Copper powder, copper paste, method for producing conductive film, and sintered body

Abstract

This copper powder contains the following copper powder A and copper powder B. [Copper powder A] Copper powder composed of a plurality of copper particles, and containing a halogen element in an amount between 0.001 at% and 0.30 at% both inclusive. [Copper powder B] Copper powder B composed of a plurality of copper particles having different aspect ratios, where the tap density is between 4.0 g / cm3 and 7.0 g / cm3 both inclusive, and the value of a dispersion degree DP, which is the ratio of a standard deviation SD of a particle size distribution to a volume cumulative particle diameter D50 at a cumulative volume of 50 vol% by a laser diffraction scattering type particle size distribution measurement method is between 0.55 and 0.90 both inclusive.

Description

Method for producing copper powder, copper paste, and conductive film, and sintered body

[0001] This invention relates to a method for producing copper powder, copper paste, and conductive films, and to a sintered body.

[0002] Copper is a highly conductive metal and a versatile material, making it widely used industrially as a conductive material. For example, copper powder, which consists of copper particles, is widely used as a raw material for manufacturing various electronic components, such as the external electrodes of multilayer ceramic capacitors (hereinafter also referred to as "MLCCs") and wiring to various main boards.

[0003] For example, Patent Documents 1 and 2 describe a paste containing copper powder, glass frit, and a solvent. These documents state that electronic components such as electrodes can be manufactured using this paste.

[0004] Japanese Patent Publication No. 2002-294310 Japanese Patent Publication No. 2007-103845

[0005] When a paste containing glass frit is fired, glass delamination sometimes occurs on the electrode surface due to the increased fluidity of the glass frit as sintering progresses. Since glass delamination hinders the formation of plating on the electrode surface, conventional attempts have been made to solve this problem by raising the sintering temperature of the copper powder in the paste to bring it closer to the sintering temperature of the glass frit. On the other hand, although a dense sintered film can be obtained by firing the paste at high temperatures, from the viewpoint of improving the performance of electronic components, a dense sintered film obtained by low-temperature firing is desired. Therefore, the object of the present invention is to provide a copper powder that enables the formation of a dense sintered film even at low temperatures and can suppress the occurrence of glass delamination.

[0006] The present invention provides copper powder comprising the following copper powder A and copper powder B: [Copper powder A] Copper powder comprising a plurality of copper particles, wherein the copper powder contains 0.001 at% to 0.3 at% of halogen elements. [Copper powder B] Copper powder comprising a plurality of copper particles having different aspect ratios, wherein the tap density is 4.0 g / cm³. ３ 7.0g / cm or more ３The following is the cumulative particle size D at 50% of the cumulative volume, as measured by laser diffraction scattering particle size distribution analysis. ５０ The degree of dispersion D is the ratio of the standard deviation (SD) of the particle size distribution to the degree of dispersion D. Ｐ Copper powder in which the value is between 0.55 and 0.90.

[0007] The present invention also provides a copper paste comprising the following copper powder A and copper powder B: [Copper powder A] Copper powder comprising a plurality of copper particles, comprising 0.001 at% to 0.3 at% of halogen elements. [Copper powder B] Copper powder comprising a plurality of copper particles having different aspect ratios, with a tap density of 4.0 g / cm³. ３ 7.0g / cm or more ３ The following is the cumulative particle size D at 50% of the cumulative volume, as measured by laser diffraction scattering particle size distribution analysis. ５０ The degree of dispersion D is the ratio of the standard deviation (SD) of the particle size distribution to the degree of dispersion D. Ｐ Copper powder in which the value is between 0.55 and 0.90.

[0008] The present invention also provides a method for manufacturing a conductive film, which involves applying the copper paste to a substrate to form a coating film and then firing the coating film.

[0009] Furthermore, the present invention provides a sintered body of the copper paste.

[0010] Figure 1 is a graph showing an example of the measurement results of thermomechanical analysis on copper powder A. Figures 2(a) to (d) are schematic diagrams showing a method for measuring the aspect ratio of copper particles b in copper powder B. Figure 3 is a distribution map created by taking the minor axis of copper particles b in copper powder B in one embodiment as the vertical axis and the circularity of said copper particles b as the vertical axis. Figure 4 is a distribution map created by taking the minor axis of copper particles b in copper powder B in one embodiment as the vertical axis and the aspect ratio of said copper particles b as the vertical axis.

[0011] The present invention will be described below based on its preferred embodiments. The copper powder of the present invention comprises copper powder A and copper powder B. Details of copper powder A and copper powder B will be described later. In recent years, from the viewpoint of successfully manufacturing high-performance electronic components, there has been a demand for obtaining dense sintered films by low-temperature firing (for example, below 800°C). In addition, there is a demand to suppress the occurrence of glass delamination during sintering. Conventionally, attempts have been made to solve the problem of glass delamination by raising the sintering temperature of the copper powder in the paste, but in this case, it becomes difficult to meet the former demand. Thus, obtaining a dense sintered film at low temperatures and suppressing the occurrence of glass delamination have been mutually exclusive. The inventors of the present invention have diligently studied how to improve this point and have found that, surprisingly, with copper powder containing copper powder A and copper powder B described later, it is possible to form a dense sintered film even at low temperatures and to suppress the occurrence of glass delamination. Preferred embodiments of copper powder A, copper powder B, and the copper powder of the present invention containing copper powder A and copper powder B will be described below.

[0012] [Copper Powder A] First, let's describe copper powder A. Copper powder A consists of a plurality of copper particles (hereinafter also simply referred to as "copper particle a"). Preferably, copper particle a is a particle mainly containing the element copper (Cu), or a copper-based alloy particle. Depending on the specific application of copper powder A, it may also contain metal elements other than copper as needed. From the viewpoint of making the effects of the present invention remarkable, it is preferable that the copper particles a constituting copper powder A are spherical. From this viewpoint, even if they are not spherical, it is preferable that the average aspect ratio of copper particles a is close to 1, and specifically, it is preferable that it is less than 1.05.

[0013] Copper powder A preferably contains halogen elements. With the miniaturization and performance improvement of electronic components, there is a demand for copper powder that sinterslowly and copper powder that exhibits low-temperature sinterability. As a result of the inventors' diligent research into improving these properties, they unexpectedly discovered that by including halogen elements in copper powder, copper powder that sinterslowly can be obtained. Moreover, they also discovered that copper powder with a low sintering temperature can be obtained. Based on this, the inventors have also discovered that with the copper powder of the present invention, including copper powder A, it is possible to form a dense sintered film even at low temperatures. In this specification, "slow sintering" means that the change from copper powder to a sintered body due to heating proceeds slowly. "Sintering temperature" is the temperature at which copper powder is pressed to 1.0 MPa to form pellets, and these pellets are fired in a nitrogen atmosphere and exhibit the maximum shrinkage rate. The reason why the presence of halogen elements in copper powder A causes sintering to proceed slowly and the sintering temperature to be low is not entirely clear. However, the inventors speculate that the halogen compounds in copper act as initiation points for sintering (i.e., sintering active sites), thereby reducing the energy required for sintering and thus lowering the sintering temperature. At the same time, a localized compositional distribution of the halogen compounds in copper occurs, which in turn creates a distribution in the degree of sintering progression. However, the scope of the present invention is not limited to this theory.

[0014] From the viewpoint of slowing down the sintering process and lowering the sintering temperature, copper powder A preferably contains 0.001 at% or more of halogen elements, more preferably 0.002 at% or more, even more preferably 0.005 at% or more, even more preferably 0.010 at% or more, and particularly preferably 0.020 at% or more. Furthermore, from the viewpoint of suppressing corrosion of the copper powder caused by halogen elements and reducing the decrease in conductivity and damage to the firing equipment, copper powder A preferably contains 0.30 at% or less of halogen elements, more preferably 0.20 at% or less, and even more preferably 0.15 at% or less. The halogen element content (at%) in copper powder A is calculated from the following formula.

[0015]

[0016] When the copper powder A contains two or more different halogen elements, for example, when it contains chlorine (Cl) element and bromine (Br) element as the halogen elements, X / M in the above formula ｘ is [(Cl / M Ｃｌ ) + (Br / M Ｂｒ )].

[0017] The method for measuring the content of halogen elements will be described in the examples below. In order to adjust the content of the halogen element within the above range, it is preferable to adjust the concentration of the water-soluble halogen compound in the production method of the copper powder A described later, or adjust the degree of washing performed after producing the copper particles a. Alternatively, in the copper production step described later, it is also suitable to control the number of generated copper crystal nuclei and the growth rate, or control the particle size of the growing copper particles. Specifically, when increasing the content of the halogen element, for example, reducing the reducing power in the copper production step, decreasing the number of generated copper crystal nuclei and slowing down the growth rate allows obtaining copper particles a with a large particle size while incorporating more halogen elements. When decreasing the content of the halogen element, for example, increasing the reducing power in the copper production step, increasing the number of generated copper crystal nuclei and accelerating the growth rate allows obtaining copper particles a with a small particle size in which the incorporation amount of the halogen element is reduced. However, the present invention is not bound by this theory.

[0018] Examples of the halogen element contained in the copper powder A include fluorine (F) element, chlorine (Cl) element, bromine (Br) element and iodine (I) element. One halogen element may be used alone, or two or more halogen elements may be used in combination. There is no particular limitation on the existing state of the halogen element. The halogen element may exist, for example, in the form of copper halide, or within the crystal structure of copper or at grain boundaries. From the viewpoints of allowing sintering of the copper powder to proceed slowly and lowering the sintering temperature, the halogen element is preferably at least one selected from the group consisting of chlorine element, bromine element and iodine element, and more preferably chlorine element.

[0019] In copper powder A, it is preferable that the halogen element and the copper particles a constituting copper powder A exist as an inseparable whole. Examples of the "inseparable whole" configuration include (i) a configuration in which the copper element and the halogen element chemically react and bond within and / or on the surface of the copper particles a, and (ii) a configuration in which particles containing the halogen element are inseparably dispersed within and / or on the surface of the copper particles a. In the former configuration, typically the copper element and the halogen element are bonded and exist in the form of copper halide, or the halogen element is incorporated into the crystalline structure of copper. In the latter configuration, typically the halogen element exists in the form of a water-soluble halogen source, as described later. In either configuration (i) or (ii) in which the halogen element and the copper element exist, the halogen element may, for example, (a) be present in the region from the center to the surface of the copper particles a, or (b) be present only on the surface of the copper particles a, and the halogen element may not be present inside the copper particles a, or the halogen element may be present only inside the copper particles a and not on the surface of the copper particles a. In this specification, "surface" refers to the region from the outermost surface of copper particle a to a depth of 10 nm, and this region is also a depth detectable by X-ray photoelectron spectroscopy (hereinafter also referred to as "XPS"). "The copper element and halogen element are chemically reacted and bonded inside and / or on the surface of copper particle a" means that, for example, when copper powder A is subjected to known methods such as measurement by X-ray photoelectron spectroscopy (XPS) and observation by transmission electron microscopy (TEM), either alone or in combination, it can be confirmed that the copper element and halogen element are chemically reacted and bonded. Furthermore, "Particles containing halogen elements are inseparably dispersed inside and / or on the surface of copper particle a" means that, for example, when copper powder A is subjected to known methods such as measurement by XPS and observation by TEM, either alone or in combination, the presence of particles containing halogen elements can be confirmed.

[0020] Copper powder A undergoes slow sintering and has a low sintering temperature, regardless of whether the copper particles a and halogen elements are present in either (i) or (ii). Such copper powder A can be suitably produced by the method for producing copper powder A described later.

