JPWO2009116349A1 - Copper nanoparticle-coated copper filler, method for producing the same, copper paste, and article having metal film - Google Patents

Abstract

Copper nanoparticle-coated copper filler capable of forming a copper metal film with a lower volume resistivity than conventional ones, a method for producing the same, a copper paste capable of forming a copper metal film with a reduced volume resistivity, and a volume resistance An article having a copper metal film with a reduced rate is provided. The surface of the copper filler having an average particle diameter of 0.5 to 20 μm is a copper nanoparticle-coated copper filler coated with copper nanoparticles having an average particle diameter of 50 to 100 nm, and the copper nanoparticle with respect to 100 parts by mass of the copper filler The copper nanoparticle covering copper filler whose quantity of particle | grains is 5-50 mass parts is used.

Description

  The present invention relates to a copper nanoparticle-coated copper filler, a production method thereof, a copper paste containing the copper nanoparticle-coated copper filler, and an article having a metal film formed from the copper paste.

There is known a method of manufacturing a printed circuit board or the like having a metal film having a desired wiring pattern by applying and baking a silver paste containing a silver filler on a substrate in a desired wiring pattern. However, the silver metal film is liable to cause ion migration.
For this reason, considering the reliability of electronic devices, the use of copper paste instead of silver paste has been studied. However, since the copper filler is easily oxidized, the volume resistivity of the copper metal film formed by firing the copper filler is increased by the influence of the oxide film on the surface of the copper filler.
As a metal paste capable of forming a metal film having a low volume resistivity, the following has been proposed.
A metal paste containing a metal filler having an average particle diameter of 0.5 to 20 μm and metal ultrafine particles having an average particle diameter of 1 to 100 nm (Patent Document 1).

However, in the metal paste, the effect is actually confirmed only when the silver filler is selected as the metal filler and the silver fine particles are selected as the metal ultrafine particles. Even if copper fine particles are selected as ultrafine particles and these are simply mixed, an increase in volume resistivity of the metal film due to the oxide film of the copper filler cannot be suppressed.
International Publication No. 02/35554 pamphlet

  The present invention relates to a copper nanoparticle-coated copper filler capable of forming a copper metal film with a lower volume resistivity than the conventional one, a method for producing the same, and a copper capable of forming a copper metal film with a reduced volume resistivity. An article having a paste and a copper metal film with low volume resistivity is provided.

  The copper nanoparticle-coated copper filler of the present invention is a copper nanoparticle-coated copper filler in which the surface of a copper filler having an average particle size of 0.5 to 20 μm is coated with copper nanoparticles having an average particle size of 50 to 100 nm. The amount of copper nanoparticles with respect to 100 parts by mass of the copper filler is 5 to 50 parts by mass.

The manufacturing method of the copper nanoparticle coating | coated copper filler of this invention has the following process (I)-(II), It is characterized by the above-mentioned.
(I) The process of obtaining the copper hydride nanoparticle covering copper filler by making the surface of the copper filler whose average particle diameter is 0.5-20 micrometers coat | cover with the copper hydride nanoparticle whose average particle diameter is 20-50 nm.
(II) The copper hydride nanoparticle-coated copper filler was fired at 50 to 100 ° C. in an inert gas atmosphere, and the surface of the copper filler was coated with copper nanoparticles having an average particle diameter of 50 to 100 nm. The process of obtaining a copper nanoparticle covering copper filler.

The step (I) preferably comprises the following steps (I-1) to (I-2).
(I-1) A step of dispersing a copper filler having an average particle diameter of 0.5 to 20 μm and copper hydride nanoparticles having an average particle diameter of 20 to 50 in a dispersion medium to obtain a dispersion.
(I-2) A step of volatilizing and removing the dispersion medium from the dispersion to coat the surface of the copper filler with copper hydride nanoparticles to obtain a copper hydride nanoparticle-coated copper filler.

The relative dielectric constant of the dispersion medium is preferably 4 to 40.
It is preferable that the quantity of the dispersion medium in the said process (I-1) is 250-1250 mass parts with respect to a total of 100 mass parts of a copper filler and a copper hydride nanoparticle.

The copper hydride nanoparticles are preferably produced through the following steps (a) to (c).
(A) A step of dissolving a water-soluble copper compound in water to prepare an aqueous solution containing copper ions.
(B) A step of adjusting the pH to 3 or less by adding an acid to the aqueous solution.
(C) While stirring the aqueous solution having a pH of 3 or less, a step of adding a reducing agent to the aqueous solution to reduce copper ions to produce copper hydride nanoparticles having an average particle size of 20 to 50 nm.

