JP2015050133A - Conductive paste and substrate with conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste capable of forming a conductive film having good conductivity and excellent durability, and to provide a substrate with a conductive film formed by using such a conductive paste.SOLUTION: The conductive paste contains (A) metal particles having a volume resistivity of 10 μΩ cm or less and an average particle diameter of 1-15 μm, (B) base metal particles having an average particle diameter of 0.1-3 μm and an oxidation-reduction potential of -440 to 320 mV (SHE), and (C) a binder resin. The base metal particles as the component (B) are contained in an amount of 0.01-3 pts.mass based on 100 pts.mass of the metal particles as the component (A).

Description

  The present invention relates to a conductive paste and a substrate with a conductive film using the same.

  Conventionally, a method using a conductive paste containing highly conductive metal particles is known for forming wiring conductors such as electronic components and printed wiring boards. Among these, a printed wiring board is manufactured by applying a conductive paste in a desired pattern shape on an insulating base material and curing it to form a conductive film forming a wiring pattern.

The conductive paste used for the above purpose should have (1) good conductivity, (2) easy screen printing and intaglio printing, and (3) application on an insulating substrate. That is, the adhesiveness of the coating film is good, and (4) a fine wire circuit can be formed.
In order to satisfy these requirements, the conductive paste contains metal particles having a low specific resistance value such as copper and silver, a binder resin, a saturated fatty acid or an unsaturated fatty acid as a dispersant, or a metal salt thereof (Patent Document). 1).

By forming the conductive film with the conductive paste having the above-described configuration, good conductivity and adhesion can be ensured. However, although the initial electrical conductivity is good, the electrical durability is lacking due to weak oxidation resistance. Therefore, there is a problem that the conductivity is deteriorated with time so that the specific resistance increases by 50% just by leaving it in the atmosphere at 25 ° C. for 30 days.
For the purpose of improving oxidation resistance, it has been proposed to coat metal particles having a low specific resistance value such as copper and silver with nickel (see Patent Document 2) and to add nickel powder as an additive to the paste (patent) Reference 3).
However, the conductive paste described in Patent Document 2 has a problem of high cost due to the complicated process of thinly coating the surface of the metal particles with nickel by electroless plating. Further, since nickel is a base metal compared to copper or silver, oxidation proceeds selectively at the nickel portion. As a result, oxidized nickel exists on the surface of the metal particles, and there is a problem that conductivity is impaired. In addition, the conductive paste described in Patent Document 3 has a conductivity hindrance because nickel particles having a large particle diameter are added to silver particles having a low specific resistance value, which is 20 to 65 as compared with the case of only silver particles. %, There is a problem that the conductivity is deteriorated.

JP 2007-184143 A JP 2004-162164 A JP-A-9-35530

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a conductive paste capable of forming a cured film having excellent durability while having high conductivity when an electronic circuit is formed by screen printing.

  In order to achieve the above object, the present invention provides (A) a metal particle having a volume resistivity of 10 μΩ · cm or less and an average particle size of 1 to 15 μm, and (B) an average particle size of 0.1 to 3 μm. A conductive paste containing base metal particles having an oxidation-reduction potential of −440 mV to 320 mV (SHE) and (C) a binder resin, in 100 parts by mass of the metal particles of the component (A). On the other hand, the electroconductive paste characterized by containing 0.01-3 mass parts of base metal particles of the said (B) component is provided.

  In the conductive paste of the present invention, the value of (average particle diameter of base metal particles of component (B)) / (average particle diameter of metal particles of component (A)) is 0.01 to 1.0. preferable.

  In the conductive paste of the present invention, the metal particles of the component (A) are preferably copper particles or silver particles having an average particle diameter of 1 to 15 μm.

  In the conductive paste of the present invention, the binder resin of the component (C) is preferably a resin made of a thermosetting resin containing formaldehyde as one component, and a group consisting of a phenol resin, a melamine resin, a xylene resin, and a urea resin. More preferably, it is at least one selected from the group consisting of:

  In the conductive paste of the present invention, the base metal particles of the component (B) are preferably one or more selected from the group consisting of nickel, tin, bismuth and iron.

