Composite copper particles, method for producing the same, and use thereof

Abstract

Provided is a copper particle that can be used for various applications even after exposure to the atmosphere by itself. A composite copper particle containing a copper particle and an organic component, wherein the composite copper particle has a value of 100 nm or more and 600 nm or less as an average particle diameter measured by a scanning electron microscope, the organic component contains at least a carboxylic acid or a salt thereof and a high-molecular dispersant, the content of the organic component is 0.3 mass% or more and 6.0 mass% or less with respect to the copper particle, the high-molecular dispersant has an acid value of 60 mgKOH / g or more, and the mass reduction rate in the atmosphere when warmed from 30°C to 250°C at a temperature increase rate of 10°C / min is 70% or more using a thermogravimetric differential thermal analysis device.

Description

Technical Field

[0001] The present invention relates to composite copper particles and methods for manufacturing the same, as well as copper paste containing the composite copper particles, bonding components or conductive materials containing the composite copper particles or the copper paste, sintered bodies containing the bonding components as raw materials, and conductive bodies containing the conductive materials. Background Technology

[0002] When manufacturing a substrate for a power semiconductor device by bonding a semiconductor element to a substrate such as a lead frame, a bonding component with high thermal conductivity is used. Among various bonding components, copper is suitable for bonding semiconductor elements because it is cheaper than silver and is less prone to ion migration.

[0003] In addition to the bonding applications mentioned above, copper is also suitable as a conductive material for inks used in printed electronics due to its high conductivity.

[0004] Patent document 1 describes a method for obtaining metal colloidal particles with suppressed coarse particle formation by constructing a protective colloid (or dispersant) for coating or protecting metal nanoparticles, which consists of an organic compound having a carboxyl group and a polymeric dispersant (especially a polymeric dispersant having a carboxyl group).

[0005] Patent Document 2 describes a copper nanoparticle dispersion with a volume average particle size of less than 500 nm, which is formed by combining copper nanoparticles with carboxylic acids, alkylamines, and polymeric dispersants with specific amine or acid values.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2009-74171

[0009] Patent Document 2: Japanese Patent Application Publication No. 2015-210973 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The inventors have confirmed that in existing bonding components using copper particles, the bonding performance decreases due to atmospheric exposure, rendering them unsuitable for use as bonding components. Furthermore, as a phenomenon observed when copper particles are exposed to the atmosphere, the exothermic reaction of the copper particles and the dissolution of copper ions during dispersion manufacturing have been identified, indicating that existing copper particles may oxidize due to atmospheric exposure.

[0012] When copper particles are used in bonding components or conductive materials, they are processed into forms suitable for their application, such as pastes or dispersions. However, when these copper particles are exposed to the atmosphere, there is concern about a decrease in their bonding and conductivity properties. Furthermore, it is difficult to completely avoid oxidation of copper particles during the manufacturing and processing stages. For these reasons, there is a need to develop copper particles that can be used for various applications even after atmospheric exposure.

[0013] Patent Document 1 discloses a high-concentration metal colloidal particle containing metal nanoparticles, and evaluates its storage stability by using the presence or absence of sedimentation and aggregation after 6 months of storage at room temperature as an indicator, where ethylene glycol is added to silver colloidal particles protected by a protective colloid to form a paste. However, the examples only disclose silver nanoparticles, and do not acknowledge the issue of metals such as copper particles that are easily oxidized in the atmosphere.

[0014] Patent Document 2 discloses a copper nanoparticle dispersion with excellent antioxidant properties. This dispersion achieves its antioxidant properties by immediately dispersing the copper nanoparticles, allowing alkylamines to adhere to the surface of the copper particles. However, the embodiments only disclose copper particles with an average primary particle size of less than 100 nm. It is generally understood that copper particles of this size are easily oxidized in the atmosphere and generate significant heat, thus making them unsuitable for various applications after atmospheric exposure.

[0015] While the stability and antioxidant properties of the paste or dispersion states have been studied in the aforementioned prior art literature, no discussion has been made regarding whether copper particles exposed to the atmosphere can still be used for various applications. Furthermore, there is no record or suggestion regarding whether the metal colloidal particles and pastes containing them, as well as copper nanoparticle dispersions disclosed in the aforementioned prior art literature, can be used for bonding applications.

[0016] The present invention addresses the aforementioned issues and aims to provide copper particles that can still be used for various purposes even after the copper particles themselves have been exposed to the atmosphere.

[0017] Problem-solving methods

[0018] Therefore, through dedicated research, the inventors discovered that by subjecting an organic component containing a carboxylic acid or its salt and a specific polymeric dispersant in a certain amount to a specific treatment with copper particles of a specific particle size, composite copper particles that can be used for various applications even after exposure to the atmosphere can be obtained, thus completing the present invention.

[0019] That is, the present invention is as follows.

[0020] (1) A composite copper particle, which is a composite copper particle containing copper particles and organic components, wherein,

[0021] The composite copper particles, with an average particle size measured by scanning electron microscopy, have a value of 100 nm or more and 600 nm or less.

[0022] The organic component comprises at least a carboxylic acid or its salt and a polymeric dispersant, and the content of the organic component is more than 0.3% by mass and less than 6.0% by mass relative to the total composite copper particles.

[0023] The polymeric dispersant has an acid value of 60 mg KOH / g or higher, and its mass reduction rate in the atmosphere is 70% or higher when heated from 30°C to 250°C at a heating rate of 10°C / min using a thermogravimetric differential thermal analysis device.

[0024] (2) The composite copper particles according to (1), wherein the polymeric dispersant, as the temperature of the exothermic peak of the polymeric dispersant measured by a thermogravimetric differential thermal analysis device, has a temperature below 300°C.

[0025] (3) The composite copper particles according to (1) or (2), wherein the carboxylic acid or its salt has a carbon number of 2 or more and 20 or less.

[0026] (4) The composite copper particles according to any one of (1) to (3), wherein the organic component, as the mass ratio of the carboxylic acid or its salt to the polymeric dispersant, has a value of 1.0 or more and 12.0 or less.

[0027] (5) The composite copper particles according to any one of (1) to (4), wherein the carboxylic acid or its salt is coated on the surface of the copper particles.

[0028] (6) A copper paste comprising any one of (1) to (5) composite copper particles and a paste solvent.

[0029] (7) A joining component, comprising composite copper particles or copper paste, wherein,

[0030] The composite copper particles are any one of (1) to (5).

[0031] The copper paste contains composite copper particles as described in any one of (1) to (5) and a solvent for the paste.

[0032] (8) A conductive material, which is a conductive material containing composite copper particles or copper paste, wherein,

[0033] The composite copper particles are any one of (1) to (5).

[0034] The copper paste contains composite copper particles as described in any one of (1) to (5) and a solvent for the paste.

[0035] (9) A sintered body containing the joining component described in (7) as a raw material.

[0036] (10) A conductor comprising the conductive material described in (8).

[0037] (11) A method for manufacturing composite copper particles, comprising a step of mixing copper particles coated with carboxylic acid, carboxylic acid or its salt, a polymeric dispersant and a solvent.

[0038] (12) The method for manufacturing composite copper particles according to (11) includes a step of mixing carboxylic acid-coated copper particles with a treatment liquid containing carboxylic acid or its salt, a polymeric dispersant and a solvent.