The copper paste of the present invention includes the copper nanoparticle-coated copper filler of the present invention and a resin binder.
The article of the present invention is characterized by having a base material and a metal film formed by applying and baking the copper paste of the present invention on the base material.

According to the copper nanoparticle-coated copper filler of the present invention, a copper metal film having a low volume resistivity can be formed.
According to the method for producing a copper nanoparticle-coated copper filler of the present invention, a copper nanoparticle-coated copper filler capable of forming a copper metal film with a low volume resistivity can be produced.
According to the copper paste of the present invention, a copper metal film having a low volume resistivity can be formed.
The article of the present invention has a copper metal film with a low volume resistivity.

It is a SEM image of a copper hydride nanoparticle covering copper filler. It is a SEM image of a copper nanoparticle covering copper filler. It is a SEM image of the mixture of a copper filler and a copper hydride nanoparticle.

<Copper filler coated with copper nanoparticles>
The copper nanoparticle-coated copper filler of the present invention is one in which at least a part of the surface of the copper filler is coated with copper nanoparticles.
The fact that the surface of the copper filler is coated with copper nanoparticles means that a scanning electron microscope (hereinafter referred to as SEM) image is observed, and a plurality of copper nanoparticles adhere to at least a part of the surface of the copper filler. This can be confirmed. By simply mixing the copper filler and copper nanoparticles, there is a separate copper filler and aggregate of copper nanoparticles, which can be clearly distinguished from the copper filler surface coated with copper nanoparticles. .

(Copper filler)
As a copper filler, the well-known copper particle used for a copper paste is mentioned.
The average particle diameter of a copper filler is 0.5-20 micrometers, and 1-10 micrometers is preferable. If the average particle diameter of a copper filler is 0.5 micrometer or more, the flow characteristic of a copper paste will become favorable. If the average particle diameter of the copper filler is 20 μm or less, it becomes easy to produce fine wiring.
The average particle size of the copper filler is calculated by measuring and averaging the particle size of 100 copper fillers randomly selected from a transmission electron microscope (hereinafter referred to as TEM) image or SEM image. To do.

(Copper nanoparticles)
The average particle diameter of the copper nanoparticles is 50 to 100 nm, and preferably 60 to 80 nm. If the average particle diameter of the copper nanoparticles is 50 nm or more, cracks generated in the metal film due to volume shrinkage accompanying the fusion / growth of the copper nanoparticles are unlikely to occur. If the average particle diameter of the copper nanoparticles is 100 nm or less, the surface melting temperature is sufficiently lowered, so that surface melting is likely to occur and a dense metal film can be formed, so that improvement in conductivity can be expected.
The average particle diameter of the copper nanoparticles is calculated by measuring and averaging the particle diameters of 100 copper nanoparticles randomly selected from the TEM image or SEM image.

The quantity of a copper nanoparticle is 5-50 mass parts with respect to 100 mass parts of copper fillers, and 10-35 mass parts is preferable. If the amount of copper nanoparticles is 5 parts by mass or more, the conductive paths between the copper fillers can be increased, and the volume resistivity of the metal film can be kept low. If the quantity of copper nanoparticles is 50 mass parts or less, the fall of the fluidity | liquidity of the copper paste accompanying the addition of copper nanoparticles can be suppressed.
The amount of the copper nanoparticles in the present invention can be calculated from the addition amount when the copper hydride nanoparticles and the copper filler are added to the dispersion medium.

  In the copper nanoparticle-coated copper filler of the present invention described above, since the surface of the copper filler is coated with copper nanoparticles, the copper nanoparticles are always present between the copper fillers when the metal film is formed. It will be. Therefore, a conductive path is reliably formed by the copper nanoparticles, and the volume resistivity of the metal film is kept low. Moreover, since there is no excess copper nanoparticle which exists independently from a copper filler, the quantity of expensive copper nanoparticle can be restrained low. Moreover, since there is no excess copper nanoparticle which exists independently from a copper filler, when it is set as a copper paste, the increase in the viscosity of a copper paste can be suppressed.