  Moreover, this invention provides the base material with an electrically conductive film characterized by having on a base material the electrically conductive film formed by apply | coating and hardening the above-mentioned electrically conductive paste of this invention.

According to the conductive paste of the present invention, it is possible to obtain a cured film having high conductivity and excellent conductivity durability. Specifically, the initial specific resistance is 30 μΩcm or less, and the durability measured according to the procedure described in the examples described later is a change (increase) in resistance value after a high temperature and high humidity test of 15% or less. is there.
Moreover, by using such a conductive paste, it is possible to obtain a highly reliable base material with a conductive film that is excellent in conductivity and in which deterioration of conductivity due to an environment during use is suppressed. As described above, the highly reliable conductive film is suitable for automobile parts and the like that require high durability.

Embodiments of the present invention will be described below. In addition, this invention is limited to the following description and is not interpreted.
<Conductive paste>
The conductive paste of the present invention has (A) a metal resistivity having a volume resistivity of 10 μΩ · cm or less and an average particle size of 1 to 15 μm, and (B) an average particle size of 0.1 to 3 μm. A conductive paste containing base metal particles having a reduction potential of −440 mV to 320 mV (SHE) and (C) a binder resin, and (B) with respect to 100 parts by mass of the component (A) metal particles. It contains 0.01 to 3 parts by mass of the component base metal particles.
Hereinafter, each component constituting the conductive paste will be described in detail.

(A) Metal particle The metal particle of (A) component is a conductive component of a conductive paste.
(A) The metal particle of a component is calculated | required that electroconductivity is favorable. In the present invention, metal particles having a volume resistivity value of 10 Ω · cm or less are used.
Gold, silver, and copper are mentioned as a metal which satisfy | fills this. Among these, silver and copper are preferable for reasons such as low resistance and availability, and copper is particularly preferable because migration phenomenon hardly occurs.

The (A) component metal particles have an average particle diameter according to the definition described later, that is, an average particle diameter of 1 to 15 μm.
The particle diameter of the metal particles in this specification is determined by measuring the Feret diameter of 100 metal particles randomly selected from a scanning electron microscope (hereinafter referred to as “SEM”) image. When the radial direction in which the Feret diameter is the maximum value is a major axis and the axis orthogonal to the major axis is a minor axis, the average value of the Feret diameter in the major axis direction and the Feret diameter in the minor axis direction ( It is calculated as (Feret diameter in the major axis direction + Feret diameter in the minor axis direction) / 2).
The particle diameter of the metal particles described above is the primary particle diameter of the metal particles.
The average value (average particle diameter) of the particle diameters of the metal particles in this specification is the average (number average) of the particle diameters of the metal particles calculated as described above.
When the average value (average particle diameter) of the particle diameter of the metal particles of the component (A) satisfies the above range, the flow characteristics of the conductive paste containing metal particles are improved, and the conductive paste is finer. Easy to fabricate wiring. When the average particle diameter (average particle diameter) of the metal particles is less than 1 μm, sufficient flow characteristics cannot be obtained when a conductive paste is obtained. On the other hand, if the average value (average particle diameter) of the particle diameter of the metal particles exceeds 15 μm, it may be difficult to produce fine wiring using the obtained conductive paste.
The average particle diameter (average particle diameter) of the metal particles (A) is preferably 1 to 15 μm, and more preferably 2 to 8 μm.

  Further, as the metal particles of the component (A), “surface modified metal particles” obtained by reducing the surface of the metal particles may be used. Since the surface-modified metal particles have a reduced oxygen concentration on the particle surface due to the reduction treatment, the contact resistance between the metal particles is further reduced, and the conductivity of the obtained conductive film is improved.

  In the conductive paste of the present invention, the compounding amount of the metal particles of the component (A) is preferably 75 to 95 parts by mass, and 80 to 90 parts by mass with respect to 100 parts by mass in total of all components of the conductive paste. Part is more preferred. If it is 75 mass parts or more, the electroconductivity of the electrically conductive film formed using an electrically conductive paste will become favorable. If it is 95 mass parts or less, the part which a metal particle and binder resin couple | bond will increase, the hardness of a cured film will improve, and the flow characteristic of an electrically conductive paste will become favorable.

