenoxy) phenyl)
Decane, 4,4'-cyclohexylidene-bis (1- (4-
Nadiimidophenoxy) phenoxy) -2-cyclohexylbenzene, 2,2-bis (4- (4-nadiimidophenoxy) phenyl) hexafluoropropane, etc.
They may be used alone or in combination of two or more.

When the above radical polymerizable compound is used, a polymerization initiator is used. As the polymerization initiator,
There is no particular limitation as long as it is a compound that generates a radical by heat or light, and there are peroxides, azo compounds, and the like, which are appropriately selected in consideration of a target connection temperature, a connection time, storage stability, and the like. From the viewpoint of reactivity and storage stability, an organic peroxide having a half-life of 10 hours at a temperature of 40 ° C. or more and a half-life of 1 minute of 180 ° C. or less is preferable.
An organic peroxide having a temperature of 0 hours of 50 ° C. or more and a half-life of 1 minute of 170 ° C. or less is particularly preferred. When the connection time is 10 seconds, the amount of the polymerization initiator for obtaining a sufficient reaction rate is preferably 1 to 20% by weight, and 2 to 1% by weight.
5% by weight is particularly preferred. Specific compounds of the organic peroxide used in the present invention include diacyl peroxide, peroxydicarbonate, peroxyester,
Peroxy ketals, dialkyl peroxides, hydroperoxides, silyl peroxides, etc. can be selected. Peroxyesters, dialkyl peroxides, hydroperoxides, and silyl peroxides contain 5000 ppm of chlorine ions and organic acids in the initiator.
This is particularly preferable because the amount of organic acid generated after thermal decomposition is small and the corrosion of the connection terminal of the circuit member can be suppressed.

The diacyl peroxides include isobutyl peroxide, 2,4-dichlorobenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinyl peroxide Nickel peroxide, benzoylperoxytoluene, benzoyl peroxide and the like can be mentioned.

The peroxydicarbonates include di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, di-2-carbonate.
Ethoxymethoxyperoxydicarbonate, di (2-
Ethylhexylperoxy) dicarbonate, dimethoxybutylperoxydicarbonate, di (3-methyl-
3-methoxybutylperoxy) dicarbonate.

The peroxy esters include cumyl peroxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, 1-cyclohexyl-1-methylethyl peroxynodecanoate. Ethate, t-hexylperoxy neodecanoate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanate,
2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanate, t
-Hexylperoxy-2-ethylhexanonate, t
-Butylperoxy-2-ethylhexanonate, t-
Butyl peroxyisobutyrate, 1,1-bis (t-
Butylperoxy) cyclohexane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanonate, t-
Butyl peroxylaurate, 2,5-dimethyl-2,
5-di (m-toluoylperoxy) hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, t-butylperoxyacetate, and the like. be able to.

The peroxyketals include 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane, 1,1- Bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,
1- (t-butylperoxy) cyclododecane, 2,2
-Bis (t-butylperoxy) decane and the like.

In the dialkyl peroxides, α,
α'-bis (t-butylperoxy) diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-
Examples thereof include 2,5-di (t-butylperoxy) hexane and t-butylcumyl peroxide.

The hydroperoxides include diisopropylbenzene hydroperoxide, cumene hydroperoxide and the like.

Examples of the silyl peroxides include t-butyltrimethylsilyl peroxide, bis (t-butyl) dimethylsilyl peroxide, t-butyltrivinylsilyl peroxide, bis (t-butyl) divinylsilyl peroxide, and tris ( (t-butyl) vinylsilyl peroxide, t-butyltriallylsilyl peroxide, bis (t-butyl) diallylsilyl peroxide, tris (t-butyl) allylsilyl peroxide and the like.

In order to suppress the corrosion of circuit electrodes, it is preferable that the chlorine ion and the organic acid contained in the organic peroxide be 5000 ppm or less as described above. Those having a small amount of organic acid generated after decomposition are more preferable. In addition, it is preferable that the adhesive for circuit connection has a weight retention of 20% by weight or more after being left open for 24 hours under normal pressure at room temperature (25 ° C.) because the stability of the produced adhesive for circuit connection is improved. These can be used by mixing as appropriate. These polymerization initiators can be used alone or as a mixture, and a decomposition accelerator, an inhibitor and the like may be used as a mixture. The above-mentioned organic peroxides may be used alone or as a mixture of two or more kinds. The organic peroxides may be coated with a polymer material such as a polyurethane-based or polyester-based material and microencapsulated. The microencapsulated one is preferable because the pot life is extended.

