JP2005060779A - Copper powder and copper paste/paint and electrode obtained by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide copper powder which has excellent oxidation resistance and excellent electric conductivity. <P>SOLUTION: Silicone oil containing at least one kind of functional group selected from among a mercapto group, an amino group, an amide group, an epoxy group, a carboxyl group, a carbinol group, a methacrylic group and a phenol group is treated to copper grains, and is made present on the surface of copper. The modified silicone oil is preferably treated in the range of 0.2 to 20 wt% to the copper grains, and when the quantity to be treated lies in the range, desired oxidation resistance can be obtained while maintaining the electroconductivity of the copper grains. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a copper powder excellent in oxidation resistance, a copper paste / paint using the copper powder, and further to an electrode.

  Copper powder is an inexpensive material with good electrical conductivity, and as a material to ensure electrical continuity such as external electrodes such as capacitors, electrode members such as printed wiring board circuits, and various electrical contact members. Widely used. In recent years, it has begun to be used for internal electrodes of multilayer ceramic capacitors. Multilayer ceramic capacitors are rapidly spreading because they are easy to obtain a large capacity compared to other types of capacitors such as electrolytic capacitors and film capacitors, are excellent in mountability, and have high safety and stability. With the recent miniaturization of electronic equipment, multilayer ceramic capacitors are also in the direction of miniaturization, but in order to maintain a large capacity, it is necessary to miniaturize without reducing the number of laminated ceramic sheets. However, since there is a limit to thinning the sheet, the miniaturization of the multilayer ceramic capacitor is realized by thinning the internal electrode using fine metal particles such as palladium, nickel and copper.

  In such fields, generally, metal particles are mixed with a binder such as an epoxy resin or a phenol resin to form a paste or paint, and the metal paste / paint is, for example, a printed wiring board on a substrate. In the case of a multilayer ceramic capacitor after printing, it is applied onto a thin ceramic sheet, the sheets are laminated, and then heated and fired to form an electric circuit, an electrode, and the like. In order to ensure electrical continuity, the metal particles used should not contain metal oxides as much as possible. However, copper powder is very easy to oxidize, and heat firing is performed using an inert gas such as nitrogen gas. Even if it is performed in an oxidizing atmosphere, the oxidation of the surface of the copper particles cannot be sufficiently prevented, and an electrode having a desired performance cannot be obtained. For this reason, copper powder excellent in oxidation resistance has been demanded. For example, higher fatty acids, phosphate esters, higher aliphatic amines, coupling agents, silicone oils, etc. are used for dendritic copper powders used in conductive pastes. For surface treatment (see Patent Document 1), and technology for coating a silica gel coat film on the surface of copper particles by condensation reaction of the hydrolysis product of organosilane compound on the surface of the copper particles (Patent Document 1) 2) and the like have been proposed.

JP 10-147801 A (page 3) JP 2003-16832 A

  When the surface of the copper powder is treated with the higher fatty acid, phosphate ester, higher aliphatic amine, coupling agent, silicone oil, and silica gel coat film described in Patent Document 2 described in Patent Document 1, oxidation resistance is improved. The improvement is not sufficient, and further improvement in oxidation resistance is required to produce high performance electrodes and the like. Therefore, the present invention provides a copper powder that is further excellent in oxidation resistance and excellent in conductivity.

  As a result of intensive studies to solve such problems, the present inventors have found that the oxidation resistance of copper particles can be improved by treating the surface of copper particles with silicone oil containing a specific functional group. The headline and the present invention were completed.

  That is, the present invention provides a silicone oil containing at least one functional group selected from a mercapto group, amino group, amide group, epoxy group, carboxyl group, carbinol group, methacryl group, and phenol group on the surface of copper particles. The copper powder is characterized by being treated. Moreover, this invention is a copper paste or copper coating material which mix | blends the said copper powder, and is an electrode using the said copper powder.

