JP2014049191A - Conductive paste and substrate with conductive membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste from which a conductive membrane having satisfactory conductivity and excellent durability can be formed and a substrate with a conductive membrane formed by using such a conductive paste.SOLUTION: A conductive paste is provided which comprises: (A) copper particles; (B) a modified dimethylsiloxane; and (C) a binder resin composed of a thermosetting resin containing formaldehyde as one component. In the conductive paste, the copper particles are those in a flat shape in which an average value of particle diameters is 1.0-15 μm and an average value of ratios of the particle diameter and thickness (average value of particle diameter/thickness) is 2-10 when a radial direction maximizing a Feret diameter of the copper particle is defined as a major axis, an axis orthogonal to the major axis is defined as a minor axis, and an average value of the Feret diameter in the major axis direction and the Feret diameter in the minor axis direction is defined as a particle diameter of the copper particle; and the component (A), copper particles, are contained in 78-94.99 mass%, the component (C), binder resin, is contained in 5-20 mass%, and the component (C), modified dimethylsiloxane, is contained in 0.01-2 mass%.

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.

  As the conductive paste, silver paste containing silver particles as metal particles has been the mainstream in the past (Patent Document 1), but there is a problem in terms of migration. In this respect, a copper paste containing copper particles as metal particles is less likely to cause a migration phenomenon, so that the connection reliability of an electric circuit can be improved.

  Various characteristics are required for wiring conductors such as printed wiring boards. Conductivity of wiring conductors, such as specific resistance and durability, has an important influence on the design of electrical circuits, so it is one of the most important characteristics. One.

  As a conductive paste for forming a conductive film having good conductivity, a conductive powder made of copper or a copper alloy treated with an aqueous solution containing an acid, a reducing agent and an alkali metal salt of a fatty acid having 8 or more carbon atoms is used. Known conductive paste (Patent Document 2), conductive composition containing copper powder, thermosetting resin, sarcosine compound, and polyamine (Patent Document 3) are known.

JP-A-5-212579 JP 2007-184143 A JP-A-4-253773

  In Patent Document 2, conductive powder obtained by treating spherical powder made of copper or a copper alloy with an aqueous solution containing an acid, a reducing agent, and an alkali metal salt of a fatty acid having 8 or more carbon atoms is kneaded with an organic vehicle and pasted. The electroconductivity of the conductive film formed by converting is evaluated. The formed conductive film has excellent conductivity immediately after the formation, but since the durability is insufficient, the conductivity is greatly increased by storage in the air at room temperature, so it cannot be used for wiring of electronic devices. Have the problem.

  In patent document 3, the electroconductivity of the electrically conductive film formed from the electroconductive copper powder, the thermosetting resin, the sarcosine compound, and the electrically conductive paste containing polyamine is evaluated. Although the formed conductive film is excellent in durability, it has a problem that its use in wiring of electronic equipment is limited due to poor initial conductivity.

  In order to solve the above-described problems of the prior art, the present invention has good conductivity and excellent durability, specifically, changes in conductivity before and after holding in a high-temperature and high-humidity environment ( It is an object of the present invention to provide a conductive paste capable of forming a conductive film and a substrate with a conductive film formed using such a conductive paste.

In order to achieve the above object, the present invention provides a conductive material containing (A) copper particles, (B) modified dimethylsiloxane, and (C) a binder resin made of a thermosetting resin containing formaldehyde as one component. Sex paste,
When the copper particle has a major axis as a radial direction in which the Feret diameter of the copper particle is a maximum value and an axis perpendicular to the major axis is a minor axis, the Feret diameter in the major axis direction and the minor axis direction When the average value of the Feret diameter is the particle diameter of the copper particles, the average value of the particle diameter of the copper particles is 1.0 to 15 μm, the particle diameter of the copper particles, and the copper particles The average value of the ratio of the thickness and the average value (particle diameter / average thickness) is 2 to 10 flat copper particles,
The conductive paste contains 78 to 94.99% by mass of the copper particles of the component (A), 5 to 20% by mass of the binder resin of the component (C), and the modified dimethylsiloxane of the component (B). Is contained in an amount of 0.01 to 2% by mass.

  In the conductive paste of the present invention, the modified dimethylsiloxane as the component (B) preferably has a structure in which some methyl groups of dimethylsiloxane are substituted with polyether or polyester.

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

The conductive paste of the present invention further contains (D) a chelating agent made of a compound having a stability constant logK _Cu of 5 to 15 with copper ions at 25 ° C. and an ionic strength of 0.1 mol / L. Is preferred.
Here, in the chelating agent (D) of the component, the functional group (a) containing a nitrogen atom and the functional group (b) containing an atom having a lone electron pair other than the nitrogen atom are ortho positions of the aromatic ring. It is preferable that it is an aromatic compound arrange | positioned.
Moreover, it is preferable that the chelating agent of the said (D) component is 1 or more types selected from the group which consists of a salicyl hydroxamic acid, a salicyl aldoxime, and o-aminophenol.
Moreover, it is preferable that the electrically conductive paste of this invention contains 0.01-1 mass% of chelating agents of the said (D) component in the said electrically conductive paste.

  In the conductive paste of the present invention, in the particle size distribution based on the number of copper particles of the component (A), the particle size when the integrated value from the small particle size side is 10% is D10, 50%. When the particle diameter of D50 is 90% and the particle diameter is D90, the value of D90 / D50 is preferably 4 or less, and the value of D90 / D10 is preferably 3 or more.

  In the conductive paste of the present invention, the copper particles of the component (A) are preferably copper particles having a surface oxygen content of 0.5 or less.

