JP2001302884A - Electrodonductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electroconductive paste excellent in curability. SOLUTION: This electroconductive paste comprises a binder comprising 10-90 wt.% of an epoxy resin and 10-90 wt.% of a phenol resin and a curing agent therefor and an electroconductive powder. The amounts of the binder and electroconductive powder are 5-15 wt.% of the binder and 95-85 wt.% of the electroconductive powder in the electroconductive paste. The electroconductive powder is preferably a copper powder, a copper alloy powder, a silver-coated copper powder or a silver-coated copper alloy powder. The silver-coated copper powder and the silver-coated copper alloy powder are preferably degrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste used for embedding in a through hole or a non-through hole for interlayer connection of a multilayer printed wiring board or the like, and more particularly to a conductive paste for filling a build-up multilayer wiring board.

[0002]

2. Description of the Related Art In a conventional multilayer printed wiring board, through holes or non-through holes for interlayer connection are formed in a multilayer substrate obtained through a multi-layer lamination process by heating and pressing, as shown in FIG. In this method, copper plating 1 is applied to the holes, or a conductive paste 2 is printed or filled. In FIG. 1, reference numeral 3 denotes a copper foil.

In general, in a multilayer lamination process using a hole-filling conductive paste, build-up layers in which holes are filled with a conductive paste and preliminarily dried are stacked, and heating and pressurizing are performed as main drying. Therefore, the conductive paste needs to be hardened after the main drying, and the conductivity needs to be improved by pressing after lamination as compared with the case where no pressing is performed.

[0004] In the conventional hole filling conductive paste, the main component of the binder is an epoxy resin, and imidazoles are generally used as a hardening agent thereof. When the conductive powder is copper powder, the copper alloy powder contains copper. When the portion is exposed on the surface, and when the copper portion is exposed on the surface of the silver-coated copper powder or the silver-coated copper alloy powder, the conductive paste tends to be uncured. It is considered that this is because the imidazole as a curing agent forms a chelate bond with copper and does not function as a curing agent for the epoxy resin, so that the epoxy resin does not cure and the conductive paste becomes uncured.

The use of a highly conductive metal powder such as silver can eliminate the disadvantages, but the conductive paste becomes expensive. In order to use copper powder or copper alloy powder or conductive powder with silver-covered copper powder or silver-coated copper alloy powder whose copper part is exposed on the surface, it does not form a chelate bond with copper and cures the epoxy resin. It is necessary to add substances that act as agents.

[0006]

The first object of the present invention is to provide a conductive paste having excellent curability. According to a second aspect of the present invention, in addition to the first aspect, a conductive paste having an excellent effect of improving curability is provided. The third and fourth aspects of the present invention provide a conductive paste having excellent migration properties in addition to the first aspect of the present invention. The invention according to claim 5 is
In addition to the first aspect, the present invention provides a conductive paste having excellent conductivity.

[0007]

According to the present invention, there is provided an epoxy resin of 10 to 90% by weight and a phenol resin of 10 to 90% by weight.
And a binder containing the curing agent, and a conductive paste containing conductive powder. In addition, the present invention, the conductive powder,
The present invention relates to a conductive paste that is copper powder or copper alloy powder. Also,
The present invention relates to a conductive paste in which the conductive powder is silver-coated copper powder or silver-coated copper alloy powder.

[0008] The present invention also relates to a conductive paste wherein the silver-coated copper powder or silver-coated copper alloy powder is pulverized silver-coated copper powder or silver-coated copper alloy powder. Further, in the present invention, the mixing ratio of the binder and the conductive powder is such that the binder is 5 to 15% by weight and the conductive powder is 85 to 95% based on the solid content of the conductive paste.
% By weight of the conductive paste.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a binder in the present invention, an epoxy resin, a phenol resin and a curing agent thereof are used. Among these, known phenol resins such as novolak type and resol type are used. The epoxy resin is preferably liquid at room temperature. Those that crystallize at room temperature can avoid crystallization by mixing with a liquid. The epoxy resin that is liquid at room temperature includes, for example, a resin that is solid at room temperature or that becomes stable at room temperature by mixing with an epoxy resin that is liquid at room temperature. In the present invention, the normal temperature means a temperature of about 25 ° C.