  The present invention can improve the oxidation resistance without impairing the conductivity of the copper powder by treating the silicone oil containing a specific functional group on the surface of the copper particles contained in the copper powder. It can be widely used as a material for ensuring electrical continuity, such as electrode members for external electrodes, internal electrodes, printed wiring board circuits, and various electrical contact members. In particular, when applied to an electrode member such as an external electrode such as a capacitor, an internal electrode, or a circuit of a printed wiring board, a thin film and a high-density electrode can be obtained. Further, since the copper powder of the present invention is treated with the silicone oil, it has good affinity with the binder resin and solvent and can be easily dispersed, and can be easily made into a paste or paint with a small amount of the binder resin or solvent.

  The present invention is a copper powder having excellent oxidation resistance in which silicone oil is treated on the surface of copper particles, wherein the silicone oil is a mercapto group, amino group, amide group, epoxy group, carboxyl group, carbinol group, It contains at least one functional group selected from a methacryl group and a phenol group. The modified silicone oil is presumed to be able to effectively cover the surface of the copper particles because the silicone oils hardly react with each other while the functional groups contained in the silicone oil are strongly bonded to the surface of the copper particles. The On the other hand, conventional silicone oil (so-called dimethylpolysiloxane) hardly reacts with the copper particles, so it is considered that the coating effect is low. In addition, the hydrolysis product of the organosilane compound binds to the surface of the copper particles, but the hydrolysis products also react with each other, and a part of the hydrolysis product forms a polycondensate in a phase separate from the copper particles. Therefore, it is considered that desired oxidation resistance cannot be obtained. The silicone oil is preferably treated in the range of 0.2 to 20% by weight with respect to the copper particles. If the treatment amount is within this range, the desired oxidation resistance is maintained while maintaining the conductivity of the copper particles. Sex is obtained. A more preferable range of the treatment amount is 1 to 15% by weight.

When the copper metal is completely oxidized, it becomes CuO and theoretically has a weight increase rate of about 25%. For example, when the weight increase rate after heating and firing is used as an index of oxidation resistance, the copper powder of the present invention is The maximum weight increase rate is 15% (ie 0 to 15%), preferably 10% or less (ie 0 to 10%), more preferably 8% or less (ie 0%). ~ 8%). The weight increase rate is based on the weight of copper metal (W ₁ ) after heating the copper powder at a temperature of 60 ° C. for 10 hours in a non-oxidizing atmosphere such as nitrogen gas, helium gas, and argon gas. The weight (W ₂ ) increase rate ((W ₂ −W ₁ ) / W ₁ × 100) after heating for 20 minutes at a temperature of 500 ° C. in an oxidizing atmosphere such as oxygen gas is calculated.

The modified silicone oil has a linear molecular structure composed of a siloxane bond (—O—Si—O—), and its side chain and terminal are methyl groups, and at least one of these methyl groups is It is modified with a substituent containing at least one functional group selected from a mercapto group, amino group, amide group, epoxy group, carboxyl group, carbinol group, methacryl group, and phenol group. As long as the effect of the present invention is not impaired, the side chain or terminal has a functional group other than the methyl group and the functional group, for example, a reactive group such as a hydrogen group or a hydroxyl group, an unreactive group such as an alkyl group or a phenyl group. It may contain an organic group or an inorganic group. Specifically, a compound represented by the following formula (1) is preferable, for example, a side chain modified type (X4 and X5 are the same or different functional groups selected from the functional groups, and X1 to 3 are methyl groups, Or X3-5 is the same or different functional group selected from the above functional groups and X1 and X2 are methyl groups), both terminal modified types (X1 and X2 are the same or different functional groups selected from the above functional groups, X3 5 is a methyl group), one-end modified type (X1 is the functional group and X2 to 5 are methyl groups), side chain end-modified type (X1 to 4 are the same or different functional groups selected from the functional groups, and X5 is Any form such as a methyl group or the same or different functional group wherein X1 to X5 are selected from the above functional groups can be used. In the present invention, these silicone oils may be used alone or two or more of them may be used as a mixture or a copolymer.
(Chemical formula 1)
CH ₃ CH ₃ CH ₃ CH ₃ CH ₃
│ │ │ │ │
Formula (1): X1-SiO (SiO) _n (SiO) _m (SiO) _lSi -X2
│ │ │ │ │
CH ₃ X3 X4 X5 CH ₃
[In the formula (1), X1 to 5 are at least one functional group selected from methyl group, mercapto group, amino group, amide group, epoxy group, carboxyl group, carbinol group, methacryl group, and phenol group, and n Is an integer of 1 or more, m and l are each 0 or an integer of 1 or more, and when at least two of X1 to 5 are functional groups, the functional groups may be the same or different. ]