<Method for producing copper filler coated with copper nanoparticles>
The manufacturing method of the copper nanoparticle covering copper filler of the present invention is a method having the following steps (I) to (II).
(I) The process of obtaining the copper hydride nanoparticle covering copper filler by making the surface of the copper filler whose average particle diameter is 0.5-20 micrometers coat | cover with the copper hydride nanoparticle whose average particle diameter is 20-50 nm.
(II) The copper hydride nanoparticle-coated copper filler was fired at 50 to 100 ° C. in an inert gas atmosphere, and the surface of the copper filler was coated with copper nanoparticles having an average particle diameter of 50 to 100 nm. The process of obtaining a copper nanoparticle covering copper filler.

Step (I):
The step (I) preferably comprises the following steps (I-1) to (I-2).
(I-1) A step of obtaining a dispersion by dispersing copper filler having an average particle diameter of 0.5 to 20 μm and copper hydride nanoparticles having an average particle diameter of 20 to 50 nm in a dispersion medium.
(I-2) A step of volatilizing and removing the dispersion medium from the dispersion to coat the surface of the copper filler with copper hydride nanoparticles to obtain a copper hydride nanoparticle-coated copper filler.

Step (I-1):
The relative dielectric constant of the dispersion medium is preferably 4 to 40, and more preferably 10 to 30. If the relative dielectric constant of the dispersion medium is 4 or more, the dispersibility of the copper hydride nanoparticles will be good. If the relative dielectric constant of the dispersion medium is 40 or less, the dispersibility of the copper filler will be good.
Examples of the dispersion medium include the following. The relative dielectric constant is shown in parentheses.
Methyl alcohol (33.0 (20 ° C.)), ethyl alcohol (25.3 (20 ° C.)), 1-propanol (20.8 (20 ° C.)), 2-propanol (20.2 (20 ° C.)), 1-butanol (17.8 (20 ° C.)), 2-butanol (17.3 (20 ° C.)), isobutyl alcohol (17.9 (20 ° C.)), 1-pentanol (15.1 (25 ° C.)) ), Isopentyl alcohol (14.7 (20 ° C.)), 1-hexanol (13.3 (20 ° C.)), 1-octanol (10.3 (20 ° C.)), cyclohexanol (16.4 (20 ° C.)) )), Cyclohexanone (16.1 (20 ° C.)), acetone (21.0 (20 ° C.)), octyl alcohol (10.3 (20 ° C.)), ethyl acetate (6.1 (20 ° C.)) and the like.
As the dispersion medium, 1-propanol (20.8 (20 ° C.)) or 2-propanol (20.2 (20 ° C.)) is preferable because both the copper filler and the copper hydride nanoparticles are excellent in dispersibility.

  The amount of the dispersion medium in the step (I-1) is preferably 250 to 1250 parts by mass and more preferably 300 to 750 parts by mass with respect to a total of 100 parts by mass of the copper filler and the copper hydride nanoparticles. When the amount of the dispersion medium is 250 parts by mass or more, the copper hydride nanoparticles and the copper filler can be uniformly dispersed in the dispersion medium. When the amount of the dispersion medium is 1250 parts by mass or less, the time required for volatilizing the dispersion medium is short, and the manufacturing cost can be suppressed.

Copper hydride nanoparticles exist in a state where copper atoms are bonded to hydrogen atoms, and have a property of decomposing into metal copper and hydrogen at 50 to 100 ° C.
As a copper hydride nanoparticle, what is obtained with the manufacturing method of the copper hydride nanoparticle mentioned later is mentioned, for example.

The average particle diameter of the copper hydride nanoparticles is 20 to 50 nm, and preferably 25 to 40 nm. If the average particle diameter of the copper hydride nanoparticles is 20 nm or more, aggregation of the copper hydride nanoparticles during firing can be suppressed. If the average particle diameter of the copper hydride nanoparticles is 50 nm or less, copper hydride nanoparticles with sufficiently high surface activity can be obtained.
The average particle diameter of the copper hydride nanoparticles is calculated by measuring and averaging the particle diameters of 100 particles randomly selected from the TEM image or SEM image.

  The amount of the copper hydride nanoparticles is 5 to 50 parts by mass, preferably 10 to 35 parts by mass with respect to 100 parts by mass of the copper filler. If the amount of copper hydride nanoparticles is 5 parts by mass or more, the conductive path between the copper fillers can be increased, and the volume resistivity of the metal film can be kept low. When the amount of the copper hydride nanoparticles is 50 parts by mass or less, deterioration of the fluidity of the dispersion accompanying the addition of the copper hydride nanoparticles can be suppressed.