  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, a conductive film having good conductivity and excellent durability can be obtained. Specifically, the initial specific resistance is 25 μΩcm or less, and the specific resistance change amount (reduction amount) before and after holding in a high-temperature and high-humidity environment is 20%, which is measured according to the procedure described in the examples described later. It is suppressed to the following.
In addition, by using such a conductive paste, it is possible to obtain a substrate with a conductive film that has high reliability as a wiring board or the like and in which deterioration of conductivity due to formation of an oxide film is suppressed.

  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 is a conductive paste containing (A) copper particles, (B) modified dimethylsiloxane, and (C) a binder resin made of a thermosetting resin containing formaldehyde as one component. The copper particles have a major axis in the radial direction in which the Feret diameter of the copper particles is a maximum value, and a minor axis is an axis perpendicular to the major axis. When the average value of the Feret diameter in the axial direction is the particle diameter of the copper particles, the average particle diameter of the copper particles is 1 μm to 15 μm, and the particle diameter of the copper particles and the copper particles It is a flat copper particle having an average value (particle diameter / thickness average) ratio of 2 to 10 in thickness, and the copper paste of component (A) is 78 to 78 in the conductive paste. 99.99% by mass, 5-20% by mass of the binder resin of component (C) A, characterized in that it contains 0.01 to 2% by weight of modified dimethylsiloxane of the component (B).
Hereinafter, each component constituting the conductive paste will be described in detail.

(A) Copper particle The copper particle of (A) component is an electroconductive component of an electroconductive paste.

The copper particles of component (A) have an average particle diameter of 1.0 to 15 μm according to the definition described later, and an average value of the ratio between the particle diameter and the thickness of the copper particles (particle diameter / thickness Of the flat copper particles having an average value of 2 to 10. Such flat copper particles can be obtained by deforming spherical copper particles with a ball mill or the like.
Moreover, as a copper particle of (A) component, 1 type or more of a copper particle, surface modification copper particle, and copper composite particle can be used so that it may mention later.

In this specification, the particle diameter of the copper particles is determined by measuring the Feret diameter of one copper particle randomly selected from the image of a scanning electron microscope (hereinafter referred to as “SEM”). When the radial direction as a major axis is the major axis and the axis perpendicular to the major axis is the minor axis, the value is calculated as (Feret diameter in the major axis direction + Feret diameter in the minor axis direction) / 2).
The average value of the particle diameter of the copper particles in the present specification is obtained by calculating the particle diameter of each copper particle by the above-described particle diameter calculation method for 100 copper particles randomly selected from the SEM image. The average (number average) of the particle diameter of 100 copper particles is taken.

(A) The average value of the particle diameter of the copper particle of a component satisfy | fills said range, the flow characteristic of the electrically conductive paste containing a copper particle becomes favorable, and it is easy to produce fine wiring with this electrically conductive paste. . When the average particle diameter of the copper particles is less than 1.0 μm, sufficient flow characteristics cannot be obtained when a conductive paste is obtained. On the other hand, when the average value of the particle diameter of the copper particles exceeds 20 μm, it may be difficult to produce fine wiring by the obtained conductive paste.
(A) It is preferable that the average value of the particle diameter of the copper particle of a component is 1.0-10 micrometers.

The ratio between the particle diameter and the thickness of the copper particles in this specification is calculated by the following procedure.
When calculating the particle diameter of the copper particles by the above procedure, the thickness of one copper particle used for the calculation is measured, and the ratio between the particle diameter of the copper particles and the thickness (particle diameter / thickness). Ask for.
The average value of the particle diameter and thickness ratio of the copper particles in this specification (average particle diameter / thickness value) is as follows for 100 copper particles randomly selected from the SEM image. This is an average (number average) of (particle diameter / thickness) of the calculated copper particles.

Flat copper particles having an average particle diameter in the above range and an average ratio of particle diameter to thickness (average particle diameter / thickness) satisfying the above range are electrically conductive. By using it for the paste, a conductive film having good conductivity and excellent durability can be obtained. About this reason, this inventor infers as follows.
When the average value of the particle diameter is in the above range and the average value of the particle diameter / thickness satisfies the above range, flat copper particles having a uniform particle diameter and shape are present in the conductive paste. Will do. When such a conductive paste is applied to a substrate, the copper particles in the paste are closely aligned so that the major axis direction is oriented in the same direction. Specifically, it arranges closely so that it may orient in the surface direction of the base material with which the conductive paste was applied. Even in the conductive film obtained by curing the conductive paste in this state, the state in which the copper particles are closely aligned is maintained, so that the conductivity of the conductive film is improved. In addition, when the conductive film is maintained in a high temperature and high humidity environment, the conductive film is oxidized and swelled. However, since the flat copper particles are maintained in a closely aligned state, before and after the retention in the high temperature and high humidity environment. The change (decrease) in conductivity is suppressed. Therefore, the conductive film has excellent durability.

If the average value of the particle diameter / thickness of the copper particles is smaller than 2, it contains a lot of spherical copper particles, so when the conductive paste is applied to the substrate, the copper particles in the paste are closely aligned It will not be in the state. For this reason, the electroconductivity of the electrically conductive film formed becomes low, and the change (decrease) of electroconductivity before and behind holding | maintenance in a high-temperature, high-humidity environment becomes large.
As described above, the flat copper particles can be obtained by deforming the spherical copper particles with a ball mill or the like. To obtain a copper particle having a particle diameter / thickness greater than 10, Since the particles are excessively deformed, it is considered that the surface of the obtained copper particles is uneven. When the average value of the particle diameter / thickness of the copper particles is larger than 10, since the copper particles containing such irregularities are included, when the conductive paste is applied to the substrate, the copper particles in the paste It will not be closely aligned. For this reason, the electroconductivity of the electrically conductive film formed becomes low, and the change (decrease) of electroconductivity before and behind holding | maintenance in a high-temperature, high-humidity environment becomes large.
(A) It is preferable that the average value of the particle diameter / thickness of the copper particle of a component is 3-8.