[0021] As described above, it is preferable that copper powder A has a low sintering temperature. The degree of low sintering temperature of copper powder A is determined by the temperature at which copper powder A shrinks by 10 volume percent relative to its maximum shrinkage rate when subjected to thermomechanical analysis (TMA) under a nitrogen atmosphere and a heating rate of 10°C / min. １０ This can be defined by the temperature T. １０ The temperature of copper powder A is defined as the "sintering start temperature". Specifically, from the viewpoint of effectively lowering the sintering temperature of copper powder A and making the copper powder of the present invention, which includes copper powder A, useful as an external electrode material for MLCCs, the temperature of copper powder A is defined as T １０ The temperature is preferably 600°C or lower, more preferably 580°C or lower, and even more preferably 550°C or lower. From the viewpoint of making the above-mentioned effects even more pronounced, temperature T １０ The lower the temperature, the better, but it may be 300°C or higher. In this specification, when TMA measurements are taken in a range of 25°C to 1000°C under conditions of a nitrogen atmosphere and a heating rate of 10°C / min, the temperature at which a 10% volume shrinkage occurs is defined as "T" when the state at 25°C is taken as the reference (0% shrinkage) and the maximum shrinkage rate is defined as 100% volume shrinkage. １０ This is defined as follows: For example, when TMA measurements are taken in the range of 25°C to 1000°C, if the temperature at which the shrinkage rate is greatest is 1000°C, and the shrinkage rate at 1000°C is 15% relative to the state at 25°C, then 15% is defined as 100 volume% shrinkage. In this case, 10 volume% shrinkage means a shrinkage rate of 1.5%, and the temperature at which a 1.5% shrinkage occurs is defined as temperature T １０ If no other elements are present on the surface of copper powder A, then the "temperature T １０ " refers to the temperature T of the copper powder A itself. １０ Therefore, if other elements described later are present on the surface of copper powder A, the "temperature T １０ "The temperature T of copper powder A after surface treatment" １０ That is. T１０ The detailed measurement method will be explained in the examples described later. Such a temperature T １０ Copper powder A having the properties described below is preferably manufactured by the method for manufacturing copper powder A described later.

[0022] As described above, it is also preferable that the copper powder A undergoes slow sintering. The degree of slowness of sintering depends on the temperature T described above for the copper powder A. １０ This value is obtained by measuring the TMA of copper powder A under similar conditions, and represents the T when it shrinks by 80 volume percent relative to the maximum shrinkage rate. ８０ and T １０ It can be defined by the slope of the change between the two. The slope of this change is the value R defined by the following equation (1). The value of R is the TMA curve when temperature is plotted on the horizontal axis and the volume shrinkage rate of copper powder is plotted on the vertical axis, as shown in Figure 1. ８０ and T １０ This corresponds to the slope between ( ). Therefore, in the following explanation, R will also be called "slope R". As shown in Figure 1, the larger the positive slope R, the slower the sintering proceeds. R = (S －０．８ -S －０．１ ) / (T ８０ -T １０ ) (1) In the formula, T ８０ This represents the temperature at which the copper powder shrinks by 80% by volume relative to its maximum shrinkage rate when subjected to thermomechanical analysis under a nitrogen atmosphere and a heating rate of 10°C / min. １０ S represents the temperature at which the copper powder shrinks by 10 volume percent relative to its maximum shrinkage rate when subjected to thermomechanical analysis under a nitrogen atmosphere and a heating rate of 10°C / min. －０．８ This represents -0.8, which is the value of the 80% heat shrinkage coefficient normalized by the maximum heat shrinkage coefficient. －０．１ This represents -0.1, which is the value of the 10% thermal shrinkage rate normalized by the maximum thermal shrinkage rate. When no other elements are present on the surface of copper powder A, the above "temperature T ８０ " refers to the temperature T of the copper powder A itself. ８０ Therefore, if other elements described later are present on the surface of copper powder A, the "temperature T ８０ "The temperature T of copper powder A after surface treatment" ８０ That is the case.

[0023] By slowly sintering the copper powder, it is possible to suppress the occurrence of cracks when forming electrodes for electronic devices such as MLCCs using the copper powder of the present invention, which includes copper powder A. From this viewpoint, the slope R is -0.00500°C. －１ Preferably, the temperature is -0.00450°C. －１ It is even more preferable that the temperature be above -0.00350°C －１ It is even more preferable that the temperature be above -0.00300°C －１ It is even more preferable that the above conditions are met. From the viewpoint of making the above-mentioned effects even more pronounced, it is preferable that the slope R is as large as positive, but -0.00100°C －１ The following may also apply. A detailed method for measuring the inclination R will be explained in the examples described later. Copper powder A having an inclination R is preferably manufactured by the method for manufacturing copper powder A described later.

[0024] In copper powder A, T ８０ It is preferable that it is within a predetermined range. Specifically, from the viewpoint of suppressing the degradation of MLCC performance when forming an external electrode of an electronic device such as an MLCC with the copper powder of the present invention containing copper powder A, T ８０ It is preferable that the temperature is 600°C or higher, more preferably 650°C or higher, and even more preferably 700°C or higher. From a similar viewpoint, T ８０ The temperature is preferably 1000°C or lower, more preferably 900°C or lower, and even more preferably 850°C or lower. ８０ The detailed measurement method will be explained in the examples described later. Such a temperature T ８０ Copper powder A having the properties described below is preferably manufactured by the method for manufacturing copper powder A described later.

[0025] Copper powder A has a cumulative volume particle size of D at 50% cumulative volume, as measured by laser diffraction scattering particle size distribution analysis. ５０ (Hereafter simply referred to as "Particle Size D") ５０ It is also called ". ) preferably within a predetermined range. Specifically, from the viewpoint of slowing down the sintering of the copper powder of the present invention containing copper powder A, the particle size D of copper powder A is preferable. ５０The particle size D of copper powder A is preferably 0.20 μm or larger, more preferably 0.35 μm or larger, and even more preferably 0.50 μm or larger. Furthermore, from the viewpoint of effectively lowering the sintering temperature of the copper powder of the present invention containing copper powder A, the particle size D of copper powder A is also preferable. ５０ The particle size is preferably 5.0 μm or less, more preferably 4.0 μm or less, and even more preferably 3.0 μm or less. ５０ The detailed measurement method will be explained in the examples described later.

[0026] It is preferable that copper powder A has a relatively non-uniform particle size. The degree of sintering progresses differently between copper powders with small particle sizes and those with large particle sizes. Therefore, by making the particle size non-uniform, the degree of sintering progress can be made different for each particle size, leading to a slower sintering process. The degree of particle size non-uniformity is determined by the volume cumulative particle size at 90% cumulative volume, measured by laser diffraction scattering particle size distribution analysis, as D ９０ (Hereafter simply referred to as "Particle Size D") ９０ It is also called ". ) and the volume cumulative particle size at a cumulative volume of 10% is D １０ (Hereafter simply referred to as "Particle Size D") １０ It is also called ". ) When this is the case, (D ９０ -D １０ ) / D ５０ It can be defined by the value defined by (D ９０ -D １０ ) / D ５０ A larger value means a wider particle size distribution, (D ９０ -D １０ ) / D ５０ A smaller value of means that the particle size distribution is narrower. Specifically, from the viewpoint of making the particle size relatively non-uniform and slowing down the sintering of the copper powder of the present invention containing copper powder A, (D ９０ -D １０ ) / D ５０ The value of is preferably 0.80 or higher, more preferably 0.85 or higher, and even more preferably 0.90 or higher. From a similar viewpoint, (D ９０ -D １０ ) / D ５０The value of is preferably 2.00 or less, more preferably 1.80 or less, and even more preferably 1.50 or less. Particle size D ９０ and particle size D １０ The detailed measurement method will be explained in the examples described later.

[0027] In copper powder A, particle size D ９０ and particle size D １０ Preferably, each of these is within a predetermined range. This is because, even though the particle size of copper powder A is relatively non-uniform, having these particle sizes within a predetermined range makes it possible to achieve both slow sintering and a low sintering temperature for the copper powder of the present invention containing copper powder A. Specifically, from the viewpoint of slowing the sintering of the copper powder of the present invention containing copper powder A, the D of copper powder A ９０ The particle size is preferably 0.50 μm or larger, more preferably 0.80 μm or larger, and even more preferably 1.00 μm or larger. Furthermore, from the viewpoint of lowering the sintering temperature of the copper powder of the present invention containing copper powder A, the particle size of copper powder A is D ９０ The particle size is preferably 10.00 μm or less, more preferably 8.00 μm or less, and even more preferably 7.00 μm or less.

[0028] From the viewpoint of slowing down the sintering of the copper powder of the present invention containing copper powder A, D １０ The particle size is preferably 0.10 μm or larger, more preferably 0.20 μm or larger, and even more preferably 0.30 μm or larger. Furthermore, from the viewpoint of lowering the sintering temperature of the copper powder of the present invention containing copper powder A, the particle size of copper powder A is D １０ The particle size is preferably 3.00 μm or less, more preferably 2.50 μm or less, and even more preferably 2.00 μm or less.

[0029] Particle size D ５０ , particle size D ９０ and particle size D １０ In order to keep the above range, it is preferable to reduce the amount of reducing agent added during the first reduction (i.e., the cuprous oxide production step) in the method for producing copper powder A described later, compared to conventional methods.

[0030] Copper powder A preferably has few voids between copper particles a in copper powder A, that is, has high fillability. This enables formation of an electrode with high compactness. From the viewpoint of making such effects more remarkable, copper powder A preferably has a bulk density within a predetermined range. Specifically, the tap density of copper powder A is 4.0 g / cm ３ or more, more preferably 4.2 g / cm ３ or more, and even more preferably 4.5 g / cm ３ or more. From the same viewpoint, the tap density of copper powder A is preferably 7.0 g / cm ３ or less, more preferably 6.0 g / cm ３ or less, and even more preferably 5.5 g / cm ３ or less. As used herein, "tap density" refers to a value measured in accordance with JIS Z2512. A detailed method for measuring tap density will be described in Examples below. Copper powder A having such a tap density is suitably produced by the method for producing copper powder A described below.

[0031] Copper powder A preferably has a BET specific surface area within a predetermined range. Specifically, from the viewpoint of achieving both slow progress of sintering of the copper powder of the present invention including copper powder A and lowering the sintering temperature, the BET specific surface area of copper powder A is 0.20 m ２ / g or more, more preferably 0.30 m ２ / g or more, and even more preferably 0.35 m ２ / g or more. From the same viewpoint, the BET specific surface area of copper powder A is preferably 2.00 m ２ / g or less, more preferably 1.50 m ２ / g or less, and even more preferably 1.30 m ２ / g or less. The method for measuring the BET specific surface area will be described in Examples below. Copper powder A having such a BET specific surface area is suitably produced by the method for producing copper powder A described below.

[0032] In copper powder A, it is preferable that the copper crystallite size of the copper particles a constituting it is relatively small. This is because the lower the crystallinity, the easier it is for sintering to proceed at a lower temperature, and the higher the crystallinity, the more difficult it is for sintering to proceed at a lower temperature. Therefore, from the viewpoint of lowering the sintering temperature, the copper crystallite size is preferably 90 nm or less, more preferably 85 nm or less, and even more preferably 80 nm or less. Furthermore, from the viewpoint of slowing down the sintering of the copper powder of the present invention, including copper powder A, the copper crystallite size is preferably 20 nm or more, more preferably 30 nm or more, and even more preferably 35 nm or more. The method for measuring the crystallite size will be explained in the examples described later.

[0033] In order to achieve the crystallite size within the above-mentioned range, it is preferable to use chlorine as a water-soluble halogen source, adjust the concentration of basic compounds, or increase the amount of reducing agent added during the second reduction (i.e., the copper production step) compared to conventional methods in the method for producing copper powder A described later.

[0034] Copper powder A preferably has a high copper content. This allows the copper powder of the present invention, including copper powder A, to be suitably used as a bonding material for power devices and as an external electrode for MLCCs. From the viewpoint of making these advantages even more pronounced, copper powder A preferably has a copper content of 95.0% by mass or more, more preferably 96.0% by mass or more, and even more preferably 97.0% by mass or more. From the viewpoint of making the above effects even more pronounced, the higher the copper content, the better, but it may be 99.5% by mass or less.

[0035] Copper powder A may contain phosphorus (P) element. The inclusion of phosphorus element improves the oxidation resistance of copper powder A and the copper powder of the present invention containing copper powder A. From the viewpoint of making this advantage even more pronounced, copper powder A preferably contains 0.001% by mass or more of phosphorus element, more preferably 0.005% by mass or more, and even more preferably 0.010% by mass or more. Furthermore, from the viewpoint of improving the electrical conductivity of copper powder A and the copper powder of the present invention containing copper powder A, copper powder A preferably contains 0.5% by mass or less of phosphorus element, more preferably 0.3% by mass or less, and even more preferably 0.1% by mass or less. In copper powder A, the phosphorus element is in an oxide state, for example, H ３ PO ４ and Na ４ P ２ O ７ It is preferable that the phosphorus element exists in such a state. The presence of the phosphorus element in an oxide state can be confirmed by XPS and TOF-SIMS. In order to include the phosphorus element in copper powder A, a phosphorus-containing compound can be added in the method for producing copper powder A described later.