(B) Base metal particles The base metal particles (B) are components that contribute to improved durability. The base metal used for the base metal particles of the component (B) is a metal that is more easily oxidized than the metal of the component (A), but is less prone to spontaneous oxidation by oxygen in the air. The base metal oxidation-reduction potential is -440 mV to 320 mV (SHE (standard hydrogen electrode)) with reference to a standard electrode potential (oxidation-reduction potential) at 25 ° C. at which stable metal ions are reduced to metal in an aqueous solution. Is in range.
Specific metals include nickel (redox potential -257 mV (SHE)), tin (redox potential -140 mV (SHE)), bismuth (redox potential 317 mV (SHE)), iron (redox potential -440 mV (SHE)). )) And the like. Among these, nickel and tin are preferable for reasons such as low resistance and availability, and nickel is particularly preferable from the viewpoint of the stability of the surface oxide film.

  The (B) component base metal particles are present between the (A) component metal particles that mainly exhibit conductivity. In the interaction with the (A) component metal particles, the (B) component base metal is ( Since it is a base metal rather than the metal of component A), it acts as a sacrificial anode when the metal particles of component (A) are in an oxidizing environment, and is considered to be able to suppress oxidation of the metal particles of component (A). It is done. On the other hand, since the base metal particles of the component (B) having a relatively high specific resistance value are hardly present at the interface between the metal particles having a low specific resistance value (particles of the component (A)) during heat curing, Conduction between metal particles is not hindered.

The base metal particles (B) have an average particle diameter according to the definition described above, that is, an average particle diameter of 0.1 to 3 μm.
When the average particle diameter (average particle diameter) of the base metal particles of the component (B) satisfies the above range, the flow characteristics of the conductive paste containing the base metal particles are improved, and the conductive paste is finer. Easy to fabricate wiring. When the average particle size (average particle size) of the base metal particles is less than 0.1 μm, it is difficult to obtain flow characteristics when conductive paste is used, and spontaneous oxidation progresses to improve durability. It becomes difficult to contribute to. On the other hand, if the average particle diameter (average particle diameter) of the base metal particles exceeds 3 μm, it may be difficult to contribute to the improvement of the conductive durability.
The average value (average particle diameter) of the base particle of the component (B) is preferably 0.1 to 3 μm, more preferably 0.1 to 2 μm, and 0.1 to 1 μm. More preferably.

In addition, when paying attention to the ratio between the average particle diameter of the base metal particles of the component (B) and the average particle diameter of the metal particles of the component (A), the average particle diameter of the base metal particles of the component (B) / (A) The average particle size of the component metal particles is preferably 0.01 to 1.0.
The average particle size of the base metal particles (B) / the average particle size of the metal particles (A) satisfies the above range, so that the base metal particles in relation to the metal particles in the conductive paste Effectively acts as a sacrificial anode, and the conductive film formed using the conductive paste has good conductivity and excellent durability. When the value of the average particle diameter of the base metal particles (B) / the average particle diameter of the metal particles (A) is less than 0.01, it is difficult to obtain flow characteristics when the conductive paste is used. Spontaneous oxidation proceeds to make it difficult to contribute to improvement of durability. On the other hand, when the average value (average particle diameter) of the base metal particles exceeds 1.0, it may be difficult to contribute to the improvement of the conductive durability.
The average particle size of the base metal particles (B) / the average particle size of the metal particles (A) is more preferably 0.03 to 0.5.