As the copper particles of the component (A), the average particle diameter and the average particle diameter / thickness are in addition to the copper particles (A1) in the above range, and the average aggregate particle diameter 20 on the surface of the copper particles. Copper composite particles (A2) to which copper hydride fine particles of ˜400 nm are attached and copper composite particles (A3) to which copper fine particles having an average aggregate particle diameter of 20 to 400 nm are attached to the surface of the copper particles can also be used.
When the copper hydride fine particles are heated, the copper hydride is converted into metallic copper to form copper fine particles. That is, the copper composite particles (A2) to which the copper hydride fine particles are attached become the copper composite particles (A3) to which the copper fine particles are attached by being heated.
In addition, when using these copper composite particles (A2) and (A3) as the copper particles of the component (A), the average value of the particle diameters in the state of the composite copper particles to which the copper fine particles or the copper hydride fine particles are attached, And the average value of particle diameter / thickness needs to satisfy said range.

In addition, in the particle size distribution based on the number of copper particles of the component (A), the particle size when the integrated value from the small particle size side is 10% is D10, and the particle size when 50% is D50 and 90%. When the particle diameter is D90, it is preferable that the value of D90 / D50 is 4 or less and the value of D90 / D10 is 3 or more. If the value of D90 / D50 is 4 or less, it becomes easy to produce a fine wiring using a conductive paste. If the value of D90 / D10 is 3 or more, the copper particle density in the conductive film formed using the conductive film paste is improved and the conductivity is improved.
The number-based particle size distribution of the component (A) copper particles is determined from the particle size measurement results obtained by the above procedure. Specifically, the integrated value from the small particle diameter side is obtained, the particle diameter when the integrated value from the small particle diameter side is 10% is D10, and the integrated value from the small particle diameter side is 50%. The particle diameter is D50, and the particle diameter when the integrated value from the small particle diameter side is 90% is D90.

Further, the copper particles as the component (A) preferably have a surface oxygen amount of 0.5 or less. When copper particles having a surface oxygen content of 0.5 or less are used, the contact resistance between the copper particles becomes smaller, and the conductivity of the obtained conductive film is improved.
The “surface oxygen amount” in the present invention is represented by the ratio of the surface oxygen concentration (unit: atomic%) to the surface copper concentration (unit: atomic%) of the copper particles. In addition, the surface copper concentration and surface oxygen concentration of a copper particle are calculated | required by X-ray photoelectron spectroscopy analysis. Measurements are made over a range from the particle surface to the center to a depth of about 3 nm. If the measurement is performed in this range, the state of the particle surface can be sufficiently grasped.
As the copper particles having a surface oxygen amount of 0.5 or less, “surface modified copper particles” formed by reducing the surface of the copper particles, or “composite metal copper particles having copper fine particles attached to at least a part of the surface of the copper particles” Can be preferably used.

The “surface-modified copper particles” in the present invention are obtained by reducing the surface of the above-described copper particles (A1) in a dispersion medium having a pH value of 3 or less. For example, (1) copper particles (2) adjusting the pH value of the copper dispersion to a predetermined value or less, and (3) adding a reducing agent to the copper dispersion by a wet reduction method. Can be manufactured.
In addition, when using surface-modified copper particles as the copper particles of the component (A), the average particle diameter and the average particle diameter / thickness in the state after the reduction treatment on the surface of the copper particles must satisfy the above ranges. There is.

The “composite metal copper particles” in the present invention are obtained by attaching metal copper fine particles to at least a part of the surface of the metal copper particles, and “copper composite particles obtained by attaching copper hydride fine particles to the surface of the metal copper particles. Is heated to convert the copper hydride fine particles into metal copper fine particles. Therefore, the “copper composite particles” referred to here correspond to the copper composite particles (A2) described above. Further, the “composite metal copper particles” referred to here corresponds to the copper composite particles (A3) described above.
In addition, the presence or absence of adhesion of fine particles on the surface of the metal copper particles can be confirmed by observing the SEM image. Moreover, the copper hydride fine particles adhering to the surface of the metal copper particles can be identified using an X-ray diffractometer (manufactured by Rigaku Corporation, TTR-III).

  The copper hydride fine particles in the copper composite particles are present mainly as secondary particles in which primary particles of about 1 to 20 nm are aggregated, and the particle shape may be spherical or plate-like. The average aggregate particle diameter of the copper hydride fine particles is preferably 20 to 400 nm, more preferably 30 to 300 nm, and still more preferably 50 to 200 nm. Most preferably, it is 80-150 nm. If the average agglomerated particle diameter of the copper hydride fine particles is less than 20 nm, the copper hydride fine particles are likely to be fused and grown, and there is a possibility that defects such as cracks due to volume shrinkage may occur when the conductive film is formed. is there. On the other hand, when the average agglomerated particle diameter of the copper hydride fine particles exceeds 400 nm, the particle surface area is not sufficient, the surface melting phenomenon hardly occurs, and it becomes difficult to form a dense conductive film. The average agglomerated particle size of the copper hydride fine particles was measured by measuring the particle size of 100 copper hydride fine particles randomly extracted from a transmission electron microscope (hereinafter referred to as “TEM”) image. It is calculated by averaging the values.