[0039] (13) The method for manufacturing composite copper particles according to (11) or (12) includes a step of mixing carboxylic acid-coated copper particles with a treatment liquid containing carboxylic acid or its salt, a polymeric dispersant and a solvent, and then drying them.

[0040] The effects of the invention

[0041] The composite copper particles according to the present invention exhibit high bonding strength not only before atmospheric exposure but also after atmospheric exposure, and further exhibit practical conductivity, thus making them suitable for bonding applications (e.g., bonding components) or conductive applications (e.g., conductive materials). Attached Figure Description

[0042] Figure 1 This is a diagram showing the X-ray diffraction (also referred to as "XRD") patterns of the composite copper particles of Example 1 before and after atmospheric exposure.

[0043] Figure 2 This is a transmission electron microscope (TEM) photograph of the composite copper particles of Example 1 before atmospheric exposure.

[0044] Figure 3 This is a transmission electron microscope (TEM) image showing composite copper particles of Example 1 after atmospheric exposure.

[0045] Figure 4 This is a scanning electron microscope (SEM) image of the composite copper particles of Example 1 before atmospheric exposure. Detailed Implementation

[0046] The composite copper particles of the present invention are composite copper particles containing copper particles and organic components. The composite copper particles, as measured by scanning electron microscopy, have an average particle size of 100 nm or more and 600 nm or less. The organic components comprise at least a carboxylic acid or its salt and a polymeric dispersant. The content of the organic components is 0.3% by mass or more and 6.0% by mass or less relative to the total composite copper particles. The polymeric dispersant has an acid value of 60 mg KOH / g or more. Furthermore, the mass reduction rate in the atmosphere when heated from 30 °C to 250 °C at a heating rate of 10 °C / min using a thermogravimetric differential thermal analysis apparatus is 70% or more.

[0047] <Copper Particles>

[0048] The composite copper particles of the present invention contain copper particles.

[0049] The copper particles used in the composite copper particles of this invention are not particularly limited. For example, commercially available copper particles can be purchased, or copper particles manufactured by known methods can be used.

[0050] The copper particles may also contain components and compounds other than copper, such as those found in raw materials or reactants used in the manufacturing process, depending on the intended use and to the extent that they do not cause any hindrance.

[0051] The shape of the copper particles used in the composite copper particles of this invention is not particularly limited. For example, any shape such as irregular, spherical, polyhedral, spindle-shaped, or plate-shaped can be used.

[0052] The average particle size of the copper particles is not particularly limited, as long as composite copper particles with a desired average particle size can be obtained. For example, it is preferably 100 nm or more and 600 nm or less, more preferably 150 nm or more and 500 nm or less, and even more preferably 200 nm or more and 400 nm or less.

[0053] The average particle size of the copper particles was measured using a scanning electron microscope (SEM). The copper particles were photographed, and for 50 primary particles in the SEM field of view, their maximum Feret diameters (hereinafter referred to as Feret diameters) were measured. The arithmetic mean of these diameters was taken as the average particle size.

[0054] The copper particles can exist as primary particles or as secondary particles formed by the condensation of primary particles.

[0055] <Organic Ingredients>

[0056] The composite copper particles of the present invention, as an organic component, contain a carboxylic acid or its salt and a polymeric dispersant, wherein the content of the organic component is 0.3% by mass or more and 6.0% by mass or less relative to the total composite copper particles.

[0057] The content of organic components in the composite copper particles of the present invention is 0.3% by mass or more and 6.0% by mass or less relative to the total composite copper particles, preferably 0.5% by mass or more and 4.5% by mass or less, and more preferably 0.7% by mass or more and 3.0% by mass or less.

[0058] Because the content of organic components is within the stated range, the properties (specifically, bonding strength and conductivity) of the composite copper particles of the present invention will not decrease even when exposed to the atmosphere, thus making them suitable for bonding applications (e.g., bonding components) or conductive applications (e.g., conductive materials). Furthermore, the phrase "when exposed to the atmosphere" in this application means "immediately after exposure to the atmosphere," but also includes the moment of atmospheric exposure.

[0059] The amount of organic components contained in the composite copper particles of the present invention was measured by a thermogravimetric differential thermal analysis apparatus (also referred to as "TG-DTA" in this application). Specifically, the composite copper particles were heated from 30°C to 500°C at a heating rate of 10°C / min under a nitrogen atmosphere. Based on the mass of the composite copper particles at the start of the measurement, the rate of mass reduction in the temperature range from 30°C to 350°C in the obtained spectrum was taken as the amount of organic components contained in the composite copper particles.

[0060] In the composite copper particles of the present invention, the state of the organic components is not particularly limited. For example, the organic components can exist on the surface of the copper particles, or they can form a chemical bond with the surface of the copper particles. Examples of such chemical bonds include ionic bonds, coordination bonds, and intermolecular forces (e.g., van der Waals forces, hydrogen bonds). Alternatively, the organic components can also be adsorbed onto the surface of the copper particles. Furthermore, in this application, "chemical bond" and "adsorption" are also referred to as "interaction".

[0061] The adsorption state of the organic component on the surface of the copper particles is not particularly limited. For example, it can be a state of physical and / or chemical adsorption of the organic component on the surface of the copper particles, or a state in which the organic component exists by means of electrical interaction (e.g., Coulomb force) with the surface of the copper particles.

[0062] When the organic component is present on the surface of the copper particles, the organic component can coat the surface of the copper particles. Specifically, the organic component can coat the entire surface of the copper particles, or it can only cover a portion of the surface of the copper particles. Furthermore, when the organic component coats the entire surface of the copper particles, the coating can be uniform or non-uniform.

[0063] <Carboxylic acids or their salts>

[0064] The composite copper particles of the present invention contain organic components, including carboxylic acids or their salts.

[0065] In the composite copper particles of the present invention, the carboxylic acid or its salt used is not particularly limited. The carboxylic acid or its salt may be one type or two or more types.

[0066] The chemical structure of the carboxylic acid or its salt is not particularly limited, as long as it contains a hydrocarbon moiety and a carboxyl moiety.

[0067] The hydrocarbon group is not particularly limited, as long as it yields the composite copper particles of this invention. For example, it can consist of only single bonds, or it can have multiple bonds along its length or at the ends. Furthermore, heteroatoms can be present at any position on the hydrocarbon group.

[0068] The carboxyl group is not particularly limited, as long as the composite copper particles of the present invention are obtained. For example, the molecule of a carboxylic acid or its salt may have one carboxyl group, or it may have two or more carboxyl groups. Preferably, the molecule of a carboxylic acid or its salt has one carboxyl group.

[0069] If the carboxylic acid or its salt has one carboxyl group, the low-temperature sintering performance is improved, and therefore it is preferred. The state of the carboxylic acid or its salt is described later, but it can be understood that the carboxylic acid or its salt exists in the composite copper particles of the present invention with the carboxyl group as the junction. For example, when the carboxylic acid or its salt is present on the surface of the copper particles, the carboxylic acid or its salt exists on the surface of the copper particles with the carboxyl group as the junction. It can be understood that the carboxylic acid or its salt with fewer junctions will thermally decompose at low temperatures, thus the low-temperature sintering performance is improved more effectively.