[0036] Preferably, copper powder A contains copper and halogen elements from copper particles a, with the remainder consisting of unavoidable elements. When unavoidable elements are present in copper particles a, it is preferable that their content is 5.0% by mass or less, as this minimizes the impairment of the inherent properties of copper particles a and allows for the best possible properties to be imparted to copper powder A, which consists of copper particles a, and to the copper powder of the present invention containing copper powder A. Unavoidable elements include, for example, oxygen (O) derived from oxygen and carbon dioxide in the atmosphere, and nitrogen (N) which may be mixed in during the manufacturing process of copper particles a. The presence and content of unavoidable elements can be measured, for example, by gas analysis.

[0037] Copper powder A may have other elements besides copper and halogens on its surface. Examples of other elements include carbon (C), oxygen (O), phosphorus (P), and sulfur (S). These other elements can be used individually or in combination of two or more. Among these elements, carbon is preferred from the viewpoint of improving oxidation resistance and dispersibility in organic solvents.

[0038] When copper powder A contains carbon, from the viewpoint of improving oxidation resistance and dispersibility in organic solvents, the carbon content is preferably 0.02% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.10% by mass or more. Furthermore, from the viewpoint of suppressing the occurrence of cracks in the sintered body due to gases generated during firing, copper powder A preferably has a carbon content of 2.00% by mass or less, more preferably 1.00% by mass or less, and even more preferably 0.50% by mass or less. In order to arrange carbon on the surface of copper powder A, the copper particles a can be surface-treated with a carbon-containing compound in the method for manufacturing copper powder A described later. The content ratios of copper, phosphorus, and carbon, as well as the presence and content ratio of unavoidable impurities, can be measured, for example, by carbon-sulfur analysis and ICP emission spectrometry.

[0039] [Copper Powder B] Next, copper powder B will be described. Copper powder B consists of a plurality of copper particles b. Preferably, copper particles b are particles that are substantially composed of copper elements or copper-based alloy particles. Preferably, copper powder B consists of an aggregate of such particles. The former particles are particles that are substantially composed of copper elements and the remainder contains unavoidable elements. In this case, it is desirable that copper particles b consist only of copper elements, but the inclusion of trace amounts of unavoidable elements is acceptable. If unavoidable elements are included in copper particles b, it is preferable that their content be 1% by mass or less, as this makes it less likely that the inherent properties of copper particles b will be impaired, and that suitable properties can be imparted to copper powder B consisting of copper particles b and to the copper powder of the present invention containing copper powder B. Unavoidable elements include, for example, oxygen (O) and carbon (C) elements derived from oxygen and carbon dioxide in the atmosphere, and nitrogen (N) elements that may be mixed in during the manufacturing process of copper particles. The presence or absence of unavoidable elements and their content can be measured, for example, by gas analysis. In the case of the latter type of particles, the copper content in the particles is preferably 80% by mass or more, and more preferably 90% by mass or more. Regardless of whether the copper particles b are the former or the latter type of particles, from the viewpoint of making the effects of the present invention remarkable, it is preferable that the copper powder B consisting of copper particles b is substantially free of halogen elements. From this viewpoint, even if halogen elements are present, it is preferable that the halogen element content is close to zero, and specifically, it is preferable that it be less than 0.001 at%.

[0040] Copper powder B is characterized by its high density. Conventionally, when manufacturing a sintered film by sintering copper powder, it was desirable for the shape of the copper particles constituting the copper powder to be uniform in order to obtain a sintered film with suppressed variations in quality. However, there were limitations to the degree to which density could be increased with conventional copper powders, and it was not easy to achieve the density required in recent years. The inventors of this invention diligently investigated how to improve this point and found that by giving the shape and size of the copper particles constituting the copper powder a predetermined distribution, the copper particles can be densely packed, and the voids between the copper particles can be made as small as possible, thereby increasing the density of the copper powder and, consequently, the density of the sintered film manufactured by sintering the copper powder. Furthermore, it was found that copper powder with a predetermined distribution of the shape and size of the copper particles has less deformation of the particle shape and crystal strain caused by processing than conventional flattened copper powder, and as a result, the formation of active sites where sintering easily progresses (i.e., sintering active sites) can be suppressed, and thus it has a sinterability that does not sinter in the debindering process. As a result, for example, when an external electrode of an MLCC is manufactured using the copper powder of the present invention, which includes copper powder B, the dried film containing the copper powder and resin is less likely to sinter during the debindering process, thus reducing the formation of cracks and voids, and allowing for the acquisition of a highly dense sintered film in the subsequent sintering process.

[0041] Specifically, it is preferable that the copper particles b have a flattened shape. In this specification, "flattened" is synonymous with "flaky" or "scattered," meaning that the particles have a thin, plate-like shape. Copper powder B may contain spherical copper particles. The degree of flattening of copper particles b is determined by the aspect ratio and circularity. In copper powder B, there is a distribution in the degree of flattening of copper particles b, and this distribution can be defined by the distribution of circularity. Details of the distribution of the degree of flattening of copper particles b will be described later.

[0042] As shown in Figures 2(a) to 2(d), the aspect ratio is defined as the ratio of the major axis W1 to the minor axis W2 (major axis W1 / minor axis W2) when the major axis W1 is the longest side of the rectangle S with the smallest area among all rectangles S circumscribing the particle P (see Figure 2(d)) and the minor axis W2 is the shortest side of the rectangle S. As will be described later, it is preferable that the raw material powder be spherical, and when copper powder B is manufactured using this raw material powder, an aspect ratio close to 1 means that the shape of the copper particles b is, for example, close to a perfect sphere. From the viewpoint of enabling the formation of a dense sintered film by low-temperature firing at approximately 800°C, for example, by increasing the density of the copper powder B, it is preferable that the average aspect ratio of the copper particles b (hereinafter also referred to as the "average aspect ratio") is 1.05 or higher, more preferably 1.20 or higher, and even more preferably 1.40 or higher. From a similar viewpoint, the copper particles b are preferably 3.00 or less in average aspect ratio, more preferably 2.70 or less, and even more preferably 2.40 or less. In the following description, firing at approximately 800°C is also referred to as "low-temperature firing." The major axis W1 and minor axis W2 of the copper particles b can be appropriately set to have the above-mentioned average aspect ratio.

[0043] The average aspect ratio can be measured by the following method. Specifically, first, at least three fields of view are captured using a scanning electron microscope (hereinafter also referred to as "SEM") at a magnification that includes at least 50 cross-sections of the copper particles b to be measured. Next, at least 300 copper particles b whose outlines can be confirmed are randomly selected from each image data, and the major axis W1 and minor axis W2 values ​​are measured for each of the selected copper particles b. Based on these values, the major axis W1 / minor axis W2 value is calculated. The value calculated in this way is referred to as the average aspect ratio in this specification. A detailed method for measuring the average aspect ratio will be explained in the examples described later.

[0044] Preferably, the copper powder B contains copper particles b having an aspect ratio within a predetermined range, and preferably, one or more copper particles have different aspect ratios. In particular, from the viewpoint of enabling the formation of a dense sintered film by low-temperature firing when using the copper powder of the present invention containing the copper powder B, it is preferable that the aspect ratio of multiple copper particles b in the copper powder B changes continuously.

[0045] In copper powder B, the distribution of the shape of copper particles b is also characterized by the distribution of the circularity of copper particles b. Here, "circularity" is a value calculated based on formula (2) described later. As described later, the raw material powder is preferably spherical, and when copper powder B is manufactured using the raw material powder, a circularity close to 1 means that the shape of copper particles b is, for example, close to a perfect sphere. Based on this circularity, it is possible to specify what shape of copper particles b are distributed and to what extent. From the viewpoint of enabling the formation of a dense sintered film by low-temperature firing by increasing the density of copper powder B, it is preferable that the average value of the circularity of copper powder B (hereinafter also referred to as "average circularity") is 0.95 or less, more preferably 0.90 or less, and even more preferably 0.85 or less. From the same viewpoint, it is preferable that the average circularity of copper powder B is 0.60 or more, more preferably 0.65 or more, and even more preferably 0.70 or more.

[0046] In copper powder B, the distribution of the shape of copper particles b is also characterized by the distribution of the number frequency of copper particles b relative to their circularity. It is preferable that the distribution map of copper powder B, with the circularity of copper particles b on the horizontal axis and the number frequency of copper particles b on the vertical axis, is convex upwards with a predetermined shape. In other words, it is particularly preferable that copper particles b having a predetermined circularity are distributed in copper powder B with a predetermined number frequency. Specifically, from the viewpoint of suppressing the formation of sintering active sites, preventing sintering in the debindering process, and enabling the formation of a dense sintered film by low-temperature firing, it is preferable that the number percentage of copper particles b with a circularity greater than 0.95 in copper powder B is 5.0 percent or less, more preferably 4.0 percent or less, and even more preferably 3.0 percent or less. A circularity greater than 0.95 means that the copper particles b are, for example, very close to a perfect sphere. From the viewpoint of making the above-mentioned effects even more pronounced, it is preferable that the number percentage of copper particles b with a circularity of more than 0.95 be as small as possible, but it may also be 0.1 percent or more.

[0047] Furthermore, from the viewpoint of enabling the formation of a dense sintered film by low-temperature firing when using the copper powder of the present invention containing copper powder B, it is preferable that copper powder B contains more copper particles b with relatively large circularity than copper particles b with relatively small circularity. This is because such a distribution in copper powder B allows the copper particles b to be densely packed, minimizing the gaps between the copper particles b as much as possible, thereby increasing the density of copper powder B and the copper powder of the present invention containing copper powder B, and consequently the density of the sintered film produced by sintering these copper powders. From the viewpoint of enabling the formation of a dense sintered film by low-temperature firing by increasing the density of copper powder B, it is preferable that the proportion of copper particles b with a circularity of more than 0.70 and 0.95 or less in copper powder B is greater than the proportion of copper particles b with a circularity of 0.70 or less. Furthermore, in copper powder B, it is preferable that the ratio of the number of copper particles b with a circularity of more than 0.70 and 0.95 or less to the number of copper particles b with a circularity of 0.70 or less (hereinafter also referred to as "ratio D") is greater than or equal to a predetermined value. Specifically, from the viewpoint of enabling the formation of a dense sintered film by low-temperature firing by increasing the density of copper powder B, it is preferable that ratio D be 1.10 or more, more preferably 1.30 or more, and even more preferably 1.50 or more. From the viewpoint of making the above-mentioned effects even more pronounced, it is preferable that ratio D be as large as possible, but it may also be 8.00 or less.

[0048] As described above, it is preferable to contain more copper particles b with relatively high circularity than copper particles b with relatively low circularity. However, it is preferable that the number proportion of copper particles b with a circularity of more than 0.70 and 0.95 or less is within a predetermined range, in order to impart high packing ability to copper powder B and the copper powder of the present invention containing said copper powder B. From the viewpoint of making this advantage even more pronounced, the number proportion of copper particles b with a circularity of more than 0.70 and 0.95 or less is preferably 50.0% or more, more preferably 55.0% or more, and even more preferably 60.0% or more, provided that the value of ratio D is within the above range. From a similar viewpoint, the number proportion of copper particles b with a circularity of more than 0.70 and 0.95 or less is preferably 95.0% or less, more preferably 90.0% or less, and even more preferably 85.0% or less, provided that the value of ratio D is within the above range.

[0049] Furthermore, it is preferable that the number percentage of copper particles b with a circularity of 0.70 or less is within a predetermined range, as this imparts high packing ability to copper powder B and the copper powder of the present invention containing said copper powder B. From the viewpoint of making this advantage even more pronounced, the number percentage of copper particles b with a circularity of 0.70 or less is preferably 1.0% or more, more preferably 5.0% or more, and even more preferably 10.0% or more, provided that the value of ratio D is within the above range. From a similar viewpoint, the number percentage of copper particles b with a circularity of 0.70 or less is preferably 45.0% or less, more preferably 40.0% or less, and even more preferably 35.0% or less, provided that the value of ratio D is within the above range.

[0050] The circularity of copper particle b is calculated by the following method. First, at least three fields of view are captured using a scanning electron microscope (SEM) at a magnification that includes at least 50 cross-sections of the copper particle b to be measured. Next, 300 copper particle b that do not overlap are randomly selected from each image data. When the area of ​​the two-dimensional projection image of the copper particle b cross-section is S and the perimeter is L, the circularity of the copper particle b cross-section is calculated based on the following formula (2). The arithmetic mean of the circularity of each copper particle b cross-section is taken as the above-mentioned circularity. If the two-dimensional projection image of copper particle b is a perfect circle, the circularity of copper particle b is 1. 4πS / L ２ ... (2) Detailed methods for measuring circularity will also be explained in the examples described later.

[0051] In order to ensure that the circularity of copper powder B and the distribution of said circularity are within the above-mentioned range, it is preferable to flatten the raw material powder using, for example, the method for manufacturing copper powder B described later.