As the thermosetting resin other than the radical polymerization type, there is an epoxy resin. As the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin, cresol Novolak epoxy resin, bisphenol A novolak epoxy resin, bisphenol F novolak epoxy resin, alicyclic epoxy resin, glycidyl ester epoxy resin,
There are a glycidylamine type epoxy resin, a hydantoin type epoxy resin, an isocyanurate type epoxy resin, an aliphatic chain epoxy resin and the like, and these epoxy resins may be halogenated or hydrogenated. These epoxy resins may be used in combination of two or more.

Examples of the curing agent for the epoxy resin include those used as ordinary curing agents for epoxy resins, such as amines, phenols, acid anhydrides, imidazoles, and dicyandiamide. Furthermore, tertiary amines and organic phosphorus compounds generally used as curing accelerators may be used as appropriate.

As a method of reacting an epoxy resin, cationic polymerization may be carried out using a sulfonium salt, an iodonium salt or the like, instead of using the curing agent.

The adhesive for circuit connection of the present invention is provided with film forming properties, adhesive properties, and stress relaxation properties upon curing.
Polymer components such as polyvinyl butyral resin, polyvinyl formal resin, polyester resin, polyamide resin, polyimide resin, xylene resin, phenoxy resin, polyurethane resin, urea resin, and acrylic rubber can also be used. These polymer components have a molecular weight of 1000
Those having 0 to 10000000 are preferable. Further, these resins may be modified with a radical polymerizable functional group or an epoxy group, and in this case, heat resistance is improved. The compounding amount of the polymer component is 2 to 80% by weight,
% By weight, and particularly preferably from 10 to 60% by weight.
If it is less than 2% by weight, stress relaxation and adhesive strength are not sufficient, and
If it exceeds 0% by weight, the fluidity decreases.

The adhesive for circuit connection of the present invention may optionally contain a filler, a softener, an accelerator, an antioxidant, a coloring agent, a flame retardant, and a coupling agent.

With the adhesive for circuit connection used in the present invention, connection can be obtained by directly contacting opposing electrodes at the time of connection even without conductive particles, but more stable when conductive particles are included. Connection is obtained. As the conductive particles, metal particles such as Au, Ag, Ni, Cu, and solder, and carbon, or particles obtained by coating non-conductive particles of glass, ceramic, or plastic with a noble metal such as Au, Ag, or platinum are used. You. In the case of metal particles, those coated with noble metals are preferable in order to suppress oxidation of the surface. Among the above conductive particles, Au, A
The particles coated with g or the like and the hot-melt metal particles are deformed by heating and pressurizing at the time of connection to increase the contact area, and absorb the height variation of the connection electrode to improve reliability. If the thickness of the noble metal coating layer is 100 ° or more, preferably 300 ° or more, good connection can be obtained. Further, those obtained by coating the conductive particles with an insulating resin can also be used.
The conductive particles are 0.1% with respect to 100 volumes of the adhesive component.
It is appropriately blended in a range of from 30 to 30% by volume, more preferably from 0.1 to 10% by volume depending on the use.

The substrate to be bonded by using the adhesive for circuit connection of the present invention is not particularly limited as long as it is provided with an electrode which requires electrical connection. There are a glass or plastic substrate, a printed wiring board, a ceramic wiring board, a semiconductor silicon chip, a TCP, a two-layer FPC, etc., on which electrodes are formed of ITO or the like, and these are used in combination as needed. In the case of connecting using the above substrate, as a circuit connection adhesive, a first adhesive layer having a high elastic modulus at 50 ° C. is arranged on the substrate side having a small coefficient of thermal expansion. Conditions for connection are not particularly limited, but a connection temperature of 90 to 250 ° C.
Connection time is 1 second to 10 minutes, use purpose, adhesive,
It may be appropriately selected depending on the substrate, and post-curing may be performed as necessary. The connection is performed by heating and pressurizing, but energy other than heat, such as light, ultrasonic waves, and electromagnetic waves, may be used as necessary.