[0070] In addition, carboxylic acids or their salts with one carboxyl group are less likely to remain as residues during sintering, thus more effectively avoiding the reduction in low-temperature sintering performance caused by residue components, and are therefore preferred.

[0071] Furthermore, the aforementioned phrase "carboxylic acid or its salts may thermally decompose at low temperatures" in this application means that, in addition to decomposition due to heat, carboxylic acid or its salts may also detach due to heat, and / or dissociate due to heat, and / or volatilize due to heat.

[0072] Furthermore, the term "low-temperature sintering performance" in this application refers to the performance of the composite copper particles and copper paste of the present invention to be fully sintered at temperatures below 300°C.

[0073] The number of carbon atoms in the molecule of the carboxylic acid or its salt is not particularly limited, as long as the composite copper particles of the present invention can be obtained. For example, it is preferably 2 or more and 20 or less, more preferably 4 or more and 18 or less, and even more preferably 6 or more and 16 or less.

[0074] The number of carbon atoms in a molecule of a carboxylic acid or its salt is defined by the total number of carbon atoms in the carboxylic acid molecule. That is, the number of carbon atoms in a molecule of a carboxylic acid or its salt is the sum of the number of carbon atoms in the hydrocarbon group and the number of carbon atoms in the carboxyl group.

[0075] This can be understood as follows: if the carbon number is 2 or more, oxidation of copper in the composite copper particles of the present invention due to atmospheric exposure can be more effectively avoided. Therefore, since the reduction in the properties (specifically, bonding strength and conductivity) of the composite copper particles of the present invention due to atmospheric exposure can be more effectively avoided, it is preferred. Furthermore, if the carbon number is 20 or less, the carboxylic acid or its salt in the composite copper particles of the present invention is prone to thermal decomposition even at low temperatures, thus improving low-temperature sintering performance more effectively, and is therefore preferred. Additionally, carboxylic acid or its salt with a carbon number of 20 or less is less likely to remain as residue during sintering, thus more effectively avoiding the reduction in low-temperature sintering performance caused by residue components, and is therefore preferred.

[0076] Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, heptanoic acid, nonanoic acid, decanoic acid, lauric acid, oleic acid, stearic acid, etc.

[0077] Examples of salts of the aforementioned carboxylic acid include alkali metal salts such as sodium or potassium salts of the carboxylic acid, alkaline earth metal salts such as magnesium or calcium salts, ammonium salts, and amine salts.

[0078] Among carboxylic acids or their salts, acetic acid, hexanoic acid, octanoic acid, or decanoic acid, or their salts, are preferred. This is because such carboxylic acids or their salts are understood to be prone to thermal decomposition even at low temperatures, thus improving low-temperature sintering performance. Furthermore, the aforementioned carboxylic acids or their salts are less likely to remain as residues during sintering, effectively preventing a decrease in low-temperature sintering performance due to residue components, and are therefore preferred.

[0079] The content of the carboxylic acid or its salt is not particularly limited, as long as the total organic content with the polymeric dispersant is in the range of 0.3% by mass or more and 6% by mass or less. If the total organic content with the polymeric dispersant is in the range of 0.3% by mass or more and 6.0% by mass or less, then the content of the carboxylic acid or its salt, for example, relative to the total composite copper particles, is preferably 0.15% by mass or more and 5.0% by mass or less, more preferably 0.15% by mass or more and 4.5% by mass or less, further preferably 0.20% by mass or more and 4.0% by mass or less, and particularly preferably 0.25% by mass or more and 3.5% by mass or less.

[0080] The content of carboxylic acids or their salts can be measured using TG-DTA, by the same method as the measurement of the content of the organic components mentioned above.

[0081] In the composite copper particles of the present invention, it is understood that if the content of carboxylic acid or its salt is 0.15% by mass or more, oxidation of copper in the composite copper particles of the present invention due to atmospheric exposure can be more effectively avoided. Therefore, it is preferable because the reduction in the properties (specifically, bonding strength and conductivity) of the composite copper particles of the present invention caused by atmospheric exposure can be more effectively avoided. If the content of carboxylic acid or its salt is 5.0% by mass or less, excess carboxylic acid or its salt in the composite copper particles of the present invention can be more effectively avoided as a residue component, thereby preventing a reduction in low-temperature sintering performance, and is therefore preferable. In addition, if the content of carboxylic acid or its salt is 5.0% by mass or less, the carboxylic acid or its salt will thermally decompose at low temperatures, and the low-temperature sintering performance will be more effectively improved, and is therefore preferable.

[0082] <Polymer Dispersants>

[0083] The organic components contained in the composite copper particles of the present invention include a polymeric dispersant having an acid value of 60 mg KOH / g or higher, and the mass reduction rate in the atmosphere when heated from 30°C to 250°C at a heating rate of 10°C / min using a thermogravimetric differential thermal analysis apparatus is 70% or higher.

[0084] By using a polymeric dispersant with the aforementioned properties in the composite copper particles of the present invention, the composite copper particles of the present invention can be used for bonding applications (e.g., bonding components) or conductive applications (e.g., conductive materials) even when exposed to the atmosphere.

[0085] In the composite copper particles of the present invention, the polymeric dispersant used has an acid value of 60 mg KOH / g or higher. More preferably, it has an acid value of 70 mg KOH / g or higher, and even more preferably, it has an acid value of 86 mg KOH / g or higher. If the acid value is 70 mg KOH / g or higher, the composite copper particles of the present invention exhibit high bonding strength before and after atmospheric exposure, and can further suppress the decrease in conductivity (specifically, the increase in volume resistivity) after atmospheric exposure, which is therefore preferred. There is no particular upper limit to the acid value of the polymeric dispersant, but if it is 200 mg KOH / g or lower, it can further suppress the decrease in bonding strength and conductivity of the composite copper particles of the present invention after atmospheric exposure, which is therefore preferred. The acid value of the polymeric dispersant is more preferably 70 mg KOH / g or higher and 200 mg KOH / g or lower, and even more preferably 86 mg KOH / g or higher and 200 mg KOH / g or lower.

[0086] For commercially available polymeric dispersants, the acid value should be determined according to the product catalog. When preparing homemade polymeric dispersants, the acid value can be measured using the following method: The acid value of the polymeric dispersant is measured by non-aqueous neutralization titration using an automatic titration apparatus (GT-310BRT, manufactured by Nitto Seiko Analytical Technology Co., Ltd.). The titration solution is prepared by dissolving 0.5 g of the polymeric dispersant in 100 mL of ethanol using a 0.1 mol / L potassium hydroxide-ethanol solution (Wako Pure Chemicals Co., Ltd.).

[0087] In the aforementioned polymeric dispersant, the polymeric dispersant used exhibits a mass reduction rate of 70% or more in the atmosphere when heated from 30°C to 250°C at a heating rate of 10°C / min using a thermogravimetric differential thermal analysis apparatus. More preferably, it has a reduction rate of 80% or more, and even more preferably, it has a reduction rate of 90% or more.