  The shape of the copper particles is not particularly limited, but is preferably a substantially spherical particle because of excellent filling properties. In addition, when the average particle size is 1.0 μm or less, a high-density electrode having almost no defects is easily obtained, and when the average particle size is 0.005 μm or more, the dispersibility in paste, paint, etc. is excellent. A range of 0.005 to 1.0 μm is preferable. A more preferable range is 0.05 to 1.0 μm, a further preferable range is 0.1 to 1.0 μm, and a most preferable range is 0.2 to 1.0 μm. The average particle diameter is expressed as a cumulative 50% diameter measured by electron microscopy, and the particle shape is also observed with an electron microscope.

  In order to obtain the copper powder of the present invention, first, copper particles are produced. Various methods can be used for the production of copper particles. For example, (1) a method in which a copper compound is reduced in a gas phase such as an atomizing method, and (2) a copper compound is reduced in a liquid phase such as a wet reduction method. The method of making it react is mentioned. Among these, the method (2) that does not require special equipment is industrially advantageous.

  In the method (2), a copper compound and a reducing agent are mixed in a medium, for example, water or an organic medium such as alcohol, preferably in water, and preferably in the presence of a protective colloid. Thus, it is preferable to carry out the reduction reaction. The reaction temperature is preferably in the range of 10 ° C. to the boiling point of the liquid medium used, since the reaction is easy to proceed, and more preferably in the range of 40 to 95 ° C. It is preferable to adjust the pH of the reaction solution in the range of 3 to 12 in advance with an acid or an alkali because precipitation of the copper compound can be prevented and the reaction can be performed uniformly. The amount of the reducing agent used can be appropriately set as long as it is an amount capable of generating copper particles from the copper compound, and is preferably in the range of 0.2 to 5 mol with respect to 1 mol of copper contained in the copper compound. .

  Examples of the raw material copper compound include copper oxide, copper chloride, copper chlorate, copper bromide, copper iodide, copper sulfate, copper nitrate, copper carbonate, copper carbonate hydroxide, tetraammine copper sulfate, potassium tetracyanocuprate, etc. And inorganic copper compounds of these hydrates, copper formate, copper acetate, copper oxalate and the like, and organic copper compounds of these hydrates can be used, among which copper oxide is preferred. In the present invention, a copper oxide is used in the sense of including a copper hydrated oxide and a copper hydroxide in addition to a normal copper oxide. As the copper oxide, cuprous oxide ( Alternatively, cuprous oxide), copper oxide (or cupric oxide), or the like can be used.

  As the reducing agent, known ones can be used, for example, hydrazine, hydrazine reducing agents such as hydrazine compounds such as hydrazine hydrochloride, hydrazine sulfate, hydrazine hydrate, sodium borohydride, sodium sulfite, sodium bisulfite, Metal salts such as sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid and sodium phosphite, metal salts such as hypophosphorous acid and sodium hypophosphite, aldehydes, alcohols, amines And saccharides may be used, and one or more of these may be used. In particular, hydrazine-based reducing agents are preferred because of their strong reducing power.

  Known protective colloids can be used, for example, protein systems such as gelatin, gum arabic, casein, sodium caseinate, ammonium caseinate, natural polymers such as starch, dextrin, agar, sodium alginate, and hydroxyethyl cellulose. , Celluloses such as carboxymethylcellulose, methylcellulose and ethylcellulose; vinyls such as polyvinyl alcohol and polyvinylpyrrolidone; acrylic acids such as sodium polyacrylate and ammonium polyacrylate; higher fatty acids such as stearic acid; Examples include molecules, polyvalent carboxylic acids such as citric acid, aniline or derivatives thereof, and one or more of these may be used. The protective colloid acts as a dispersion stabilizer for the produced copper particles. When the amount used is in the range of 1 to 100 parts by weight with respect to 100 parts by weight of the copper compound, the produced copper particles are easily dispersed and stabilized. Therefore, the range of 2 to 50 parts by weight is more preferable.

