JP2020126855A - Conductive composition - Google Patents

Abstract

To provide a conductive composition having three following characteristics: (1) excellent in conductivity of a conductor obtained by sintering; (2) contributing to productivity improvement of a composite body of a ceramic and a conductor; and (3) excellent in adhesion with a ceramic when a composite body of the ceramic and a conductor is manufactured by a co-fire method.SOLUTION: A conductive composition contains either or both of an oxidized filler selected from the group consisting of copper powder, cuprous oxide powder and copper oxide powder, a binder resin and a dispersion medium, has an arithmetic average roughness Ra of a coated film formed on the predetermined condition of 0.2 μm or less, has a ratio of a peak area corresponding to the oxidized filler in (111) plane to a peak area corresponding to the copper powder in the (111) plane in XRD of the coated film of 0.05-0.5, and has a volume shrinkage at 650°C when a green compact is molded from powder obtained by crushing the coated film and the green compact is measured by TMA measurement on the predetermined condition of 15% or less.SELECTED DRAWING: None

Description

The present disclosure relates to electrically conductive compositions.

Conventionally, metal particles such as Ag, Cu, Ni or Pt and a glass powder having a low softening point have been used as a conductive material for producing a composite of a ceramic and a conductor when an electrode or a circuit is formed on the surface of a ceramic substrate. A conductive composition in which and are mixed in an organic vehicle is generally known. As a method for producing a composite of a ceramic and a conductor, a method (cofire method) of simultaneously firing a ceramic-containing green sheet and a conductive composition is known. For example, a chip monolithic ceramic capacitor is manufactured by printing a conductive composition for an electrode layer on a green sheet (dielectric sheet) by a screen printing method and then performing a firing step performed at a high temperature of about 1000°C.

Such a conductive composition is required to have excellent adhesion to a ceramic substrate after firing. Therefore, for example, Japanese Patent Laid-Open No. 2006-73836 (Patent Document 1) discloses a conductive composition for a ceramic electronic component, which contains a rosin or terpene oil polymerized resin taken from pine resin in order to improve the adhesion with the ceramic body. Is disclosed.

Further, Japanese Patent Laid-Open No. 2005-267858 (Patent Document 2) discloses a dielectric paste for a conductive paste for internal electrodes containing nickel powder, in order to suppress delamination that occurs in the sintered body when the temperature is lowered after firing is completed. Disclosed is a technique of suppressing the difference in thermal shrinkage behavior between the dielectric layer and the internal electrode layer by adding the same or similar ceramic powder as the body layer as a co-material to the conductive paste.

JP, 2006-73836, A JP, 2005-267858, A

When industrially producing composites of ceramics and conductors, high adhesion between them is of course an important characteristic, but not only that, but also high electrical conductivity of conductors and high productivity. It is desirable to combine them.

Then, the objective of this indication in one side is to provide the electroconductive composition which combines the following three characteristics.
(1) The conductor obtained by sintering is excellent in conductivity.
(2) Contributes to improvement in productivity of a composite of ceramic and conductor.
(3) Excellent adhesion to the ceramic when a composite of ceramic and conductor is produced by the co-firing method.

In order to solve the above problems, the present inventor first examined improvement in productivity in the case of producing a composite of a ceramic and a conductor by using the cofire method. Then, they have found that firing in a steam atmosphere is effective in order to improve the desorption rate of the binder resin contained in the green sheet and the binder resin contained in the conductive composition. This is due to the large penetration of the heated steam into the material to be fired.

The present inventor next examined means for improving the adhesion between the ceramic and the conductor. In order to prevent the separation of the ceramic and the conductor (decrease in adhesion) during the cooling process after firing, it is possible to reduce the difference in heat shrinkage behavior between the metal powder and the ceramic contained in the conductive composition. Desired. As one of the means, it is effective to raise the sintering start temperature of the metal powder contained in the conductive composition, in other words, to raise the sintering delay property.

In this regard, the present inventor has conducted diligent research and found that it is effective to mix a predetermined amount of at least one of the cuprous oxide powder and the copper oxide powder into the conductive composition containing the copper powder. It was found that according to the method, an effect of improving the sintering delay property is exhibited even when the conductive composition is fired in a steam atmosphere, and a sintered body having excellent conductivity can be obtained.

The present invention has been completed based on the above findings and is exemplified below.
(1)
Copper powder, one or both of the oxide filler selected from the group consisting of cuprous oxide powder and copper oxide powder, a binder resin, a conductive composition containing a dispersion medium,
The conductive composition was applied on a slide glass at a moving speed of 5 cm/sec using an applicator with a gap of 25 μm and dried at 120° C. for 10 minutes, and then the coating film was applied with a stylus roughness meter. The arithmetic mean roughness Ra in the direction is 0.2 μm or less,
In the XRD of the coating film, the ratio of the peak area corresponding to the oxide filler on the (111) plane to the peak area corresponding to the copper powder on the (111) plane is 0.05 to 0.5,
A cylindrical green compact having a density of 4.7±0.2 gcm ⁻³ and a diameter of 5 mm was formed from 0.5 g of the powder obtained by crushing the coating film, and a load of 98 mN was applied to the green compact. The volumetric shrinkage ratio at 650° C. is 15% or less when measured by TMA at a temperature rising rate of 1° C./min in a residual nitrogen atmosphere having a total pressure of 1 atm and a water vapor partial pressure of 0.05 atm while being applied to the upper bottom surface.
Conductive composition.
(2)
A sintered body obtained by heating the conductive composition to 850° C. at a total pressure of 1 atm and a steam partial pressure of 0.03 atm at the balance of nitrogen atmosphere at a temperature rising rate of 1° C./min and firing at 850° C. for 30 minutes. The conductive composition according to (1), wherein the total concentration of Si, Ti, Al, and Zr is 1,000 to 10,000 mass ppm when measured by ICP emission spectroscopy.
(3)
A sintered body obtained by heating the conductive composition at a total pressure of 1 atm and a partial pressure of water vapor of 0.03 atm in the remaining nitrogen atmosphere to 850° C. at a rate of 0.75° C./min and firing at 850° C. for 20 minutes. The conductive composition according to (1) or (2), which has a specific resistance of 3.0 μΩ·cm or less.
(4)
The conductive composition according to any one of (1) to (3), wherein the copper powder and/or the oxide filler is surface-treated with a coupling agent.
(5)
Any one of (1) to (4) including kneading copper powder, one or both oxide fillers selected from the group consisting of cuprous oxide powder and copper oxide powder, a binder resin, and a dispersion medium. The method for producing a conductive composition according to one item.
(6)
The method for producing a conductive composition according to (5), wherein the copper powder has a compacted bulk density of 3.0 g/cm ³ or less.
(7)
The manufacturing method according to (5) or (6), wherein the ratio of the BET specific surface area of the oxide filler to the BET specific surface area of the copper powder is 0.2 to 3.0.
(8)
The manufacturing method according to any one of (5) to (7), wherein the ratio of the mass of the oxide filler to the total mass of the copper powder and the oxide filler is 0.05 to 0.35.
(9)
A composite of a ceramic and a conductor, which is manufactured using the conductive composition according to any one of (1) to (4).
(10)
A monolithic ceramic capacitor manufactured by using the conductive composition according to any one of (1) to (4).
(11)
A ceramic circuit board manufactured using the conductive composition according to any one of (1) to (4).

In one embodiment, the conductive composition according to the present disclosure has excellent conductivity when made into a sintered body. Further, in one embodiment, the conductive composition according to the present disclosure is suitable for firing in a steam atmosphere for improving productivity. Further, in one embodiment, the conductive composition according to the present disclosure has excellent adhesion to the ceramic when a composite of the ceramic and the conductor is manufactured by the co-firing method.