[0088] If the mass reduction rate of the polymeric dispersant exceeds the stated value, the composite copper particles exposed to the atmosphere are suitable not only for bonding applications (e.g., bonding components) or conductive applications (e.g., conductive materials), but the polymeric dispersant also readily undergoes thermal decomposition at low temperatures. Furthermore, the decomposition products obtained from the thermal decomposition readily detach or dissociate from the composite copper particles at low temperatures, thus more effectively improving the low-temperature sintering performance, which is therefore preferred. Additionally, the polymeric dispersant is unlikely to remain during sintering, which more effectively avoids the reduction in low-temperature sintering performance caused by residue components, which is also preferred.

[0089] The mass reduction rate of the polymeric dispersant was measured by TG-DTA. Specifically, the polymeric dispersant was heated from 25°C to 1000°C in the atmosphere at a heating rate of 10°C / min. Using the initial mass of the polymeric dispersant as a baseline, the mass reduction rate of the polymeric dispersant in the atmosphere was calculated based on the mass reduction during the heating process from 30°C to 250°C.

[0090] The amine value of the polymeric dispersant is not particularly limited. For example, the amine value of the polymeric dispersant is preferably 45 mg KOH / g or less, more preferably 20 mg KOH / g or less, and even more preferably 5 mg KOH / g or less. Most preferably, a polymeric dispersant without an amine value is used.

[0091] If the amine value of the polymeric dispersant is below the stated value, it is more effective to prevent the carboxylic acid or its salt treated on the surface of the copper particles from reacting with components derived from the amine value.

[0092] The temperature of the exothermic peak formed by the thermal decomposition of the polymeric dispersant is not particularly limited. For example, the exothermic peak temperature formed by the thermal decomposition of the polymeric dispersant is preferably below 300°C, more preferably below 280°C, and even more preferably below 250°C. When multiple exothermic peaks can be identified, the temperature of the exothermic peak observed at the highest temperature is used among the observed peaks.

[0093] If the exothermic peak temperature formed by the thermal decomposition of the polymeric dispersant is below the stated value, the polymeric dispersant is also prone to thermal decomposition at low temperatures. Furthermore, the decomposition products obtained through this thermal decomposition easily detach or dissociate from the composite copper particles at low temperatures, thus more effectively improving the low-temperature sintering performance; therefore, this is preferred. Additionally, the polymeric dispersant is unlikely to remain during sintering, which more effectively avoids the reduction in low-temperature sintering performance caused by residue components; therefore, this is also preferred.

[0094] The temperature of the exothermic peak formed by the thermal decomposition of polymeric dispersants can be measured using TG-DTA, by the same method as the measurement of the mass reduction rate of polymeric dispersants described above.

[0095] The weight-average molecular weight of the polymeric dispersant is not particularly limited. For example, it is preferred that the weight-average molecular weight is 600 or more and 10,000 or less, more preferably 650 or more and 9,000 or less, and even more preferably 700 or more and 8,000 or less.

[0096] If the weight-average molecular weight of the polymeric dispersant is 600 or higher, then, as described later in the preferred manner, the carboxylic acid or its salt can be retained on the surface of the copper particles, which is therefore preferred. Furthermore, it effectively prevents the aggregation of the composite copper particles of the present invention, which is also preferred. This further effectively prevents the degradation of the properties (specifically, bonding strength and conductivity) of the composite copper particles of the present invention when exposed to the atmosphere, which is also preferred. If the weight-average molecular weight is 10,000 or lower, the polymeric dispersant is also prone to thermal decomposition at low temperatures. Furthermore, the decomposition products obtained from the thermal decomposition are easily detached or dissociated from the composite copper particles at low temperatures, thus more effectively improving the low-temperature sintering performance, which is also preferred. In addition, the polymeric dispersant is less likely to remain during sintering, which more effectively prevents the degradation of low-temperature sintering performance caused by residue components, which is also preferred.

[0097] The weight-average molecular weight of the polymeric dispersant can be measured by gel permeation chromatography (also referred to as "GPC" in this application). Specifically, the polymeric dispersant is dissolved in tetrahydrofuran (also referred to as "THF" in this application), filtered through a membrane filter, thereby preparing a sample solution for GPC analysis.

[0098] Furthermore, the error range of the weight-average molecular weight of the aforementioned polymeric dispersant is based on the average value of the weight-average molecular weight measured three times by the GPC, and is within the range of 500 or less and 500 or more of the benchmark (for example, when the average of the three weight-average molecular weight measurements is 1000, the error range is between 500 and 1500).

[0099] The content of the polymeric dispersant is not particularly limited, but the organic content, together with the carboxylic acid or its salt, is in the range of 0.3% by mass or more and 6.0% by mass or less. If the organic content, together with the carboxylic acid or its salt, is in the range of 0.3% by mass or more and 6.0% by mass or less, then the content of the polymeric dispersant, for example, relative to the total amount of the composite copper particles, is preferably 0.15% by mass or more and 1.5% by mass or less, more preferably 0.16% by mass or more and 1.25% by mass or less, and even more preferably 0.17% by mass or more and 1.0% by mass or less.

[0100] In the composite copper particles of the present invention, if the content of the polymeric dispersant is 0.15% by mass or more, the composite copper particles of the present invention can more effectively prevent carboxylic acids or their salts from detaching from the surface of the copper particles when exposed to the atmosphere, which is therefore preferred. If the content of the polymeric dispersant is 1.5% by mass or less, the polymeric dispersant is also prone to thermal decomposition at low temperatures, and the decomposition products obtained through said thermal decomposition are easily detached or dissociated from the composite copper particles at low temperatures, thus more effectively improving the sintering performance at low temperatures, which is therefore preferred. In addition, it is more effective to avoid the reduction in the low-temperature sintering performance of the composite copper particles of the present invention due to the residue of polymeric dispersant contained in the composite copper particles during sintering, which is therefore preferred.

[0101] The content of polymeric dispersants was measured using TG-DTA, in the same manner as the measurement of the content of organic components described above.

[0102] <Composite Copper Particles>

[0103] The average particle size of the composite copper particles of the present invention is 100 nm or more and 600 nm or less, preferably 150 nm or more and 500 nm or less, and more preferably 200 nm or more and 400 nm or less.

[0104] Since the average particle size of the composite copper particles is within the range described, the composite copper particles of the present invention are suitable for bonding applications (e.g., bonding components) or conductive applications (e.g., conductive materials) even when exposed to the atmosphere.

[0105] The average particle size of the composite copper particles can be determined using SEM, by the same method as the measurement of the average particle size of copper particles described above.

[0106] Furthermore, in the composite copper particles of the present invention, the particle size variation of the copper particles is minimal due to the presence of organic components. Therefore, the average particle size of the composite copper particles of the present invention can be considered to be the same as the average particle size of the copper particles.

[0107] When evaluating whether copper oxide is formed in the composite copper particles of the present invention using an X-ray diffraction (XRD) apparatus, the composite copper particles of the present invention exposed to the atmosphere are measured using an XRD apparatus, and the evaluation is performed based on the obtained X-ray diffraction pattern. For example, based on the X-ray diffraction pattern, when peaks are observed only near the peaks caused by metallic copper, i.e., around 2θ = 43.3° (Cu(111) plane) and around 2θ = 50.4° (Cu(200) plane), it can be evaluated that only metallic copper is present (in other words, no copper oxide is formed). In addition, when a peak is observed near the peak caused by metallic copper, around 2θ = 74.08° (Cu(220) plane), it can also be evaluated that only metallic copper is present (in other words, no copper oxide is formed). Furthermore, as an XRD apparatus, SmartLab SE (Rigaku Corporation) can be used, for example. In addition, dedicated software can be used for apparatus control, data collection, calculation, and report generation; such software can be used, for example, SmartLab Studio II (Rigaku Corporation).

