JPH08293213A - Conductive paste for metal plating substrate - Google Patents

Abstract

PURPOSE: To provide circuit material which has a low cost and is solderable in a flexible printcircuit. CONSTITUTION: Conductive paste for metal plating substrate is used when metal plating is conducted so as to form a circuit after the conductive paste is printed on insulating base material. Main components are composed of conductive powder A whose main component is silver powder in which primary particles of particle diameter of 0.1 to 5μm are three dimensionally coupled to form secondary particles of higher-order structure of 1 to 20μm in a shape, a binding agent B whose glass transition point temperature is -50 to 20 deg.C and whose reduction viscosity is 0.3dl/g or more, a curing agent C which can react with the binding agent B, and solvent D. Where, A/(B+C) is 60/40 to 95/5 (weight ratio), B/C is 50/50 to 99/1 (weight ratio), and breaking ductility is 20% or more after curing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste, more specifically, a conductive paste is printed and cured on a film or a substrate to form a circuit, and a metal plating is applied on the circuit to form a circuit. The present invention relates to a conductive paste for metal plating base used for producing.

[0002]

2. Description of the Related Art At present, an FPC having a circuit formed by etching a copper-clad polyimide film (FCL) is used for a flexible printed circuit. This FPC is an excellent material that can be soldered and has a high degree of bending resistance, reliability, and heat resistance, but the polyimide film that is the base material is expensive, and many processes including etching processes are required. It is very expensive because it requires a process.
There is a demand for the development of inexpensive circuit materials that replace C. On the other hand, a membrane circuit in which a conductive paste is printed on a PET film is low in cost and lightweight, and is widely used for keyboards, switches and the like. However, since silver or carbon paste is usually used as the conductive paste, soldering cannot be performed and it is difficult to mount components. Also,
Since the circuit resistance is also much higher than that of copper foil, the impedance characteristics are inferior, and the application is greatly limited.

[0003]

In order to solve the above-mentioned problems, an insulating base material is printed with an electrically conductive paste, cured, and then plated with a metal to provide an inexpensive circuit material having performance equivalent to that of an FPC. The additive method of creating is being considered. For example, Japanese Patent Laid-Open No. 6-
No. 1,206,43, JP-A-60-136394, JP-A-64-51691 and the like are known, and as the conductive pastes described therein, commercially available conductive pastes for membranes are used as they are. It hasn't been examined enough, and there is nothing satisfactory. That is, the above-mentioned conductive paste has sufficient adhesiveness to the base material in a state where it is printed and cured on the insulating base material, but if metal plating is applied on this, good adhesiveness to the base material cannot be obtained. Moreover, it is not practically used because it is inferior in durability such as humidity resistance and heat resistance. In addition, JP-A-61-22
Japanese Patent No. 4491 and Japanese Patent Application Laid-Open No. 57-15487 discuss an additive method using an ultraviolet or electron beam curable conductive paste, but these require high temperature heat treatment when the conductive paste is cured. Therefore, the deformation of the substrate such as a paper phenol substrate can be prevented, but the adhesive strength after metal plating is poor and it has not been put to practical use. In particular, it cannot be used for a flexible substrate such as a polyimide film or a PET film due to its remarkably poor adhesion. In addition, since these materials are inferior in heat resistance and humidity resistance, they have hardly been put into practical use. Further, as a known conductive paste, there is JP-A-59-206459. This is a silver paste for membrane circuits that uses ordinary flake-shaped or spherical silver powder and a polybutadiene-based binder, but relatively good properties are obtained in normal use (applications without metal plating). However, if metal plating is applied on this, good adhesive strength cannot be obtained. In JP-A-1-159906, flakes (flakes)
A silver paste using silver powder and a copolyester resin as a binder is known, and in this case as well, it has excellent adhesion, flexibility, and conductivity in normal use, but it is good when used as a base for metal plating. Can not obtain good adhesive strength. That is, this silver paste uses flakes as silver powder, and further, the fracture elongation described later of the cured product of this silver paste is as low as about 5%, so good adhesive strength after metal plating cannot be obtained. ..