Hereinafter, the present disclosure will be described in detail with reference to embodiments. The present disclosure is not limited to the specific embodiments described below.

[Conductive composition]
In one embodiment, the conductive composition according to the present disclosure includes copper powder, one or more oxide fillers selected from the group consisting of cuprous oxide powder and copper oxide powder, a binder resin, and a dispersion medium. The conductive composition can be produced by kneading these various components. The kneading can be performed using a known means. The conductive composition is provided as a paste in one embodiment.

In one embodiment, the conductive composition is coated on a glass slide using a 25 μm gap applicator at a moving speed of 5 cm/sec, and dried at 120° C. for 10 minutes, and then the roughness of the stylus is measured. The arithmetic average roughness Ra in the coating direction is 0.2 μm or less. The arithmetic mean roughness Ra is based on JIS B0633:2001, and is represented as an average value when measured at a plurality of points with a stylus type roughness meter. When the arithmetic mean roughness Ra becomes large, voids are likely to be formed at the interface between the conductor and the ceramic when the composite of the ceramic and the conductor is manufactured by the co-firing method, and the joint strength between the both tends to decrease. The arithmetic average roughness Ra is preferably 0.1 μm or less, more preferably 0.05 μm or less.

In one embodiment, when XRD (X-ray diffraction) measurement is performed on the coating film, the ratio of the peak area corresponding to the oxide filler on the (111) plane to the peak area corresponding to the copper powder on the (111) plane is: It is 0.05 to 0.5. When the ratio is 0.05 or more, preferably 0.1 or more, the sintering retardation property is significantly improved. Further, when the ratio is 0.5 or less, preferably 0.3 or less, excellent conductivity can be secured.

The peak area corresponding to the copper powder on the (111) plane represents the peak area of copper on the (111) plane. The peak area corresponding to the oxide filler on the (111) plane represents the peak area of cuprous oxide on the (111) plane when only cuprous oxide powder is used as the oxide filler, and when only copper oxide powder is used as the oxide filler. Represents the peak area of copper oxide on the (111) plane, and when both cuprous oxide powder and copper oxide powder are used as the oxide filler, the peak area of cuprous oxide and the peak area of copper oxide on the (111) plane Represents the total.

In one embodiment, 0.5 g of powder obtained by crushing the coating film is molded into a cylindrical green compact having a density of 4.7±0.2 gcm ⁻³ and a diameter of 5 mm, and a load of 98 mN. Is applied to the top and bottom surfaces of the green compact, the volumetric shrinkage ratio at 650° C. is 15% or less when TMA measurement is performed at a temperature rising rate of 1° C./min in a residual nitrogen atmosphere with a total pressure of 1 atm and a steam partial pressure of 0.05 atm. Is. The small volume contraction rate means that the sintering delay property in a steam atmosphere is excellent. The volumetric shrinkage is preferably 15% or less, more preferably 10% or less. Most preferably, the volumetric shrinkage is 0%, but is usually 2% or more, and typically 5% or more.

In a preferred embodiment, the conductive composition is heated to 850° C. at a temperature increase rate of 1° C./min with a balance of 1 atm and a partial pressure of steam of 0.03 atm for the balance of nitrogen atmosphere, and baked at 850° C. for 30 minutes. The total concentration of Si, Ti, Al, and Zr when the obtained sintered body was measured by ICP emission spectroscopy was 1,000 to 10,000 mass ppm. When the total concentration is 1000 ppm by mass or more, the sintering delay property in a steam atmosphere is further improved. When the total concentration is 10000 mass ppm or less, it is possible to suppress deterioration of the conductivity and heat dissipation of the sintered body. The total concentration is preferably 1500 to 7000 mass ppm, more preferably 1500 to 4000 mass ppm.

Sintering obtained by heating the conductive composition at a total pressure of 1 atm and a steam partial pressure of 0.03 atm in the balance nitrogen atmosphere to 850° C. at a rate of 0.75° C./min and firing at 850° C. for 20 minutes The specific resistance of the body is preferably 3.0 μΩ·cm or less, more preferably 2.5 μΩ·cm or less, and can be, for example, 1.7 to 3.0 μΩ·cm.

In one embodiment, the conductive composition according to the present disclosure can be used to produce a composite of ceramic and conductor. As a method for producing a composite of a ceramic and a conductor, a method of cofiring a ceramic-containing green sheet (dielectric sheet) and a conductive composition (cofire method) can be suitably adopted. In particular, by using the conductive composition according to the present disclosure, even if firing is performed in a steam atmosphere to improve productivity, the specific resistance of the conductor is small, and the adhesion between the ceramic and the conductor is improved. An excellent conductor-ceramics composite can be obtained. This property is at least partly due to the fact that the oxide filler contained in the conductive composition has excellent sintering retardation even in a steam atmosphere.

Since the sintered body obtained by firing the conductive composition according to the present disclosure is a conductor, it can be used, for example, as an electrode or a circuit. For example, a monolithic ceramic capacitor can be manufactured by applying a conductive composition for an electrode layer on a green sheet by a screen printing method or the like and then performing a firing process at 500 to 1000° C., for example. In this case, the sintered body of the conductive composition is used as the internal electrode of the laminated ceramic capacitor. Similarly, a ceramic circuit board can be manufactured by applying a conductive composition for forming a circuit on a green sheet by a screen printing method or the like and then performing a firing step at 400 to 1000° C., for example.

[Copper powder]
The copper powder includes pure copper powder and copper alloy powder (in particular, copper alloy powder having a Cu content of 80% by mass or more).

The BET specific surface area of the copper powder is preferably 1.5 to 10 m ² /g, more preferably 1.5 to ⁵ m ² /g. Here, the BET specific surface area is measured according to JIS Z 8830:2013 after degassing copper powder in vacuum at 200° C. for 5 hours. The BET specific surface area can be measured using, for example, BELSORP-miniII manufactured by Microtrac Bell.

The concentration of the copper powder in the conductive composition is preferably 20% by mass or more, and more preferably 25% by mass or more, from the viewpoint of improving the coating film density and thus improving the electrode density. Further, the concentration of the copper powder in the conductive composition is preferably 90% by mass or less, and more preferably 85% by mass or less from the viewpoint of printability.

The higher the dispersibility of the copper powder, the more easily the oxide filler, which will be described later, penetrates into the gaps of the copper powder, and the sintering delay property improves. Further, the surface roughness of the coating film can be reduced. Therefore, it is preferable that the compacted bulk density, which is an index of the dispersibility of the copper powder, is low. Specifically, the compacted bulk density of the copper powder is preferably 3.0 g/cm ³ or less, and more preferably 2.5 g/cm ³ or less. However, the solidified bulk density of the copper powder is preferably 1.0 g/cm ³ or more, because if the copper powder is too low, the bulk of the copper powder becomes large and it is difficult to handle when adjusting the conductive composition. It is more preferably 5 g/cm ³ or more. The compacted bulk density can be lowered, for example, by improving the crushability by performing a pH treatment step in which copper powder is brought into contact with an alkaline aqueous solution having a pH of 8 to 14.

The compacted bulk density is measured by the following procedure. A guide is attached to a 10 cc cup having a diameter of 2 cm, powder exceeding 10 cc is put therein, and tapping is performed 1000 times. Next, leaving the guide, the portion exceeding the volume of 10 cc is cut off, and in this state, the density determined based on the weight of the powder contained in the cup and the volume (10 cc) of the cup is the compacted bulk density. The compacted bulk density can be measured using, for example, Powder Tester PT-X (Hosokawa Micron Co., Ltd.).

As the copper powder, both a copper powder manufactured by a dry method and a copper powder manufactured by a wet method can be used. When the copper powder produced by the wet method is used, it is suitable in that the wet process is consistently performed by the surface treatment with a coupling agent described later.