As the epoxy resin used in the present invention, known resins are used, and compounds containing two or more epoxy groups in the molecular weight, such as bisphenol A, bisphenol AD, bisphenol F, novolak, cresol novolaks and epichlorohydrin Aliphatic epoxy resins such as polyglycidyl ether, dihydroxynaphthalenediglycidyl ether, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, and heterocyclic epoxies such as diglycidyl hydantoin, vinylcyclohexene dioxide, Alicyclic epoxy resins such as cyclopentanedienedoxide and alicyclic diepoxy adipate are exemplified.

In the present invention, a flexibility-imparting agent is used if necessary. As the flexibility-imparting agent, known compounds are used, and compounds having only one epoxy group in the molecular weight, for example, n-butyl glycidyl ether, versidic acid glycidyl ester, styrene oxide, ethylhexyl glycidyl ether, phenyl glycidyl ether, cresylate Conventional epoxy resins such as jyl glycidyl ether, butylphenyl glycidyl ether and the like can be mentioned. These epoxy resins and flexibility-imparting agents can be used alone or in combination of two or more.

It is preferable to use a phenolic resin and a conventionally used curing agent since the solvent resistance of the cured conductive paste is improved. It is also preferable to use or combine curing agents having different melting points and dissociation temperatures because the semi-cured state of the conductive paste can be controlled.

As the curing agent, imidazoles are preferable from the viewpoint of pot life, and other examples thereof include amines such as mensendiamine, isophoronediamine, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, and methylenedianiline. , Phthalic anhydride, trimellitic anhydride, pyromellitic anhydride,
Succinic anhydride, acid anhydrides such as tetrahydrophthalic anhydride, compound-based curing agents such as dicyandiamide may be used, if necessary, may be used in combination with a curing agent such as a latent amine curing agent, Further, a compound such as a tertiary amine, triphenylphosphine, or tetraphenylphosphenyl borate may be added.

The content of the above curing agent is in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the epoxy resin in terms of the glass transition point (hereinafter referred to as Tg) of the cured conductive paste. It is more preferable that the content is in the range of 1 to 10 parts by weight.

The mixing ratio of the epoxy resin and the phenol resin is preferably 10 to 90% by weight of the epoxy resin and 10 to 90% by weight of the phenol resin, and 10 to 70% by weight of the epoxy resin and 30 to 90% by weight of the phenol resin.
Is more preferable. If the blending ratio of the phenolic resin is less than 10% by weight, the curability of the conductive paste may not be improved. By using 10% by weight or more of the phenol resin, the conductivity is improved. The conductivity increases as the blending ratio increases, but the upper limit is also limited. In some cases, the subsequent conductivity may not be improved as compared with the case where no pressure is applied.

This is because the gelling of the phenol resin proceeds to some extent during predrying, so that the volume of the conductor does not become so small even when heated and pressed after predrying, and the conductive powder does not become dense, so that the conductivity is improved. It is considered not to be. Even when the blending ratio of the phenolic resin exceeds 90% by weight, the pre-drying can be performed under appropriate conditions to improve the conductivity after heating and pressing, but the working width of the pre-drying conditions is reduced, It is difficult to control the semi-cure state of the conductive paste, which is not preferable.

To the binder used in the present invention, a thixotropic agent, a coupling agent, an antifoaming agent, a powder surface treating agent, an anti-settling agent, etc. are added, if necessary, in addition to the above-mentioned materials, followed by uniform mixing. can get. Thixotropic agents added as needed,
The content of the coupling agent, the defoaming agent, the powder surface treating agent, the anti-settling agent and the like is preferably in the range of 0.01 to 1% by weight based on the conductive paste, and is preferably 0.03 to 0.5% by weight. % Is more preferable.

As the conductive powder, it is preferable to use copper powder, copper alloy powder, silver-coated copper powder, or silver-coated copper alloy powder, and the smaller the particle size, the more preferable. Preferably, a powder of 1 to 10 μm is more preferred. In addition, when silver-coated copper powder or silver-coated copper alloy powder is used, if the pulverized silver-coated copper powder or silver-coated copper alloy powder is used, agglomerated silver-coated copper powder or silver-coated copper alloy powder that is not subjected to pulverization treatment is used. Since it has a higher bulk density, it is preferable as a conductive powder to be filled in small-diameter holes.