[0108] When evaluating the presence or absence of copper oxide in the composite copper particles of the present invention using a transmission electron microscope (TEM), the composite copper particles of the present invention exposed to the atmosphere are observed by TEM, and the evaluation is based on the lattice spacing of the atomic arrangement (i.e., lattice fringes) in the crystal. For example, if only the lattice spacing of the observed lattice fringes is observed for the metallic copper (111) plane, which is 2.1 Å (0.21 nm), it can be evaluated that only metallic copper is present (no copper oxide is formed). Furthermore, as the TEM, an H-9000 (Hitachi High Technology Co., Ltd.) can be used, for example.

[0109] In the organic components contained in the composite copper particles of the present invention, the mass ratio of carboxylic acid or its salt to the polymeric dispersant is only required to be at least gram equivalents, and there is no particular limitation. For example, the mass ratio is expressed as "(mass of carboxylic acid or its salt) / (mass of polymeric dispersant)", preferably 1.0 or more and 12.0 or less, more preferably 1.2 or more and 11.0 or less, and even more preferably 1.5 or more and 10.0 or less.

[0110] If the mass ratio is 1.0 or higher, it is preferable that the copper particles are in the form of carboxylic acid or its salts, as described later. This improves the low-temperature sintering performance of the composite copper particles of the present invention. If the mass ratio is 12.0 or lower, it is preferable to more effectively avoid increased manufacturing costs due to the large-scale use of carboxylic acid or its salts.

[0111] The mass ratio of carboxylic acid or its salt to the polymeric dispersant (“(mass of carboxylic acid or its salt) / (mass of polymeric dispersant)”) can be measured using TG-DTA, by the same method as the measurement of the content of the organic components described above. Here, in the obtained chromatogram, the mass reduction rate in the temperature range from 30°C to 200°C is the mass of the carboxylic acid or its salt, and the mass reduction rate in the temperature range from 200°C to 350°C is the mass of the polymeric dispersant. Furthermore, the mass reduction rate in the temperature range from 200°C to 350°C is obtained by subtracting the mass reduction rate of the carboxylic acid or its salt from the overall mass reduction rate (30°C to 350°C).

[0112] In the composite copper particles of the present invention, the presence state of carboxylic acids or their salts is not particularly limited. For example, carboxylic acids or their salts may be contained within the composite copper particles, and / or, carboxylic acids or their salts may exist on the surface of the copper particles. When carboxylic acids or their salts exist on the surface of the copper particles, for example, they may exist by forming a chemical bond with the surface of the copper particles, and / or they may exist by forming a chemical bond with a polymeric dispersant. Alternatively, carboxylic acids or their salts may also exist by adsorbing onto the surface of the copper particles and / or the polymeric dispersant.

[0113] Regarding chemical binding and adsorption, the relevant explanations on chemical binding and adsorption of "<organic components>" above apply.

[0114] When the carboxylic acid or its salt is present on the surface of the copper particles, the carboxylic acid or its salt can coat the surface of the copper particles. Specifically, the carboxylic acid or its salt can coat the entire surface of the copper particles, or it can only cover a portion of the surface of the copper particles. Furthermore, when the carboxylic acid or its salt coats the entire surface of the copper particles, the coating can be uniform or non-uniform.

[0115] Furthermore, when the carboxylic acid or its salt coats the surface of copper particles, the carboxylic acid or its salt can coat the surface of the copper particles as a monolayer or as a cumulative film. Moreover, the carboxylic acid or its salt constituting the monolayer and the cumulative film can be composed of only the same type or of two or more different types. Also, the term "cumulative film" here refers to a film composed of a monolayer of carboxylic acid or its salt in direct contact with the surface of the copper particles, and a film composed of carboxylic acid or its salt existing on the monolayer through chemical bonding or adsorption.

[0116] In the composite copper particles of the present invention, the state of the polymeric dispersant is not particularly limited. For example, the polymeric dispersant may be included in the composite copper particles, and / or the polymeric dispersant may also be present on the surface of the copper particles. When the polymeric dispersant is present on the surface of the copper particles, for example, it may interact with the surface of the copper particles, and / or it may also interact with carboxylic acids or their salts present on the surface of the copper particles.

[0117] As for the aforementioned interactions with carboxylic acids or their salts present on the surface of copper particles, examples include the interaction between the polymeric dispersant and the carboxylic acid or its salt through physical adsorption and / or chemical adsorption, and / or the electro-interaction (e.g., Coulomb force) between the polymeric dispersant and the carboxylic acid or its salt, and / or the chemical bonding between the polymeric dispersant and the carboxylic acid or its salt.

[0118] When the polymeric dispersant interacts with a carboxylic acid or its salt present on the surface of copper particles, the polymeric dispersant can coat a film (specifically a monomolecular film or a cumulative film) composed of the carboxylic acid or its salt. Specifically, the polymeric dispersant can coat the entire surface of the film, or it can cover only a portion of the film.

[0119] In a more preferred embodiment of the composite copper particles of the present invention, the surface of the copper particles is coated with a molecular film containing a carboxylic acid or its salt, and a polymeric dispersant is coated on the molecular film containing the carboxylic acid or its salt. In this manner, the composite copper particles of the present invention can better suppress agglomeration between composite copper particles. It can be understood that because agglomeration within the composite copper particles can be better suppressed, the low-temperature sintering performance can be better maintained even after the composite copper particles of the present invention are exposed to the atmosphere.

[0120] When the composite copper particles are a more preferred embodiment, the decomposition temperature of the carboxylic acid or its salt is preferably lower than that of the polymeric dispersant. During sintering of the composite copper particles of the present invention, the carboxylic acid or its salt, which is more easily thermally decomposed, is better released, and simultaneously, the polymeric dispersant is also better released. Therefore, it can be understood that the composite copper particles of the present invention have excellent low-temperature sintering performance.

[0121] In a more preferred embodiment, the molecular membrane of the carboxylic acid or its salt may be composed of a monomolecular membrane or a cumulative membrane, and the monomolecular membrane or the cumulative membrane may be coated with a polymeric dispersant.

[0122] When a monomolecular film of carboxylic acid or its salt is formed on the surface of the copper particles, the composite copper particles of the present invention can be understood to be suitable not only for bonding applications after atmospheric exposure (e.g., bonding components) or conductive applications (e.g., conductive materials), but also to better facilitate the manifestation of low-temperature sintering performance.

[0123] When an accumulation film of carboxylic acid or its salt is formed on the monomolecular film, in the composite copper particles of the present invention, it is understood that they are not only suitable for bonding applications (e.g., bonding components) or conductive applications (e.g., conductive materials) after atmospheric exposure, but also better able to help suppress the oxidation of copper contained in the composite copper particles.

[0124] In addition, it can be understood that the monomolecular film or cumulative film of carboxylic acid or its salt coated on the surface of copper particles can also serve as a basis for better functioning when coating polymeric dispersants.