[0052] It is preferable that the copper powder B has a bulk density within a predetermined range. In other words, it is preferable that there are few voids between the copper particles b in the copper powder B, i.e., that it has high density. By using the copper powder of the present invention containing such copper powder B, it becomes possible to form a dense sintered film by low-temperature firing. Specifically, from the viewpoint of enabling the formation of a dense sintered film by low-temperature firing, the tap density of the copper powder B is 4.0 g / cm³. ３ Preferably, it is 4.2 g / cm³ or more. ３ It is even more preferable that the amount be greater than or equal to 4.4 g / cm³. ３ It is even more preferable that the above conditions are met. Also, from a similar viewpoint, the tap density of copper powder B is 7.0 g / cm³. ３ Preferably, it is 6.5 g / cm³. ３ It is even more preferable that the following conditions apply: 6.0 g / cm³ ３ The following is even more preferable. Copper powder B having such a tap density can be suitably produced by the method for producing copper powder B described later.

[0053] Preferably, copper powder B consists of copper particles b having different particle sizes. In other words, it is preferable that copper particles b in copper powder B have a broad particle size distribution. This also allows for dense packing of copper particles b, minimizing the gaps between copper particles b as much as possible, thereby increasing the density of copper powder B and the copper powder of the present invention containing copper powder B. As a result, it becomes possible to form a dense sintered film by low-temperature firing. In copper powder B, having a broad particle size distribution of copper particles b is preferable for particle size D ５０ The degree of dispersion D is the ratio of the standard deviation SD (μm) of the particle size distribution to (μm). Ｐ This can be defined by the degree of dispersion D. Specifically, by increasing the density of copper powder B and the copper powder of the present invention containing said copper powder B, it is possible to form a dense sintered film by low-temperature firing. Ｐ The value of is preferably 0.55 or higher, more preferably 0.60 or higher, and even more preferably 0.65 or higher. From a similar viewpoint, the degree of variance D Ｐ The value of is preferably 0.90 or less, more preferably 0.89 or less, and even more preferably 0.88 or less.

[0054] As described above, it is preferable that the copper particles b have a broad particle size distribution, but the particle size D ５０ It is preferable that the particle size D of copper powder B is within a predetermined range, as this suppresses the formation of sintering active sites and imparts to copper powder B and the copper powder of the present invention containing copper powder B a degree of sinterability that prevents sintering in the debindering process. From the viewpoint of making this advantage even more pronounced, the particle size D of copper powder B is ５０ The degree of dispersion is D Ｐ Provided that the value of is within the above range, it is preferably 2.00 μm or larger, more preferably 2.50 μm or larger, and even more preferably 3.00 μm or larger. Also, particle size D ５０ The degree of dispersion is D Ｐ Provided that the value is within the range described above, it is preferably 8.00 μm or less, more preferably 7.00 μm or less, and even more preferably 6.00 μm or less.

[0055] In copper powder B, the standard deviation SD of the particle size distribution is equal to the degree of dispersion D. ＰProvided that the value of is within the above range, it is preferably 1.00 μm or larger, more preferably 1.50 μm or larger, and even more preferably 2.00 μm or larger. Furthermore, the standard deviation SD of the particle size distribution is the degree of dispersion D Ｐ Provided that the value is within the above range, it is preferably 6.00 μm or less, more preferably 5.00 μm or less, and even more preferably 4.00 μm or less. When the standard deviation SD of the particle size distribution is within the above range, the formation of sintering active sites can be suppressed, and as a result, sintering does not occur in the debindering process, and a dense sintered film can be formed by low-temperature firing. The method for measuring the standard deviation SD of the particle size distribution will be explained in the examples described later.

[0056] In copper powder B, the distribution of copper particles b having a predetermined degree of circularity at a predetermined number frequency, and the broad particle size distribution of copper particles b, can also be defined by the product of the number ratio of copper particles b with a certain degree of circularity and their particle size. Specifically, the number ratio of copper particles b with a circularity of 0.70 or less, and the particle size D ９０ Product P with (μm) ９０ It is preferable that the value of (number of particles %・μm) is within a predetermined range. From the viewpoint of suppressing the formation of sintering active sites, preventing sintering in the debindering process, and enabling the formation of a dense sintered film by low-temperature firing, the cumulative P ９０ It is preferable that the number of particles is 500 particles, several percent / μm or less, more preferably 450 particles, several percent / μm or less, and even more preferably 400 particles, several percent / μm or less. ９０ A small value of means that the degree of particle flattening is not large, and product P ９０ A large value of indicates a greater degree of particle flattening. From the perspective of making the above-mentioned effect even more pronounced, the product P ９０ The smaller the value, the better, but it may be 100% μm or more.

[0057] In copper powder B, the distribution of copper particles b having a predetermined degree of circularity at a predetermined number frequency, and the broad particle size distribution of copper particles b, can also be defined by a product of circularity and particle size, which differs from the above-mentioned circularity and particle size. Specifically, the number ratio of copper particles b with a circularity greater than 0.70 and less than or equal to 0.95, and the particle size D ５０ Product P with (μm) ５０ It is preferable that the value of (number of particles %・μm) is within a predetermined range. From the viewpoint of suppressing the formation of sintering active sites, preventing sintering in the debindering process, and enabling the formation of a dense sintered film by low-temperature firing, the cumulative P ５０ It is preferable that the number of particles is 180 particles / some percentage / μm or more, more preferably 200 particles / some percentage / μm or more, and even more preferably 220 particles / some percentage / μm or more. From a similar viewpoint, product P ５０ It is preferable that the number of particles is 400 particles, several percent / μm or less, more preferably 350 particles, several percent / μm or less, and even more preferably 300 particles, several percent / μm or less. ５０ A value within the aforementioned range indicates that the particle shape is deformed (e.g., flattened), but not to a large degree.

[0058] In copper powder B, the distribution of copper particles b having a predetermined degree of circularity at a predetermined number frequency, and the broad particle size distribution of copper particles b, can also be defined by a product of circularity and particle size that is different from the above-mentioned product of circularity and particle size. Specifically, the number ratio of copper particles b with a circularity greater than 0.95 and particle size D １０ Product P with (μm) １０ It is preferable that the value of (number of particles %・μm) is within a predetermined range. From the viewpoint of suppressing the formation of sintering active sites, preventing sintering in the debindering process, and enabling the formation of a dense sintered film by low-temperature firing, the cumulative P １０ It is preferable that the particle size is 0.1 percent / μm or more, more preferably 0.2 percent / μm or more, and even more preferably 0.3 percent / μm or more. １０ A value greater than or equal to the above-mentioned value means that the degree of particle flattening is not significant. From the viewpoint of making the above-mentioned effect even more pronounced, the product P １０A larger value is preferable, but a value of 3.5 particles (percentages / μm) or less is also acceptable.

[0059] In copper powder B, particle size D １０ and particle size D ９０ Preferably, each of these is within a predetermined range. By having copper particles b have a broad particle size distribution while their particle sizes are within a predetermined range, the formation of sintering active sites is suppressed, and it becomes possible to impart sinterability to copper powder B and the copper powder of the present invention containing copper powder B to such an extent that they do not sinter in the debindering process. From the viewpoint of making the above advantages even more pronounced, the particle size D of copper powder B is １０ is the product P １０ Provided that the value of is within the above range, it is preferably 0.4 μm or larger, more preferably 0.7 μm or larger, and even more preferably 1.0 μm or larger. From a similar viewpoint, the particle size D of copper powder B １０ is the product P １０ Provided that the value of is within the above range, it is preferably 4.0 μm or less, more preferably 3.0 μm or less, and even more preferably 2.0 μm or less. From the viewpoint of making the above advantages even more pronounced, the particle size D of copper powder B ９０ is the product P ９０ Provided that the value of is within the above range, it is preferably 4.0 μm or larger, more preferably 5.0 μm or larger, and even more preferably 6.0 μm or larger. From a similar viewpoint, the particle size D of copper powder B ９０ is the product P ９０ Provided that the value is within the range described above, it is preferably 16.0 μm or less, more preferably 14.0 μm or less, and even more preferably 12.0 μm or less.

[0060] Copper powder B particle size D ５０ , particle size D ９０ and particle size D １０ , dispersion D Ｐ Value, and product P ９０ , product P ５０ and product P １０ In order to set the value within the above range, it is preferable to flatten the raw material powder using, for example, the method for producing copper powder B described later.

[0061] In copper powder B, it is preferable that there is a predetermined relationship between the minor axis of the copper particles b constituting the copper powder B and the circularity of the copper particles b, from the viewpoint of increasing the density of copper powder B and the copper powder of the present invention including copper powder B, thereby enabling the formation of a dense sintered film by low-temperature firing. Specifically, it is preferable that the degree of dependence of the circularity of the copper particles b on the minor axis of the copper particles b is small. Figure 3 is a distribution diagram created in copper powder B of one embodiment, with the minor axis of the copper particles b on the horizontal axis and the circularity of the copper particles b on the vertical axis. As is clear from the results shown in Figure 3, in copper powder B, regardless of the distribution of the minor axis of the copper particles b, the circularity of the copper particles b is generally concentrated in a range with a certain value or a certain width. Therefore, it is understood that copper powder B can take on various degrees of circularity regardless of the value of the minor axis of the copper particles b. In order for copper powder B to have such a relationship, it is preferable, for example, to flatten the raw material powder in the method for manufacturing copper powder B described later.

[0062] Furthermore, from the viewpoint of enabling the formation of a dense sintered film by low-temperature firing by increasing the density of copper powder B and the copper powder of the present invention containing copper powder B, it is preferable that copper powder B has a predetermined relationship between the minor axis of the copper particles b constituting the copper powder B and the aspect ratio of the copper particles b. Specifically, it is preferable that the degree of dependence of the aspect ratio of copper particles b on the minor axis of copper particles b is small. Figure 4 is a distribution diagram created in copper powder B of one embodiment, with the minor axis of copper particles b on the horizontal axis and the aspect ratio of copper particles b on the vertical axis. As is clear from the results shown in Figure 4, in copper powder B, regardless of the distribution of the minor axis of copper particles b, the aspect ratio of copper particles b is generally concentrated in a range with a certain value or a certain width. Therefore, it is understood that copper powder B can take various aspect ratios regardless of the value of the minor axis of copper particles b. For copper powder B to have such a relationship, it is preferable to flatten the raw material powder using a method for producing copper powder B, as described later.

[0063] Furthermore, it is preferable that copper powder B has a predetermined relationship between the aspect ratio and particle size of the copper particles b constituting the copper powder B, from the viewpoint of increasing the density of copper powder B and the copper powder of the present invention including copper powder B, thereby enabling the formation of a dense sintered film by low-temperature firing. Specifically, it is preferable that there is a positive correlation between the aspect ratio and the image analysis particle size of copper particles b in a distribution map created by plotting the image analysis particle size of copper particles b on the horizontal axis and the aspect ratio of the copper particles b on the vertical axis. In other words, it is preferable that the larger the particle size of copper particles b, the larger the aspect ratio. Because copper powder B has this relationship, the voids between copper particles b with large aspect ratios and image analysis particle sizes can be filled with copper particles b with small aspect ratios and image analysis particle sizes, thereby further increasing the density of copper powder B and the copper powder of the present invention including copper powder B. In this specification, "image analysis particle size" refers to the major axis W1 of the copper particle measured in the aspect ratio measurement method described above.

[0064] As described above, copper powder B has high density and sinterability to the extent that it does not sinter in the debindering process. The degree of such sinterability can be evaluated by the sintering initiation temperature obtained by thermomechanical analysis of copper powder B. The "sintering initiation temperature" here is the temperature at which copper powder B shrinks by 10 volume percent relative to its maximum shrinkage rate when TMA is performed on copper powder B under a nitrogen atmosphere and a heating rate of 10°C / min, similar to the explanation for copper powder A. １０ Therefore, in the debindering process, the temperature T of the copper powder B is set to the extent that it does not sinter. １０ It is preferable that the temperature is 500°C or higher, more preferably 515°C or higher, and even more preferably 530°C or higher. From the viewpoint of making the above-mentioned effects even more pronounced, temperature T １０ Higher temperatures are preferable, but temperatures below 800°C are also acceptable.

[0065] [Copper Powder] Next, the copper powder of the present invention will be described. The copper powder of the present invention contains the above-mentioned copper powder A and copper powder B, which enables the formation of a dense sintered film even at low temperatures and suppresses the occurrence of glass delamination. The reason for this is that by mixing copper powder A and copper powder B, which have the above-mentioned physical properties, the individual properties of copper powder A and copper powder B can be synergistically enhanced. For example, one example of this is that the occurrence of glass delamination can be suppressed by adding copper powder B, which consists of flattened copper particles b, to copper powder A, which has relatively high density.