A suitable method for producing copper powder by a wet method will be described as an example. The manufacturing method is a step of adding a dispersant (eg, gum arabic, gelatin, collagen peptide, a surfactant, etc.) to the cuprous oxide powder slurry, and then adding dilute sulfuric acid to the slurry at once within 5 seconds. And carrying out a disproportionation reaction. In a preferred embodiment, the slurry can be maintained at room temperature (20 to 25° C.) or lower, and dilute sulfuric acid similarly maintained at room temperature or lower can be added to carry out the disproportionation reaction. The BET specific surface area (size, compacted bulk density) of the copper powder can be controlled by the addition amount of the dispersant, the addition rate of dilute sulfuric acid, and the like. As an example, when the amount of organic substances such as gum arabic is large, the BET specific surface area becomes large, and when the addition rate of dilute sulfuric acid is fast, the BET specific surface area tends to become large. In a preferred embodiment, the dilute sulfuric acid can be added so that the slurry has a pH of 2.5 or less, preferably pH 2.0 or less, more preferably pH 1.5 or less. In a preferred embodiment, the addition of dilute sulfuric acid to the slurry is performed within 5 minutes, preferably within 1 minute, more preferably within 30 seconds, further preferably within 10 seconds, further preferably within 5 seconds. , Can be added. In a preferred embodiment, the disproportionation reaction can be completed within 10 minutes, for example, within 5 seconds when dilute sulfuric acid is added to the slurry instantaneously. In a preferred embodiment, the concentration of the dispersant such as gum arabic in the slurry before the addition of dilute sulfuric acid can be 0.2 to 1.2 g/L. The principle of this disproportionation reaction is as follows:
Cu ₂ O+H ₂ SO ₄ → Cu↓+CuSO ₄ +H ₂ O
The copper powder obtained by this disproportionation can be washed, rust-prevented, filtered, dried, crushed, and classified, if desired. When the surface treatment is performed with the aqueous coupling agent solution, the copper powder slurry obtained after washing, rust prevention and filtration can be directly mixed with the aqueous coupling agent solution without drying, if desired.

[Oxidizing filler]
Along with copper powder, one or both oxide fillers selected from the group consisting of cuprous oxide powder (Cu ₂ O powder) and copper oxide powder (CuO), preferably reduced to Cu during firing, contributing to improvement in conductivity By adding a cuprous oxide powder (Cu ₂ O powder) that is easy to do in the conductive composition, the sintering start temperature of the copper powder is significantly increased. While not intending to limit the invention by theory, for the same particle size, cuprous oxide powder and copper oxide powder are less likely to sinter than non-reducing atmospheres and shrink on higher temperatures. Sintering of the copper powder progresses from the portion where the copper powder contacts each other as a starting point, and thus such cuprous oxide powder and copper oxide are interspersed between the copper powders to prevent contact between the copper powders, It is considered to inhibit sintering.

The BET specific surface area of the oxide filler is preferably 1 to 5 m ² /g, more preferably 1.5 to 4.5 m ² /g. Here, the BET specific surface area is measured in accordance with JIS Z 8830:2013 after degassing an oxide filler (when a plurality of types are used, measuring each oxide filler) in vacuum at 200° C. for 5 hours. It

The ratio of the BET specific surface area of the oxide filler to the BET specific surface area of the copper powder is preferably 0.2 or more because the oxide filler is more likely to enter the gaps of the copper powder when the ratio is larger. However, when the oxide filler has a small particle size and the ratio becomes too large, the difference between the sintering start temperature of the oxide filler and the sintering start temperature of the copper powder becomes small, and the conductive composition contains the oxide filler. This may reduce the effect of improving the sintering delay property. Therefore, the ratio of the BET specific surface area of the oxide filler to the BET specific surface area of the copper powder is preferably 3.0 or less, more preferably 2.0 or less, and further preferably 1.5 or less. Is more preferable.

The ratio of the mass of the oxide filler to the total mass of the copper powder and the oxide filler is preferably 0.05 or more from the viewpoint of enhancing the sintering delay property. Further, the ratio is preferably 0.35 or less, and more preferably 0.30 or less from the viewpoint of increasing the conductivity of the sintered body.

[Coupling agent]
At least one, preferably both of the copper powder and the oxide filler are preferably surface-treated with a coupling agent. Specifically, it is more preferable that the surface treatment is performed with a coupling agent containing one or more elements selected from the group consisting of Si, Ti, Al and Zr. When the copper powder and/or the oxide filler is surface-treated with the coupling agent, the adhesion between the ceramic and the conductor can be improved in the conductor/ceramic composite.

Examples of coupling agents include silane coupling agents, titanate coupling agents, aluminate coupling agents, and zirconate coupling agents. One type of coupling agent may be used, or two or more types may be used in combination. As the coupling agent, Si was used when a silane coupling agent was used, Ti was used when a titanate coupling agent was used, Al was used when an aluminate coupling agent was used, and a zirconate coupling agent was used. In some cases, Zr can be attached to the surfaces of the copper powder and the oxide filler, respectively.

Aminosilane can be preferably used as the silane coupling agent. In a preferred embodiment, the aminosilane used may be a silane containing one or more amino groups and/or imino groups. The number of amino groups and imino groups contained in the aminosilane can be, for example, 1 to 4, preferably 1 to 3, and more preferably 1 to 2, respectively. In a preferred embodiment, the number of amino groups and imino groups contained in the aminosilane can each be one. An aminosilane in which the total number of amino groups and imino groups contained in the aminosilane is 1 can be called monoaminosilane, 2 aminosilanes can be called diaminosilane, 3 aminosilanes can be called especially triaminosilane. .. Particularly, monoaminosilane and diaminosilane can be preferably used. In a preferred embodiment, the aminosilane used may be a monoaminosilane containing one amino group. In a preferred embodiment, the aminosilane may contain at least one, for example one, amino group at the end of the molecule, preferably at the end of a linear or branched chain molecule.

Examples of the aminosilane include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 1- Aminopropyltrimethoxysilane, 2-aminopropyltrimethoxysilane, 1,2-diaminopropyltrimethoxysilane, 3-amino-1-propenyltrimethoxysilane, 3-amino-1-propynyltrimethoxysilane, 3- Aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl- 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-(N-phenyl)amino Mention may be made of propyltrimethoxysilane.

In a preferred embodiment, aminosilanes of formula I can be used.
^{_{H 2 N-R 1 -Si (}} OR 2) 2 (R 3) ( Formula I)
In the above formula I,
R ¹ is a linear or branched, saturated or unsaturated, substituted or unsubstituted, cyclic or acyclic, heterocyclic or non-heterocyclic C1-C12 hydrocarbon. Is a divalent group of
R ² is a C1-C5 alkyl group,
R ³ is an alkyl group, or an alkoxy group of C1 to C5 of C1 to C5.

In a preferred embodiment, R ¹ of the above formula I is linear or branched, saturated or unsaturated, substituted or unsubstituted, cyclic or acyclic, heterocyclic or heterocyclic. Is a C1 to C12 hydrocarbon divalent group, more preferably R ¹ is a substituted or unsubstituted C1 to C12 linear saturated hydrocarbon divalent group, substituted or unsubstituted. A C1 to C12 branched saturated hydrocarbon divalent group, a substituted or unsubstituted C1 to C12 linear unsaturated hydrocarbon divalent group, a substituted or unsubstituted C1 to C12 A branched unsaturated hydrocarbon divalent group, a substituted or unsubstituted C1 to C12 cyclic hydrocarbon divalent group, a substituted or unsubstituted C1 to C12 heterocyclic hydrocarbon divalent group, It may be a group selected from the group consisting of a substituted or unsubstituted C1 to C12 divalent group of an aromatic hydrocarbon. In a preferred embodiment, R ¹ in the above formula I is a C1 to C12 saturated or unsaturated chain hydrocarbon divalent group, more preferably atoms at both ends of the chain structure are free atoms. It is a divalent group having a valence. In a preferred embodiment, the carbon number of the divalent group can be, for example, C1 to C12, preferably C1 to C8, preferably C1 to C6, preferably C1 to C3.