Step (I-2):
The volatilization of the dispersion medium is preferably performed gradually under a reduced pressure of −40 to −20 kPa. When the pressure is −40 kPa or more, the copper hydride nanoparticles and the copper filler can be uniformly dispersed until immediately before the dispersion medium is completely volatilized. When the pressure is −20 kPa or less, the time required for volatilizing the dispersion medium is short, and the manufacturing cost can be suppressed.
The fact that the surface of the copper filler is coated with copper hydride nanoparticles can be confirmed by observing the SEM image and confirming that a plurality of copper hydride nanoparticles are attached to at least a part of the surface of the copper filler.

Step (II):
By firing the copper hydride nanoparticle-coated copper filler at 50 to 100 ° C. in an inert gas atmosphere, the copper hydride nanoparticles on the surface of the copper filler are decomposed into metallic copper and hydrogen, and at the same time the nanoparticles are bonded to each other. It sinters and the copper nanoparticle whose particle diameter is 50-100 nm is obtained.

Examples of the inert gas include nitrogen gas, helium, neon, argon, krypton, xenon, and radon, and nitrogen gas is preferable.
A calcination temperature is 50-100 degreeC, and 60-80 degreeC is preferable. If a calcination temperature is 50 degreeC or more, the copper nanoparticle covering copper filler which can suppress generation | occurrence | production of the crack which arises in a metal film will be obtained. If a calcination temperature is 100 degrees C or less, the copper nanoparticle covering copper filler in which the activity of the copper nanoparticle surface is not lost is obtained.

(Method for producing copper hydride nanoparticles)
Copper hydride nanoparticles are produced, for example, by a method (wet reduction method) having the following steps (a) to (d).
(A) A step of dissolving a water-soluble copper compound in water to prepare an aqueous solution containing copper ions.
(B) A step of adjusting the pH to 3 or less by adding an acid to the aqueous solution.
(C) While stirring the aqueous solution having a pH of 3 or less, a step of adding a reducing agent to the aqueous solution to reduce copper ions to produce copper hydride nanoparticles having an average particle size of 20 to 50 nm.
(D) A step of purifying the copper hydride nanoparticles by redispersing them in a dispersion medium as necessary.

Step (a):
Examples of the water-soluble copper compound include copper sulfate, copper nitrate, copper formate, copper acetate, copper chloride, copper bromide, copper iodide and the like.
The concentration of the water-soluble copper compound is preferably 0.1 to 30% by mass in 100% by mass of the aqueous solution. If the density | concentration of the water-soluble copper compound in aqueous solution is 0.1 mass% or more, the quantity of water will be restrained and the production efficiency of a copper hydride nanoparticle will become favorable. If the density | concentration of the water-soluble copper compound in aqueous solution is 30 mass% or less, the fall of the yield of a copper hydride nanoparticle will be suppressed.

Step (b):
Examples of the acid for adjusting the pH of the aqueous solution to 3 or less include citric acid, maleic acid, malonic acid, acetic acid, formic acid, propionic acid, sulfuric acid, nitric acid, hydrochloric acid and the like, and the copper hydride nanoparticles are less likely to be oxidized. Therefore, formic acid is preferred.
By adjusting the pH of the aqueous solution to 3 or less, copper ions in the aqueous solution are easily reduced by the reducing agent, and copper hydride nanoparticles are easily generated. When pH of aqueous solution exceeds 3, there exists a possibility that a metal copper nanoparticle may produce | generate, without producing | generating a copper hydride nanoparticle.
The pH of the aqueous solution is preferably 2 to 2.5 because copper hydride nanoparticles can be generated in a short time.
In addition, you may perform a process (a) and a process (b) simultaneously.

Step (c):
Copper ions are reduced by a reducing agent under acidic conditions, and hydride copper nanoparticles are gradually grown to produce hydride copper nanoparticles having an average particle diameter of 20 to 50 nm. When formic acid is used as the acid that adjusts the pH of the aqueous solution to 3 or less, the copper hydride nanoparticles are immediately covered with the formic acid present together and stabilized.

  As the reducing agent, metal hydride or hypophosphorous acid is preferable because of its large reducing action. Examples of metal hydrides include lithium aluminum hydride, lithium borohydride, sodium borohydride, lithium hydride, potassium hydride, calcium hydride, and the like. Lithium aluminum hydride, lithium borohydride, borohydride Sodium is preferred.