[0004]

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to solve such a problem. As a result, primary particles having a particle diameter of 0.1 to 5 μm are connected in a three-dimensional shape. A conductive powder mainly composed of silver powder having a secondary particle having a higher-order structure of 1 to 20 μm and a glass transition temperature of −50 to 20 ° C.,
A conductive paste characterized by using a binder having a reduced viscosity of 0.3 dl / g or more and having a breaking elongation after curing of 20% or more is an insulating substrate, particularly an organic film represented by PET. The inventors of the present invention have found that the adhesiveness after plating can be remarkably improved, and further, the heat resistance and the moisture resistance are excellent, and have reached the present invention. That is, the present invention is a conductive paste for a metal plating base used for forming a circuit by metal plating after printing a conductive paste on an insulating base material, and having a particle size of 0.1 to 5 μm. Of the conductive powder (A) mainly composed of silver powder in which the primary particles of (1) are three-dimensionally connected to form secondary particles having a higher-order structure of 1 to 20 μm, the glass transition temperature is −50 to 20 ° C., and the reduced viscosity is 0.3 dl / g
The above-mentioned binder (B), a curing agent (C) capable of reacting with the binder (C) and a solvent (D) as the main components, and (A) / ((B) +
(C)) is 60/40 to 95/5 (weight ratio) and (B)
/ (C) is 50/50 to 99/1 (weight ratio), and the breaking elongation after curing is 20% or more.

The conductive powder (A) used in the present invention has a shape as shown in FIG. 1 in which primary particles having a particle size of 0.1 to 5 μm, preferably 0.2 to 1 μm are connected in a three-dimensional manner. 1 to
The conductive powder is mainly composed of silver powder in which secondary particles having a higher order structure of 20 μm, preferably 2 to 10 μm are formed. The shape of this silver powder is completely different from the known dendritic (dendritic) shape found in electrolytic silver and the like described in JP-A-1-159906.
The preferred specific surface area of this silver powder is 1.0 to ^2.5 m ² /
g, and more preferably 1.3 to 2.2 m ² / g.
Surprisingly, the use of this form of silver powder provides excellent post-metal-plating adhesion to insulating substrates, especially flexible organic films typified by PET. Good specific resistance can be obtained with known flake silver powder, but the adhesive strength after metal plating is low and not practical,
Spherical silver powder cannot be used because of its extremely high specific resistance. Further, the above-mentioned known dendritic silver powder is not preferable because the paste viscosity becomes high, and the adhesive strength after metal plating is also poor. As the conductive powder (A) used in the present invention, known flaky silver powder, spherical silver powder, dendritic silver powder, graphite powder, carbon powder, nickel powder, copper powder, aluminum powder, indium powder, etc. 1 may be used in combination, but the shape as shown in FIG. 1 is obtained by connecting primary particles having a particle diameter of 0.1 to 5 μm in a three-dimensional shape.
It is necessary to use at least 50% or more, preferably 70% or more of the total amount of the conductive powder, of the silver powder on which secondary particles having a high-order structure of 20 μm are formed.

The blending amount of the conductive powder (A) used in the present invention is (A) / ((B) + (C)) (weight ratio) is 60/4.
0 to 95/5, preferably 70/30 to 85/1
It is 5. When (A) is less than 60/40 in (A) / ((B) + (C)), good conductivity cannot be obtained, and 95 /
When it exceeds 5, the adhesiveness to the organic film after metal plating is deteriorated.

The type of the binder (B) used in the present invention is not limited, but as described later, it is necessary that a breaking elongation of 20% or more can be obtained after the silver paste is cured. Further, as the kind of the binder (B), when an organic film such as a PET film is used as a base material,
Polyurethane resin and / or copolyester resin are most preferred from the viewpoint of adhesion and flex resistance after metal plating on a substrate.

The compounding ratio of the binder (B) and the curing agent (C) used in the present invention is such that (B) / (C) (weight ratio) is 50.
/ 50 to 99/1, preferably 70/30 to 85/15
Is. If (B) / (C) is out of the above range, the bending resistance and the adhesiveness after metal plating become poor.