In a preferred embodiment, R ¹ of the above formula I is —(CH ₂ ) _n —, —(CH ₂ ) _n —(CH) _m —(CH ₂ ) _j−1 −, —(CH ₂ ) _n —. _{(CC) - (CH 2)} n-1 -, - (CH 2) n -NH- (CH 2) m -, - (CH 2) n -NH- (CH 2) m -NH- (CH 2) _{j -, - (CH 2)} n-1 - (CH) NH 2 - (CH 2) m-1 -, - (CH 2) n-1 - (CH) NH 2 - (CH 2) m-1 - NH- (CH _{2) j} - is selected based from the group consisting of (where, n, m, j is 1 or more is an integer) can be. (However, the (CC) represents a triple bond between C and C.) In embodiments of the preferred embodiments, R ¹ is, - (CH ₂₎ n-, or _{- (CH 2) n-NH-} (CH 2 ) M-. (However, the above (CC) represents a triple bond of C and C.) In a preferred embodiment, the hydrogen of the above divalent group R ¹ may be substituted with an amino group, for example, 1 ~3 hydrogens, for example 1-2 hydrogens, for example 1 hydrogen, may be replaced by amino groups.

In a preferred embodiment, n, m and j in the above formula I are each independently an integer of 1 or more and 12 or less, preferably an integer of 1 or more and 6 or less, more preferably an integer of 1 or more and 4 or less. It can be, for example, an integer selected from 1, 2, 3, 4 and can be, for example, 1, 2 or 3.

In a preferred embodiment, R ^{2 in} formula I above can be a C1-C5 alkyl group, preferably a C1-C3 alkyl group, more preferably a C1-C2 alkyl group, such as a methyl group, It may be an ethyl group, an isopropyl group, or a propyl group, and preferably a methyl group or an ethyl group.

In a preferred embodiment, R ³ of the above formula I can be a C1-C5 alkyl group, preferably a C1-C3 alkyl group, more preferably a C1-C2 alkyl group, as an alkyl group, for example, , A methyl group, an ethyl group, an isopropyl group, or a propyl group, and preferably a methyl group or an ethyl group. Further, R ^{3 of the} above formula I can be an alkoxy group of C1 to C5, preferably an alkoxy group of C1 to C3, and more preferably an alkoxy group of C1 to C2, for example, a methoxy group, It may be an ethoxy group, an isopropoxy group or a propoxy group, preferably a methoxy group or an ethoxy group.

Examples of titanate coupling agents include compounds represented by the following formula II:
^{_{(H 2 N-R 1 -O}} ) p Ti (OR 2) q ( Formula II)
(However, in the above formula II,
R ¹ is a linear or branched, saturated or unsaturated, substituted or unsubstituted, cyclic or acyclic, heterocyclic or non-heterocyclic C1-C12 hydrocarbon. Is a divalent group of
R ² is a linear or branched C1-C5 alkyl group,
p and q are integers of 1 to 3 and p+q=4. )
An amino group-containing titanate represented by

As R ^{1 in the} above formula II, the groups mentioned as R ^{1 in the} above formula I can be preferably used. Examples of R ^{1 in the} above formula II include, for example, —(CH ₂ ) _n —, —(CH ₂ ) _n —(CH) _m —(CH ₂ ) _j−1 —, —(CH ₂ ) _n —(CC)—. _{(CH 2) n-1 -} , - (CH 2) n -NH- (CH 2) m -, - (CH 2) n -NH- (CH 2) m -NH- (CH 2) j -, - (CH ₂ ) _n-1 -(CH)NH ₂ -(CH ₂ ) _m-1 -, -(CH ₂ ) _n-1 -(CH)NH ₂ -(CH ₂ ) _m-1 -NH-(CH ₂ ) It can be a group selected from the group consisting of _j − (where n, m, and j are integers of 1 or more). Particularly preferred R ₁ is -(CH ₂ ) _n -NH-(CH ₂ ) _m- (provided that n+m=4, particularly preferably n=m=2).

As R ^{2 in the} above formula II, the groups mentioned as R ^{2 in the} above formula I can be preferably used. In a preferred embodiment, a C3 alkyl group can be mentioned, and a propyl group and an isopropyl group can be particularly preferably mentioned. In the above formula II, p and q are integers of 1 to 3, p+q=4, preferably p=q=2, p=3 and q=1.

In the above, the description was made using the coupling agent having an amino group at the terminal, but the surface treatment of the copper powder and the oxide filler by the coupling agent is performed by using a coupling agent having no amino group at the terminal (a non-amino coupling agent). Agent) can also be preferably used. Examples of the non-amino coupling agent include coupling agents having an organic functional group such as an epoxy group, a mercapto group, an acryloyl group, a methacryloyl group, a vinyl group and an acid anhydride group at the terminal.

Examples of the silane coupling agent having an epoxy group include 3-glycidoxytrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropylmethyldiethoxy. Examples thereof include silane, 3-glycidoxypropyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

Examples of the silane coupling agent having a mercapto group include 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane.

Examples of the silane coupling agent having an acryloyl group include 3-acryloxypropyltrimethoxysilane.

Examples of the silane coupling agent having a methacryloyl group include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane. Is mentioned.

Examples of the silane coupling agent having a vinyl group include vinyltrimethoxysilane and vinyltriethoxysilane.

Examples of the silane coupling agent having an acid anhydride group include 3-trimethoxysilylpropyl succinic anhydride.

It is preferable that the coupling agent be subjected to a pretreatment for promoting the self-condensation reaction before being mixed with the copper powder and/or the oxide filler. In one embodiment, the pretreatment is preferably pH 11.5 or more and 13.5 or less, more preferably pH 12 by adding an alkaline aqueous solution such as aqueous ammonia, an aqueous NaOH solution, an aqueous KOH solution or an aqueous monoethanolamine solution to the coupling agent. The method includes a step of preparing an aqueous coupling agent solution adjusted to 0.0 or more and 13.5 or less, and a step of stirring while maintaining the aqueous coupling agent solution at 10°C to 40°C.

The higher the pH, the more the self-condensation reaction of the coupling agent can be promoted. However, if the self-condensation reaction is promoted too much, the coupling agent gels and the dispersibility of the copper powder and/or the oxide filler decreases. As a result, the coating film becomes rough. Further, a longer stirring time can accelerate the self-condensation reaction to some extent, but a longer stirring time deteriorates the productivity. Therefore, the stirring time can be preferably 1 to 72 hours, more preferably 6 to 24 hours.

The aqueous solution of the coupling agent after the pretreatment can be subjected to the surface treatment of the copper powder and/or the oxide filler by a known method. For example, after the pretreatment, the aqueous coupling agent solution is mixed with copper powder and/or oxide filler to form a dispersion liquid, and then appropriately coupled by a known method to perform a coupling reaction with the copper powder and/or oxide filler. Can be promoted. In a preferred embodiment, stirring can be performed at room temperature, for example, at a temperature in the range of 5 to 80°C, 10 to 40°C and 20 to 30°C. Further, the stirring is preferably carried out for 1 minute or longer, more preferably 30 minutes or longer, in order to promote the coupling reaction between the copper powder and/or the oxide filler and the coupling agent.