The amount of the reducing agent added is preferably 1.5 to 10 times the number of equivalents of copper ions. If the amount of the reducing agent added is 1.5 times the number of equivalents or more of copper ions, the reducing action is sufficient. When the addition amount of the reducing agent is 10 times the number of equivalents or less with respect to copper ions, the amount of impurities (sodium, boron, phosphorus, etc.) contained in the copper hydride nanoparticles can be suppressed.
5-60 degreeC is preferable and, as for the temperature of the aqueous solution at the time of adding a reducing agent, 20-50 degreeC is more preferable. If the temperature of aqueous solution is 60 degrees C or less, decomposition | disassembly of a copper hydride nanoparticle will be suppressed.

Step (d):
When the suspension containing copper hydride nanoparticles is allowed to stand, the copper hydride nanoparticles aggregate and precipitate. After the precipitate is redispersed in a dispersion medium, the copper hydride nanoparticles are purified again by aggregating and precipitating, whereby highly purified copper hydride nanoparticles are obtained.

<Copper paste>
The copper paste of the present invention includes the copper nanoparticle-coated copper filler of the present invention and a resin binder.
Examples of the resin binder include known resin binders (thermosetting resins, thermoplastic resins, etc.) used for metal pastes, and a resin component that can be sufficiently cured at the firing temperature is selected and used. Is preferred.
Thermosetting resins include phenol resin, epoxy resin, unsaturated polyester, vinyl ester resin, diallyl phthalate resin, oligoester acrylate resin, xylene resin, bismaleidotriazine resin, furan resin, urea resin, polyurethane resin, melamine resin, silicon Examples thereof include resins, acrylic resins, oxetane resins, oxazine resins, and the like, and pheno resins, epoxy resins, or oxazine resins are preferable.
Examples of the thermoplastic resin include polyamide, polyimide, acrylic resin, ketone resin, polystyrene, and polyester.

  The amount of the resin binder in the copper paste may be appropriately selected according to the ratio between the volume of the copper nanoparticle-coated copper filler and the voids present between the fillers, and is usually 100 parts by mass of the copper nanoparticle-coated copper filler. On the other hand, 5-50 mass parts is preferable and 5-20 mass parts is more preferable. When the amount of the resin binder is 5 parts by mass or more, the flow characteristics of the paste are good. When the amount of the resin binder is 50 parts by mass or less, the volume resistivity of the metal film can be kept low.

The copper paste of the present invention contains a solvent, known additives (leveling agents, coupling agents, viscosity modifiers, antioxidants, etc.), etc., as necessary, as long as the effects of the present invention are not impaired. May be.
Since the copper paste of the present invention described above includes the copper nanoparticle-coated copper filler of the present invention, a metal film having a volume resistivity lower than that of a conventional copper paste can be formed.

<Article>
The article of the present invention has a base material and a metal film formed by applying and baking the copper paste of the present invention on the base material.

  Examples of the substrate include glass substrates, plastic substrates (polyimide substrates, polyester substrates, etc.), fiber reinforced composite materials (glass fiber reinforced resin substrates, etc.) and the like.

  Examples of the coating method include known methods such as screen printing, roll coating, air knife coating, blade coating, bar coating, gravure coating, die coating, and slide coating.

Examples of the firing method include warm air heating and thermal radiation.
The firing temperature and firing time may be appropriately determined according to the characteristics required for the metal film. The firing temperature is preferably 100 to 300 ° C. If a calcination temperature is 100 degreeC or more, it will become easy to sinter with a copper filler and a copper nanoparticle. When the firing temperature is 300 ° C. or lower, a plastic film can be used as a base material for forming a metal film.

The volume resistivity of the metal film is preferably 1.0 × 10 ⁻⁴ Ωcm or less. If the volume resistivity exceeds 1.0 × 10 ⁻⁴ Ωcm, it may be difficult to use as a conductor for electronic equipment.
In the article of the present invention described above, since the metal film is formed from the copper paste of the present invention, the volume resistivity of the metal film is lower than that of the conventional copper metal film.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
Examples 1 to 5 are examples, and examples 6 to 9 are comparative examples.

(Identification of copper hydride nanoparticles)
The copper hydride nanoparticles were identified with an X-ray diffractometer (manufactured by Rigaku Corporation, TTR-III).

(Average particle size)
The average particle size of the copper filler and nanoparticles was measured by measuring the particle size of 100 particles randomly selected from TEM images obtained by TEM (manufactured by JEOL Ltd., JEM-1230). It was calculated by doing.

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

(Volume resistivity of metal film)
The volume resistivity of the metal 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 container, 5.2 g of copper (II) acetate hydrate was dissolved in 30 g of distilled water and 3.3 g of formic acid to prepare an aqueous solution containing copper ions. The pH of the aqueous solution was 2.7.
While the aqueous solution was vigorously stirred, 23 g of a 4 mass% sodium borohydride aqueous solution was slowly added dropwise to the aqueous solution at 20 ° C. After completion of the dropwise addition, stirring was continued for 10 minutes to obtain a suspension.