The conductive paste of the present invention must have a breaking elongation after curing of 20% or more, preferably 80% or more. If the breaking elongation is less than 20%, good adhesiveness after metal plating cannot be obtained.

The binder (B) of the present invention has a glass transition temperature of −50 to 20 ° C., preferably −35 to 0 ° C., more preferably −35 to −15 ° C., and a reduced viscosity of 0.3 dl.
/ G or more, preferably 0.5 to 1.5 dl / g. If the glass transition temperature is less than -50 ° C, good adhesion after metal plating cannot be obtained, and environmental characteristics such as moisture resistance deteriorate. If it exceeds 20 ° C, good breaking strength and breaking elongation after curing cannot be obtained, and therefore good adhesiveness after metal plating cannot be obtained. The reduced viscosity is 0.
If it is less than 3 dl / g, good elongation at break cannot be obtained after curing, and thus good adhesion after metal plating cannot be obtained. In addition, the paste viscosity decreases, which is not preferable.

When a polyurethane resin is used as the binder (B) of the present invention, a molecular weight of 500 is obtained by a known method.
What was synthesize | combined by making the above-mentioned polyol and the chain extender of molecular weight less than 500 react with an isocyanate compound as needed can be used. Polyether polyols, (meth) acrylic polyols, polyester polyols, polycarbonate diols, polybutadiene polyols and the like are used as the polyol having a molecular weight of 500 or more for the polyurethane resin.
Polyester polyols are preferred for durability. Among the polyester polyols, it is particularly preferable to use the aliphatic polyester polyol in an amount of 50% by weight or more of the polyester polyol from the viewpoint of adhesive strength after metal plating. Known polyols such as neopentyl glycol, 1,6-hexanediol, ethylene glycol, HPN (hydroxypivalic acid ester of neopentyl glycol), trimethylolpropane, and glycerin are used as the chain extender having a molecular weight of less than 500. Can be mentioned. Further, a carboxyl group-containing polyol such as dimethylolpropionic acid can be used as a chain extender. The diisocyanate compound used for the polyurethane resin is tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate,
Examples thereof include hydrogenated xylylene diisocyanate and isophorone diisocyanate.

When a polyurethane resin is used as the binder (B), a urethane group obtained by reacting 100 parts by weight of a polyester diol having a molecular weight of 500 or more with 0 to 40 parts by weight of a chain extender having a molecular weight of less than 500 with an organic diisocyanate compound. A polyurethane resin having a concentration of 500 to 4000 equivalents / 10 ⁶ g is more preferable in terms of adhesive strength and durability after metal plating.

When the copolymerized polyester resin is used as the binder (B) of the present invention, the one obtained by polycondensation under reduced pressure by a known method can be used. The copolyester is preferably saturated polyester. Also,
After polymerization of polyester resin, cyclic ester such as ε-caprolactone is post-added (ring-opening addition) at 180 to 230 ° C.
It may be blocked to give an acid value by post-adding an acid anhydride such as trimellitic anhydride or phthalic anhydride. Dicarboxylic acids copolymerized with polyester include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid and 2,6-naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, azelaic acid. Aliphatic dicarboxylic acids, such as
SLB-12, ULB-20, SL-20, SB-2
0, ST-2, PML-6CM, IPU-22 (all manufactured by Okamura Oil Co., Ltd.), etc., a dibasic acid having 12 to 28 carbon atoms, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid. 1,2-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic anhydride, 3
-Methylhexahydrophthalic anhydride, 2-methylhexahydrophthalic anhydride, dicarboxyhydrogenated bisphenol A, dicarboxyhydrogenated bisphenol S, dimer acid, hydrogenated dimer acid, hydrogenated naphthalene dicarboxylic acid, tricyclodecane dicarboxylic acid And alicyclic dicarboxylic acids such as In addition, polyvalent carboxylic acids such as trimellitic anhydride and pyromellitic anhydride, unsaturated dicarboxylic acids such as fumaric acid, and sulfonic acids such as 5-sulfoisophthalic acid sodium salt, etc., within a range not impairing the content of the invention. You may use together the metal-base containing dicarboxylic acid. The alkylene glycol used in the polyester used as the binder (B) of the present invention is ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol. , 1,6-hexanediol, 3-methyl-1,5-pentanediol,
2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,9-nonanediol, 1,10- Examples include decanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, and dimer diol. Further, polyhydric polyols such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, and polyglycerin may be used in combination as long as the content of the invention is not impaired. this house,
From the viewpoint of moisture resistance, the acid component is an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid, an aliphatic dicarboxylic acid having 10 or more carbon atoms,
A combination of a dibasic acid having 12 to 28 carbon atoms and a hydrogenated dimer acid is preferable, and the glycol component is preferably neopentyl glycol, a long chain aliphatic diol having 5 to 10 carbon atoms, or a dimer diol.