In the conductive paste of the present invention, the compounding amount of the base metal particles (B) is 0.01 to 3 parts by mass with respect to 100 parts by mass of the metal particles (A). The blending amount is preferably 0.02 to 2.5 parts by mass, more preferably 0.02 to 1.5 parts by mass, particularly preferably 0.02 to 1.0, and extremely preferably 0.02 to 0.3. .
(B) Since the blending amount of the base metal particles of the component satisfies the above range, the base metal particles effectively act as a sacrificial anode in relation to the metal particles in the conductive paste, and are formed using the conductive paste. The conductive film to be formed has good conductivity and excellent durability.
When the blending amount of the base metal particles of the component (B) is less than 0.01 parts by weight with respect to 100 parts by weight of the metal particles of the component (A), the blending amount of the base metal particles is insufficient, so the metal in the conductive paste Base metal particles do not function sufficiently as sacrificial anodes in relation to the particles. For this reason, it becomes difficult to contribute to the improvement of durability.
On the other hand, when the blending amount of the base metal particles of the component (B) is more than 3 parts by mass with respect to 100 parts by mass of the metal particles of the component (A), the metal particles having a low specific resistance value during the heat curing (component (A) Base metal particles (particles of component (B)) having a relatively high specific resistance value are present at the interface between each other), and conduction between metal particles having a low specific resistance value is hindered. The conductivity of the conductive film is considered to be low.

(C) Binder resin In the conductive paste conductive paste containing metal particles, a binder resin is used to maintain the structure of the conductor made of metal particles formed after curing.
In the electrically conductive paste of this invention, it is preferable to use what consists of thermosetting resin which has formaldehyde as one component as binder resin of (C) component. The reason is that a thermosetting resin containing formaldehyde as one component has a large shrinkage at the time of heat-curing and has a strong force to press metal particles, so that high conductivity is easily obtained. In particular, when copper fine particles are used as the metal particles, the reduction of the methylol group generated from formaldehyde can suppress the oxidation of the surface of the copper particles, and further the curing shrinkage proceeds to ensure the contact between the copper particles. Because.

  Examples of the thermosetting resin containing formaldehyde as one component include phenol resin, melamine resin, xylene resin, and urea resin. Of these, a phenol resin is preferred from the viewpoint of the reducing action of the methylol group and the degree of cure shrinkage. If the curing shrinkage is too large, unnecessary stress accumulates in the conductive film, causing mechanical breakdown. If the curing shrinkage is too small, sufficient contact between the metal particles cannot be ensured.

  In the conductive paste of the present invention, the blending amount of the binder resin as the component (C) is appropriately selected according to the ratio between the volume of the copper particles as the component (A) and the volume of the voids existing between the metal particles. Although it can do, it is preferable that it is 5-25 mass parts with respect to 100 mass parts of total of all the components of an electrically conductive paste, and 10-20 mass parts is more preferable. If it is 5 mass parts or more, the part which binder resin and the metal particle surface couple | bond will increase, the hardness of a cured film will improve, and the flow characteristic of an electrically conductive paste will become favorable. If it is 25 mass parts or less, the electroconductivity of the electrically conductive film formed using an electrically conductive paste will become favorable.

(D) Other components In addition to the components (A) to (C) described above, the conductive paste of the present invention includes a solvent and various additives (leveling agent, viscosity modifier, etc.) as necessary. May be included as long as the effects of the present invention are not impaired. In particular, in order to obtain a paste having appropriate fluidity, it is preferable to contain a solvent capable of dissolving the thermosetting resin.
Examples of the solvent include cyclohexanone, cyclohexanol, terpineol, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether. Diethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate can be used. From the viewpoint of setting an appropriate viscosity range as a printing paste, the amount of the solvent contained in the conductive paste is 5 to 40 parts by mass with respect to 100 parts by mass in total of all components of the conductive paste. Is preferred.

The conductive paste can be obtained by mixing the components (A) to (C) above and other components such as the solvent as necessary. When mixing each component of said (A)-(C), it can carry out, heating at the temperature which does not produce the hardening of a thermosetting resin, or volatilization of a solvent.
The temperature during mixing and stirring is preferably 10 to 40 ° C. More preferably, it is good to set it as 20-30 degreeC. By heating to a temperature of 10 ° C. or higher when preparing the conductive paste, the viscosity of the paste can be sufficiently reduced, and stirring can be performed smoothly and sufficiently. On the other hand, if the temperature at which the conductive paste is prepared exceeds 120 ° C., the resin may be cured in the paste or the particles may be fused. In order to prevent the metal particles from being oxidized during mixing, it is preferable to mix in a container substituted with an inert gas.