The concentration of the coupling agent in the aqueous coupling agent solution is preferably 10% by volume or more, and more preferably 20% by volume or more in order to promote the self-condensation reaction. The concentration of the coupling agent in the aqueous coupling agent solution is preferably 60% by volume or less and 45% by volume or less in order to prevent excessive self-condensation reaction from gelling. Is more preferable.

In some embodiments, stirring may be done by sonication. The treatment time of ultrasonic treatment is selected according to the state of the dispersion liquid, but is preferably 1 to 180 minutes, more preferably 3 to 150 minutes, still more preferably 10 to 120 minutes, and most preferably 20 to 80 minutes. Can be In a preferred embodiment, the ultrasonic treatment can be performed at an output of preferably 50 to 600 W, more preferably 100 to 600 W per 100 mL. In a preferred embodiment, sonication can be performed at a frequency of preferably 10-1 MHz, more preferably 20-1 MHz, even more preferably 50-1 MHz.

After the surface treatment with the coupling agent, the surface-treated copper powder and/or oxide filler can be separated and recovered from the copper powder and/or oxide filler dispersion liquid. For this separation/recovery, known means can be used, for example, filtration, centrifugation, decantation and the like can be used.

A known means can be used for drying the cake after separation/collection, and for example, drying by heating can be performed. The heat-drying can be performed, for example, at a temperature of 50 to 400° C. and 60 to 350° C., for example, by a heat treatment of 5 to 180 minutes and 30 to 120 minutes. Following the heat drying, the copper powder and/or the oxide filler may be further subjected to a crushing treatment, if desired. Further, with respect to the recovered surface-treated copper powder and/or oxide filler, copper further surface-treated with an organic substance or the like for the purpose of preventing rust or improving dispersibility in the paste. It may be adsorbed on the surface of the powder and/or the oxide filler.

In a preferred embodiment, the surface-treated copper powder and/or oxide filler may be subjected to a surface treatment with a coupling agent and then further surface-treated. As such a surface treatment, for example, an anticorrosion treatment with an organic anticorrosion agent such as benzotriazole or imidazole can be mentioned. Even with such a usual treatment, the surface treatment layer with the coupling agent is detached. There is no such thing. Therefore, a person skilled in the art can carry out such known surface treatments as desired, within the limits that the excellent sintering retardation is not lost. That is, the surface of the surface-treated copper powder and/or oxide filler according to the present disclosure is subjected to a further surface treatment within a range that does not lose the excellent sintering retardation property, and the obtained copper powder and/or oxide filler. Are also within the scope of the present disclosure.

[Binder resin]
Examples of the binder resin used in the conductive composition include cellulose resins, acrylic resins, alkyd resins, polyvinyl alcohol resins, polyvinyl acetals, ketone resins, urea resins, melamine resins, polyesters, polyamides and polyurethanes. it can. The binder resins may be used alone or in combination of two or more. The binder resin in the conductive composition can be contained in a proportion of, for example, 0.1 to 10%, preferably 1 to 8% with respect to the mass of the copper powder. By setting the blending ratio of the binder resin within the above range, it is possible to enhance the structural stability and uniform coating property of the conductive composition.

[Dispersion medium]
The dispersion medium used in the conductive composition is, for example, an alcohol solvent (for example, one or more selected from the group consisting of terpineol, dihydroterpineol, isopropyl alcohol, butylcarbitol, terpineloxyethanol, dihydroterpineloxyethanol). ), glycol ether solvent (eg butyl carbitol), acetate solvent (eg butyl carbitol acetate, dihydroterpineol acetate, dihydrocarbitol acetate, carbitol acetate, linalyl acetate, terpinyl acetate) 1 Or more), a ketone solvent (for example, methyl ethyl ketone), a hydrocarbon solvent (for example, one or more selected from the group consisting of toluene and cyclohexane), and a cellosolve (for example, one or more selected from the group consisting of ethyl cellosolve and butyl cellosolve). , Diethyl phthalate, or a propyneate-based solvent (for example, one or more selected from the group consisting of dihydroterpinylpropyneote, dihydrocarbylpropyneote, and isobonylpropyneote). As the dispersion medium, one kind may be used alone, or two or more kinds may be used in combination. The conductive composition may contain a dispersion medium in a ratio of, for example, 10 to 400% with respect to the mass of the copper powder.

[Other additives]
The electrically conductive composition according to the present disclosure may appropriately contain known additives such as glass frit, a dispersant, a thickener, and a defoaming agent.

The glass frit is useful for improving the adhesion between the ceramic and the conductor. As the glass frit, for example, a BET specific surface area of 1 to 10 m ² g ^-1, preferably 2 to 10 m ² g ^-1, more preferably may use a glass frit 2 to 8 m ² g ^-1. The conductive composition may contain a glass frit in a ratio of 0 to 5% with respect to the mass of the copper powder.

Examples of the dispersant include oleic acid, stearic acid and oleylamine. The conductive composition may contain a dispersant in a proportion of, for example, 0 to 5% with respect to the mass of the copper powder.

Examples of the defoaming agent include organic modified polysiloxane and polyacrylate. The conductive composition may contain an antifoaming agent in a proportion of, for example, 0 to 5% with respect to the mass of the copper powder.

In addition, the ratio of the copper powder, the oxide filler, the binder resin, and the dispersion medium in the conductive composition may be appropriately determined within a range that does not impair the coating property according to the application of the conductive composition.

Hereinafter, the present disclosure will be described in more detail with reference to Examples. The present disclosure is not limited to the examples below.

(Procedure 1: Copper powder of Examples 1 to 4 and Comparative Examples 1 and 2)
6 L of pure water was added to a 50 L container and heated so that the liquid temperature became 70°C. To this, 3.49 kg of copper sulfate pentahydrate was added, and it was visually confirmed that all the crystals of copper sulfate were dissolved while stirring at 350 rpm. D-glucose 1.39kg was added here. A 5 wt% aqueous ammonia solution was added thereto at a rate of 300 mL/min until a pH of 5 was reached. When the pH reached 5, an aqueous ammonia solution was added dropwise with a dropper to raise the pH to 8.4. From here, the liquid temperature was maintained at 70±2° C. and pH 8.5±0.1 for 3 hours. The pH was adjusted with an aqueous ammonia solution. After the reaction was completed, decantation, discharge of the supernatant, and washing with pure water were repeated until the pH of the supernatant fell below 8.0 to obtain a cuprous oxide powder slurry. A part of the solid content was taken out and dried at 70° C. in nitrogen, and it was confirmed by XRD that the solid content was cuprous oxide.

The water content of the cuprous oxide powder slurry obtained above was adjusted to 20% by mass, and the cuprous oxide powder slurry (25° C.) was diluted with pure water (25 (°C) was added, 4 g of glue was further added, and the mixture was stirred at 500 rpm. 2 L (25° C.) of 25 vol% dilute sulfuric acid was instantaneously added to adjust the pH to 0.7. The powder was settled by decantation, the supernatant was removed, 7 L of pure water (25° C.) was added, and the mixture was stirred at 500 rpm for 10 minutes. The operations of decantation and water washing were repeated until the Cu concentration derived from Cu ²⁺ in the supernatant fell below 1 g/L. Then, it was put into 3 L of ammonia water adjusted to pH 13 and stirred. The stirring was performed at 25° C. for 1 hour. Then, solid-liquid separation was performed by suction filtration to obtain a pH-treated cake of copper powder. The cake thus obtained was washed with pure water by using as a standard that the pH of pure water after filtration was below 8. The washed cake was dried under a nitrogen atmosphere at 100° C. for 2 hours. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill.

(Procedure 2: Determination of compacted bulk density)
The compacted bulk density of the obtained copper powder was measured by using the powder tester PT-X manufactured by Hosokawa Micron Co., Ltd. according to the method described above.