[0125] Because the carboxylic acid or its salt coated on the surface of the copper particles can be adsorbed and desorbed, if the composite copper particles of the present invention are a more preferred embodiment as described above, then when the composite copper particles of the present invention are exposed to the atmosphere, even if some of the carboxylic acid or its salt detaches, it is still coated by the polymeric dispersant, thus better reducing copper exposure. Therefore, it can be understood that the composite copper particles of the present invention have a high oxidation inhibition effect.

[0126] By coating a polymeric dispersant onto a monolayer or cumulative layer of the carboxylic acid or its salt, the composite copper particles of the present invention are suitable for bonding applications (e.g., bonding components) after atmospheric exposure or for conductive applications (e.g., conductive materials).

[0127] That is, when monolayers and cumulative films of carboxylic acids or their salts form under relatively weak forces (such as intermolecular forces), the polymeric dispersant coats the surface of the monolayers and cumulative films, making it difficult for the carboxylic acids or their salts to detach. Thus, the polymeric dispersant plays an auxiliary role in enabling the aforementioned monolayers and cumulative films of carboxylic acids or their salts to exhibit their effects (specifically, suppressing property degradation even after atmospheric exposure). Furthermore, one of the general effects of polymeric dispersants is their ability to better help suppress the aggregation of composite copper particles.

[0128] <Manufacturing of Composite Copper Particles>

[0129] The method for manufacturing the composite copper particles of the present invention will be described.

[0130] The composite copper particles of the present invention are manufactured by a method comprising the steps of mixing copper particles coated with carboxylic acid, carboxylic acid or its salt, a polymeric dispersant, and a solvent.

[0131] Furthermore, the composite copper particles of the present invention can be manufactured by a method including a step of mixing carboxylic acid-coated copper particles with a treatment liquid containing carboxylic acid or its salt, a polymeric dispersant and a solvent.

[0132] Furthermore, the composite copper particles of the present invention can also be manufactured by a method including mixing carboxylic acid-coated copper particles with a treatment liquid containing carboxylic acid or its salt, a polymeric dispersant and a solvent, and then drying them.

[0133] (Preparation process of carboxylic acid coated copper particles)

[0134] In the composite copper particles of the present invention, the copper particles used are not particularly limited. For example, commercially available copper particles can be purchased, or copper particles manufactured by known methods can be used. As for copper particles manufactured by known methods, copper particles treated with carboxylic acid will be described later.

[0135] The copper particles may also contain components and compounds other than copper, such as those found in raw materials or reactants used in the manufacturing process, depending on the intended use and to the extent that they do not cause any hindrance.

[0136] In the composite copper particles of the present invention, the shape of the copper particles used is not particularly limited. For example, any shape such as irregular shape, spherical, polyhedral, spindle-shaped, plate-shaped, etc., can be used.

[0137] The average particle size of the copper particles is not particularly limited. For example, it is 100 nm or more and 600 nm or less, preferably 150 nm or more and 500 nm or less, and more preferably 200 nm or more and 400 nm or less.

[0138] If the average particle size of the copper particles is within the specified range, composite copper particles with the desired average particle size can be obtained, which is therefore preferred.

[0139] <Solvent>

[0140] The solvent is not particularly limited as long as it does not react with the carboxylic acid or its salt and the polymeric dispersant. Examples of such solvents include methanol, ethanol, 1-propanol, 2-propanol, acetone, and methyl ethyl ketone.

[0141] The raw materials used in the manufacturing method can be appropriately used in conjunction with the above description.

[0142] (Surface treatment process)

[0143] In the composite copper particles of the present invention, copper particles coated with carboxylic acid, carboxylic acid or its salt, polymeric dispersant and solvent are mixed as raw materials, and the carboxylic acid or its salt and polymeric dispersant are used to perform surface treatment on the carboxylic acid coated copper particles.

[0144] The mixing order of the raw materials is not particularly limited. For example, all raw materials can be mixed at once, or the solvent can be mixed with the other raw materials one by one in any order. Furthermore, when preparing a liquid composed of a solvent and at least one raw material, the liquid can be mixed in any order. Specifically, a treatment solution composed of a solvent, a polymeric dispersant, a carboxylic acid, or a salt thereof can be prepared in advance, and this treatment solution can be mixed with carboxylic acid-coated copper particles. Alternatively, a dispersion containing carboxylic acid-coated copper particles, which contains both a solvent and carboxylic acid-coated copper particles, can be mixed with a treatment solution containing a solvent, a polymeric dispersant, a carboxylic acid, or a salt thereof.

[0145] The process of mixing the raw materials can be carried out using a known mixer. Examples include planetary mixers, ultrasonic dispersers, blade mixers, high-speed dispersers, and homogenizers. Alternatively, materials can be mixed without a mixer. Mixing also includes the contact and coexistence of materials with each other.

[0146] Regarding the mixing time and speed, it is sufficient to thoroughly mix all the raw materials; there are no particular limitations. For example, a mixing time of 1 minute or more is acceptable, and more preferably 5 minutes or more. Additionally, a mixing speed of 50 rpm or more is preferred, and more preferably 100 rpm or more. If the mixing time is 5 minutes or more and the mixing speed is 100 rpm or more, the organic components can be uniformly processed by the carboxylic acid-coated copper particles, which is therefore preferable.

[0147] The composite copper particles of the present invention can be manufactured by a method comprising mixing carboxylic acid-coated copper particles with a treatment liquid containing a polymeric dispersant, a carboxylic acid or a salt thereof, and a solvent. This manufacturing method is preferred because it allows the carboxylic acid or its salt and the polymeric dispersant contained in the treatment liquid to be more effectively present on the surface of the copper particles.

[0148] (Preparation process of the treatment solution)

[0149] In the method for manufacturing composite copper particles of the present invention, the processing liquid is prepared by a method including the step of mixing a carboxylic acid or its salt, a polymeric dispersant, and a solvent.

[0150] In the preparation process of the treatment solution, there is no particular limitation on the order in which the raw materials are added. For example, all raw materials can be mixed at once, or the solvent can be mixed with the other raw materials one by one in any order.

[0151] In the preparation step of the treatment liquid, when mixing the treatment liquid, a known mixer can be used for stirring. Examples of such mixers include planetary mixers, ultrasonic dispersers, blade mixers, high-speed dispersers, and homogenizers.

[0152] In the mixing process, the mixing conditions, such as mixing time and mixing speed, are not particularly limited as long as they can thoroughly mix the raw materials. For example, a mixing time of 1 minute or more is acceptable, and more preferably 5 minutes or more. Additionally, a mixing speed of 50 rpm or more is acceptable, and more preferably 100 rpm or more. If the mixing time is 5 minutes or more and the mixing speed is 100 rpm or more, the raw materials can be mixed evenly, which is therefore preferable.

[0153] The total amount of carboxylic acid or its salt and polymeric dispersant in the treatment solution is sufficient to treat the copper particles with a specified amount of organic components, and is not particularly limited. For example, the total amount of carboxylic acid or its salt and polymeric dispersant in the treatment solution is preferably 1.0% by mass or more and 30% by mass or less relative to the total amount of the treatment solution, more preferably 1.5% by mass or more and 25% by mass or less, and even more preferably 2.0% by mass or more and 20% by mass or less.