  The amount of the copper hydride fine particles adhering to the surface of the metal copper particles is preferably 5 to 50% by mass, and more preferably 10 to 35% by mass of the amount of the metal copper particles. When the amount of the copper hydride fine particles is less than 5% by mass of the amount of the metal copper particles, the conductive path is not sufficiently formed between the metal copper particles, and the conductivity of the conductive film may not be improved. On the other hand, when the amount of copper hydride fine particles exceeds 50% by mass of the amount of metal copper particles, it becomes difficult to ensure sufficient fluidity as a conductive paste. The amount of copper hydride fine particles adhering to the surface of the metal copper particles is, for example, the copper ion concentration in the water-soluble copper compound solution before adding the reducing agent and the reaction liquid after the completion of copper hydride fine particle production. It can be calculated from the difference from the remaining copper ion concentration.

  In the conductive paste of the present invention, the blending amount of the copper particles as the component (A) is 78 to 94.99% by mass in the conductive paste.

(B) Modified dimethylsiloxane The modified dimethylsiloxane of component (B) has a structure in which polydimethylsiloxane is a basic structure, and some methyl groups of dimethylsiloxane are replaced with substituted parts. The nature of the silicon skeleton and the substitution part is a major factor that determines the characteristics, and the number of silicon skeletons is preferably 2 to 400, more preferably 40 to 400. Further, the substituted part preferably has a structure in which a methyl group is substituted with polyether or polyester.

In the conductive paste using silver particles as the conductive particles, a thermoplastic resin such as a polyester resin or a phenoxy resin is used as the binder resin because it can be cured at a low temperature in a short time.
On the other hand, in the case of the conductive paste of the present invention, since the copper particles of the component (A) are more easily oxidized than the silver particles, from the viewpoint of improving the reliability of the conductive film, as described later, As the binder resin of component (C), a thermosetting resin is used.

  However, when a thermosetting resin is used as the binder resin, the fluidity of the copper particles tends to be difficult to ensure during the heat curing. The reason is that the thermoplastic resin softens when heated, but in the case of a thermosetting resin, the curing progresses when heated and the viscosity increases. In particular, since the conductive paste of the present invention uses flat copper particles as the component (A), it is difficult to ensure sufficient fluidity of the copper particles during heat curing. Therefore, it may be difficult for the copper particles in the conductive paste to be closely aligned.

On the other hand, in the conductive paste of the present invention, by blending modified dimethylsiloxane as the component (B), it becomes easy for the copper particles in the conductive paste to be closely aligned. For this reason, the present inventors have estimated the following mechanism of action.
Since the modified dimethylsiloxane of the component (B) is also used as a leveling agent, the surface tension of the binder resin of the component (C) is reduced and the leveling property of the conductive paste is improved. It becomes easy for the copper particles to be closely aligned.

However, when an acrylic copolymer generally used as a leveling agent is used as the component (B), a conductive film having good conductivity cannot be obtained. For this reason, the present inventors presume that this is due to the difference in compatibility between the component (B) and the binder resin of the component (C).
That is, when the modified dimethylsiloxane as the component (B) is compared with the acrylic copolymer, the modified dimethylsiloxane has a higher compatibility with the binder resin as the component (C). Therefore, the modified dimethylsiloxane is dispersed in the binder resin of the component (C) at the time of heat curing and does not exist so much at the interface between the closely aligned copper particles, and the conductivity of the formed conductive film is improved. . On the other hand, an acrylic copolymer having a low compatibility with the binder resin of the component (C) cannot exist so much in the binder resin of the component (C) at the time of heat curing, and between the closely aligned copper particles. As a result of the conductivity being hindered by the acrylic copolymer present at the interface, the conductivity of the formed conductive film is lowered.

  A commercially available product may be used as the modified dimethylsiloxane constituting the component (B). Specific examples of commercially available products include BYK (registered trademark) 310, BYK (registered trademark) 322, BYK (registered trademark) 323, BYK (registered trademark) 307, BYK (registered trademark) 315, BYK (registered trademark) 322, There are BYK (registered trademark) 323, BYK (registered trademark) 330, and BYK (registered trademark) 333 (all manufactured by Big Chemie Japan Co., Ltd.).

In the conductive paste of the present invention, the amount of the component (B) modified dimethylsiloxane is 0.01 to 2% by mass in the conductive paste.
Since the blending amount of the component (B) modified dimethylsiloxane satisfies the above range, the conductive film formed using the conductive paste has good conductivity and excellent durability.
When the blending amount of the component (B) -modified dimethylsiloxane is less than 0.01% by mass in the conductive paste, it is difficult to arrange the copper particles in the conductive paste in a dense arrangement. For this reason, the electroconductivity of the electrically conductive film formed becomes low, and the change (decrease) of electroconductivity before and behind holding | maintenance in a high-temperature, high-humidity environment becomes large.
On the other hand, if the blending amount of the component (B) modified dimethylsiloxane exceeds 2% by mass in the conductive paste, even if it is a modified dimethylsiloxane having a high compatibility with the component (C) binder resin, heat curing is performed. It is considered that the conductivity of the formed conductive film is lowered as a result of being present at the interface between the closely aligned copper particles and impeding the conductivity.