(Procedure 3: BET specific surface area measurement)
The BET specific surface area of the obtained copper powder was measured after pretreatment by heating at 200° C. for 5 hours in vacuum using BELSORP-miniII manufactured by Microtrac Bell.

(Procedure 4: Cuprous oxide powders of Examples 1 to 6, 10 to 13, 15 and Comparative Examples 1 to 3)
6 L of pure water and 9 g of gum arabic were added to a 50 L container and heated so that the liquid temperature became 70°C. To this, 3.49 kg of copper sulfate pentahydrate was added, and it was visually confirmed that all the crystals of copper sulfate were dissolved while stirring at 350 rpm. D-glucose 1.39kg was added here. A 5 wt% aqueous ammonia solution was added thereto at a rate of 300 mL/min until a pH of 5 was reached. When the pH reached 5, an aqueous ammonia solution was added dropwise with a dropper to raise the pH to 8.4. From here, the liquid temperature was maintained at 70±2° C. and pH 8.5±0.1 for 3 hours. The pH was adjusted with aqueous ammonia solution. After the reaction was completed, decantation, discharge of the supernatant, and washing with pure water were repeated until the pH of the supernatant fell below 8.0. Then, solid-liquid separation was performed by suction filtration to obtain a cake. The obtained cake was washed with pure water by using as a standard that the pH of pure water after filtration was below 8. The washed cake was dried under a nitrogen atmosphere at 100° C. for 2 hours. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill. It was confirmed by XRD that the obtained powder was a cuprous oxide powder. The compacted bulk density and the BET specific surface area were determined in accordance with the procedures 2 and 3.

(Procedure 5: Surface-treated copper powders of Examples 9 to 11 and 14 to 16)
Dilute sulfuric acid was instantaneously added to the cuprous oxide powder slurry (25° C.) produced in Procedure 1. The powder was settled by decantation, the supernatant was removed, 7 L of pure water (25° C.) was added, and the mixture was stirred at 500 rpm for 10 minutes. The operations of decantation and washing were repeated until the pH of the supernatant liquid exceeded 4. An appropriate amount of the supernatant liquid was removed to obtain a copper powder slurry having a water content of 20% by mass. In addition, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) (hereinafter referred to as “diaminosilane”) was prepared as a coupling agent. This coupling agent and pure water were mixed, and the pH was adjusted to 12.5 with aqueous ammonia to obtain an aqueous coupling agent solution. The diaminosilane concentration in the aqueous coupling agent solution was 15 wt %. This was stirred at 25° C. for 14 hours to accelerate the self-condensation reaction of the coupling agent. Next, 550 g of the copper powder slurry having the above-mentioned water content of 20 mass% was mixed with the pretreated aqueous solution and stirred at 25° C. and 500 rpm for 1 hour. Then, solid-liquid separation was performed by suction filtration, and the copper powder was collected as a cake having a different water content depending on the test number. The amount of Si attached was adjusted by increasing or decreasing the water content of the cake after solid-liquid separation. The higher the water content of the cake, the greater the amount of Si attached to the copper powder. The cake obtained was dried under a nitrogen atmosphere at 100° C. for 2 hours. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill. The solidified bulk density and the BET specific surface area were determined according to the same procedure as the procedure 2 and the procedure 3.

(Procedure 6: Surface-treated cuprous oxide powder of Examples 9 and 14)
Pure water was added to the cuprous oxide powder cake washed with pure water obtained in step 4 to prepare a cuprous oxide powder slurry having a water content of 20 mass %. In addition, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) (hereinafter referred to as “diaminosilane”) was prepared as a coupling agent. This coupling agent and pure water were mixed, and the pH was adjusted to 12.5 with aqueous ammonia to obtain an aqueous coupling agent solution. The diaminosilane concentration in the aqueous coupling agent solution was 15 wt %. This was stirred at 25° C. for 14 hours to accelerate the self-condensation reaction of the coupling agent. Next, 1250 g of the above-treated aqueous solution and 1250 g of the cuprous oxide powder slurry having the above-mentioned water content of 20 mass% were mixed and stirred at 25° C. and 500 rpm for 1 hour. Then, solid-liquid separation was performed by suction filtration to collect a cuprous oxide powder cake. The cake obtained was dried under a nitrogen atmosphere at 100° C. for 2 hours. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill. The BET specific surface area was determined according to the same procedure as the procedure 3.

(Procedure 7: Copper powder of Example 5)
Dilute sulfuric acid was instantaneously added to the cuprous oxide powder slurry (25° C.) produced in Procedure 1. The powder was settled by decantation, the supernatant was removed, 7 L of pure water (25° C.) was added, and the mixture was stirred at 500 rpm for 10 minutes. The operations of decantation and water washing were repeated until the Cu concentration derived from Cu ²⁺ in the supernatant fell below 1 g/L. Then, the mixture was poured into 3 L of ammonia water adjusted to pH 8 and stirred. The stirring was performed at 25° C. for 1 hour. Then, solid-liquid separation was performed by suction filtration to obtain a pH-treated copper powder cake. The obtained cake was washed with pure water by using as a standard that the pH of pure water after filtration was below 8. The washed cake was dried under a nitrogen atmosphere at 100° C. for 2 hours. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill. The solidified bulk density and the BET specific surface area were determined according to the same procedure as the procedure 2 and the procedure 3.

(Procedure 8: Copper powder of Example 6)
Dilute sulfuric acid was instantaneously added to the cuprous oxide powder slurry (25° C.) produced in Procedure 1. The powder was settled by decantation, the supernatant was removed, 7 L of pure water (25° C.) was added, and the mixture was stirred at 500 rpm for 10 minutes. The operations of decantation and water washing were repeated until the pH of the supernatant reached 7. Then, solid-liquid separation was performed by suction filtration, and the obtained cake was dried at 100° C. for 2 hours under a nitrogen atmosphere. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill. The solidified bulk density and the BET specific surface area were determined according to the same procedure as the procedure 2 and the procedure 3.

(Procedure 9: Copper powder of Example 7)
In step 1, collagen peptide having a molecular weight of 5000 was used instead of glue, and dilute sulfuric acid was instantaneously added to the cuprous oxide powder slurry (25° C.). The powder was settled by decantation, the supernatant was removed, 7 L of pure water (25° C.) was added, and the mixture was stirred at 500 rpm for 10 minutes. The operations of decantation and water washing were repeated until the Cu concentration derived from Cu ²⁺ in the supernatant fell below 1 g/L. Then, the mixture was poured into 3 L of ammonia water adjusted to pH 13 and stirred. The stirring was performed at 25° C. for 1 hour. Then, solid-liquid separation was performed by suction filtration to obtain a pH-treated copper powder cake. The cake thus obtained was washed with pure water by using as a standard that the pH of pure water after filtration was below 8. The washed cake was dried under a nitrogen atmosphere at 100° C. for 2 hours. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill. The solidified bulk density and the BET specific surface area were determined according to the same procedure as the procedure 2 and the procedure 3.

(Procedure 10: Copper powder of Example 8)
In step 1, diluted sulfuric acid was added at 50 mL/min to the cuprous oxide powder slurry (25° C.). The operations of decantation and water washing were repeated until the Cu concentration derived from Cu ²⁺ in the supernatant fell below 1 g/L. Then, the mixture was poured into 3 L of ammonia water adjusted to pH 13 and stirred. The stirring was performed at 25° C. for 1 hour. Then, solid-liquid separation was performed by suction filtration to obtain a pH-treated cake of copper powder. The cake thus obtained was washed with pure water by using as a standard that the pH of pure water after filtration was below 8. The washed cake was dried under a nitrogen atmosphere at 100° C. for 2 hours. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill. The solidified bulk density and the BET specific surface area were determined according to the same procedure as the procedure 2 and the procedure 3.