  The aggregate in the suspension was precipitated by centrifugation, and the precipitate was separated. The precipitate was redispersed in 30 g of 2-propanol, and then the aggregate was precipitated again by centrifugation to separate the precipitate. When the precipitate after purification was identified by X-ray diffraction, it was confirmed to be copper hydride nanoparticles. The average particle diameter of the copper hydride nanoparticles was 30 nm.

  0.8 g of copper hydride nanoparticles and 3.2 g of copper filler (Mitsui Metal Mining Co., Ltd., 1400 YP, average particle size: 7 μm) were each 2-propanol (relative permittivity: 20.2 (20 ° C.)). The mixture was dispersed in 20 g, and both were mixed to obtain a dispersion. The addition amount of the copper hydride nanoparticles was 25 parts by mass with respect to 100 parts by mass of the copper filler. Moreover, the addition amount of 2-propanol was 500 mass parts with respect to a total of 100 mass parts of a copper filler and a copper hydride nanoparticle. 2-Propanol was volatilized and removed gradually from the dispersion under a reduced pressure of -35 kPa, and the surface of the copper filler was coated with copper hydride nanoparticles to obtain a copper hydride nanoparticle-coated copper filler. An SEM image of the copper hydride nanoparticle-coated copper filler is shown in FIG.

  The copper hydride-coated copper filler was baked at 80 ° C. for 30 minutes in a nitrogen gas atmosphere to obtain a copper nanoparticle-coated copper filler. The average particle diameter of the copper nanoparticles was 70 nm, and the average particle diameter of the copper filler was 7 μm. Moreover, the quantity of the copper nanoparticle with respect to 100 mass parts of copper fillers was 25 mass parts. An SEM image of the copper nanoparticle-coated copper filler is shown in FIG.

  Resin binder solution in which 1.2 g of copper nanoparticle coated copper filler and 0.135 g of amorphous polyester resin (byron 103, manufactured by Toyobo Co., Ltd.) are dissolved in 0.315 g of cyclohexanone (manufactured by Junsei Chemical, special grade). Of 0.45 g. The addition amount of the amorphous polyester resin was 11.3 parts by mass with respect to 100 parts by mass of the copper filler and the copper hydride nanoparticles. The mixture was mixed in a mortar and then placed under reduced pressure at room temperature to remove cyclohexanone and obtain a copper paste.

  Copper paste was applied to a glass substrate and baked at 150 ° C. for 1 hour in a nitrogen gas atmosphere to form a metal film having a thickness of 100 μm. The volume resistivity of the metal film was measured. The results are shown in Table 1.

[Example 2]
A copper nanoparticle-coated copper filler was obtained in the same manner as in Example 1, except that the copper hydride-coated copper filler was baked at 50 ° C. for 30 minutes in a nitrogen gas atmosphere. The average particle diameter of the copper nanoparticles was 51 nm, and the average particle diameter of the copper filler was 7 μm. Moreover, the quantity of the copper nanoparticle with respect to 100 mass parts of copper fillers was 25 mass parts.

  A copper paste was prepared in the same manner as in Example 1 except that the copper nanoparticle-coated copper filler was used, and a metal film was formed. The volume resistivity of the metal film was measured. The results are shown in Table 1.

[Example 3]
A copper nanoparticle-coated copper filler was obtained in the same manner as in Example 1, except that the copper hydride-coated copper filler was baked at 100 ° C. for 30 minutes in a nitrogen gas atmosphere. The average particle diameter of the copper nanoparticles was 97 nm, and the average particle diameter of the copper filler was 7 μm. Moreover, the quantity of the copper nanoparticle with respect to 100 mass parts of copper fillers was 25 mass parts.

  A copper paste was prepared in the same manner as in Example 1 except that the copper nanoparticle-coated copper filler was used, and a metal film was formed. The volume resistivity of the metal film was measured. The results are shown in Table 1.

[Example 4]
A copper nanoparticle-coated copper filler is obtained in the same manner as in Example 1 except that methyl alcohol (relative dielectric constant: 33.0 (20 ° C.)) is used as a dispersion medium when obtaining the copper hydride-coated copper filler. It was. The average particle diameter of the copper nanoparticles was 70 nm, and the average particle diameter of the copper filler was 7 μm. Moreover, the quantity of the copper nanoparticle with respect to 100 mass parts of copper fillers was 25 mass parts.