If the conductive powder has few contact points, the resistance tends to increase. In order to increase the contact area between the particles of the conductive powder and obtain high conductivity, it is preferable to apply an impact to the conductive powder to deform the shape of the particles into a flat shape, but the conductive paste using the flat conductive powder is Since the viscosity is higher than that of the conductive paste using the substantially spherical conductive powder, the embedding work becomes difficult. Further, from the viewpoint of workability and conductivity in the Y-axis direction of the hole when the conductive paste is embedded in the hole, it is preferable to use a conductive paste using a substantially spherical conductive powder rather than a flat conductive powder.

In order to coat the surface of copper powder or copper alloy powder with silver or silver alloy, there are methods such as displacement plating, electroplating, and electroless plating. It is preferable to cover with displacement plating because of high adhesion and low running cost. The coating amount of silver or silver alloy on the surface of copper powder or copper alloy powder is preferably in the range of 5 to 25% by weight based on copper powder or copper alloy powder from the viewpoints of migration resistance, cost, and improvement in conductivity. , 1
The range of 0 to 23% by weight is more preferable.

The exposed area of the copper powder or copper alloy powder is preferably in the range of 10 to 50% from the viewpoints of migration resistance, solderability, oxidation of the exposed portion, conductivity, etc., and 10 to 30%.
Is more preferable. In addition, it is preferable to use an alloy powder of copper and tin, copper and zinc, etc. as the above-mentioned copper alloy powder. As the silver alloy, an alloy of silver and palladium, silver and platinum, or the like is preferably used.

The substantially spherical conductive powder of the present invention has an aspect ratio of 1 to 1.5 and an average long particle diameter of 1 to 20.
It is preferable to use conductive powder of μm, and it is more preferable to use conductive powder having an aspect ratio of 1 to 1.3 and a long diameter having an average particle diameter of 1 to 10 μm. The average particle size mentioned above can be measured by a laser scattering type particle size distribution measuring device. In the present invention, the measurement was performed using a master sizer (manufactured by Malvern) as the device.

The aspect ratio in the present invention refers to the ratio of the major axis to the minor axis (major axis / minor axis) of the conductive powder particles. In the present invention, the particles of the conductive powder are mixed well in the curable resin having a low viscosity, and the resin is cured while allowing the particles to settle by standing, and the obtained cured product is cut in the vertical direction. The shape of the particles appearing on the cut surface is observed under magnification with an electron microscope, and the major axis / minor axis of each particle is obtained for at least 100 particles, and the average value thereof is defined as the aspect ratio.

Here, the minor axis is selected so that a particle appearing on the cut surface sandwiches a combination particle of two parallel lines contacting the outside of the particle, and two of the combinations having the shortest interval are selected. The distance between the parallel lines. On the other hand, the major axis is the two parallel lines perpendicular to the parallel line that determines the minor axis, and is the distance between the two parallel lines that are the longest among the combinations of the two parallel lines that contact the outside of the particle. is there. The rectangle formed by these four lines is sized to fit the particle exactly inside it. The specific method used in the present invention will be described later.

The mixing ratio of the binder and the conductive powder is preferably in the range of 5 to 15% by weight of the binder and 85 to 95% by weight of the conductive powder, and 7 to 13% by weight of the binder. The conductive powder is more preferably in the range of 87 to 93% by weight. When the amount of the binder is less than 5% by weight and the amount of the conductive powder exceeds 95% by weight, the viscosity, adhesive strength, strength and reliability of the conductive paste tend to decrease, and
If it exceeds 5% by weight and the conductive powder is less than 85% by weight, the conductivity tends to decrease.

The conductive paste of the present invention can be used together with the binder, conductive powder and thixo agent, coupling agent, defoaming agent, powder surface treating agent, anti-settling agent, etc. It can be obtained by uniformly mixing and dispersing with a kneader, three rolls or the like.

[0027]

The present invention will be described below with reference to examples.

Example 1 Bisphenol A type epoxy resin (oiled shell epoxy)
54 parts by weight, phenolic resin (manufactured by Kanebo Co., Ltd., trade name Bellpearl S-890)
40 parts by weight and 6 parts by weight of 2-phenyl-4-methyl-5-hydroxymethylimidazole (manufactured by Shikoku Chemicals Co., Ltd., trade name: Curesol 2P4MHZ) were uniformly mixed to prepare a binder. The mixing ratio of the epoxy resin and the phenol resin was 57.5% by weight of the epoxy resin and 42.5% by weight of the phenol resin.