[0066] In the copper powder of the present invention, it is preferable that the content ratio of copper powder A and copper powder B is within a predetermined range. Specifically, from the viewpoint of synergistically enhancing the individual properties of copper powder A and copper powder B, enabling the formation of a dense sintered film even with low-temperature firing, and suppressing the occurrence of glass delamination, it is preferable that the content ratio of copper powder A to the total of copper powder A and copper powder B is 45% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. From the same viewpoint, it is preferable that the content ratio of copper powder A is 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less. Furthermore, from the viewpoint of synergistically enhancing the individual properties of copper powder A and copper powder B, enabling the formation of a dense sintered film even with low-temperature firing, and suppressing the occurrence of glass delamination, it is preferable that the content ratio of copper powder B to the total of copper powder A and copper powder B is 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. From a similar viewpoint, it is preferable that the content of copper powder B is 55% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0067] The copper powder of the present invention preferably contains only copper powder A and copper powder B. In other words, it is preferable that it does not contain any other copper powders besides copper powder A and copper powder B. This synergistically enhances the individual properties of copper powder A and copper powder B, enabling the successful formation of a dense sintered film even at low temperatures, and effectively suppressing the occurrence of glass delamination. For this reason, the copper powder of the present invention preferably contains 5% by mass or less of the other copper powders, more preferably 2% by mass or less, and even more preferably 0% by mass. However, it is not prohibited that copper powder A and copper powder B themselves contain unavoidable elements.

[0068] The copper powder of the present invention enables the formation of a dense sintered film even at low temperatures, and it is preferable that the sintering density of the sintered film is not excessively high. An excessively high sintering density means that the copper has sintered too much. In other words, the glass will naturally separate from the sintered film, making glass delamination more likely. In contrast, the copper powder of the present invention enables the formation of a dense sintered film within a range that suppresses the occurrence of glass delamination.

[0069] Next, a preferred method for producing the copper powder of the present invention will be described. The copper powder of the present invention is suitably produced by mixing copper powder A and copper powder B in the preferred content ratio described above. Below, preferred methods for producing copper powder A and copper powder B, and preferred methods for mixing copper powder A and copper powder B will be described, respectively.

[0070] [Method for Manufacturing Copper Powder A] First, a preferred method for manufacturing copper powder A will be described. In this manufacturing method, a reducing agent is added to an aqueous solution containing a copper compound to reduce copper. This manufacturing method comprises the following steps in this order. Additional steps may be performed between each step as needed. - Copper-containing solution preparation step - Cupric oxide production step - Cuprous oxide production step - Water-soluble halogen source addition step - Copper production step Each of these steps will be described below.

[0071] [Preparation Process for Copper-Containing Solution] In this process, first, an aqueous solution containing a divalent copper compound (hereinafter also referred to as "copper-containing solution") is prepared. As the copper compound, for example, water-soluble divalent copper compounds such as copper sulfate, copper nitrate, copper acetate, or hydrates thereof can be used. One type of copper compound or two or more types can be used. Copper sulfate is preferred as the copper compound because its high water solubility allows for a high concentration of copper ions in the copper-containing solution.

[0072] If necessary, a phosphorus compound may be added to the copper-containing liquid. This allows trace amounts of phosphorus to be included in the copper particles a that make up copper powder A, thereby improving the oxidation resistance of copper powder A. Furthermore, particle size D ５０ , particle size D ９０ and particle size D １０ This effectively yields copper powder A within the above-mentioned range. As the phosphorus compound, it is preferable to use a compound that can generate phosphate ions such as orthophosphate ions, pyrophosphate ions, and metaphosphate ions in the presence of water. Examples of such phosphorus compounds include orthophosphate; polyphosphates such as pyrophosphate and tripolyphosphate; metaphosphates such as trimetaphosphate; orthophosphate salts such as sodium orthophosphate and potassium orthophosphate; polyphosphate salts such as sodium pyrophosphate and potassium pyrophosphate; and metaphosphate salts such as sodium trimetaphosphate and potassium trimetaphosphate. One or more phosphorus compounds can be used. From the viewpoint of effectively obtaining copper powder A with a relatively uniform particle size, it is preferable that the phosphorus compound is at least one of pyrophosphate salts, tripolyphosphate salts, and orthophosphate salts, and more preferably pyrophosphate salts.

[0073] Copper-containing solutions can be prepared by dissolving or dispersing copper compounds and, optionally, phosphorus compounds in water. Dissolution methods include, for example, stirring water and then adding the copper compound and / or phosphorus compound and stirring again.

[0074] From the viewpoint of successfully obtaining copper powder A, the concentration of copper in the copper-containing liquid is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. From the same viewpoint, the concentration of copper in the copper-containing liquid is preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 15% by mass or less.

[0075] From the viewpoint of obtaining copper powder A with improved oxidation resistance, the concentration of the phosphorus compound in the copper-containing solution is preferably adjusted to 0.01 mmol or more of phosphorus atoms per mole of copper atoms, more preferably 0.05 mmol or more, and even more preferably 0.10 mmol or more. From the viewpoint of improving the electrical conductivity of copper powder A, the concentration of the phosphorus compound in the copper-containing solution is preferably adjusted to 0.100 mmol or less of phosphorus atoms per mole of copper atoms, more preferably 0.010 mmol or less, and even more preferably 0.001 mmol or less.

[0076] [Cupric Oxide Production Process] Once a copper-containing solution is obtained, a basic compound is then added to the copper-containing solution to produce cupric oxide (CuO). Examples of basic compounds include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, as well as ammonia. One basic compound or two or more basic compounds can be used. The produced cupric oxide is suspended in the solution in the form of fine solid particles.

[0077] Methods for adding basic compounds to a copper-containing solution include, for example, stirring the copper-containing solution and then adding an aqueous solution of the basic compound and stirring again. When using a combination of two or more basic compounds, they may be added simultaneously or sequentially. The concentration of the basic compound in the copper-containing solution can be appropriately set depending on the type of basic compound.

[0078] It is preferable to continue stirring the copper-containing solution and allow it to mature even after cupric oxide has been formed by adding a basic compound to the solution. This is because maturation allows sufficient cupric oxide to be formed, making it easier to obtain copper powder A with a relatively uniform particle size.

[0079] [Cuprous oxide formation process] Once cupric oxide is formed, the cuprous oxide formation process is then carried out. In this process, a reducing agent is added while stirring the copper-containing liquid to form cuprous oxide (Cu) in the copper-containing liquid. ２ The process is to reduce to O). Therefore, the reducing agent used in this process is preferably one that reduces cupric oxide to cuprous oxide. Examples of such reducing agents include hydrazine and its hydrate, and reducing sugars. One or more reducing agents can be used. From the viewpoint of ensuring that the reduction reaction from cupric oxide to cuprous oxide proceeds sufficiently, the reducing agent is preferably hydrazine.

[0080] In this process, from the viewpoint of ensuring that the reduction reaction from cupric oxide to cuprous oxide proceeds sufficiently, it is preferable to add a reducing agent in an amount of 0.01 moles or more per mole of copper in the copper-containing solution, more preferably 0.10 moles or more, and even more preferably 0.20 moles or more. Furthermore, from the viewpoint of obtaining copper powder A with a non-uniform particle size distribution, it is preferable to reduce the amount of reducing agent added compared to conventional methods. Specifically, it is preferable to add a reducing agent in an amount of 2.0 moles or less per mole of copper in the copper-containing solution, more preferably 1.5 moles or less, and even more preferably 1.0 mole or less.

[0081] Even after reducing cupric oxide to cuprous oxide in this process, it is preferable to continue stirring the liquid and allow it to mature. This is because maturation allows sufficient cuprous oxide to be generated, making it easier to obtain copper powder A with a relatively uniform particle size.

[0082] [Water-soluble halogen source addition step] Once cuprous oxide is obtained, a water-soluble halogen source is added to the copper-containing solution before copper particles are produced from the cuprous oxide. In this manufacturing method, the water-soluble halogen source is used for the first time in this step. In other words, halogen elements are absent from the reaction system in the copper-containing solution preparation step, the cupric oxide production step, and the cuprous oxide production step. The water-soluble halogen source has the function of agglomerating copper nuclei during the copper particle production process. This is because, in a solution with a halogen source, the electrical double layer on the surface of the copper particles changes and stabilizes due to agglomeration. As the copper nuclei grow while agglomerating, copper powder A with relatively non-uniform particle size can be effectively obtained. Furthermore, the crystallite size of copper in copper particles a can be made relatively small.

[0083] Examples of water-soluble halogen sources include alkali metal salts such as lithium halide, sodium halide, and potassium halide, and halides of Group II elements such as calcium halide and magnesium halide. One or more water-soluble halogen sources can be used. The water-soluble halogen source can be selected according to the type of halogen element to be included in copper powder A. From the viewpoint of effectively agglomerating and growing copper nuclei while they are being formed in the copper-containing liquid, the water-soluble halogen source is preferably an alkali metal halide of sodium halide and potassium halide, and more preferably sodium halide. From a similar viewpoint, the halogen element is preferably at least one of chlorine, bromine, and iodine, and more preferably chlorine.

[0084] The concentration of the water-soluble halogen source added to the copper-containing liquid is preferably low. If the amount of halogen atoms present in the copper-containing liquid is high, this can lead to undesirable conditions such as particle aggregation and the formation of linked particles. However, in this manufacturing method, these undesirable conditions can be eliminated by minimizing the amount of halogen atoms. Specifically, from the viewpoint of suppressing copper nucleus aggregation while promoting growth, the concentration of the water-soluble halogen source in the copper-containing liquid is preferably such that the halogen atoms are 1.0 mol / L or less, more preferably 0.5 mol / L or less, and even more preferably 0.2 mol / L or less. Furthermore, from the viewpoint of effectively incorporating halogen elements into copper nuclei while they are being formed and growing in the copper-containing liquid, the concentration of the water-soluble halogen source in the copper-containing liquid is preferably such that the halogen atoms are 0.001 mol / L or more, more preferably 0.01 mol / L or more, and even more preferably 0.02 mol / L or more.

[0085] From the viewpoint of effectively incorporating halogens into copper nuclei while copper nuclei are being formed and growing in the copper-containing solution, the concentration of the water-soluble halogen source in the copper-containing solution is preferably such that the amount of halogen atoms is 0.001 moles or more per mole of copper atoms, more preferably 0.01 moles or more, and even more preferably 0.02 moles or more. Furthermore, from the viewpoint of suppressing copper nucleus aggregation while promoting growth, the concentration of the water-soluble halogen source in the copper-containing solution is preferably such that the amount of halogen atoms is 1.0 mole or less per mole of copper atoms, more preferably 0.5 moles or less, and even more preferably 0.2 moles or less.

[0086] From the viewpoint of further enhancing the advantages derived from the water-soluble halogen source, it is preferable to carry out the copper-containing solution preparation step, the cupric oxide production step, and the cuprous oxide production step in the absence of the water-soluble halogen source, and to carry out the copper production step described later in the presence of the water-soluble halogen source. By carrying out such steps, copper particles a in which the halogen element is present throughout the region from the center to the surface of the particle can be successfully obtained. In order to eliminate the presence of the water-soluble halogen source in the reaction system, for example, the raw materials containing halogens can be omitted in the copper-containing solution preparation step, the cupric oxide production step, and the cuprous oxide production step. By carrying out the copper-containing solution preparation step, the cupric oxide production step, and the cuprous oxide production step in the absence of the water-soluble halogen source, the particle size of intermediates such as cuprous oxide becomes relatively uniform, making it easier to control the production reaction of copper particles a.

[0087] [Copper Production Process] Next, the copper production process is carried out. In this process, a reducing agent is added to the copper-containing liquid while stirring, thereby reducing the cuprous oxide in the copper-containing liquid to copper in the presence of a water-soluble halogen source, and generating copper particles a. This yields copper powder A consisting of copper particles a. In this manufacturing method, it is believed that when copper particles a are produced, copper elements and halogen elements chemically react and bond inside and on the surface of the copper particles a, thereby forming copper halides. The reducing agent used in this process is preferably one that reduces cuprous oxide to copper. Examples of such reducing agents include hydrazine and its hydrate. One type of reducing agent may be used alone or two or more types may be used. From the viewpoint of ensuring that the reduction reaction from cuprous oxide to copper proceeds sufficiently, the reducing agent is preferably at least one of hydrazine and its hydrate, and more preferably hydrazine. In this process, the above-mentioned phosphorus compound may also be used together with the reducing agent. This effectively improves the oxidation resistance of copper and effectively yields copper powder A with a relatively uniform particle size.