  A copper paste was prepared in the same manner as in Example 1 except that the copper nanoparticle-coated copper filler was used, and a metal film was formed. The volume resistivity of the metal film was measured. The results are shown in Table 1.

[Example 5]
A copper nanoparticle-coated copper filler is obtained in the same manner as in Example 1 except that ethyl acetate (relative dielectric constant: 6.1 (20 ° C.)) is used as a dispersion medium when obtaining the copper hydride nanoparticle-coated copper filler. It was. The average particle diameter of the copper nanoparticles was 71 nm, and the average particle diameter of the copper filler was 7 μm. Moreover, the quantity of the copper nanoparticle with respect to 100 mass parts of copper fillers was 25 mass parts.

  A copper paste was prepared in the same manner as in Example 1 except that the copper nanoparticle-coated copper filler was used, and a metal film was formed. The volume resistivity of the metal film was measured. The results are shown in Table 1.

[Example 6]
1.2 g of copper filler (Mitsui Metals Mining Co., Ltd., 1400 YP, average particle size: 7 μm) and 0.135 g of amorphous polyester resin (Toyobo Co., Ltd., Byron 103) cyclohexanone (manufactured by Junsei Chemical Co., Ltd., special grade) ) Was added to 0.45 g of the resin binder solution dissolved in 0.315 g. The addition amount of the amorphous polyester tree was 11.3 parts by mass with respect to 100 parts by mass of the copper filler. The mixture was mixed in a mortar and then placed under reduced pressure at room temperature to remove cyclohexanone and obtain a copper paste.

  Copper paste was applied to a glass substrate and baked at 150 ° C. for 1 hour in a nitrogen gas atmosphere to form a metal film having a thickness of 100 μm. The volume resistivity of the metal film was measured. The results are shown in Table 1.

[Example 7]
0.8 g of the copper hydride nanoparticles obtained in Example 1 and 3.2 g of a copper filler (Mitsui Metal Mining Co., Ltd., 1400 YP, average particle size: 7 μm) were mixed in a mortar. An SEM image of a mixture of copper hydride nanoparticles and copper filler is shown in FIG. It was confirmed that a copper filler (center of SEM image) and an aggregate of copper hydride nanoparticles (upper and lower right of SEM image) existed individually. The mixture was baked at 80 ° C. for 30 minutes in a nitrogen gas atmosphere to obtain a mixture of copper nanoparticles and a copper filler. The average particle diameter of the copper nanoparticles was 70 nm, and the average particle diameter of the copper filler was 7 μm. The addition amount of the copper nanoparticles was 25 parts by mass with respect to 100 parts by mass of the copper filler.

  1.2 g of a mixture of copper nanoparticles and copper filler is dissolved in 0.315 g of cyclohexanone (manufactured by Junsei Kagaku Co., Ltd.) 0.135 g of amorphous polyester resin (Toyobo Co., Ltd., Byron 103) Of the resin binder solution was added to 0.45 g. The addition amount of the amorphous polyester tree was 11.3 parts by mass with respect to 100 parts by mass of the mixture of copper nanoparticles and copper filler. The mixture was mixed in a mortar and then placed under reduced pressure at room temperature to remove cyclohexanone and obtain a copper paste.

  Copper paste was applied to a glass substrate and baked at 150 ° C. for 1 hour in a nitrogen gas atmosphere to form a metal film having a thickness of 100 μm. The volume resistivity of the metal film was measured. The results are shown in Table 1.

[Example 8]
After mixing 0.8 g of the copper hydride nanoparticles obtained in Example 1 and 3.2 g of a copper filler (Mitsui Metal Mining Co., Ltd., 1400 YP, average particle size: 7 μm) in a mortar, the mixture Was baked at 50 ° C. for 30 minutes in a nitrogen gas atmosphere to obtain a mixture of copper nanoparticles and a copper filler. The average particle diameter of the copper nanoparticles was 51 nm, and the average particle diameter of the copper filler was 7 μm. The addition amount of the copper nanoparticles was 25 parts by mass with respect to 100 parts by mass of the copper filler.

  A copper paste was prepared and a metal film was formed in the same manner as in Example 7 except that the mixture of the copper nanoparticles and the copper filler was used. The volume resistivity of the metal film was measured. The results are shown in Table 1.