(Procedure 11: Surface-treated copper powder of Example 12)
A surface-treated copper powder was prepared in the same procedure as in Procedure 5, except that the coupling agent in Procedure 5 was titanium aminoethylaminoaminoethanolate (Organix TC-510 manufactured by Matsumoto Fine Chemical Co., Ltd.) described below, and Procedures 2 and 3 were used. The bulk density and BET specific surface area were determined in accordance with.

(Procedure 12: Surface-treated copper powder of Example 13)
The same procedure as in Step 5 except that the coupling agent in Step 5 was changed to a mixed solution of diaminosilane and the following zirconium lactate ammonium salt (manufactured by Matsumoto Fine Chemical, Organix ZC-300) at 70:30 (mass ratio). The surface-treated copper powder was prepared in step 2, and the compacted bulk density and BET specific surface area were determined according to steps 2 and 3.

(Procedure 13: Copper powder of Comparative Example 3)
Dilute sulfuric acid was instantaneously added to the cuprous oxide powder slurry (25° C.) produced in Procedure 1. The powder was settled by decantation, the supernatant was removed, 7 L of pure water (25° C.) was added, and the mixture was stirred at 500 rpm for 10 minutes. The operations of decantation and water washing were repeated until the pH of the supernatant reached 7. Then, solid-liquid separation was performed by suction filtration, and the obtained cake was dried at 100° C. for 2 hours under a nitrogen atmosphere. The resulting dry powder was crushed in a pestle mortar until it passed through a sieve having 0.1 mm holes. The solidified bulk density and the BET specific surface area were determined according to the same procedure as the procedure 2 and the procedure 3.

(Procedure 14: Cuprous oxide powder of Example 7)
6 L of pure water and 9 g of gum arabic were added to a 50 L container and heated so that the liquid temperature became 70°C. To this, 3.49 kg of copper sulfate pentahydrate was added, and it was visually confirmed that all the crystals of copper sulfate were dissolved while stirring at 350 rpm. D-glucose 1.39kg was added here. A 5 wt% aqueous ammonia solution was added thereto at a rate of 300 mL/min until a pH of 5 was reached. When the pH reached 5, an aqueous ammonia solution was added dropwise with a dropper to raise the pH to 8.4. From here, the liquid temperature was maintained at 70±2° C. and pH 8.5±0.1 for 3 hours. The pH was adjusted with an aqueous ammonia solution. After the reaction was completed, decantation, discharge of the supernatant, and washing with pure water were repeated until the pH of the supernatant fell below 8.0. Then, solid-liquid separation was performed by suction filtration to obtain a cake. The obtained cake was dispersed in an aqueous solution containing 6 L of pure water and 9 g of gum arabic in a 50 L container, and heated so that the liquid temperature became 70°C. To this, 3.49 kg of copper sulfate pentahydrate was added, and it was visually confirmed that all the crystals of copper sulfate were dissolved while stirring at 350 rpm. D-glucose 1.39kg was added here. A 5 wt% aqueous ammonia solution was added thereto at a rate of 300 mL/min until a pH of 5 was reached with a liquid feed pump. When the pH reached 5, an aqueous ammonia solution was added dropwise with a dropper to raise the pH to 8.4. From here, the liquid temperature was maintained at 70±2° C. and pH 8.5±0.1 for 3 hours. The pH was adjusted with an aqueous ammonia solution. After completion of the reaction, decantation, discharge of the supernatant, and washing with pure water were repeated until the pH of the supernatant liquid fell below 8.0. Then, solid-liquid separation was performed by suction filtration to obtain a cake. The cake thus obtained was washed with pure water with a guideline that the pH of pure water after filtration was below 8. The washed cake was dried under a nitrogen atmosphere at 100° C. for 2 hours. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill. It was confirmed by XRD that the obtained powder was cuprous oxide powder. The BET specific surface area was determined according to the same procedure as the procedure 3.

(Procedure 15: Cuprous oxide powder of Example 8)
A cuprous oxide powder was produced according to the procedure 4 except that the gum arabic was changed to the collagen peptide having a molecular weight of 5000 in the procedure 4. The BET specific surface area was determined according to the same procedure as the procedure 3.

(Procedure 16: Copper oxide powder of Example 16)
According to procedure 4, a cuprous oxide powder slurry was prepared and washed until the pH was lower than 8. Then, pure water was added so that the solid content was 20% by mass, and the mixture was heated to 40° C. and stirred at 300 rpm for 2 hours. Then, solid-liquid separation was performed by suction filtration to obtain a cake. The cake was dried under a nitrogen atmosphere at 100° C. for 2 hours. The obtained dry powder was crushed with a pestle mortar until it passed through a sieve having 0.7 mm holes, and further crushed with a jet mill. It was confirmed by XRD that the obtained powder was a copper oxide powder. The BET specific surface area was determined according to the same procedure as Procedures 2 and 3.

(Procedure 17: Metal adhesion amount derived from coupling agent in surface-treated powder)
Each of the surface-treated copper powder, the surface-treated cuprous oxide powder, and the surface-treated copper oxide powder (hereinafter referred to as "surface-treated powder") obtained in the above-mentioned procedure and the comparative example is dissolved with an acid to emit ICP light. The mass (μg) of Si, Ti, and Zr attached to the unit mass (g) of the surface-treated powder was determined by a spectroscopic analysis method (ICP-OES manufactured by Hitachi High-Tech Science Co., Ltd.). The results are shown in Table 1. The element concentrations below the lower limit of detection are not shown in the table.

(Procedure 18: Paste preparation)
A vehicle was prepared in advance by passing terpineol and ethyl cellulose through an orbital revolution mixer AR-100 and three rolls and thoroughly kneading. Next, the various copper powders, cuprous oxide powders, and copper oxide powders produced in steps 1 to 16 were mixed according to the oxide filler/(copper powder+oxide filler) ratio in the table. The powder after this mixing is called an inorganic powder. Inorganic powder: Ethyl cellulose: Oleic acid: Terpineol = 80:2.3:1.6:16.1 (weight ratio), and the mixture was pre-kneaded in a rotation/revolution mixer and passed through a three-roll mill (finishing). A roll gap of 5 μm) was used and defoaming was performed using a rotation/revolution mixer to prepare pastes of Examples (excluding Example 15) and Comparative Examples.
For Example 15, the inorganic powder prepared by mixing the surface-treated copper powder prepared in Step 5 and the cuprous oxide powder prepared in Step 4 in the oxide filler/(copper powder+oxide filler) ratio shown in Table 1 was used. A paste was prepared according to the same procedure as above so that the inorganic powder:ethyl cellulose:terpineol=35:1.8:63.2 (weight ratio).

(Procedure 19: Surface roughness (Ra) of paste coating film)
The pastes of Examples and Comparative Examples obtained by the above procedure were applied on a slide glass at a moving speed of 5 cm/sec using an applicator having a 25 μm gap and dried at 120° C. for 10 minutes. Ra in the coating direction of the obtained coating film (according to JIS B0633:2001) was measured at 5 points with a stylus roughness meter, and the average value was taken as the measured value. The results are shown in Table 1.