  In the conductive paste of the present invention described above, the (A) component has a volume resistivity of 10 μΩ · cm or less and an average particle size of 1 to 15 μm, and (B) an average particle size of 0.1 μm. Since it contains base metal particles having a redox potential of −440 μm to 320 mV (SHE) and a binder resin of component (C), the conductive film formed from this conductive paste is conductive Excellent in durability and durability.

<Substrate with conductive film>
The base material with a conductive film of the present invention has a base material and a conductive film formed by applying and curing the conductive paste of the present invention described above on the base material.
Examples of the base body include a glass substrate, a plastic substrate (for example, a polyimide substrate, a polyester substrate, etc.), and a substrate (for example, a glass fiber reinforced resin substrate, etc.) made of a fiber reinforced composite material.

  Examples of the method of applying the conductive paste include known methods such as screen printing, roll coating, air knife coating, blade coating, bar coating, gravure coating, die coating, and slide coating. Among these, the screen printing method is preferable.

  The coating layer is cured by heating with a method such as warm air heating or heat radiation heating to cure the resin (thermosetting resin) in the conductive paste.

  What is necessary is just to determine a heating temperature and a heating time suitably according to the characteristic calculated | required by the electrically conductive film. The heating temperature is preferably 80 to 200 ° C. If heating temperature is 80 degreeC or more, hardening of binder resin will advance smoothly, the contact between metal particles will become favorable, and electroconductivity and durability will improve. If heating temperature is 200 degrees C or less, since a plastic substrate can be used as a base-material main body, the freedom degree of base-material selection increases.

  The thickness of the conductive film formed on the substrate is preferably 1 to 200 μm and more preferably 5 to 100 μm from the viewpoint of ensuring stable conductivity and maintaining the wiring shape.

  The specific resistance (also referred to as volume resistivity) of the conductive film is preferably 30 μΩcm or less. When the specific resistance of the conductive film exceeds 30 μΩcm, it may be difficult to use it as a conductor for electronic equipment.

Moreover, it is preferable that the amount of change (increase) in the specific resistance after the durability test is 20% or less as measured by the procedure described in the examples described later. It is more preferably 10% or less, and particularly preferably 5% or less.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. Examples 1 to 8 are examples, and examples 9 to 13 are comparative examples. In addition, the average particle diameter of the metal particles (copper particles) and the base metal particles (nickel particles), the thickness of the conductive film, and the specific resistance were measured using the following apparatuses.

(Average particle size)
Copper particles were used as the metal particles. The particle diameter of the copper particles was determined by measuring the Feret diameter of 100 particles randomly selected from SEM images obtained by SEM (manufactured by Hitachi High-Technologies Corporation, S-4300). When the major axis is the radial direction where the diameter is the maximum, and the minor axis is the axis orthogonal to the major axis, the average value of the Feret diameter in the major axis direction and the Feret diameter in the minor axis direction (( It was calculated as Feret diameter in the major axis direction + Feret diameter in the minor axis direction) / 2). And the average value (average particle diameter) of the particle diameter was calculated | required by averaging the particle diameter of the calculated copper particle (number average).

(Thickness of conductive film)
The thickness of the conductive film was measured by using DEKTAK3 (manufactured by Veeco metrology group).

(Specific resistance of conductive film)
The specific resistance of the conductive film was measured using a four-probe type volume resistivity meter (manufactured by Mitsubishi Yuka Co., Ltd., model: lorestaIP MCP-T250).