[Example 9]
After mixing 0.8 g of the copper hydride nanoparticles obtained in Example 1 and 3.2 g of a copper filler (Mitsui Metal Mining Co., Ltd., 1400 YP, average particle size: 7 μm) in a mortar, the mixture Was baked at 100 ° C. for 30 minutes in a nitrogen gas atmosphere to obtain a mixture of copper nanoparticles and a copper filler. The average particle diameter of the copper nanoparticles was 97 nm, and the average particle diameter of the copper filler was 7 μm. The addition amount of the copper nanoparticles was 25 parts by mass with respect to 100 parts by mass of the copper filler.

  A copper paste was prepared and a metal film was formed in the same manner as in Example 7 except that the mixture of the copper nanoparticles and the copper filler was used. The volume resistivity of the metal film was measured. The results are shown in Table 1.

The copper nanoparticle-coated copper filler and copper paste of the present invention can be used for various applications, for example, formation and repair of wiring patterns in printed wiring boards, interlayer wiring in semiconductor packages, printed wiring boards and electronic components. It can be used for applications such as bonding.

It should be noted that the entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2008-074448 filed on March 21, 2008 are cited herein as disclosure of the specification of the present invention. Incorporated.

Claims (12)

The surface of the copper filler having an average particle diameter of 0.5 to 20 μm is a copper nanoparticle-coated copper filler coated with copper nanoparticles having an average particle diameter of 50 to 100 nm,
The copper nanoparticle coating | coated copper filler whose quantity of the copper nanoparticle with respect to 100 mass parts of copper fillers is 5-50 mass parts. A method for producing the copper nanoparticle-coated copper filler according to claim 1,
The manufacturing method of the copper nanoparticle covering copper filler which has the following process (I)-(II).
(I) The process of obtaining the copper hydride nanoparticle covering copper filler by making the surface of the copper filler whose average particle diameter is 0.5-20 micrometers coat | cover with the copper hydride nanoparticle whose average particle diameter is 20-50 nm.
(II) The copper hydride nanoparticle-coated copper filler is fired at 50 to 100 ° C. in an inert gas atmosphere, and the surface of the copper filler is coated with copper nanoparticles having an average particle diameter of 50 to 100 nm. Obtaining a copper filler coated with copper nanoparticles. The method for producing a copper nanoparticle-coated copper filler according to claim 2, wherein the step (I) comprises the following steps (I-1) to (I-2).
(I-1) A step of obtaining a dispersion by dispersing copper filler having an average particle diameter of 0.5 to 20 μm and copper hydride nanoparticles having an average particle diameter of 20 to 50 nm in a dispersion medium.
(I-2) A step of volatilizing and removing the dispersion medium from the dispersion to coat the surface of the copper filler with copper hydride nanoparticles to obtain a copper hydride nanoparticle-coated copper filler.   The manufacturing method of the copper nanoparticle coating | coated copper filler of Claim 3 whose relative dielectric constants of the said dispersion medium are 4-40.   Copper of Claim 3 or 4 whose quantity of the dispersion medium in the said process (I-1) is 250-1250 mass parts with respect to a total of 100 mass parts of the said copper filler and the said copper hydride nanoparticle. A method for producing a nanoparticle-coated copper filler. The method for producing a copper nanoparticle-coated copper filler according to any one of claims 2 to 5, wherein the copper hydride nanoparticles are produced through the following steps (a) to (c).
(A) A step of dissolving a water-soluble copper compound in water to prepare an aqueous solution containing copper ions.
(B) A step of adjusting the pH to 3 or less by adding an acid to the aqueous solution.
(C) While stirring the aqueous solution having a pH of 3 or less, a step of adding a reducing agent to the aqueous solution to reduce copper ions to produce copper hydride nanoparticles having an average particle size of 20 to 50 nm.   The method for producing a copper nanoparticle-coated copper filler according to claim 6, wherein the acid in the step (b) is formic acid.   The manufacturing method of the copper nanoparticle coating | coated copper filler of Claim 6 whose reducing agent in the said process (c) is a metal hydride or hypophosphorous acid.   A copper paste comprising the copper nanoparticle-coated copper filler according to claim 1 and a resin binder.   The copper paste according to claim 9, wherein the amount of the resin binder is 5 to 50 parts by mass with respect to 100 parts by mass of the copper nanoparticle-coated copper filler.   An article comprising: a base material; and a metal film formed by applying and baking the copper paste according to claim 9 on the base material. The article according to claim 11, wherein the volume resistivity of the metal film is 1.0 × 10 ⁻⁴ Ωcm or less.

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