  After producing | generating a copper particle, it filters, wash | cleans and dries suitably, and grind | pulverizes as needed. Drying is preferably performed in an atmosphere of a non-oxidizing gas (inert gas) such as nitrogen gas, helium gas, or argon gas so that the copper particles are not easily oxidized.

  Next, the silicone oil is treated on the surface of the copper particles. As a treatment method, (a) a so-called dry treatment in which copper particles and silicone oil are mixed using a high-speed stirrer such as a Henschel mixer or a super mixer, (b) an organic solvent such as alcohols, or a dispersant is added. A so-called wet process or the like in which copper particles and silicone oil are brought into contact with each other in water can be used.

  After the silicone oil treatment, solid-liquid separation (filtration), washing, drying, and pulverization are performed as necessary. Drying is preferably performed in an atmosphere of a non-oxidizing gas (inert gas) such as nitrogen gas, helium gas, or argon gas so that the copper particles are not easily oxidized. Moreover, it is preferable to heat-treat after the silicone oil treatment since the oxidation resistance is further improved. The heating temperature is preferably in the range of 80 to 400 ° C, more preferably in the range of 100 to 350 ° C. The heat treatment is preferably performed in an atmosphere of a non-oxidizing gas (inert gas) such as nitrogen gas, helium gas, or argon gas so that the copper particles are not easily oxidized. You may grind | pulverize the copper powder after heat processing again as needed.

  The copper powder of the present invention is used as a copper paste or a copper paint (copper ink) by mixing with a solvent or a binder resin as necessary. The solvent can be appropriately selected depending on the application, for example, a relatively high boiling nonpolar solvent or low polarity solvent, specifically, terpineol, mineral spirit, xylene, toluene, ethylbenzene, mesitylene, hexane, heptane, Octane, decane, dodecane, cyclohexane, cyclooctane and the like can be used. Further, the binder resin can also be appropriately selected according to the application, for example, phenol resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, diallyl phthalate resin, oligoester acrylate resin, xylene resin, bismaleimide triazine resin, Examples include thermosetting resins such as furan resin, urea resin, polyurethane resin, melamine resin, and silicon resin. Phenol resin and epoxy resin are more preferable as resin components because they have good adhesion to the substrate. It is. The blending amount of the solvent and the binder resin can be appropriately set according to the use. For example, the solvent is about 1 to 500 parts by weight and the binder resin is about 1 to 50 parts by weight with respect to 100 parts by weight of the copper powder. be able to. Such a copper paste or copper paint (copper ink) is applied to a substrate by a normal method and then heated and fired to produce an internal electrode of a multilayer ceramic capacitor, a circuit of a printed wiring board, and other electrodes. Can be used. Since the copper powder of the present invention is excellent in oxidation resistance, the electrode manufactured using the copper powder has excellent electrical characteristics.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
Add 2 g of gum arabic as protective colloid to 2900 ml of pure water, then add 125 g of industrial copper oxide (N-120: manufactured by NC Tech) and add 360 ml of 80% hydrazine monohydrate with stirring. did. After addition of hydrazine monohydrate, the temperature was raised from room temperature to 60 ° C. over 3 hours, and further reacted with copper oxide over 2 hours to produce copper particles having an average particle size of 0.6 μm. Thereafter, the solution was filtered and washed until the filtrate specific resistance was 100 μS / cm or less, and dried at a temperature of 60 ° C. for 10 hours in an atmosphere of nitrogen gas to obtain copper particles. Next, copper particles and mercapto-modified silicone oil corresponding to 8% by weight (KF-2004: l in the above formula (1) is 0, X4 is a mercapto group, and X1 to X3 are methyl groups, Shin-Etsu (Chemical Industry Co., Ltd.) was dry-treated by stirring for 5 minutes using a blender, and then heat-treated at a temperature of 120 ° C. for 2 hours under an atmosphere of nitrogen gas to obtain the copper powder (sample A) of the present invention. It was.