Example 1
In a glass beaker, 3.0 g of formic acid and 9.0 g of a 50 mass% hypophosphorous acid aqueous solution were placed, and the beaker was placed in a water bath and maintained at 40 ° C. In this beaker, 5.0 g of copper particles having an average particle diameter of 6 μm (Mitsui Metal Mining Co., Ltd., trade name: 1400 YP) were gradually added and stirred for 30 minutes to obtain a copper dispersion.
The resulting copper dispersion was centrifuged at 3000 rpm for 10 minutes using a centrifuge to collect a precipitate. This precipitate was dispersed in 30 g of distilled water, and the aggregate was precipitated again by centrifugation, thereby separating the precipitate. Thereafter, the obtained precipitate is heated at 80 ° C. under a reduced pressure of −35 kPa for 60 minutes to volatilize and remove residual moisture, thereby obtaining copper particles (A) whose particle surfaces are surface-modified. It was.
The average particle diameter of the copper particles after the surface modification is 6 μm without changing. In addition, it is the same also about the other example shown below that the average value of a particle diameter does not change the copper particle after surface modification.
Next, 12 g of the obtained surface-modified copper particles (A) was added to 3.7 g of a phenol resin as a component (C) (manufactured by Gunei Chemical Co., Ltd., trade name: Regitop PL 6220, all in the following examples). Was added to a resin solution dissolved in 4.3 g of ethylene glycol monobutyl ether acetate. Furthermore, together with this mixture, 0.02 g of nickel powder (average particle size 0.3 μm, oxidation-reduction potential −257 mV (SHE)) as component (B) was put in a mortar and mixed at room temperature to obtain a copper paste. . In addition, the compounding quantity of (B) component was 0.17 mass part with respect to 100 mass parts of copper particle of (A) component. (C) The compounding quantity of the component was 11 mass parts with respect to a total of 100 mass parts of all the components of a copper paste. Moreover, the value of the average particle diameter of the nickel powder (particles) of the component (B) / the average particle diameter of the copper particles of the component (A) is 0.05.

Example 2
Copper particles were obtained in the same manner as in Example 1 except that the copper particles were changed to copper particles having an average particle diameter of 7 μm (manufactured by Nippon Atomizing Co., Ltd., trade name: AFS-Cu) and nickel powder was changed to an average particle size of 0.5 μm A paste was obtained. The value of (B) component nickel powder (particles) average particle size / (A) component copper particles average particle size is 0.07.

Example 3
A copper paste was obtained in the same manner as in Example 1 except that the copper particles were changed to copper particles having an average particle diameter of 3 μm (manufactured by Nippon Atomizing Co., Ltd., trade name: AFS-Cu). The value of the average particle diameter of the (B) component nickel powder (particles) / the average particle diameter of the (A) component copper particles is 0.1.

Example 4
12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 3.7 g of phenol resin as component (C) in 4.3 g of ethylene glycol monobutyl ether acetate, Along with this mixture, 0.004 g of nickel powder (average particle size 0.1 μm) as component (B) was put in a mortar and mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B) component was 0.03 mass part with respect to 100 mass parts of copper particle of (A) component. Moreover, the value of the average particle diameter of the nickel powder (particles) of the component (B) / the average particle diameter of the copper particles of the component (A) is 0.03.

Example 5
12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 3.7 g of phenol resin as component (C) in 4.3 g of ethylene glycol monobutyl ether acetate, Together with this mixture, 0.02 g of nickel powder (average particle size 2.5 μm) as component (B) was placed in a mortar and mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B) component was 0.17 mass part with respect to 100 mass parts of copper particle of (A) component. Moreover, the value of the average particle diameter of nickel powder (particles) of component (B) / the average particle diameter of copper particles of component (A) is 0.42.

Example 6
12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 3.7 g of phenol resin as component (C) in 4.3 g of ethylene glycol monobutyl ether acetate, Together with this mixture, 0.1 g of nickel powder (average particle size 0.3 μm) as component (B) was put in a mortar and mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B) component was 0.8 mass part with respect to 100 mass parts of copper particles of (A) component. Moreover, the value of the average particle diameter of the nickel powder (particles) of the component (B) / the average particle diameter of the copper particles of the component (A) is 0.05.

Example 7
12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 3 was added to a resin solution obtained by dissolving 3.7 g of phenol resin as component (C) in 4.3 g of ethylene glycol monobutyl ether acetate. Together with this mixture, 0.02 g of nickel powder (average particle size 2.5 μm) as component (B) was placed in a mortar and mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B) component was 0.17 mass part with respect to 100 mass parts of copper particle of (A) component. Moreover, the value of the average particle diameter of the nickel powder (particles) of the component (B) / the average particle diameter of the copper particles of the component (A) is 0.83.