[0154] The content of carboxylic acid or its salt in the treatment solution is not particularly limited. For example, the content of carboxylic acid or its salt in the treatment solution is preferably 0.7% by mass or more and 25% by mass or less relative to the total content of the treatment solution, more preferably 1.5% by mass or more and 18% by mass or less, and even more preferably 2.0% by mass or more and 16% by mass or less.

[0155] The content of the polymeric dispersant in the treatment solution is not particularly limited. For example, the content of the polymeric dispersant in the treatment solution is preferably 0.3% by mass or more and 5.0% by mass or less relative to the total content of the treatment solution, more preferably 0.4% by mass or more and 4.5% by mass or less, and even more preferably 0.5% by mass or more and 4.0% by mass or less.

[0156] If the composition of the treatment liquid is within the range described, the copper particles can be treated in a manner that yields the composite copper particles of the present invention more effectively from a specified amount of organic components, which is therefore preferred.

[0157] The process of mixing the carboxylic acid-coated copper particles with the treatment solution can be performed using a known mixer. Examples include planetary mixers, ultrasonic dispersers, blade mixers, high-speed dispersers, and homogenizers. Alternatively, the materials can be mixed without a mixer. Mixing also includes contact and coexistence between materials. Examples include methods of immersing copper particles in the treatment solution and methods of permeating copper particles into the treatment solution.

[0158] Regarding the stirring time and speed, there are no particular limitations as long as the raw materials are thoroughly mixed. For example, a stirring time of 1 minute or more is preferred, and 5 minutes or more is more preferred. Additionally, a stirring speed of 50 rpm or more is preferred, and 100 rpm or more is more preferred. If the stirring time is 5 minutes or more and the stirring speed is 100 rpm or more, the organic components can be uniformly treated by the carboxylic acid-coated copper particles, which is therefore preferable. Furthermore, during impregnation or permeation, the impregnation or permeation time can be 10 minutes or more.

[0159] After the surface treatment process, solid-liquid separation can be performed as needed. Known filtration methods can be used for solid-liquid separation. For example, pressure filtration devices such as rotary presses and filter presses, vacuum filtration devices such as Nutsche filters and Moore filters, centrifuges, etc., can be used. Decanting operations are also suitable.

[0160] After the surface treatment process, the recovered solid components can be cleaned as needed. Known cleaning methods can be used for cleaning the solid components. Furthermore, there are no particular limitations on the solvents used for cleaning.

[0161] (Drying process)

[0162] The composite copper particles of the present invention can be manufactured by a method comprising a process of drying a mixture of carboxylic acid-coated copper particles and a treatment liquid as needed.

[0163] The drying temperature, drying time, and drying atmosphere of the drying process can be appropriately set. For example, the drying temperature is preferably above 20°C and below 120°C, the drying time is preferably above 0.5 hours and below 10 hours, and the drying atmosphere is preferably under vacuum, or under inactive gases such as nitrogen or argon.

[0164] In the drying process, known dryers can be used. For example, heating equipment such as dryers, ovens, and electric furnaces, as well as desiccators, vacuum dryers, and vacuum desiccators that are controlled at a specified temperature, can be used.

[0165] When using a desiccator in the drying process, the desiccator is kept at a specified temperature and in a vacuum atmosphere, which allows the mixture of copper particles and processing liquid to dry.

[0166] A vacuum pump can be used to achieve a vacuum atmosphere inside the dehumidifier. For example, a vacuum pump such as the ULVAC G-20DA manufactured by ULVAC Corporation can be used.

[0167] After the drying process, the particle size of the composite copper particles can be adjusted by crushing or grinding as needed. Crushing or grinding can be performed using known pulverizers or classifiers.

[0168] (Example of manufacturing carboxylic acid coated copper particles)

[0169] The following is an example of a method for manufacturing carboxylic acid-coated copper particles (steps A and B).

[0170] (Process A)

[0171] This process involves mixing a copper compound, a carboxylic acid or its salt, an amine compound, and a solvent. This process yields a mixture containing a copper compound.

[0172] The copper compound used in step A may contain only one type of copper compound or may contain two or more types.

[0173] For example, examples include copper carboxylate, copper acetate, copper propionate, copper butyrate, copper valerate, copper hexanoate, copper octanoate, copper decanoate, copper formate (II), copper acetate (II), copper propionate (II), copper butyrate (II), copper valerate (II), copper hexanoate (II), copper octanoate (II), copper decanoate (II), copper citrate (II), copper carboxylate, copper oxide (II), copper oxide (I), copper hydroxide (II), copper hydroxide (I), copper hydroxide (I), copper nitride, etc.

[0174] From the viewpoint of suppressing manufacturing costs, copper(II) oxide is preferred among the copper compounds.

[0175] The amount of copper compound added is not particularly limited. For example, it is preferred if it is more than 1 part by mass and less than 100 parts by mass relative to the solvent.

[0176] If the copper compound is 1 part by mass or more relative to the solvent, it is possible to effectively avoid a reduction in the amount of copper particles generated in step B, and therefore this is preferred. If the copper compound is 100 parts by mass or less relative to the solvent, it is possible to effectively avoid uneven reaction caused by thickening when mixing the solvent and the copper compound in this step, and therefore this is preferred.

[0177] The chemical structure of the carboxylic acid or its salt is not particularly limited, as long as it has a hydrocarbon moiety and a carboxyl moiety in its structure.

[0178] The hydrocarbon group is not particularly limited, as long as it provides carboxylic acid-coated copper particles for manufacturing the composite copper particles of the present invention. For example, it may consist of only single bonds, or it may have multiple bonds along its length or at the ends. Furthermore, heteroatoms may be present at any position on the hydrocarbon group.

[0179] The carboxyl group is not particularly limited, as long as it allows for the production of carboxylic acid-coated copper particles used in the manufacture of the composite copper particles of the present invention. For example, a molecule of a carboxylic acid or its salt may contain one carboxyl group or two or more carboxyl groups. Preferably, a molecule of a carboxylic acid or its salt contains one carboxyl group.

[0180] The number of carbon atoms in the molecule of the carboxylic acid or its salt is not particularly limited, as long as it is sufficient to obtain carboxylic acid-coated copper particles for manufacturing the composite copper particles of the present invention. For example, it is preferably 2 or more and 20 or less, more preferably 2 or more and 18 or less, and even more preferably 2 or more and 16 or less.

[0181] Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, octanoic acid, heptanoic acid, nonanoic acid, decanoic acid, lauric acid, oleic acid, stearic acid, etc.

[0182] Salts of the carboxylic acid, for example, include alkali metal salts such as sodium and potassium salts of the carboxylic acid mentioned above, alkaline earth metal salts such as magnesium and calcium salts, ammonium salts, amine salts, etc.

[0183] The carboxylic acid or its salt preferably contains acetic acid, hexanoic acid, octanoic acid, or decanoic acid. By using such a carboxylic acid or its salt, the copper particles obtained in step B described later can achieve the desired average particle size more efficiently, and are therefore preferred.

[0184] The amount of the carboxylic acid or its salt added is not particularly limited, but it can be more than 0.01 mol and less than 2 mol relative to 1 mol of copper compound.