As the binder (B) of the present invention, an epoxy resin or a phenol resin may be blended with the above-mentioned polyurethane resin, copolyester resin or the like within a range not impairing the content of the invention. By mixing these resins in appropriate amounts, the adhesive force after metal plating is increased. The type of the curing agent (C) that can react with the binder (B) used in the present invention is not limited, but an isocyanate compound is particularly preferable in terms of adhesiveness, flex resistance, curability and the like. Further, it is preferable to use these isocyanate compounds in a blocked state in terms of storage stability. Examples of the curing agent other than the isocyanate compound include known compounds such as amino resins such as methylated melamine, butylated melamine, benzoguanamine and urea resins, acid anhydrides, imidazoles, epoxy resins and phenol resins.

As the isocyanate compound, aromatic compounds,
There are aliphatic diisocyanates and polyisocyanates having 3 or more valences, and either low molecular weight compounds or high molecular weight compounds may be used. For example, tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate or trimer of these isocyanate compounds, and excess of these isocyanate compounds. Amount and, for example, ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine low molecular weight active hydrogen compounds or various polyester polyols, polyether polyols, polyamides of Obtained by reacting with a polymer active hydrogen compound Terminal isocyanate group-containing compounds to be.

Examples of the blocked isocyanate agent include phenols such as phenol, thiophenol, methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol, and chlorophenol, oximes such as acetoxime, methylethylketoxime, and cyclohexanone oxime. , Alcohols such as methanol, ethanol, propanol, butanol, ethylene chlorohydrin,
Halogen-substituted alcohols such as 1,3-dichloro-2-propanol, tertiary alcohols such as t-butanol and t-pentanol, ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propyrolactam. Other examples include lactams such as aromatic amines, imides, acetylacetone, acetoacetic acid esters, active methylene compounds such as malonic acid ethyl ester, mercaptans, imines, imidazoles, ureas, diaryl compounds. , Sodium bisulfite, etc. are also included. Of these, oximes, imidazoles, and amines are particularly preferable because of their curability.

The cross-linking agent may be used in combination with a known catalyst or accelerator selected according to its type.

The type of the solvent (D) used in the present invention is not limited, and examples thereof include ester type, ketone type, ether ester type, chlorine type, alcohol type, ether type and hydrocarbon type. Among them, in the case of screen printing, high boiling point solvents such as ethyl carbitol acetate, butyl cellosolve acetate, isophorone and cyclohexanone are preferable.

[0019]

The present invention will be described with reference to the following examples.
The present invention is not limited to these. In the examples
Some parts are simply parts by weight. Moreover, each measurement item followed the following method.

1. Viscosity 25 ± 1 ℃, E-type rotary viscometer 3 ° cone, 5rpm
It was measured at.

2. Tilt degree 25 ± 1 ℃, E-type rotational viscometer 3 ° cone, 2.5r
It was measured at pm / 10 rpm. The fluctuation degree was calculated by the following formula. Thickness = Viscosity (2.5 rpm) / Viscosity (10 rpm)

3. Reduced viscosity (ηsp / c) Sample resin is phenol / tetrachloroethane (60
(/ 40 weight ratio) It was dissolved in a mixed solvent at a concentration of 0.400 g / 100 ml and measured at 30 ° C. using an Ostwald viscometer.

4. Molecular weight The polystyrene-equivalent number average molecular weight was measured by GPC.

5. Glass transition temperature (Tg) The temperature was measured with a differential scanning calorimeter (DSC) at a temperature rising rate of 20 ° C / min. As a sample, 5 mg of the sample was placed in an aluminum pressing lid type container and crimped.