[0028]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. (Preparation of Adhesive) Each of the following formulations was blended and applied to a PET (polyethylene terephthalate) film having a surface treated on one side with a thickness of 50 μm using a simple coating machine (manufactured by Tester Sangyo). A film was prepared by drying with hot air for 5 minutes.

Example 1 (First adhesive layer) A bisphenol A type epoxy resin (Epicoat 828; trade name, manufactured by Yuka Shell Epoxy Co., Ltd.) was used as a thermosetting component. A phenoxy resin (PKHC; trade name, manufactured by Union Carbide, weight average molecular weight 45,000) was used as a film forming material. As a curing agent, a microcapsule type curing agent (HX3941HP; trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.)
And a 0.04 μm thick gold layer was provided on the outside of the nickel layer to produce conductive particles having an average particle size of 4 μm. 40 g of phenoxy resin in solid weight ratio,
Bisphenol A type epoxy resin 20g, microcapsule type curing agent 40g, silane coupling agent (SH
6040; trade name, manufactured by Toray Dow Silicone Co., Ltd.)
1g, and 3% by volume of conductive particles
The mixture was dispersed to obtain a circuit connecting material having an adhesive layer thickness of 6 μm. 50 ° C of cured product obtained by curing this circuit connection material
Had an elastic modulus of 1800 MPa.

(Second adhesive layer) A bisphenol A type epoxy resin (Epicoat 828; trade name, manufactured by Yuka Shell Epoxy Co., Ltd.) was used as a thermosetting component. Acrylic rubber (weight average molecular weight about 800,000, T
g, -22 ° C). As a curing agent, a microcapsule type curing agent (HX3941HP; trade name, manufactured by Asahi Kasei Kogyo Co., Ltd.)
And a 0.04 μm thick gold layer was provided on the outside of the nickel layer to produce conductive particles having an average particle size of 4 μm. 40 g of an acrylic rubber, 10 g of a bisphenol A type epoxy resin, 50 g of a microcapsule type curing agent, and 1 g of a silane coupling agent (SH6040; trade name, manufactured by Dow Silicone Toray Silicone Co., Ltd.), and 3 g of conductive particles % Mixed and dispersed,
A circuit connection material having an adhesive layer thickness of 12 μm was obtained. The cured product obtained by curing this circuit connection material has an elastic modulus at 50 ° C. of 5
It was 00 MPa. The first adhesive layer and the second adhesive layer were laminated using a roll laminator to form a two-layer circuit-connecting adhesive.

(Example 2) (First adhesive layer) A circuit connecting material was obtained in the same manner as in the first adhesive layer of Example 1 except that the thickness of the adhesive layer was 10 µm. (Second adhesive layer) A circuit connecting material was obtained in the same manner as in the second adhesive layer of Example 1 except that the thickness of the adhesive layer was changed to 8 μm. The first adhesive layer and the second adhesive layer were laminated using a roll laminator to form a two-layer circuit connecting adhesive.

(Embodiment 3) As in Embodiment 1, except that T
CP (polyimide 75 μm, adhesive; Toray # 7100,
The connection was made using a copper foil of 18 μm (surface Sn plating).

Comparative Example 1 A circuit connecting material was obtained by using only the first adhesive layer of Example 1 and setting the thickness of the adhesive layer to 18 μm.

Comparative Example 2 A circuit connecting material was obtained by using only the second adhesive layer of Example 1 and setting the thickness of the adhesive layer to 18 μm.

(Preparation of connection structure) The above-mentioned adhesive for circuit connection was slit to a width of 1.5 mm, and ITO was used as an electrode.
The first adhesive layer having a high modulus of elasticity E1 at 50 ° C. of the cured product is placed on the glass substrate on which is formed a glass substrate having a small coefficient of thermal expansion at 80 ° C. for 5 seconds at 1 MPa. Then, it was temporarily connected. After that, the PET substrate is peeled off,
Electrode and a two-layer FPC (pitch 50 μm)
The position of the electrode having a copper foil thickness of 8 μm) was
The main connection was made at 3 ° C. for 15 seconds at 15 ° C. Further, as a reference example of the present invention, the two-layer adhesive of Example 1 was arranged so that the second adhesive layer was on the glass side, and connected under the same conditions.
The circuit connection adhesives of Comparative Examples 1 and 2 were also prepared in the same manner as described above. In the case of the third embodiment, the first adhesive layer is disposed on the glass substrate on which the ITO is formed so that the first adhesive layer is on the glass side.
Temporarily connect under the conditions of 0 ° C, 5 seconds, 1MPa, and double-layer FPC
The connection was made in the same manner as above using TCP instead of.