Thereafter, spherical copper powder (trade name: SFR-Cu, manufactured by Nippon Atomize Processing Co., Ltd.) 4 having an average particle size of 5.1 μm, prepared by the atomization method, was added to 50 g of the binder obtained above.
50 g and 15 g of 3-methyl-3-methoxybutanol (manufactured by Kuraray Co., Ltd., Solfit) as a solvent were added, and the mixture was uniformly mixed and dispersed with a stirrer and a three-roll mill to obtain a conductive paste. The mixing ratio of the binder and the conductive powder is such that the binder is 1 to the solid content of the conductive paste.
0% by weight and 90% by weight of conductive powder.

Next, using the conductive paste obtained above, a test pattern 4 shown in FIG. 2 was printed on a polyethylene terephthalate film pre-shrinked at 172 ° C., preliminarily dried at 90 ° C. for 20 minutes, and then dried at 170 ° C. 2.5MP
Heating and pressurizing treatment was performed for 1 hour under the condition of a to obtain a wiring board. In FIG. 2, reference numeral 5 denotes a polyethylene terephthalate film.

Next, the curability of the conductive paste of the obtained wiring board was evaluated by the hand-drawing method (K5400) of the pencil scratch test for paint film of JIS, and the evaluation was 6H. The specific resistance of the conductor was 57.2 μΩ · m.

Comparative Example 1 Bisphenol A type epoxy resin 86 used in Example 1
Parts by weight, 5 parts by weight of phenol resin and 2-phenyl-4
9 parts by weight of -methyl-5-hydroxymethylimidazole was uniformly mixed to prepare a binder. The mixing ratio of the epoxy resin and the phenol resin is 94.5 for the epoxy resin.
Wt% and 5.5 wt% phenolic resin.

Next, 50 g of the binder obtained above had an average particle size of 5.1 μm produced by the atomizing method used in Example 1.
m of spherical copper powder (450 g) and 15 g of 3-methyl-3-methoxybutanol used in Example 1 were added, and the mixture was uniformly mixed and dispersed with a stirrer and a three-roll mill to obtain a conductive paste. The blending ratio of the binder and the conductive powder was 10% by weight of the binder and 90% by weight of the conductive powder based on the solid content of the conductive paste.

Thereafter, a wiring board was obtained through the same steps as in Example 1. As to the obtained wiring board, the curability of the conductive paste was evaluated by the same scratching method as in Example 1 in a pencil scratch test for a coating film. As a result, the evaluation was 6B, and the conductive paste was uncured.

Example 2 1 kg of spherical copper powder having an average particle size of 5.1 μm produced by the atomizing method used in Example 1 was washed with diluted hydrochloric acid and pure water, and then 80 g of AgCN and 1 g of NaCN per liter of water.
Substitution plating was performed with a plating solution containing 75 g so that the amount of silver was 18% by weight with respect to the spherical copper powder, washed with water and dried to obtain a silver-plated copper powder.

Thereafter, 750 g of the silver-plated copper powder obtained above and 3 kg of zirconia balls having a diameter of 5 mm were put into a 2 liter ball mill container, and rotated for 40 minutes. A substantially spherical silver-plated copper powder having a particle size of 5.5 μm was obtained. Five particles of the obtained substantially spherical silver-plated copper powder were taken out and quantitatively analyzed with a scanning Auger electron spectrometer to examine the exposed area of copper.
The average was 20% in the range of 0%.

Next, 450 g of the substantially spherical silver-plated copper powder obtained above and 15 g of 3-methyl-3-methoxybutanol used in Example 1 were added to 50 g of the binder obtained in Example 1, and a stirrer was used. The conductive paste was obtained by uniformly mixing and dispersing with a three-roll mill. The mixing ratio of the binder and the conductive powder is such that the binder is 10% based on the solid content of the conductive paste.
% By weight and 90% by weight of conductive powder.