6. Acid value A sample of 0.2 g was precisely weighed and dissolved in 20 ml of chloroform. Then, it was determined by titration with 0.01 N potassium hydroxide (ethanol solution). A phenolphthalein solution was used as the indicator.

7. Specific resistance The specific resistance of the conductive paste heat-cured at 150 ° C. for 30 minutes was measured using a 4-deep needle resistance measuring instrument.

8. Adhesive strength after metal plating A line of 1 mm width is screen-printed on a 75 μm-annealed PET film using an electrically conductive paste.
It was heat-cured at 50 ° C. for 30 minutes. Then 5% NaOH
After surface washing with 50 Baume degree sulfuric acid,
Copper sulfate plating bath (copper sulfate 200 g / l, sulfuric acid 50 g /
1, a chloride ion of 50 mg / l, consisting of a brightening agent) was used to perform a copper plating at 3 A / dm ^{2 so} that the copper thickness was 30 to 35 μm. A reinforcing plate was attached to the back surface of the test piece with a double-sided tape, and a 90 ° peeling test was performed with a tensile tester at 50 mm / min.

9. Breaking Elongation The conductive paste was applied to a Teflon sheet with an applicator, heated and cured at 150 ° C./30 minutes, the coating film was peeled off, and this was pulled at 50 mm / min with a tensile tester to measure the breaking extension. . The sample width was 1 cm, the sample length was 5 cm, and the film thickness was 30 to 40 μm.

Synthesis example. 1 (Polyurethane resin I) Aliphatic polyester diol OD-in a four-necked flask
X-688 (Dainippon Ink and Chemicals, Inc.) 100 parts, neopentyl glycol as a chain extender 6 parts, 1,6-hexanediol 2 parts, ethyl carbitol acetate 1
57 parts, butyl cellosolve acetate 52 parts,
Heat to 60 ° C with nitrogen gas flow, add 31 parts of diphenylmethane diisocyanate, and slowly heat to 80 ° C until no residual isocyanate is detected.
Reacted for hours. The obtained polyurethane resin had a reduced viscosity of 1.10 dl / g, a number average molecular weight of 38,000, and Tg =-.
It was 32 ° C.

Synthesis example. 2 (Polyurethane resin II) Aliphatic polyester diol OD-in a four-necked flask
X-688 (Dainippon Ink and Chemicals, Inc.) 70 parts, aromatic polyester diol Byron 220 (Toyobo Co., Ltd.) 30 parts, neopentyl glycol 6 parts as an extender, 1,6-hexanediol 2 parts , 157 parts of ethyl carbitol acetate and 52 parts of butyl cellosolve acetate were charged, heated to 60 ° C. under a nitrogen stream, and further charged with 31 parts of diphenylmethane diisocyanate,
The mixture was gently heated to 80 ° C. and reacted for 5 hours until no residual isocyanate was detected. The obtained polyurethane resin has a reduced viscosity of 1.25 dl / g and a number average molecular weight of 42.
000 and Tg = -15 ° C.

Synthesis example. 3 (polyester resin I) 49 parts of dimethyl terephthalic acid and 107 parts of dimethyl isophthalic acid were placed in a four-necked flask equipped with a Gubilieu rectification column.
33 parts of neopentyl glycol, 186 parts of 1,5-pentanediol and 0.068 part of tetrabutyl titanate were charged, and transesterification was performed at 180 ° C. for 3 hours. Then, 40 parts of sebacic acid was charged and further esterification reaction was carried out. Next, gradually reduce the pressure to 1 mmHg or less, and
Polymerization was carried out at 40 ° C. for 1 hour. The composition of the obtained copolyester is terephthalic acid / isophthalic acid / sebacic acid /
/ Neopentyl glycol / 1,5-pentanediol = 25/55/20 // 15/85 (molar ratio), reduced viscosity 0.55 dl / g, number average molecular weight 16000, acid value 1.1 mgKOH / g, Tg = It was -14 ° C.