Example 8
12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 3.7 g of phenol resin as component (C) in 4.3 g of ethylene glycol monobutyl ether acetate, Together with this mixture, 0.2 g of nickel powder (average particle size 2.5 μm) as component (B) was placed in a mortar and mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B) component was 1.7 mass parts with respect to 100 mass parts of copper particles of (A) component. Moreover, the value of the average particle diameter of nickel powder (particles) of component (B) / the average particle diameter of copper particles of component (A) is 0.42.

Example 9
To 12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 1, the copper powder was mixed at room temperature in the same manner as in Example 1 except that the nickel powder of component (B) was not added. A paste was obtained.

Example 10
12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 3.7 g of phenol resin as component (C) in 4.3 g of ethylene glycol monobutyl ether acetate, Along with this mixture, 0.001 g of nickel powder (average particle size 0.3 μm) as component (B) was put in a mortar and mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B) component was 0.008 mass part with respect to 100 mass parts of copper particle of (A) component. Moreover, the value of the average particle diameter of the nickel powder (particles) of the component (B) / the average particle diameter of the copper particles of the component (A) is 0.05.

Example 11
12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 3.7 g of phenol resin as component (C) in 4.3 g of ethylene glycol monobutyl ether acetate, Together with this mixture, 0.4 g of nickel powder (average particle size 0.3 μm) as component (B) was put in a mortar and mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B) component was 3.3 mass parts with respect to 100 mass parts of copper particles of (A) component. Moreover, the value of the average particle diameter of the nickel powder (particles) of the component (B) / the average particle diameter of the copper particles of the component (A) is 0.05.

Example 12
12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 3.7 g of phenol resin as component (C) in 4.3 g of ethylene glycol monobutyl ether acetate, Together with this mixture, 0.02 g of nickel powder (average particle size 0.05 μm) as component (B) was placed in a mortar and mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B) component was 0.17 mass part with respect to 100 mass parts of copper particle of (A) component. Moreover, the value of the average particle diameter of the nickel powder (particles) of the component (B) / the average particle diameter of the copper particles of the component (A) is 0.008.

Example 13
12 g of the surface-modified copper particles (A) obtained in the same manner as in Example 1 was added to a resin solution obtained by dissolving 3.7 g of phenol resin as component (C) in 4.3 g of ethylene glycol monobutyl ether acetate, Along with this mixture, 0.02 g of nickel powder (average particle size 10 μm) as component (B) was put in a mortar and mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B) component was 0.17 mass part with respect to 100 mass parts of copper particle of (A) component. Moreover, the value of the average particle diameter of the nickel powder (particles) of the component (B) / the average particle diameter of the copper particles of the component (A) is 1.7.

Next, each of the copper pastes obtained in Examples 1 to 13 was applied onto a glass having a thickness of 3 mm and heated at 150 ° C. for 30 minutes to cure the phenol resin as the component (C). A 15 μm conductive film was formed. And the electrical resistance value of the obtained electrically conductive film was measured using the resistance meter (The product name: Milliohm Hitester by the Keithley company), and the specific resistance (volume resistivity; unit microohm cm) was measured. Further, after the same conductive film was stored in a high-temperature and high-humidity tank at 85 ° C. and 85% RH for 250 hours, the electrical resistance value was measured, and the change amount of the electrical resistance value was measured.
The results are summarized in Table 1.

表１からわかるように、粒子径の平均値が１．０〜１５μｍの銅粒子とともに、銅粒子１００質量部に対し、粒子径の平均値が０．１〜３μｍのニッケル粉を０．０１〜３質量部含有する例１〜８の導電性ペーストを用いることにより、該導電性ペーストを基材に塗布し、硬化させた導電膜は、比抵抗が低く、２５μΩｃｍ以下であった。また、高温高湿保存後での導電性の変化（低下）も抑制されていた。これは銅粒子の間に適切な量のニッケル粒子が存在することができ、銅粒子とニッケル粒子間の接触面積が大きくなったために犠牲陽極としての機能が有効に働いたためであると考える。
これに対し、（Ｂ）成分のニッケル粉を配合しなかった例９、（Ｂ）成分のニッケル粉の配合量が、（Ａ）成分の金属粒子１００質量部に対して、０．０１質量部未満の例１０、３質量部超の例１１、（Ｂ）成分のニッケル粉として平均粒径が０．１〜３μｍではなく平均粒径が０．０５μｍのニッケル粉を配合した例１２、（Ｂ）成分のニッケル粉として平均粒径が０．１〜３μｍではなく平均粒径が１０μｍのニッケル粉を配合した例１３は、いずれも、導電性ペーストを用いて作製した導電膜は高温高湿保存後の導電性の変化（低下）が大きかった。
また、特許文献１の銅粉を使用した金属ペーストから形成した導電膜は２５℃の大気中に３０日間放置しただけで比抵抗が５０％も上昇するほどに導電性の変化（低下）が大きく、この導電膜を使用して電子部品の導体配線を形成することは困難である。