(C) Binder Resin As described above, in the conductive paste using copper particles as the conductive particles, a thermosetting resin is used as the binder resin. In the conductive paste of the present invention, a binder resin made of a thermosetting resin containing formaldehyde as one component is used as the binder resin of component (C). The reason is that the reduction of the methylol group produced 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.
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 copper particles cannot be ensured.
In the conductive paste of the present invention, as described above, the compatibility between the component (B) modified dimethylsiloxane and the component (C) binder resin is high, so that the copper particles in the conductive paste are dense. However, when a thermosetting resin having low compatibility with the modified dimethylsiloxane is used as the binder resin, such as an epoxy resin, the copper particles in the conductive paste may be closely aligned. It becomes difficult. As a result, the conductivity of the conductive film formed becomes low, and the change (decrease) in the conductivity before and after holding in a high temperature and high humidity environment becomes large.

  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 copper particles. However, it is preferable that it is 5-20 mass% in an electrically conductive paste, and 5-10 mass% is more preferable. If it is 5 mass% or more, the flow characteristics of the conductive paste will be good. If it is 20 mass% or less, the electroconductivity of the electrically conductive film formed using an electrically conductive paste will become favorable.

In addition to the components (A) to (C) described above, the conductive paste of the present invention has, as component (D), a stability constant logK _Cu with copper ions at 25 ° C. and an ionic strength of 0.1 mol / L. It is preferable to contain the chelating agent which consists of a compound whose is 5-15. By containing such a chelating agent as component (D), the durability of the conductive film formed using the conductive paste is further improved. The reason for this is that the chelating agent comprising a compound having a stability constant logK _Cu of 5 to 15 with a copper ion at an ionic strength of 0.1 mol / L at 25 ° C. is derived from the copper particles of the component (A) which is a conductive component. This is thought to be due to the formation of a complex with the generated copper ions to suppress the formation of copper oxide in the conductive paste.

With regard to the “stability constant logK _Cu ” in the present invention, specific numerical values for various compounds include, for example, Chemical Handbook (Maruzen), Stability Constants of Metal-Ion Complexes (PERGAMON PRESS), Journal of Chemical Engine ( (ACS Publications).

As a chelating agent for component (D), a copper ion generated in a conductive paste by blending a compound having a stability constant logK _Cu of 5 or more with a copper ion at an ionic strength of 0.1 mol / L at 25 ° C. At least a part of is considered to form a complex with the compound. Therefore, the amount of copper ions that react with moisture, oxygen, etc. (for example, O ₂ , H ₂ O, etc.) in the atmosphere can be reduced, and the formation of copper oxide in the paste can be suppressed.
In addition, the above-described compound that forms a complex with copper ions is unlikely to dissociate from the copper ions, so that the complex state can be maintained for a long time even when left in a high humidity environment. Therefore, the formation of copper oxide is suppressed even in the conductive film, and as a result, a conductive paste capable of forming a conductive film in which a change (decrease) in conductivity before and after holding in a high-temperature and high-humidity environment is suppressed is obtained.

When the stability constant logK _Cu of the compound used as the chelating agent of component (D) is less than 5, the binding force to copper ions is not sufficient, so the amount of copper ions that react with moisture, oxygen, etc. in the atmosphere is sufficient. It cannot be reduced, and it becomes difficult to suppress the production of copper oxide.
On the other hand, when the stability number logK _Cu of the compound used as the chelating agent of the component (D) exceeds 15, the binding force of the compound used as the chelating agent of the component (D) to the copper ion is too strong, and the contact between the copper particles is caused. There is a risk of hindering and reducing conductivity. This is presumably because the compound used as the chelating agent for component (D) acts not only on the copper ions present in the conductive paste but also on the copper particles.
The stability constant logK _Cu of the compound used as the chelating agent for component (D) is more preferably 7-14.

In the conductive paste of the present invention, the blending amount of the (D) component chelating agent is preferably 0.01 to 1% by mass in the conductive paste.
When the content of the chelating agent (D) is less than 0.01% by mass, a sufficient effect of suppressing the change (decrease) in conductivity before and after holding in a high temperature and high humidity environment can be obtained. There is a risk of not being able to. On the other hand, when content of a chelating agent (D) exceeds 1 mass%, there exists a possibility that the contact of copper particles may be inhibited and electroconductivity may be reduced.

  As the chelating agent of component (D), a functional group (a) containing a nitrogen atom and a functional group (b) containing an atom having a lone pair other than the nitrogen atom are arranged at the ortho position of the aromatic ring. Aromatic compounds can be used. Here, examples of the functional group (a) containing a nitrogen atom include an amino group amide group or an imino group. Examples of the functional group (b) containing an atom having a lone electron pair other than a nitrogen atom include a hydroxyl group or a carboxyl group.

Specific examples of the chelating agent for component (D) include salicylhydroxamic acid (logK _Cu = 12), salicylaldoxime (logK _Cu = 13), o-aminophenol (logK _Cu = 7.8). At least one or more compounds selected from can be used.

(E) Other components In addition to the components (A) to (D) above, the conductive paste of the present invention includes a solvent and various additives (coupling 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 the printing paste, the amount of the solvent contained in the conductive paste is preferably 5 to 40% by mass in the conductive paste.