[0088] In this process, from the viewpoint of ensuring that the reduction reaction from cuprous oxide to copper proceeds sufficiently and that the crystallite size of copper is within the above-mentioned range, it is preferable to add a reducing agent in an amount of 0.01 moles or more per mole of copper in the copper-containing solution, more preferably 0.05 moles or more, and even more preferably 0.10 moles or more. Furthermore, from the viewpoint of ensuring that the reduction reaction from cuprous oxide to copper proceeds sufficiently, it is preferable to add a reducing agent in an amount of 10.0 moles or less per mole of copper in the copper-containing solution, more preferably 5.0 moles or less, and even more preferably 2.0 moles or less.

[0089] After reducing cuprous oxide to copper in this process, it is preferable to continue stirring the liquid and allow it to mature. This is because maturation allows sufficient copper to be generated, making it easier to obtain copper powder A with a relatively uniform particle size. After that, for example, impurities present on the surface of copper particles a can be removed by washing with water using decantation washing to obtain the desired copper powder A.

[0090] When washing copper particles a by decantation, it is preferable to add a liquid medium such as water and continue washing until the conductivity of the dispersion becomes 3 mS or less, and more preferably 2.5 mS or less. The washing temperature is preferably 20°C to 60°C, and more preferably 25°C to 50°C. The copper particles a obtained in this way are preferably spherical.

[0091] Once copper powder A is obtained, other elements other than copper and halogen elements may be arranged on the surface of copper powder A. This allows for various effects caused by the other elements. The other elements are arranged by applying a surface treatment agent containing the other elements. Examples of surface treatment agents include carboxylic acids and amines. One type of surface treatment agent can be used alone or in combination of two or more. The carboxylic acid may be monovalent or polyvalent. The carboxylic acid may also be saturated or unsaturated. Preferably, the carboxylic acid is an aliphatic carboxylic acid. If the carboxylic acid is an aliphatic carboxylic acid, it may be linear, branched, or cyclic. From the viewpoint of improving oxidation resistance and dispersibility in organic solvents, the number of carbon atoms in the carboxylic acid is preferably 6 to 20, and more preferably 10 to 18. Examples of such carboxylic acids include saturated aliphatic carboxylic acids such as hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, palmitic acid, and stearic acid, as well as unsaturated aliphatic carboxylic acids such as oleic acid. The amine may be monovalent or polyvalent. The amine may also be primary, secondary, or tertiary. Preferably, the amine is an aliphatic amine. If the amine is an aliphatic amine, it may be a saturated aliphatic amine or an unsaturated aliphatic amine. In this case, the aliphatic amine may be linear, branched, or cyclic. From the viewpoint of improving oxidation resistance and dispersibility in organic solvents, the amine preferably has 2 to 18 carbon atoms, and more preferably 5 to 18 carbon atoms. Examples of such amines include saturated primary aliphatic amines such as pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, myristylamine, and stearylamine, as well as unsaturated primary aliphatic amines such as oleylamine.From the viewpoint of improving oxidation resistance and dispersibility in organic solvents, the surface treatment agent preferably contains at least one selected from carboxylic acids and amines, more preferably contains at least one selected from carboxylic acids having 6 to 20 carbon atoms, and even more preferably contains at least one selected from lauric acid.

[0092] One method for surface treatment of copper powder A is to add a solution of a surface treatment agent to a dispersion of copper powder A. When using a combination of two or more surface treatment agents, they may be added simultaneously or sequentially. The solvent for the solution of the surface treatment agent is not particularly limited as long as it can dissolve the surface treatment agent, and examples of solvents that can be used include water, ethanol, 2-propanol, acetone, toluene, butanol, and terpineol.

[0093] When a surface treatment agent solution is added to a dispersion of copper powder A to perform the treatment, from the viewpoint of successfully performing the treatment, the concentration of the surface treatment agent is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.10% by mass or more, relative to the copper in the dispersion. From a similar viewpoint, the concentration of the surface treatment agent is preferably 5.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.0% by mass or less, relative to the copper in the dispersion.

[0094] Once the surface treatment is complete, the copper particles a are dried to obtain copper powder A consisting of the copper particles a.

[0095] [Method for Manufacturing Copper Powder B] Next, a preferred method for manufacturing copper powder B will be described. This manufacturing method includes a step of plastically deforming the raw material powder into a flattened shape.

[0096] First, the raw material powder is prepared. The raw material powder consists of copper particles b. The shape of the raw material powder can be spherical, polygonal, spindle-shaped, or irregular. From the viewpoint of successfully obtaining copper powder B with an aspect ratio and circularity within the above range through the flattening operation described later, it is preferable to use raw material powder consisting of spherical copper particles.

[0097] It is preferable to use raw material powder whose physical properties are within a predetermined range, as this allows for the successful acquisition of copper powder B whose physical properties, such as aspect ratio, circularity, and particle size, are within the aforementioned range.

[0098] Particle size D of raw material powder ５０ Regarding this, from the above viewpoint, it is preferable to use raw material powder with a particle size of 1.0 μm or larger. From a similar viewpoint, particle size D ５０ It is preferable to use raw material powder with a particle size of 10.0 μm or less.

[0099] From the above viewpoint, it is preferable to use raw material powder with a standard deviation (SD) of particle size distribution of 0.5 μm or larger. Similarly, it is preferable to use raw material powder with a standard deviation (SD) of particle size distribution of 10.0 μm or smaller.

[0100] Raw material powders having such physical properties can be obtained, for example, by atomization methods such as gas atomization and water atomization, as well as by plasma methods. Alternatively, they can be easily obtained by a wet reduction method in which copper hydroxide is precipitated by reacting an aqueous copper salt solution with an alkaline agent, this copper hydroxide is first reduced to cuprous oxide in liquid, and the cuprous oxide is secondarily reduced to metallic copper in liquid. From the viewpoint of successfully obtaining copper powder B with aspect ratio, circularity, and particle size within the above range, it is preferable to use raw material powder obtained by a wet reduction method, which contains a large amount of spherical copper particles.

[0101] Once the raw material powder is prepared, the material to be processed containing the raw material powder is prepared. The material to be processed consists of a slurry containing the raw material powder and a liquid medium. Examples of the liquid medium include water and organic solvents. A mixed solvent of water and an organic solvent can also be used. As an organic solvent, for example, an aliphatic alcohol having 1 to 22 carbon atoms can be used. These organic solvents can be used individually or in combination of two or more. Of these liquid mediums, the use of an organic solvent is preferable because it improves the dispersibility of the raw material powder in the material to be processed and improves the stability of the quality when performing the flattening operation. It is preferable to use a monohydric alkyl alcohol having 1 to 4 carbon atoms because the medium volatilizes easily and does not easily remain on the target copper powder B. Examples of such alcohols include methanol, ethanol, n-propanol, sec-propanol, n-butanol, sec-butanol, and tert-butanol.

[0102] If necessary, additives such as lubricants may be included in the material to be treated. Lubricants have the property of suppressing aggregation between particles and reducing friction between particles, thereby making them slippery. Examples of lubricants include carboxylic acids such as citric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, palmitic acid, oleic acid, and stearic acid. These additives can be used individually or in combination of two or more. It is preferable to use lubricants, and particularly preferable to use stearic acid, from the viewpoint of effectively flattening particles that are relatively close to monodisperse and effectively reducing the number proportion of copper particles b that have a shape very close to a perfect sphere, such as copper particles with a circularity of more than 0.95.

[0103] To prepare the material to be processed, it is simply necessary to mix the raw material powder, the liquid medium, and additives as needed. In some cases, a dispersion may be prepared using a stirring and dispersion device. Examples of such devices include a fluid mill and the T.K. Filmix® manufactured by Primix Corporation.

[0104] From the viewpoint of successfully plastically deforming the raw material powder, the concentration of raw material powder in the material to be processed is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. From the same viewpoint, the concentration of raw material powder in the material to be processed is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

[0105] When the workpiece contains a lubricant, the lubricant content in the workpiece is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.08% by mass or more, relative to the copper particle b content in the raw material powder, from the viewpoint of successfully obtaining copper powder B with aspect ratio, roundness, and particle size within the above ranges. From the viewpoint of suppressing sintering defects caused by residual lubricant, the lubricant content in the workpiece is preferably 1.0% by mass or less, more preferably 0.7% by mass or less, and even more preferably 0.4% by mass or less, relative to the copper particle b content in the raw material powder.

[0106] Once the material to be processed is ready, the raw material powder consisting of copper particles b in the material is plastically deformed into a flattened shape. The flattening of the raw material powder can be carried out using a media stirring mill device such as a bead mill, ball mill, or attritor. From the viewpoint of successfully obtaining copper powder B with aspect ratio, circularity, and particle size within the above-mentioned range, it is preferable to use a device that can apply relatively small stress to the raw material powder in the material to be processed. By performing such a process, the raw material powder can be flattened without excessively changing the aspect ratio, circularity, and particle size that the raw material powder consisting of copper particles b originally possesses. This makes it less likely that the inherent properties of copper particles b will be impaired, and it is possible to successfully obtain copper powder B with high density. In particular, it is possible to successfully obtain copper particles that can take on various circularities and aspect ratios, and copper powder B composed of these copper particles b, without excessively deforming the original shape (e.g., spherical) of the raw material powder. Furthermore, it is possible to suppress the formation of active sites, which are the starting points for sintering, and to impart sinterability to a degree that prevents sintering during the binder removal process.

[0107] As a media stirring mill device that can apply relatively small stress to the raw material powder in the material being processed, one example is a material-passing type (so-called pass-through type) device. Generally, media stirring mill devices employ three operating methods: material-passing type, multiple material-passing type, and circulation type. The circulation type flattens the material being processed while circulating it within the device, making it difficult to adjust the magnitude of the stress applied to the raw material powder. In contrast, the material-passing type and multiple material-passing type flatten the material by setting the number of times the material is passed through the device, making it easier to adjust the magnitude of the stress applied to the raw material powder. From the viewpoint of flattening the raw material powder with relatively small stress, it is particularly preferable to use a material-passing type device. As such a device, for example, the Star Mill (registered trademark) LMZ10 bead mill manufactured by Ashizawa Finetech Co., Ltd. can be used.

[0108] From the viewpoint of minimizing the damage to the inherent properties of copper particles b, successfully obtaining highly dense copper powder B, and suppressing the formation of sintering active sites, thereby imparting sinterability to the extent that sintering does not occur in the debindering process, it is most preferable to flatten the material to be processed by passing it through a medium stirring mill device that allows the material to pass through only once. In this case, the peripheral speed of the mill is preferably 4 m / sec or more, more preferably 6 m / sec or more, and even more preferably 8 m / sec or more, from the viewpoint of minimizing the damage to the inherent properties of copper particles, successfully obtaining highly dense copper powder B, and suppressing the formation of sintering active sites, thereby imparting sinterability to the extent that sintering does not occur in the debindering process. From a similar viewpoint, the peripheral speed of the mill is preferably 20 m / sec or less, more preferably 17 m / sec or less, and even more preferably 14 m / sec or less.

[0109] The diameter of the grinding media is preferably 0.050 mm to 0.5 mm, and more preferably 0.075 mm to 0.3 mm, from the viewpoint of not impairing the inherent properties of copper particles b, successfully obtaining highly dense copper powder B, and suppressing the formation of sintering active sites, thereby imparting sinterability to the extent that sintering does not occur in the debindering process. The material of the grinding media is generally zirconia and alumina.

[0110] After flattening the raw material powder, solid-liquid separation is performed using solid-liquid separation methods such as vacuum dehydration, filter pressing, centrifugation, and ultrafiltration to separate and remove copper powder B from the material to be processed. Subsequently, copper powder B is washed with a solvent and dried.

[0111] Copper powder B is obtained in this way. A metal can be placed on the surface of copper powder B, to the extent that the effects of the present invention are not impaired. This allows for the utilization of various properties of the metal. The metal is not particularly limited as long as it is a metal other than copper and silver.

[0112] [Method for mixing copper powder A and copper powder B] Next, a method for mixing copper powder A and copper powder B will be described. The method for mixing copper powder A and copper powder B is not particularly limited and can be done dry or wet. When mixing dry, a known dry mixing apparatus can be used. When mixing wet, for example, it can be done in an organic solvent or aqueous solvent. From the viewpoint of ease of mixing, it is preferable to mix copper powder A and copper powder B dry. In this way, the copper powder of the present invention can be obtained.