Example 2
Other than replacing mercapto-modified silicone oil with amino-modified silicone oil (KF-867: l in the above formula (1) is 0, X4 is an amino group, X1 to X3 are methyl groups, manufactured by Shin-Etsu Chemical Co., Ltd.) Obtained the copper powder (sample B) of the present invention in the same manner as in Example 1.

Comparative Examples 1 and 2
Normal silicone oil (dimethylpolysiloxane) instead of mercapto-modified silicone oil (SH-200: m and l in formula (1) are 0 and X1 to X3 are methyl groups, manufactured by Toray Dow Corning Silicone) Or methyl hydrogen polysiloxane (SH-1107: m and l in the formula (1) are 0, X3 is a hydrogen group, X1 and X2 are methyl groups, manufactured by Toray Dow Corning Silicone) Obtained copper powder (samples C and D) in the same manner as in Example 1. These are designated as Comparative Examples 1 and 2, respectively.

Comparative Example 3
After obtaining copper particles in the same manner as in Example 1, the copper particles are dispersed in 2-propanol to form a slurry of 143 g / liter, which corresponds to 17.4% by weight with respect to the copper particles (5 in terms of SiO _2). Tetraethoxylane and 20 g of pure water were added to this slurry. Next, 28% ammonia water was added over 30 minutes to adjust the pH of the slurry to 8.5, and then the temperature was raised to 40 ° C. and stirred for 1 hour to hydrolyze tetraethoxylane into copper particles. A polycondensate of the product was deposited. Thereafter, the copper particles were separated, heat-treated at 120 ° C. for 2 hours in an atmosphere of nitrogen gas, and then pulverized in a mortar to obtain a copper powder (Sample E).

Comparative Example 4
A copper powder (sample F) was obtained in the same manner as in Example 1 except that the mercapto-modified silicone oil was not treated.

Evaluation 1: Evaluation of oxidation resistance Metal copper weight after heating Samples A to F 10g obtained in Examples 1 and 2 and Comparative Examples 1 to 4 at a temperature of 60 ° C in a non-oxidizing nitrogen gas atmosphere for 10 hours After that, the weight after heating and baking for 20 minutes at 150 ° C., 200 ° C., 300 ° C., 400 ° C., and 500 ° C. in an oxidizing air atmosphere was measured, and the weight increase rate was calculated. The results are shown in Table 1. The smaller the increase in weight, the better the oxidation resistance. The copper powder of the present invention is a conventional treatment of hydrolysis products of silicone oils and organosilane compounds and methyl groups modified with hydrogen groups. From the hydrogen polysiloxane treatment, it can be seen that the rate of weight increase is lower and the oxidation resistance is superior. In particular, the copper powder of the present invention had a good weight increase rate of 15% or less after being heated and fired at a temperature of 500 ° C.

  Using the copper powder obtained in the examples of the present invention, a copper paste or a copper paint (copper ink) is prepared by mixing with a solvent and a binder resin, applied to a substrate by a normal method, and then heated and fired. The electrode was used. It was confirmed that the obtained electrode had excellent electrical characteristics.

INDUSTRIAL APPLICABILITY The present invention is useful as a material for ensuring electrical continuity, such as external electrodes such as capacitors, internal electrodes, electrode members such as printed wiring board circuits, and various electrical contact members. In particular, when the copper powder of the present invention is used as a copper paste, copper paint (copper ink) or the like, for example, for an internal electrode of a multilayer ceramic capacitor, a circuit of a printed wiring board, or other electrodes, it has excellent electrical characteristics. Expect to get something.

Claims (3)

The surface of the copper particles is treated with a silicone oil containing at least one functional group selected from mercapto groups, amino groups, amide groups, epoxy groups, carboxyl groups, carbinol groups, methacrylic groups, and phenol groups. Features copper powder. A copper paste or copper paint comprising the copper powder according to claim 1. An electrode using the copper powder according to claim 1.