  The conductive paste can be obtained by mixing the components (A) to (D) above and other components such as the solvent as necessary. When mixing each component of said (A)-(D), 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 copper 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 average value of the particle diameter of the component (A) is 1.0 μm to 15 μm, and the average particle diameter / thickness is 2 to 10 in a flat shape In addition to the copper particles, (B) component dimethylsiloxane and (C) binder resin made of thermosetting resin containing formaldehyde as a component are contained. The conductive film is excellent in conductivity and durability. And when a conductive paste contains the chelating agent which consists of a compound whose stability constant logK _Cu is 5-15 with copper ion in 25 degreeC and ionic strength 0.1 mol / L as (D) component, it is durable. The nature is further improved. Therefore, the electrically conductive film obtained from the electrically conductive paste of this invention has the further outstanding electroconductivity 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 above-described conductive paste of the present invention on the base material.
Examples of the substrate main 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 copper 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 25 μΩcm or less. When the specific resistance of the conductive film exceeds 25 μΩcm, it may be difficult to use it as a conductor for electronic equipment.
Moreover, it is preferable that the amount of change (decrease) in specific resistance before and after holding in a high-temperature and high-humidity environment measured by the procedure described in the examples described later is 20% 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 20 are comparative examples. The particle diameter, particle diameter / thickness, conductive film thickness, and specific resistance of the copper particles were measured using the following apparatuses.

(Particle size)
The particle diameter of the copper particles was determined by measuring the Feret diameter of one particle randomly selected from the SEM image 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 about 100 copper particles selected from the SEM image, after calculating the particle diameter of each copper particle by the calculation method of said particle diameter, the particle diameter of the calculated copper particle is averaged (number average) Thus, the average value of the particle diameter was obtained.
Further, the particle size distribution based on the number of copper particles was determined from the measurement result of the particle size obtained by the above procedure. Specifically, the integrated value from the small particle diameter side is obtained, the particle diameter when the integrated value from the small particle diameter side is 10% is D10, and the integrated value from the small particle diameter side is 50%. The particle diameter was D50, and the particle diameter when the integrated value from the small particle diameter side was 90% was D90. The values of D90 / D50 and D90 / D10 are shown in the following table.

(Particle diameter / thickness)
When calculating the particle diameter of the copper particles by the above procedure, the thickness of one copper particle used for the calculation is measured, and the ratio between the particle diameter of the copper particles and the thickness (particle diameter / thickness). Asked. Then, for 100 copper particles randomly selected from the SEM image, by averaging (number average) the (particle diameter / thickness) of the copper particles calculated as described above, the particle diameter / thickness The average value was obtained.

(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 flat copper particles (Mitsui Metal Mining Co., Ltd., trade name: 1400YP) having an average particle diameter of 6 μm and an average particle diameter / thickness of 7.0 are 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 was heated at 80 ° C. for 60 minutes under a reduced pressure of −35 kPa to volatilize and remove residual moisture, and the copper particles (A-1) whose particle surfaces were surface-modified Got.
The surface-modified copper particles have an average particle diameter and an average particle diameter / thickness of 6 μm and 7.0, respectively, without change. It is to be noted that the average value of the particle diameter and the average value of the particle diameter / thickness of the copper particles after the surface modification are not changed in the other examples and comparative examples described below.

  The surface oxygen content of the obtained copper particles (A-1) was 0.16. This value is calculated by obtaining the surface oxygen concentration [atomic%] and the surface copper concentration [atomic%] by X-ray photoelectron spectroscopy (PHI5500, manufactured by ULVAC-PHI Co., Ltd.), and dividing the surface oxygen concentration by the surface copper concentration. did. In addition, when it measured using the oxygen meter (the product number: "ROH-600" by LECO Japan Co., Ltd.), the oxygen amount in a copper particle (A-1) was 460 ppm.

  Next, 12 g of the obtained surface-modified copper particles (A-1) was added to a phenol resin as a component (C) (manufactured by Gunei Chemical Co., Ltd., trade name: RESITOP PL6220, all the same in the following examples). 0.7 g was added to a resin solution dissolved in 4.3 g of ethylene glycol monobutyl ether acetate. Furthermore, together with this mixture, 0.048 g of polyether-modified dimethylsiloxane (BIC Chemie Japan Co., Ltd .: BYK (registered trademark) 333) as component (B) is put in a mortar and mixed at room temperature to obtain a copper paste. Obtained. The blending amount of component (B) (polyether-modified dimethylsiloxane) was 0.2% by mass in the copper paste.

Example 2
The copper particles were changed to flat copper particles (trade name: AFS-Cu, manufactured by Nippon Atomizing Co., Ltd.) having an average particle diameter of 7 μm and an average particle diameter / thickness of 6.0. A copper paste was obtained in the same manner as in Example 1.

Example 3
The copper particles were changed to flat copper particles (trade name: AFS-Cu, manufactured by Nippon Atomizing Co., Ltd.) with an average particle diameter of 5 μm and an average particle diameter / thickness of 3.5. A copper paste was obtained in the same manner as in Example 1.

Example 4
12 g of the surface-modified copper particles (A-1) 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. Further, together with this mixture, 0.048 g of polyether-modified dimethylsiloxane (BIC Chemie Japan Co., Ltd .: BYK (registered trademark) 307) as component (B) is put in a mortar and mixed at room temperature to obtain a copper paste. Obtained. The blending amount of component (B) (polyether-modified dimethylsiloxane) was 0.2% by mass in the copper paste.

Example 5
12 g of the surface-modified copper particles (A-1) 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. Furthermore, together with this mixture, 0.19 g (active ingredient: 0.048 g) of (B) polyester-modified dimethylsiloxane (BIC Chemie Japan Co., Ltd .: BYK (registered trademark) 315) is put in a mortar and mixed at room temperature. A copper paste was obtained. In addition, the compounding quantity of (B) component (polyester modified dimethylsiloxane) was 0.2 mass% in the copper paste.