[0113] The copper powder of the present invention can be dispersed in an organic solvent and a resin, etc., and used in the form of a conductive resin composition such as a copper paste. The copper paste is composed of at least the copper powder of the present invention and an organic solvent. As the organic solvent, any organic solvent that has been used in the art of conductive resin compositions containing metal powders can be used without particular limitation. Examples of such organic solvents include monohydric alcohols such as terpineol; polyhydric alcohols; polyhydric alcohol alkyl ethers such as ethyl carbitol; polyhydric alcohol aryl ethers; polyethers; esters such as carbitol acetate, butyl cellosolve acetate and butyl carbitol acetate; nitrogen-containing heterocyclic compounds; amides; amines and saturated hydrocarbons. These organic solvents can be used individually or in combination of two or more. From the viewpoint of having a high reducing effect and suppressing unintended oxidation of the copper powder during sintering, it is preferable to use polyethers such as polyethylene glycol and polypropylene glycol. From the same viewpoint, when polyethylene glycol is used as the organic solvent, its number average molecular weight is preferably 120 or more and 400 or less, and more preferably 180 or more and 400 or less.

[0114] The copper paste preferably contains, in addition to copper powder, at least one of a dispersant, an organic vehicle, and glass frit. Examples of dispersants include nonionic surfactants that do not contain sodium, calcium, phosphorus, sulfur, and chlorine. Examples of organic vehicles include mixtures containing resin components such as acrylic resin, epoxy resin, ethylcellulose, and carboxyethylcellulose, and solvents such as terpene solvents such as terpineol and dihydroterpineol, or ether solvents such as ethyl carbitol and butyl carbitol. Examples of glass frit include SiO ２ , BaO, ZnO, B ２ O ３ Examples include glasses containing alkali metal oxides or alkaline earth metal oxides. These can be used individually or in combination of two or more.

[0115] By applying the above-mentioned copper paste onto a substrate to form a coating film and then firing it, a conductive film, which is a sintered body of copper powder, can be formed. The conductive film is suitably used, for example, for circuit formation on printed circuit boards, and for ensuring electrical conductivity of electrodes in solar cells and external electrodes in multilayer ceramic capacitors. Examples of printed circuit boards include those made of glass epoxy resin, flexible printed circuit boards made of polyimide, etc., depending on the type of electronic circuit in which the copper powder is used. However, the uses of the copper powder of the present invention are not limited to the above-mentioned uses.

[0116] The content of copper powder and organic solvent in the copper paste can be appropriately set according to the specific application and application method of the copper paste, but it is preferably 5% by mass or more and 95% by mass or less, and more preferably 80% by mass or more and 90% by mass or less.

[0117] If the copper paste contains glass frit, its content is preferably within a predetermined range. Specifically, from the viewpoint of successfully obtaining a conductive film that enables the formation of a dense sintered film and suppresses the occurrence of glass delamination, the copper paste preferably contains 1 part by mass or more of glass frit per 100 parts by mass of copper powder, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more. From a similar viewpoint, the copper paste preferably contains 20 parts by mass or less of glass frit per 100 parts by mass of copper powder, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

[0118] Copper paste can be applied using methods such as inkjet printing, dispenser printing, microdispenser printing, gravure printing, screen printing, dip coating, spin coating, spray coating, bar coating, and roll coating.

[0119] The copper powder of the present invention enables the formation of a dense sintered film even with low-temperature firing and suppresses the occurrence of glass delamination. Therefore, the sintering temperature of the coating film can be, for example, 700°C to 900°C. Sintering can be carried out, for example, under an oxidizing atmosphere or a non-oxidizing atmosphere. An oxidizing atmosphere is, for example, an oxygen-containing atmosphere. A non-oxidizing atmosphere is, for example, a reducing atmosphere such as hydrogen and carbon monoxide, a weakly reducing atmosphere such as a hydrogen-nitrogen mixed atmosphere, and an inert atmosphere such as argon, neon, helium and nitrogen. In any atmosphere, the firing time is preferably 0.1 hours to 5 hours, and more preferably 0.5 hours to 2 hours, provided that the temperature is within the above-mentioned temperature range.

[0120] The conductive film obtained in this manner is dense and capable of suppressing glass delamination, as it is obtained by firing the copper powder of the present invention.

[0121] Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments.

[0122] Further disclosure relating to the above embodiments are copper powder, copper paste, a method for manufacturing a conductive film, and a sintered body. [1] Copper powder comprising the following copper powder A and copper powder B. [Copper powder A] Copper powder comprising a plurality of copper particles, wherein the halogen element is contained in an amount of 0.001 at% or more and 0.30 at% or less. [Copper powder B] Copper powder comprising a plurality of copper particles having different aspect ratios, wherein the tap density is 4.0 g / cm³ ３ 7.0g / cm or more ３ The following is the cumulative particle size D at 50% of the cumulative volume, as measured by laser diffraction scattering particle size distribution analysis. ５０ The degree of dispersion D is the ratio of the standard deviation (SD) of the particle size distribution to the degree of dispersion D. Ｐ[2] Copper powder having a value of 0.55 or more and 0.90 or less. [2] The copper powder according to [1], wherein the content ratio of copper powder A to the total of copper powder A and copper powder B is 45% by mass or more and 99% by mass or less, and the content ratio of copper powder B is 1% by mass or more and 55% by mass or less. [3] When copper powder A is subjected to thermomechanical analysis under a nitrogen atmosphere and a heating rate of 10°C / min, the temperature T at which it shrinks by 10 volume% relative to the maximum shrinkage rate is １０ Copper powder as described in [1] or [2], wherein the temperature is 600°C or lower. [4] Copper powder A has a value R defined by the following formula (1) of -0.00500°C －１ The copper powder described in any one of [1] to [3] above. R = (S －０．８ -S －０．１ ) / (T ８０ -T １０ ) (1) In the formula, T ８０ This represents the temperature at which copper powder A shrinks by 80% by volume relative to its maximum shrinkage rate when subjected to thermomechanical analysis under nitrogen atmosphere and a heating rate of 10°C / min. １０ S represents the temperature at which copper powder A shrinks by 10 volume percent relative to its maximum shrinkage rate when subjected to thermomechanical analysis under nitrogen atmosphere and a heating rate of 10°C / min. －０．８ This represents -0.8, which is the value of the 80% heat shrinkage coefficient normalized by the maximum heat shrinkage coefficient. －０．１ This represents -0.1, which is the value of the 10% heat shrinkage rate normalized by the value of the maximum heat shrinkage rate. [5] Copper powder according to any one of [1] to [4], wherein the average aspect ratio of the copper particles constituting copper powder B is 1.05 or more and 3.00 or less.

[0123] [6] Copper powder according to any one of [1] to [5], wherein the average circularity of copper powder B is 0.60 or more and 0.95 or less. [7] Copper paste comprising the following copper powder A and copper powder B. [Copper powder A] Copper powder consisting of a plurality of copper particles, containing 0.001 at% or more and 0.3 at% or less of halogen elements. [Copper powder B] Copper powder consisting of a plurality of copper particles having different aspect ratios, with a tap density of 4.0 g / cm ３ 7.0g / cm or more ３The following is the cumulative particle size D at 50% of the cumulative volume, as measured by laser diffraction scattering particle size distribution analysis. ５０ The degree of dispersion D is the ratio of the standard deviation (SD) of the particle size distribution to the degree of dispersion D. Ｐ Copper powder having a value of 0.55 or more and 0.90 or less. [8] The copper paste according to [7], comprising glass frit. [9] A method for producing a conductive film, comprising applying the copper paste according to [7] or [8] to a substrate to form a coating film and firing the coating film.

[10] A sintered body of the copper paste according to [7] or [8].

[0124] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" means "mass%".

[0125] [Examples 1 to 6] First, copper powder A was produced by the following method. (1) Preparation of copper-containing solution 6 kg of copper sulfate pentahydrate was added to 6.5 L of pure water at 25°C and stirred. Sodium pyrophosphate was then added and stirring was continued for 30 minutes to prepare a copper-containing solution. The amount of sodium pyrophosphate added was 0.0003 moles per mole of copper.

[0126] (2) Cupric Oxide Production Process: While the copper-containing liquid was being stirred, 1.4 L of 25% ammonia water and 3.3 L of 25% sodium hydroxide aqueous solution were simultaneously added to the copper-containing liquid to produce cupric oxide. The process was then continued with maturation.

[0127] (3) Cuprous Oxide Production Process Hydrazine monohydrate and 0.6 L of 25% aqueous ammonia were added to a dispersion containing cuprous oxide to reduce cuprous oxide to cuprous oxide. The mixture was then aged. The amount of hydrazine monohydrate added was 0.4 moles per mole of copper.

[0128] (4) Addition of water-soluble halogen source step Sodium chloride was added to the dispersion containing cuprous oxide and stirred. The amount of sodium chloride added was 0.05 moles per mole of copper. The concentration of sodium chloride in the dispersion at this time was 0.08 mol / L. In this example, the addition of a water-soluble halogen source step was not performed after the copper production step.

[0129] (5) Copper production process Hydrazine monohydrate was added to the dispersion containing cuprous oxide to reduce the cuprous oxide to copper. The reaction was then completed by aging. The amount of hydrazine monohydrate added was 0.3 moles per mole of copper.

[0130] (6) Surface treatment step The obtained dispersion of copper particles was washed by decantation using pure water until the conductivity was 2 mS / cm or less, and a dispersion with a solid content of 10% was prepared. A methanol solution of lauric acid was added to this dispersion in one go to perform surface treatment. After that, the dispersion was filtered to recover the copper particle cake, and the cake was vacuum dried at 70°C to obtain copper powder. The amount of lauric acid added was 0.3% relative to the copper.

[0131] Next, copper powder B was manufactured by the following method. As the raw material powder, 1110, a wet copper particle manufactured by Mitsui Mining & Smelting Co., Ltd., was prepared. A workpiece consisting of a slurry was prepared by mixing 1 kg of the wet copper particle with 1 kg of methanol. Next, the raw material powder was flattened using a Star Mill (registered trademark) LMZ10 bead mill manufactured by Ashizawa Finetech Co., Ltd. Specifically, zirconia beads with a diameter of 0.2 mm were used, and the workpiece was passed through the mill at a peripheral speed of 12 m / sec to flatten it. No lubricant was used at this time. After that, the copper powder was subjected to solid-liquid separation, washed, and dried to obtain the target copper powder B.

[0132] Once copper powders A and B were prepared, they were dry-mixed using a small ball mill (AV-1, manufactured by Asahi Rika) to the proportions shown in Table 3 below. In this way, the desired copper powder was obtained. This copper powder consists only of copper powders A and B and does not contain any other types of copper powder.

[0133] [Comparative Example 1] In Example 1, copper powder B was not used. Otherwise, the target copper powder was obtained in the same manner as in Example 1.

[0134] [Comparative Example 2] In Example 1, copper powder A was not used. Otherwise, the target copper powder was obtained in the same manner as in Example 1.

[0135] [Evaluation] The copper powder A obtained in the examples and comparative examples was evaluated according to the method described below, determining the content ratio of copper and carbon elements, the content of halogen elements, and the temperature T. １０ and temperature T ８０ The slope R, BET specific surface area, and copper crystallite size were measured. These results are shown in Table 1. For copper powder B obtained in the examples and comparative examples, the average aspect ratio, average circularity, and temperature T were measured according to the method described later. １０ The particle size D was measured. These results are shown in Table 2. The copper powder obtained in the examples and comparative examples was measured according to the method described later. １０ , particle size D ５０ and particle size D ９０ The tap density was also measured. For copper powder B, the standard deviation (SD) of the particle size distribution was also measured. The sintering density was measured according to the method described later, and the glass delamination was evaluated. These results are shown in Table 3.

[0136] [Copper content] The measurement was performed using an energy-dispersive X-ray fluorescence spectrometer (Epsilon® 3) manufactured by Malvern Panalogical. Specifically, 5 g of copper powder A was placed in the measurement container and measured. The copper content was obtained from the peak area ratio of Kα 8.042 keV and Kβ 8.906 keV in the resulting spectrum.

[0137] [Carbon Content] The carbon content in copper powder A was measured using a carbon-sulfur analyzer (CS844, manufactured by LECO Japan LLC). 0.50 g of copper powder A was placed in a magnetic crucible, oxygen gas (purity: 99.5%) was used as the carrier gas, and the analysis time was 40 seconds.