Thereafter, a wiring board was obtained through the same steps as in Example 1. As to the obtained wiring board, the curability of the conductive paste was evaluated by the same method as that of Example 1 in the pencil scratch test for paint film, and the evaluation was 6H. The specific resistance of the conductor was 7.2 μΩ · m. The specific resistance of the conductor was lower in the conductive paste using the silver-plated copper powder than in the conductive paste using the copper powder alone.

The specific method of measuring the aspect ratio in this embodiment will be described below. 8 g of a base material (No. 10-8130) of a low-viscosity epoxy resin (manufactured by Buehler) and 2 g of a curing agent (No. 10-8132) are mixed, and 2 g of conductive powder is mixed and dispersed well, and the mixture is left as it is. After degassing in vacuo at a temperature of 30 ° C., the particles were allowed to stand at 30 ° C. for 10 hours to settle and harden the particles. Thereafter, the obtained cured product was cut in the vertical direction, the cut surface was magnified 1000 times with an electron microscope, and the long diameter / short diameter of 150 particles that appeared on the cut surface was obtained. Ratio.

Example 3 Bisphenol A type epoxy resin 20 used in Example 1
Parts by weight, 78 parts by weight of a phenol resin and 2-phenyl-
2 parts by weight of 4-methyl-5-hydroxymethylimidazole was uniformly mixed to obtain a binder. The mixing ratio of the epoxy resin and the phenol resin is 20.
4% by weight and 79.6% by weight of phenolic resin.

Next, 450 g of the substantially spherical silver-plated copper powder obtained in Example 2 and 15 g of 3-methyl-3-methoxybutanol used in Example 1 were added to 50 g of the binder obtained above, and a stirrer was used. The conductive paste was obtained by uniformly mixing and dispersing with a three-roll mill. The mixing ratio of the binder and the conductive powder is such that the binder is 10% based on the solid content of the conductive paste.
% By weight and 90% by weight of conductive powder.

Thereafter, a wiring board was obtained through the same steps as in Example 1. As to the obtained wiring board, the curability of the conductive paste was evaluated by the same method as that of Example 1 in the pencil scratch test for paint film, and the evaluation was 6H. The specific resistance of the conductor was 4.1 μΩ · m.

Comparative Example 2 Bisphenol A type epoxy resin 86 used in Example 1
Parts by weight, 5 parts by weight of phenol resin and 2-phenyl-4
9 parts by weight of -methyl-5-hydroxymethylimidazole was uniformly mixed to prepare a binder. The mixing ratio of the epoxy resin and the phenol resin is 94.5 for the epoxy resin.
Wt% and 5.5 wt% phenolic resin.

Next, 450 g of the substantially spherical silver-plated copper powder obtained in Example 2 and 15 g of 3-methyl-3-methoxybutanol used in Example 1 were added to 50 g of the binder obtained above, and the mixture was stirred. The conductive paste was obtained by uniformly mixing and dispersing with a three-roll mill. The mixing ratio of the binder and the conductive powder is such that the binder is 10% based on the solid content of the conductive paste.
% By weight and 90% by weight of conductive powder.

Thereafter, a wiring board was obtained through the same steps as in Example 1. As to the obtained wiring board, the curability of the conductive paste was evaluated by the same scratching method as in Example 1 in a pencil scratch test for a coating film. As a result, the evaluation was 6B, and the conductive paste was uncured.

Comparative Example 3 6 parts by weight of the bisphenol A type epoxy resin used in Example 1, 93 parts by weight of the phenol resin and 2-phenyl-4
1 part by weight of -methyl-5-hydroxymethylimidazole was uniformly mixed to obtain a binder. The mixing ratio of the epoxy resin and the phenol resin was 6.1% by weight of the epoxy resin and 93.9% by weight of the phenol resin.

Next, 450 g of the substantially spherical silver-plated copper powder obtained in Example 2 and 15 g of 3-methyl-3-methoxybutanol used in Example 1 were added to 50 g of the binder obtained above, and the mixture was stirred. The conductive paste was obtained by uniformly mixing and dispersing with a three-roll mill. The mixing ratio of the binder and the conductive powder is such that the binder is 10% based on the solid content of the conductive paste.
% By weight and 90% by weight of conductive powder.