Example 6
12 g of the surface-modified copper particles (A-1) 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. Furthermore, together with this mixture, 0.012 g of polyether-modified dimethylsiloxane (BIC Chemie Japan Co., Ltd .: BYK (registered trademark) 333) as component (B) is placed in a mortar and mixed at room temperature to obtain a copper paste. Obtained. The amount of component (B) (polyether-modified dimethylsiloxane) was 0.05% by mass in the copper paste.

Example 7
12 g of the surface-modified copper particles (A-1) 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. Furthermore, together with this mixture, 0.24 g of polyether-modified dimethylsiloxane (BIC Chemie Japan Co., Ltd .: BYK (registered trademark) 333) as component (B) is placed in a mortar and mixed at room temperature to obtain a copper paste. Obtained. The blending amount of component (B) (polyether-modified dimethylsiloxane) was 1.0% by mass in the copper paste.

Example 8
12 g of the surface-modified copper particles (A-1) 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. Furthermore, together with this mixture, 0.048 g of polyether-modified dimethylsiloxane (BIC Chemie Japan Co., Ltd .: BYK (registered trademark) 333) as component (B) and 0.024 g of salicylaldoxime as component (D) It was put in a mortar and mixed at room temperature to obtain a copper paste. The blending amount of the component (B) (polyether-modified dimethylsiloxane) is 0.2% by mass in the copper paste, and the blending amount of the component (D) (chelating agent) is 0.00% in the copper paste. It was 1% by mass.

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

Example 10
The copper particles were changed to flat copper particles (trade name: AFS-Cu, manufactured by Nippon Atomizing Co., Ltd.) having an average particle diameter of 7 μm and an average particle diameter / thickness of 6.0. 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1, except that the modified dimethylsiloxane as the component (B) was not added, at room temperature in the same manner as in Example 1. The copper paste was obtained by mixing.

Example 11
The copper particles were changed to flat copper particles (trade name: AFS-Cu, manufactured by Nippon Atomizing Co., Ltd.) with an average particle diameter of 5 μm and an average particle diameter / thickness of 3.5. 12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1, except that the modified dimethylsiloxane as the component (B) was not added, at room temperature in the same manner as in Example 1. The copper paste was obtained by mixing.

Example 12
12 g of the surface-modified copper particles (A-1) 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. Furthermore, together with this mixture, 0.0012 g of polyether-modified dimethylsiloxane (BIC Chemie Japan Co., Ltd .: BYK (registered trademark) 333) as component (B) is placed in a mortar and mixed at room temperature to obtain a copper paste. Obtained. The blending amount of component (B) (polyether-modified dimethylsiloxane) was 0.005% by mass in the copper paste.

Example 13
12 g of the surface-modified copper particles (A-1) 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. Further, together with this mixture, 0.72 g of polyether-modified dimethylsiloxane (BIC Chemie Japan Co., Ltd .: BYK (registered trademark) 333) as component (B) is put in a mortar and mixed at room temperature to obtain a copper paste. Obtained. In addition, the compounding quantity of (B) component (polyether modified dimethyloxane) was 3.0 mass% in copper paste.

Example 14
12 g of the surface-modified copper particles (A-1) 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. Further, together with this mixture, 0.096 g (active ingredient: 0.048 g) of silicon-modified acrylic copolymer (BIC Chemie Japan Co., Ltd .: BYK (registered trademark) 3550) as a component (B ′) in a mortar The mixture was mixed at room temperature to obtain a copper paste. In addition, the compounding quantity of (B ') component (silicon-modified acrylic copolymer) was 0.2 mass% in copper paste.

Example 15
12 g of the surface-modified copper particles (A-1) 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. Further, together with this mixture, 0.048 g of an acrylic copolymer (BYK (registered trademark) 350) manufactured by Big Chemie Japan Co., Ltd. was placed in a mortar as a component (B ′) instead of the component (B) at room temperature. To obtain a copper paste. In addition, the compounding quantity of (B ') component (acrylic-type copolymer) was 0.2 mass% in copper paste.

Example 16
An example except that the copper particles were changed to spherical copper particles (trade name: HXR-Cu manufactured by Nippon Atomizing Co., Ltd.) having an average particle diameter of 5 μm and an average particle diameter / thickness of 1.0. In the same manner as in No. 1, a copper paste was obtained.

Example 17
Example 1 except that the copper particles were changed to flat copper particles having a mean particle diameter of 16 μm and a mean particle diameter / thickness of 20 (made by Nippon Atomizing Co., Ltd., trade name: AFS-Cu). In the same manner, a copper paste was obtained.

Example 18
Example 1 except that the copper particles were changed to flat copper particles having a mean particle diameter of 8 μm and a mean particle diameter / thickness of 20 (made by Nippon Atomizing Co., Ltd., trade name: AFS-Cu). A copper paste was obtained in the same manner.

Example 19
12 g of the surface-modified copper particles (A-1) 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. Furthermore, with this mixture, 0.048 g of dimethyl silicone (manufactured by Shin-Etsu Chemical Co., Ltd .: KF-96) as a component (B ″) is placed in a mortar instead of the component (B) and mixed at room temperature. A copper paste was obtained. In addition, the compounding quantity of (B '') component (dimethyl silicone) was 0.2 mass% in copper paste.

Example 20
12 g of the surface-modified copper particles (A-1) obtained in the same manner as in Example 1 was replaced with (C ′) instead of the component (C) as an epoxy resin (product name: jER828) 1 .9 g and a curing agent (trade name: Amicure MY-24, manufactured by Ajinomoto Fine Techno Co., Ltd.) 0.2 g were added to a resin solution obtained by dissolving 4.3 g of ethylene glycol monobutyl ether acetate, and together with this mixture, component (B) 0.048 g of polyether-modified dimethylsiloxane (BYK (registered trademark) 333 manufactured by BYK Japan) was put in a mortar and mixed at room temperature to obtain a copper paste. The blending amount of component (B) (polyether-modified dimethylsiloxane) was 0.2% by mass in the copper paste.