[0138] [Halogen Element Content] The measurement was performed using a Metrohm ion chromatograph (930 Compact IC Flex). Specifically, 10 mg of copper powder A and 50 mg of tungsten were placed in a ceramic boat, and then completely combusted while argon gas flowed through the inner tube and oxygen gas through the outer tube of a double quartz combustion tube. While completely combusting, the generated gas was passed through a mixed aqueous solution of sodium carbonate and sodium bicarbonate, and the chlorine concentration in this solution was measured. The halogen element content (at%) in copper powder A was calculated based on the following formula.

[0139]

[0140] [Temperature T １０ , temperature T ８０ [and slope R] A TMA / EXSTAR 6000 manufactured by Seiko Instruments Inc. was used as the TMA measuring device. 0.2 g of copper powder was placed in a φ4.0 mm aluminum mold container, and a pellet was prepared by pressure molding so that a pressure of 1.0 MPa was applied to the copper powder. This pellet was used as the sample. This sample was set in the measuring device, and the sample was heated at a rate of 10°C / min under a load of 49 mN and a nitrogen atmosphere. TMA measurements were taken in the range of 25°C to 1000°C, and a graph showing the relationship between temperature and volume change rate (%) was obtained. From the graph normalized to a maximum shrinkage rate of 100%, the temperature T when a 10% shrinkage occurred (i.e., volume change rate -10%) was obtained. １０ And the temperature T when it has contracted by 80% (i.e., volume change rate -80%). ８０ We calculated the following. Based on the calculated value, we calculated the slope R.

[0141] [BET Specific Surface Area] Measured using the nitrogen adsorption method with "Macsorb" manufactured by Mountec Co., Ltd. The amount of powder to be measured was 0.2 g, and preliminary degassing was performed under vacuum at 80°C for 30 minutes before the main measurement.

[0142] [Crystallite Size] Copper particles were classified using a sieve with a mesh size of 75 μm, and the portion below the sieve was used as the sample. This sample was packed into a sample holder, and measurements were performed using an X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation) under the following conditions. Subsequently, the crystallite size was calculated using Scherrer's formula based on the total width at half maximum of the main peak corresponding to the (111) plane of copper among the diffraction peaks. The results are shown in Table 1 below.

[0143] <X-ray diffraction measurement conditions> • Tube: CuKα ray • Tube voltage: 40kV • Tube current: 50mA • Measured diffraction angle: 2θ = 20-100° • Measurement step size: 0.01° • Acquisition time: 3 seconds / step • Receiving slit width: 0.3mm • Divergence longitudinal limiting slit width: 10mm • Detector: High-speed 1D X-ray detector D / teX Ultra250

[0144] <Method for preparing X-ray diffraction samples> The copper powder to be measured was spread in the measuring holder and smoothed using a glass plate so that the thickness of the copper powder was 0.5 mm and the surface was smooth.

[0145] The X-ray diffraction patterns obtained under the above measurement conditions were analyzed using analysis software under the following conditions. LaB was used for peak width correction. ６ The following was used. The crystallite size was calculated using the total width at half maximum of the peaks and Scherrer's constant (0.94).

[0146] <Measurement Data Analysis Conditions> • Analysis Software: Rigaku PDXL2 • Smoothing: Gaussian function, smoothing parameter = 10 • Background Removal: Fitting method • Kα2 Removal: Intensity ratio 0.497 • Peak Search: Second derivative method • Profile Fitting: FP method • Crystallite Size Distribution Type: Lorentz model • Scherrer Constant: 0.9400

[0147] The peaks of the X-ray diffraction pattern used in the analysis are as follows. The Miller indices shown below are equivalent to the copper crystal planes mentioned above. • Peaks indexed by the Miller index (111) around 2θ = 40° to 45°.

[0148] [Average Aspect Ratio and Average Circularity] 10 g of butyl carbitol (manufactured by Daishin Chemical Co., Ltd.) dissolved in 35% of 1256 (bisphenol A type solid epoxy resin, manufactured by Mitsubishi Chemical Corporation) was added to 10 g of copper powder B. This was mixed at 2000 rpm for 1 minute using a rotation-orbit mixer manufactured by Thinky Co., Ltd., and degassed at 2200 rpm for 30 seconds to obtain a paste. The obtained paste was subjected to a three-roll process under the condition of 20 μm and three passes to break up agglomeration and obtain the final paste. The final paste was printed onto copper foil using a squeegee in a pattern of 2 cm long x 1 cm wide x approximately 55 μm thick. This coating was heated at 150°C for 10 minutes in an atmospheric environment to obtain a dried coating. Using a JEOL cross-section polisher (SM-09010), the dried coating obtained under conditions of 6 kV and 40-50 mA was cross-sectionally processed, and a particle cross-sectional image was obtained using a JEOL scanning electron microscope (JSM-7100F). Using image analysis particle size distribution measurement software (Mac-View) from Mountec Co., Ltd., more than 300 copper particles in the obtained particle cross-sectional image were measured to obtain the aspect ratio and circularity. The average of the obtained aspect ratios was defined as the average aspect ratio, and the average of the circularity values ​​was defined as the average circularity.

[0149] [Particle size D ５０ , particle size D １０ , particle size D ９０ , and standard deviation SD] Using an automatic sample feeder for laser diffraction particle size distribution analyzers (Microtrac SDC, manufactured by Microtrac-Bell Corporation), copper powder was mixed with two drops of pure water containing 0.1% polyoxyethylene octylphenyl ether, and this pure water was added to a 0.1% aqueous solution of SN Dispersant 5468, manufactured by Sunopco. After irradiating this aqueous solution with 40W ultrasound for 5 minutes, the particle size distribution was measured using a Microtrac-Bell Corporation laser diffraction particle size distribution analyzer "MT3300EX II", and the particle size D was determined from the obtained volume-based particle size distribution chart. ５０ , particle size D １０ , particle size D ９０ The standard deviation (SD) was also measured. Particle size D ５０ , particle size D １０ , particle size D ９０When measuring the standard deviation (SD), the flow rate was set to 65%, the solvent refractive index to 1.33, the particle permeability condition to "reflection", the measurement range to 0.122 μm or more and 704.0 μm or less, and the measurement time to 30 seconds.

[0150] [Tap Density] Tap density was measured in accordance with JIS Z2512 using a tapping machine (model: KSR-406, manufactured by Kuramochi Kagaku Kikai Seisakusho Co., Ltd.). In detail, a volume of 150 cm³ was measured. ３ 120g of copper powder was placed in the graduated cylinder. The tap stroke was set to 4cm and the number of taps to 300, and measurements were taken.

[0151] [Sintering Density] 10 g of copper powder obtained in the examples and comparative examples was mixed with 0.5 g of glass frit (Takara Standard, CK5454, pulverized) and 1.5 g of terpineol dissolved in 10% of Techpolymer (registered trademark) IBM-2 (acrylic resin, Sekisui Chemicals Co., Ltd.). This was mixed at 2000 rpm for 1 minute using a rotation-orbit mixer manufactured by Thinky Co., Ltd., and degassed at 2200 rpm for 30 seconds to obtain a paste. The obtained paste was subjected to a 3-roll process under the condition of 5 passes at 20 μm to break up agglomeration and obtain the final paste. The final paste was printed on a 5 cm x 5 cm alumina substrate using a squeegee in a pattern of 2 cm x 1 cm x approximately 55 μm thick. This coating was heated at 150°C for 10 minutes in an atmospheric environment to obtain a dried coating. Using a KTF773N1 firing furnace manufactured by JTEKT Thermo Systems Corporation, the temperature was raised to 800°C at a heating rate of 30°C / min under a nitrogen atmosphere, and the dry coating film was fired at 800°C for 10 minutes to obtain a sintered film. Subsequently, the mass of the sintered film, including the mass of the alumina substrate, was weighed using a 5-digit balance manufactured by Shimadzu Corporation's AUW220D. From this value, the mass of the sintered film was calculated by subtracting the mass of the alumina substrate, which had been weighed beforehand. In addition, the thickness of the sintered film was measured at three arbitrary locations using a MICROGRANITE manufactured by PRECISION LAPPING. The average value of the obtained values ​​was taken as the thickness of the sintered film. The volume of the sintered film was calculated by multiplying this thickness by the vertical and horizontal lengths obtained from the sintered film measurements. Based on the mass and volume of the sintered film, the density of the sintered film was calculated. A higher density of the sintered film indicates higher sintering density.

[0152] [Glass Delamination] In the evaluation of sintering density, the sintered film was cut to obtain a cross-section. This cross-section was progressively rotary polished using abrasive paper #500, #1200, #2400, and #4000, and finally buffed to a mirror finish to be used as the measurement surface. SEM-EDS was performed on this measurement surface to obtain a Si mapping image of the measurement surface, and the distribution percentage (%) of Si elements in the upper part of the measurement surface was measured. A higher distribution percentage of Si elements indicates that glass delamination has occurred.

[0153]

[0154]

[0155]

[0156] As is clear from the results shown in Table 3, the copper powders of Examples 1 to 6 provide copper powders and copper pastes that, compared to the copper powders of Comparative Examples 1 and 2, enable the formation of a dense sintered film even at low temperatures and suppress the occurrence of glass delamination.

[0157] The present invention provides copper powder and copper paste that enable the formation of a dense sintered film even at low temperatures and suppress the occurrence of glass delamination. Furthermore, a method for manufacturing a conductive film that enables the formation of a dense sintered film and suppresses the occurrence of glass delamination is provided. Finally, a sintered body that is dense and exhibits suppressed glass delamination is provided.

Claims

Copper powder containing the following copper powder A and copper powder B. [Copper powder A] Copper powder consisting of multiple copper particles, Copper powder containing halogen elements in an amount of 0.001 at% to 0.30 at%. [Copper powder B] A copper powder comprising a plurality of copper particles having different aspect ratios, Tap density is 4.0 g / cm³ ３ 7.0g / cm or more ３ The following: Volume cumulative particle size D at 50% cumulative volume, as measured by laser diffraction scattering particle size distribution analysis. ５０ The degree of dispersion D is the ratio of the standard deviation (SD) of the particle size distribution to the degree of dispersion D. Ｐ Copper powder in which the value is between 0.55 and 0.

90. The copper powder according to claim 1, wherein the content ratio of copper powder A to the total of copper powder A and copper powder B is 45% by mass or more and 99% by mass or less, and the content ratio of copper powder B is 1% by mass or more and 55% by mass or less. 　 When copper powder A was subjected to thermomechanical analysis under a nitrogen atmosphere at a heating rate of 10°C / min, the temperature at which it shrank by 10 volume percent relative to its maximum shrinkage rate was T １０ The copper powder according to claim 1 or 2, wherein the temperature is 600°C or lower. 　 Copper powder A has a value R defined by the following formula (1) at -0.00500°C －１ The copper powder according to claim 1 or 2. R=(S －０．８ -S －０．１ ) / (T ８０ -T １０ ) (1) In the ceremony, T ８０ This represents the temperature at which copper powder A shrinks by 80% by volume relative to its maximum shrinkage rate when subjected to thermomechanical analysis under nitrogen atmosphere and a heating rate of 10°C / min. T １０ This represents the temperature at which copper powder A shrinks by 10 volume percent relative to its maximum shrinkage rate when subjected to thermomechanical analysis under a nitrogen atmosphere and a heating rate of 10°C / min. S －０．８ This represents -0.8, which is the value of the 80% heat shrinkage coefficient normalized by the maximum heat shrinkage coefficient. S －０．１ This represents -0.1, which is the value of the 10% heat shrinkage coefficient normalized by the maximum heat shrinkage coefficient. 　 The copper powder according to claim 1 or 2, wherein the average aspect ratio of the copper particles constituting copper powder B is 1.05 or more and 3.00 or less. 　 The copper powder according to claim 1 or 2, wherein the average circularity of copper powder B is 0.60 or more and 0.95 or less. 　 A copper paste containing the following copper powders A and B. [Copper powder A] Copper powder consisting of multiple copper particles, Copper powder containing halogen elements in an amount of 0.001 at% to 0.30 at%. [Copper powder B] A copper powder comprising a plurality of copper particles having different aspect ratios, Tap density is 4.0 g / cm³ ３ 7.0g / cm or more ３ The following: Volume cumulative particle size D at 50% cumulative volume, as measured by laser diffraction scattering particle size distribution analysis. ５０ The degree of dispersion D is the ratio of the standard deviation (SD) of the particle size distribution to the degree of dispersion D. Ｐ Copper powder in which the value is between 0.55 and 0.

90. The copper paste according to claim 7, comprising glass frit. 　 A method for manufacturing a conductive film, comprising applying the copper paste described in claim 7 or 8 to a substrate to form a coating film, and then firing the coating film. 　 A sintered body of copper paste according to claim 7 or 8.

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