Thereafter, a wiring board was obtained through the same steps as in Example 1. For the obtained wiring board, the curability of the conductive paste was evaluated by the same scratching method as in Example 1 by a pencil scratch test for a coating film. The evaluation was 6H. Compared to 2 and 3, it was as high as 8.6 μΩ · m despite the large amount of phenolic resin.

Example 4 A substantially spherical silver-plated copper powder obtained in Example 2 and 1 kg of zirconia balls having a diameter of 1 mm were placed in a 2 liter ball mill container.
And then rotated for 30 minutes to pulverize the substantially spherical silver-plated copper powder and use the same process as in Example 2 to obtain a wiring board. As to the obtained wiring board, the curability of the conductive paste was evaluated by the same method as that of Example 1 in the pencil scratch test for paint film, and the evaluation was 6H. The specific resistance of the conductor was 6.9 μΩ · m.

Example 5 A wiring board was obtained by performing the same steps as in Example 3 except that the substantially spherical silver-plated copper powder obtained in Example 2 was pulverized and used in the same manner as in Example 4. . As to the obtained wiring board, the curability of the conductive paste was evaluated by the same method as that of Example 1 in the pencil scratch test for paint film, and the evaluation was 6H. The specific resistance of the conductor was 4.6 μΩ · m.

Comparative Example 4 A wiring board was obtained by performing the same process as in Comparative Example 2 except that the substantially spherical silver-plated copper powder obtained in Comparative Example 2 was pulverized and used in the same manner as in Example 4. . As to the obtained wiring board, the curability of the conductive paste was evaluated by the same scratching method as in Example 1 in a pencil scratch test for a coating film. As a result, the evaluation was 6B, and the conductive paste was uncured.

Comparative Example 5 A wiring board was obtained by performing the same steps as in Comparative Example 3 except that the substantially spherical silver-plated copper powder obtained in Comparative Example 3 was granulated and used in the same manner as in Example 4. . For the obtained wiring board, the curability of the conductive paste was evaluated by the same scratching method as in Example 1 by a pencil scratch test for a coating film. The evaluation was 6H. Compared with Nos. 4 and 5, although the amount of the phenol resin was large, it was as high as 9.2 μΩ · m.

[0053]

The conductive paste according to the first aspect of the present invention is
Excellent curability. The conductive paste according to the second aspect of the invention has the effects described in the first aspect, and is further excellent in the effect of improving curability. The conductive paste according to the third and fourth aspects of the present invention has the effect of the first aspect, and is further excellent in migration properties. The conductive paste of the invention according to claim 5 is:
The effects described in claim 1 are achieved, and the conductivity is further improved.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing a state in which through holes for interlayer connection of a multilayer printed wiring board are connected by copper plating, and FIG.
FIG. 3 is a cross-sectional view showing a state in which through holes for interlayer connection of a multilayer printed wiring board are connected by a conductive paste.

FIG. 2 is a plan view showing a test pattern formed on a polyethylene terephthalate film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper plating 2 Conductive paste 3 Copper foil 4 Test pattern 5 Polyethylene terephthalate film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 1/22 H01B 1/22 A H05K 3/46 H05K 3/46 NF term (Reference) 4J002 CC04X CD01W CD02W CD04W CD05W CD06W CD13W DA077 DC007 EF066 EL136 EN036 EN076 ER026 EU116 EV216 EW016 EY016 FB047 FB077 FD117 FD14X FD146 FD200 GQ02 HA08 4J036 AA01 DA01 FA02 FB07 JA08 JA15 KA07 5E346 DA31 CC31 DA31 CC31 DA31 CC01

Claims (5)

[Claims] 1. A conductive paste comprising a binder containing 10 to 90% by weight of an epoxy resin and 10 to 90% by weight of a phenol resin and a curing agent thereof, and a conductive powder. 2. The conductive paste according to claim 1, wherein the conductive powder is copper powder or copper alloy powder. 3. The conductive paste according to claim 1, wherein the conductive powder is silver-coated copper powder or silver-coated copper alloy powder. 4. The conductive paste according to claim 1, wherein the silver-coated copper powder or silver-coated copper alloy powder is pulverized silver-coated copper powder or silver-coated copper alloy powder. 5. The compounding ratio of the binder and the conductive powder is 5 to 15% by weight of the binder and 85 to 95% by weight of the conductive powder based on the solid content of the conductive paste. The conductive paste as described in the above.