Synthesis example. 4 (Polyester Resin II) 101 parts of dimethyl terephthalic acid, 35 parts of dimethyl isophthalic acid were placed in a four-necked flask equipped with a Gubilieu rectification column.
93 parts ethylene glycol, neopentyl glycol 7
Charge 3 parts, tetrabutyl titanate 0.068 parts,
Transesterification was performed at 180 ° C. for 3 hours. Next, 61 parts of sebacic acid was charged and further esterification reaction was carried out. Next, gradually reduce the pressure to 1 mmHg or less, and
Polymerization was carried out at ℃ for 1 hour. The composition of the obtained copolyester is terephthalic acid / isophthalic acid / sebacic acid // ethylene glycol / neopentyl glycol = 52/1.
Reduced viscosity of 0.64 at 8/30 // 55/45 (molar ratio)
dl / g, number average molecular weight 22,000, acid value 1.5 mgK
OH / g, Tg = 7 ° C.

Example. 1 The shape shown in FIG. 1 is a shape in which primary particles having a particle diameter of 0.1 to 5 μm are three-dimensionally connected to form secondary particles having a higher-order structure of 1 to 20 μm, and a specific surface area is 1.62 m. ² / g of silver powder A-1, 77.0 parts, polyurethane resin I varnish (solid content 40%) 43.3 parts, blocked isocyanate compound C-1 solution (hexamethylene diisocyanate,
7.1 parts of butanooxime block of isocyanurate adduct, solid content of 80%) and 0.2 solid parts of dispersant were mixed and thoroughly premixed, and then passed through a chilled three-roll kneader 3 times. Dispersed. The obtained silver paste had a viscosity of 34.1 (pa · s), a thixotropy of 1.47 and a specific resistance of 9.
It was 5 × 10 ⁻⁵ Ω · cm, the elongation at break was 180%, and the adhesive strength after copper plating was 1.2 kg / cm, which was good. In addition, after applying copper plating, 100 at 60 ° C and 95% RH
The adhesive strength retention rate after the 0-hour environmental test was 95%, which was a very good humidity resistance. The results are shown in Table 1 together with the composition.

Examples 2 to 7 Examples. The silver pastes of Examples 2 to 7 are prepared in the same manner as in Table 1.
Was prepared and evaluated according to the formulation. The results are shown in Table 1.

Comparative Examples 1-8 Examples. The silver pastes of Comparative Examples 1 to 8 are prepared in the same manner as in Table 1.
Was prepared and evaluated according to the formulation. Table 2 shows the results.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

EFFECTS OF THE INVENTION By using the conductive paste of the present invention, the adhesiveness after metal plating to various insulating substrates, especially organic films typified by PET, can be significantly improved, and the circuit material can be soldered at low cost. Can be created.

[Brief description of drawings]

FIG. 1 is a magnified image of an electron micrograph of silver powder having secondary particles of higher order structure used in the present invention.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H05K 3/24 7511-4E H05K 3/24 A (72) Inventor Takao Aoki 2-1-1 Katata, Otsu City, Shiga Prefecture No. 1 Toyobo Co., Ltd. Research Institute (72) Inventor Koji Kondo 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Institute (72) Inventor Takaaki Funabiki Osaka Prefecture Kadoma City 1006 Kadoma Address Matsushita Electric Industrial Co., Ltd. (72) Inventor Toshiharu Fukui 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hiroshi Hatase, 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Koji Tanabe 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A conductive paste for a metal plating base, which is used when a circuit is formed by printing a conductive paste on an insulating substrate and then plating the metal with a particle size of 0.1 to 5 μm. Primary particles are connected in a three-dimensional manner 1
Conductive powder (A) mainly composed of silver powder having secondary particles of higher order structure of ˜20 μm, glass transition temperature of −50 to 20
(A) / ((B) + (C) containing as a main component a binder (B) having a reduced viscosity of 0.3 dl / g or more, a curing agent (C) and a solvent (D) capable of reacting with this, ) Is 60/40 to 95
/ 5 (weight ratio) and (B) / (C) is 50/50 to 99
/ 1 (weight ratio), and the breaking elongation after curing is 20%
The above is a conductive paste for a metal plating base, which is characterized by the above.