  Next, each of the copper pastes obtained in Examples 1 to 20 was applied on a glass substrate, heated at 150 ° C. for 30 minutes to cure the phenol resin as the component (C), and a conductive film having a thickness of 10 μm. 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. The obtained conductive film was stored in an environment of 85 ° C. and 85% RH for 240 hours, and the change in specific resistance was measured together. The results are summarized in Table 1.

As can be seen from Table 1, the modified dimethylsiloxane as the component (B) is used together with the flat copper particles having an average particle diameter of 1.0 to 15 μm and an average particle diameter / thickness of 2 to 10. By using the conductive paste of Examples 1 to 8 blended in an amount of 0.01 to 2% by mass in the conductive paste, the conductive film obtained by applying the conductive paste to a substrate and curing it has a low specific resistance. 25 μΩcm or less. Moreover, the change (decrease) in conductivity before and after holding in a high-temperature and high-humidity environment was also suppressed, and the amount of change (reduction) in specific resistance before and after holding in a high-temperature and high-humidity environment was 20% or less. The conductive film produced using the conductive paste of Example 8 in which 0.01 to 1% by mass of salicylaldoxime is blended in the conductive paste as the chelating agent for component (D) has a particularly low specific resistance and high temperature. The amount of change (decrease) in specific resistance before and after holding in a high humidity environment was particularly small.
In contrast, Examples 9 to 11 in which the modified dimethylsiloxane as the component (B) was not blended, and the blended amount of the modified dimethylsiloxane as the component (B) was less than 0.01% by mass in the conductive paste. 12, Exceeding 3% by mass of Example 13, (B) Examples 14 and 15 in which an acrylic copolymer was blended in place of the modified dimethylsiloxane as the component, (A) As the copper particles of the component, the particle diameter / thickness Examples 16 and 10 having an average value of less than 2 and Comparative Examples 17 and 18 in excess of 10, Example 19 in which dimethyl silicone having no modification was blended in place of modified dimethylsiloxane as component (B), and binder resin of component (C) As for Example 20 which mix | blended epoxy resin, as for all, the specific resistance of the electrically conductive film produced using the electrically conductive paste is high, and the electrically conductive film apply | coated and hardened to the base material has low specific resistance, and exceeds 25 microhm-cm Met. Further, the change (decrease) in conductivity before and after holding in a high temperature and high humidity environment was large, and the amount of change (reduction) in specific resistance before and after holding in a high temperature and high humidity environment was more than 20%.

  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 (10)

A conductive paste containing (A) copper particles, (B) modified dimethylsiloxane, and (C) a binder resin made of a thermosetting resin containing formaldehyde as a component,
When the copper particle has a major axis as a radial direction in which the Feret diameter of the copper particle is a maximum value and an axis perpendicular to the major axis is a minor axis, the Feret diameter in the major axis direction and the minor axis direction When the average value of the Feret diameter is the particle diameter of the copper particles, the average value of the particle diameter of the copper particles is 1.0 to 15 μm, the particle diameter of the copper particles, and the copper particles The average value of the ratio of the thickness and the average value (particle diameter / average thickness) is 2 to 10 flat copper particles,
The conductive paste contains 78 to 94.99% by mass of the copper particles of the component (A), 5 to 20% by mass of the binder resin of the component (C), and the modified dimethylsiloxane of the component (B). In an amount of 0.01 to 2% by mass.   2. The conductive paste according to claim 1, wherein the modified dimethylsiloxane of the component (B) has a structure in which a part of methyl groups of dimethylsiloxane is substituted with polyether or polyester.   The conductive paste according to claim 1 or 2, wherein the binder resin of the component (C) is at least one selected from the group consisting of a phenol resin, a melamine resin, a xylene resin, and a urea resin. Further, (D) a chelating agent further comprising a compound having a stability constant logK _Cu of 5 to 15 with a copper ion at 25 ° C. and an ionic strength of 0.1 mol / L is further contained. The conductive paste described in 1.   In the chelating agent of the component (D), the functional group (a) containing a nitrogen atom and the functional group (b) containing an atom having a lone pair other than the nitrogen atom are arranged at the ortho position of the aromatic ring. The electrically conductive paste of Claim 4 which is an aromatic compound.   The conductive paste according to claim 4 or 5, wherein the chelating agent of the component (D) is one or more selected from the group consisting of salicylhydroxamic acid, salicylaldoxime, and o-aminophenol.   The electrically conductive paste in any one of Claims 4-6 which contains 0.01-1 mass part of chelating agents of the said (D) component with respect to a total of 100 mass parts of all the components of the said electrically conductive paste.   In the particle size distribution based on the number of copper particles of the component (A), when the integrated value from the small particle size side is 10%, the particle size is D10, and when the particle size is 50%, the particle size is D50, 90%. The conductive paste according to any one of claims 1 to 7, wherein the value of D90 / D50 is 4 or less and the value of D90 / D10 is 3 or more, when the particle diameter of D90 is D90.   9. The conductive paste according to claim 1, wherein the copper particles of the component (A) are copper particles having a surface oxygen content of 0.5 or less.   A base material with a conductive film, comprising a conductive film formed by applying and curing the conductive paste according to claim 1 on the base material.