(Procedure 20: XRD of paste coating film)
The paste prepared in Procedure 19 was applied on a slide glass at a moving speed of 5 cm/sec using an applicator with a gap of 25 μm and dried at 120° C. for 10 minutes to obtain a dry coating film. XRD measurement is performed on this dried coating film under the following conditions to calculate the area of the (111) peak of cuprous oxide, copper oxide, and copper, and Cu ₂ O(111)/Cu(111), or CuO(111)/Cu(111) was determined. When both cuprous oxide powder and copper oxide powder are used as the oxide filler, {Cu ₂ O(111)+CuO(111)}/Cu(111) is calculated.
The background processing when calculating the peak area was performed by the automatic processing mode of the integrated powder X-ray analysis software PDXL2 manufactured by RIGAKU. By selecting this mode, the software performs a simple peak search, removes the peak portion, and then fits a polynomial to the remaining data to remove the background.
Device: Rint 2200 Ultima (manufactured by RIGAKU)
X-ray: CuKα
X-ray output: 40kV, 40mA
Scan speed: 4°/min Step width: 0.02°
Scan range: 20-80°
Divergence slit: 2°
Divergence vertical restriction slit: 10 mm
Scattering slit: 2°
Emitting slit: 0.6mm
Peak area calculation software: PDXL2

(Procedure 21: Steam firing of paste)
The dried coating film obtained in step 20 was peeled off from the slide glass, sufficiently crushed with a pestle and a mortar, and 0.5 g of the obtained powder was hand-pressed to 4.7 ± 0. A cylindrical green compact having a density of 2 gcm ^-3 was molded. This green compact was removed from the mold, loaded into a thermomechanical analyzer (TMA4000 (Netch Japan)) so that the central axis was in the vertical direction, and the total pressure was 1 atm with a steam generator (HC9800 (Netch Japan)). , Nitrogen gas with a water vapor partial pressure of 0.05 atm was flowed at 100 mL/min (22°C conversion), and a load of 98 mN was applied to the upper and bottom surfaces of the green compact while heating from 20°C at a rate of 1°C/min. Then, the volumetric shrinkage ratio was obtained from the amount of height shrinkage of the green compact at 650°C. Shrinkage of the green compact represents combustion and decomposition of the binder resin and sintering of the copper powder. The results are shown in Table 1.

(Procedure 22: Specific resistance of sintered body)
Using the pastes and screen plates (stainless steel mesh, wire diameter 18 μm, gauze thickness 38 μm, opening 33 μm, aperture ratio 42%) of the examples and comparative examples obtained by the above procedure, a green sheet (Yamamura Photonics GCS71) Then, three lines having a width of 5 mm and a length of 20 mm were printed. While supplying the remaining nitrogen gas at a total pressure of 1 atm and a steam partial pressure of 0.03 atm at 2 L/min, the temperature was raised to 850° C. at a rate of 0.75° C./min and maintained at 850° C. for 20 minutes. Then, it was cooled to room temperature at a rate of 5° C./min in a pure nitrogen atmosphere containing no water vapor. In this way, a sintered body of the paste was formed on the ceramic substrate to obtain a sintered body/ceramic laminated body. The surface resistance and the thickness of a circuit having a width of 5 mm and a length of 20 mm obtained by cooling to room temperature were measured, and the specific resistance was calculated as a three-point average. The results are shown in Table 1.

(Procedure 23: Tape peeling test)
After a carbon double-sided tape (manufactured by Nisshin EM Co., Ltd.) was attached to the circuit and the substrate obtained by the above procedure, a tape peeling test was performed at a peeling angle of 90° and a peeling speed of 5 mm/s in accordance with JIS Z 0237:2009. , It was confirmed that the circuit did not adhere to the adhesive surface of the tape. When at least a part of the circuit (sintered body) was peeled from the substrate in one peel test, it was judged as ×, when peeled twice or three times, and when it was peeled four times or more.

(Procedure 24: Metal concentration analysis derived from coupling agent in sintered body)
Each of the pastes of Examples and Comparative Examples obtained by the above procedure was heated to 850° C. at a total pressure of 1 atm and a residual nitrogen atmosphere of steam partial pressure of 0.03 atm at a temperature rising rate of 1° C./min, and at 850° C. It was fired for 30 minutes and then cooled to room temperature at a rate of 10° C./minute to obtain a sintered body. This sintered body was dissolved with an acid, and the concentrations of Si, Ti, and Zr in the sintered body were analyzed by ICP emission spectroscopy (ICP-OES manufactured by Hitachi High-Tech Science Co., Ltd.). The results are shown in Table 1. The element concentrations below the lower limit of detection are not shown in the table.

[Discussion]
Example 1 in which the compounding ratio (peak area ratio) of the copper powder and the oxide filler (cuprous oxide and/or copper oxide), the surface roughness (Ra) of the coating film, and the volume shrinkage rate during firing were appropriate. When the paste of No. 16 was used, a conductor/ceramics laminate having a small specific resistance of the conductor and excellent adhesiveness between the ceramics and the conductor was obtained even if the paste was fired in a steam atmosphere.
On the other hand, in Comparative Example 1, the resistivity was increased because the blending ratio of the oxide filler was too high.
In Comparative Example 2, since the compounding ratio of the oxide filler was too low, the sintering delay property was insufficient and the adhesion between the ceramic and the conductor was insufficient.
In Comparative Example 3, since the compacted bulk density of the copper powder used was too high, the surface roughness of the coating film increased and the adhesion between the ceramic and the conductor was insufficient.

Claims (11)

Copper powder, one or both of the oxide filler selected from the group consisting of cuprous oxide powder and copper oxide powder, a binder resin, a conductive composition containing a dispersion medium,
The conductive composition was applied onto a slide glass at a moving speed of 5 cm/sec using an applicator with a gap of 25 μm and dried at 120° C. for 10 minutes. The arithmetic mean roughness Ra in the direction is 0.2 μm or less,
In the XRD of the coating film, the ratio of the peak area corresponding to the oxide filler on the (111) plane to the peak area corresponding to the copper powder on the (111) plane is 0.05 to 0.5,
A cylindrical green compact having a density of 4.7±0.2 gcm ⁻³ and a diameter of 5 mm was formed from 0.5 g of the powder obtained by crushing the coating film, and a load of 98 mN was applied to the green compact. The volumetric shrinkage ratio at 650° C. is 15% or less when measured by TMA at a temperature rising rate of 1° C./min in a residual nitrogen atmosphere having a total pressure of 1 atm and a water vapor partial pressure of 0.05 atm while being applied to the upper bottom surface.
Conductive composition. A sintered body obtained by heating the conductive composition to 850° C. at a total pressure of 1 atm and a steam partial pressure of 0.03 atm at the balance of nitrogen atmosphere at a temperature rising rate of 1° C./min and firing at 850° C. for 30 minutes. The conductive composition according to claim 1, wherein the total concentration of Si, Ti, Al, and Zr when measured by ICP emission spectroscopy is 1,000 to 10,000 mass ppm. A sintered body obtained by heating the conductive composition at a total pressure of 1 atm and a partial pressure of water vapor of 0.03 atm in the remaining nitrogen atmosphere to 850° C. at a rate of 0.75° C./min and firing at 850° C. for 20 minutes. The conductive composition according to claim 1 or 2, having a specific resistance of 3.0 µΩ·cm or less. The electroconductive composition according to claim 1, wherein the copper powder and/or the oxide filler is surface-treated with a coupling agent. 5. Kneading copper powder, one or both oxide fillers selected from the group consisting of cuprous oxide powder and copper oxide powder, a binder resin, and a dispersion medium. A method for producing the electrically conductive composition according to. The method for producing a conductive composition according to claim 5, wherein the copper powder has a compacted bulk density of 3.0 g/cm ³ or less. The manufacturing method according to claim 5, wherein the ratio of the BET specific surface area of the oxide filler to the BET specific surface area of the copper powder is 0.2 to 3.0. The manufacturing method according to any one of claims 5 to 7, wherein a ratio of the mass of the oxide filler to the total mass of the copper powder and the oxide filler is 0.05 to 0.35. A composite of a ceramic and a conductor, which is manufactured using the conductive composition according to claim 1. A monolithic ceramic capacitor manufactured using the conductive composition according to claim 1. A ceramic circuit board manufactured using the conductive composition according to claim 1.