As can be seen from Table 1, together with copper particles having an average particle diameter of 1.0 to 15 μm, nickel powder having an average particle diameter of 0.1 to 3 μm with respect to 100 parts by mass of copper particles is 0.01 to By using the conductive paste of Examples 1 to 8 containing 3 parts by mass, the conductive film obtained by applying the conductive paste to a substrate and curing it had a low specific resistance and was 25 μΩcm or less. Moreover, the change (decrease) in conductivity after storage at high temperature and high humidity was also suppressed. It is considered that this is because an appropriate amount of nickel particles can be present between the copper particles, and the contact area between the copper particles and the nickel particles has increased, so that the function as a sacrificial anode has worked effectively.
In contrast, Example 9 in which the nickel powder of the component (B) was not blended, the blending amount of the nickel powder of the component (B) was 0.01 parts by mass with respect to 100 parts by mass of the metal particles of the component (A). Less than Example 10, more than 11 parts by weight of Example 11, (B) as the nickel powder of the component (B), Example 12 in which the average particle diameter is not 0.1 to 3 μm but the average particle diameter is 0.05 μm, (B In Example 13, in which nickel powder having an average particle size of 10 μm instead of 0.1 to 3 μm was used as the component nickel powder, all the conductive films prepared using the conductive paste were stored at high temperature and high humidity. The later change (decrease) in conductivity was large.
In addition, the conductive film formed from the metal paste using the copper powder of Patent Document 1 has a large change (decrease) in conductivity as the specific resistance increases by 50% just by leaving it in the atmosphere at 25 ° C. for 30 days. It is difficult to form a conductor wiring of an electronic component using this conductive film.

  The conductive paste of the present invention can be used for various purposes, for example, for the formation and repair of wiring patterns in printed wiring boards, interlayer wiring in semiconductor packages, and bonding between printed wiring boards and electronic components. it can.

Claims (7)

  (A) a metal particle having a volume resistivity of 10 μΩ · cm or less and an average particle diameter of 1 to 15 μm, and (B) an average particle diameter of 0.1 to 3 μm and an oxidation-reduction potential of −440 mV to 320 mV ( SHE) and a conductive paste containing (C) a binder resin, and 0 parts of the base metal particles of the component (B) with respect to 100 parts by mass of the metal particles of the component (A). A conductive paste containing 0.01 to 3 parts by mass.   2. The conductive paste according to claim 1, wherein the average particle diameter of the base metal particles of the component (B) / the average particle diameter of the metal particles of the component (A) is 0.01 to 1.0.   The conductive paste according to claim 1 or 2, wherein the metal particles of the component (A) are copper particles or silver particles having an average particle diameter of 1 to 15 µm.   The electrically conductive paste in any one of Claims 1-3 whose binder resin of said (C) component is resin which consists of thermosetting resin which uses formaldehyde as one component.   The electrically conductive paste in any one of Claims 1-4 whose base metal particle of the said (B) component is 1 or more types selected from the group which consists of nickel, tin, bismuth, and iron.   The electrically conductive paste in any one of Claims 1-5 whose binder resin of the said (C) component is 1 or more types selected from the group which consists of a phenol resin, a melamine resin, a xylene resin, and a urea resin.   A base material with a conductive film comprising a conductive film formed by applying and curing the conductive paste according to claim 1 on a base material.