(Method of evaluating characteristics) Connection resistance: Multimeter TR manufactured by Advantest Corporation
Using 6848, the resistance between adjacent circuits was measured at a constant current of 1 mA. Adhesive strength: Measured at 90 degrees peel according to JIS Z-0237. Observation of the connection part: Peeling of the connection part and the presence or absence of bubbles were observed with a metallographic microscope. Reliability evaluation: Regarding the above connection resistance and adhesive strength, 80
A high-temperature and high-humidity test was performed under the conditions of ° C. and 95% RH. Table 1 shows the evaluation results.

[0037]

[Table 1]

Examples 1 to 3 were all good in connection resistance, adhesive strength and appearance, and showed good connection reliability. On the other hand, in Comparative Examples 1 and 2 having the single-layer structure, in Comparative Example 1, the adhesive strength in the two-layer FPC was reduced. In Comparative Example 2, although the adhesive strength with the two-layer FPC was good, the change in connection resistance was large even after the moisture resistance test, and the connection reliability was poor.

[0039]

According to the present invention, good connection can be obtained by using a so-called two-layer FPC in which a polyimide resin is directly applied to a copper foil or a circuit is formed electrically on the polyimide resin.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 1/24 H01B 1/24 D 5G307 5/16 5/16 H01L 21/60 311 H01L 21/60 311R 311S (72) Inventor Izuo Watanabe 1150 Goshomiya, Shimodate, Ibaraki Pref. HA066 JA09 KA03 LA06 LA09 NA20 5F044 LL09 NN13 NN19 5G301 DA03 DA05 DA06 DA10 DA18 DA29 DA57 DD03 5G307 HA02 HB03 HB06 HC01

Claims (7)

[Claims] An adhesive for circuit connection that is interposed between substrates having opposing circuit electrodes and presses the substrates having opposing circuit electrodes to electrically connect the electrodes in the pressing direction. The adhesive has a first adhesive layer and a second adhesive layer, and the elastic modulus E1 at 50 ° C. of the cured product of the first adhesive layer is 50 ° C. of the cured product of the second adhesive layer. An adhesive for circuit connection, wherein the adhesive has a higher elastic modulus E2. 2. The elastic modulus El of the cured product of the first adhesive layer at 50 ° C. and the elastic modulus E of the cured product of the second adhesive layer at 50 ° C.
2. The adhesive for circuit connection according to claim 1, wherein E1 / E2 = 1.1 to 50 obtained from (2). 3. The adhesive for circuit connection according to claim 1, wherein at least one of the first adhesive layer and the second adhesive layer contains conductive particles. 4. The ratio of the thickness of the first adhesive layer to the thickness of the second adhesive layer is: thickness of the second adhesive layer / thickness of the first adhesive layer = 0.3.
The adhesive for circuit connection according to any one of claims 1 to 3, wherein the adhesive is from 3.0 to 3.0. 5. The adhesive for circuit connection according to claim 1, which is interposed between substrates having opposing circuit electrodes, and the substrate having opposing circuit electrodes is pressurized and applied. A circuit connection method for electrically connecting between electrodes in a pressure direction, wherein a first adhesive layer is arranged and connected to a substrate having a smaller coefficient of thermal expansion among substrates having opposing circuit electrodes. 6. The adhesive for circuit connection according to claim 1, which is interposed between substrates having opposing circuit electrodes, and the substrate having opposing circuit electrodes is pressurized and applied. A connection structure in which electrodes in a pressure direction are electrically connected, wherein the adhesive has a first adhesive layer and a second adhesive layer, and a cured product of the first adhesive layer at 50 ° C. The modulus of elasticity El is higher than the modulus of elasticity E2 of the cured product of the second adhesive layer at 50 ° C., and the first adhesive layer is formed on the side of the substrate having the smaller coefficient of thermal expansion among the substrates having opposing circuit electrodes. Connection structure placed and connected. 7. A connection structure according to claim 6, wherein one of the circuit electrodes facing each other has a height of 5 to 14 μm.