[0185] If the amount of carboxylic acid or its salt added is within the range, copper particles with a desired average particle size can be obtained from step B, which is therefore preferred.

[0186] The amine compound used in step A is not particularly limited, as long as it has an amino group and a hydroxyl group in its structure.

[0187] Specifically, amino alcohols are preferred as the amine compound. By using amino alcohols, foaming of the copper-containing mixture in step A can be effectively suppressed.

[0188] Examples of amino alcohols include methanolamine, monoethanolamine (also known as "2-aminoethanol"), diethanolamine, triethanolamine, 3-amino-1-propanol, 1-dimethylamino-2-propanol, 3-(dimethylamino)-1-propanol, 4-ethylamino-1-butanol, N-methylethanolamine, 2-diethylethanolamine, 2-aminodibutanol, heptaaminool, isoethylaminophen, sphingosine, 3-dimethylamino-1,2-propanediol, and 3-diethylamino-1,2-propanediol. 2-Propanediol, 3-methylamino-1,2-propanediol, 3-(dimethylamino)-1,2-propanediol, 2-amino-2-methyl-1,3-propanediol, 3-(diethylamino)-1,2-propanediol, 2-amino-2-ethyl-1,3-propanediol, 3-amino-1,2-propanediol, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-1,3-propanediol, etc.

[0189] The amine compound preferably contains monoethanolamine. Even if monoethanolamine remains in the synthesized copper particles, it will thermally decompose at low temperatures, thus more effectively preventing a decrease in low-temperature sintering performance, and is therefore preferred.

[0190] The amount of the amine compound added is not particularly limited, but preferably it is 0.25 mol or more and 2 mol or less relative to 1 mol of the carboxylic acid.

[0191] If the amount of amine compound added is within the specified range, thickening of the mixture containing copper compound can be effectively avoided, and is therefore preferred.

[0192] The addition time of the amine compound is not particularly limited, but is preferably 10 seconds or more and 30 minutes or less. This effectively suppresses the violent exothermic reaction of the copper-containing compound mixture in step A.

[0193] The solvent used in step A is not particularly limited, as long as it does not react with other raw materials and hinder the formation of copper particles. Only one solvent may be used, or two or more may be used.

[0194] Alcohols may be appropriately used as solvents. Examples of such alcohols include 1-propanol, 2-propanol, butanol, pentanol, hexanol, heptanol, octanol, and ethyl carbitol. These alcohols exhibit high miscibility with the aforementioned carboxylic acids or their salts, as well as amine compounds, and are therefore preferred.

[0195] There is no particular limitation on the mixing order of the raw materials. For example, all raw materials can be mixed at once, or the solvent can be mixed with the other raw materials one by one in any order. Preferably, the solvent, copper compound, and carboxylic acid or its salt are mixed first, and then the amine compound is mixed.

[0196] In the mixing process, known mixers can be used. Examples include planetary mixers, ultrasonic dispersers, blade mixers, high-speed dispersers, and homogenizers. Alternatively, materials can be mixed without using a mixer. Mixing also includes the contact and coexistence of materials with each other.

[0197] The mixing conditions in the mixing process can be appropriately set. For example, a stirring time of 1 minute or more is acceptable, more preferably 5 minutes or more. A stirring speed of 50 rpm or more is acceptable, more preferably 100 rpm or more. Under these mixing conditions, the raw materials can be thoroughly mixed. Furthermore, if the stirring time is 5 minutes or more and the stirring speed is 100 rpm or more, the raw materials are mixed more thoroughly, and the reaction proceeds uniformly, which is therefore preferable.

[0198] (Process B)

[0199] This process involves intermittently or continuously adding a reducing agent to the copper compound mixture obtained in process A, wherein the temperature of the mixture during the addition of the reducing agent is above 40°C and below 95°C. This process yields a dispersion containing copper particles.

[0200] The reducing agent can be any agent that reduces copper compounds. Specifically, it is preferable to have a boiling point of 70°C or higher, and more preferably, the boiling point of the reducing agent is above the heating temperature of the heating process. By using such a reducing agent, copper compounds can be reduced more effectively even when the liquid temperature of the mixture is 40°C or higher and 95°C or lower, which is therefore preferred. In addition, only one reducing agent or two or more agents can be used.

[0201] Examples of reducing agents include, for instance, hydrazine derivatives. Examples of hydrazine derivatives include hydrated hydrazine, hydrous hydrazine, methylhydrazine, ethylhydrazine, n-propylhydrazine, isopropylhydrazine, n-butylhydrazine, isobutylhydrazine, sec-butylhydrazine, tert-butylhydrazine, n-pentylhydrazine, isopentylhydrazine, neopentylhydrazine, tert-pentylhydrazine, n-hexylhydrazine, isohexylhydrazine, n-heptylhydrazine, n-octylhydrazine, n-nonylhydrazine, n-decylhydrazine, n-undecylhydrazine, n-dodecylhydrazine, cyclohexylhydrazine, phenylhydrazine, 4-methylphenylhydrazine, benzylhydrazine, 2-phenylethylhydrazine, 2-hydrazinoethanol, acetylhydrazine, adipic acid dihydrazine, sebacate dihydrazine, dodecanoic acid dihydrazine, isophthalic acid dihydrazine, salicylic acid dihydrazine, etc.

[0202] When the reducing agent is added to the copper-containing compound mixture obtained in step A, it is added intermittently or continuously, rather than in a short, single addition. The addition time of the reducing agent is preferably 50 minutes or more and 6 hours or less, more preferably 60 minutes or more and 6 hours or less.

[0203] In this application, "adding intermittently or continuously" means adding it little by little over a period of time. Alternatively, the reducing agent can be added in multiple stages.

[0204] In this application, the term "addition time" refers to the time required from the addition of a reducing agent to a mixture containing a copper compound until all of the reducing agent has been added to the mixture (hereafter referred to as "time required to add all of the reducing agent").

[0205] By adding reducing agent intermittently or continuously, the exothermic reaction generated during the reduction reaction can be suppressed, thus ensuring that the average particle size of the copper particles obtained in this process is within the desired range.

[0206] The amount of reducing agent added is preferably 1.0 mol or more and 4.0 mol or less relative to 1.0 mol of the copper compound. If it is 1.0 mol or more, the copper compound can be sufficiently reduced, which is therefore preferred. Furthermore, if it is 4.0 mol or less, the burden on the solid components containing copper particles during cleaning can be further reduced, which is also preferred.

[0207] The temperature of the copper-containing compound mixture when the reducing agent is added is preferably above 40°C and below 95°C, more preferably above 45°C and below 90°C.

[0208] Since the liquid temperature of the mixture containing copper compounds is within the aforementioned range, copper particles with a desired average particle size can be obtained.

[0209] The temperature of the mixture containing copper compounds can be adjusted either before or during the addition of the reducing agent. Preferably, the temperature of the mixture containing copper compounds is adjusted to the aforementioned range before the addition of the reducing agent.

[0210] In this process, any known mixer, such as a magnetic stirrer, blender, homogenizer, or mixer, can be used as needed. The stirring speed is not limited, but 50 rpm or higher is acceptable. More preferably, it is 100 rpm or higher. By reaching 100 rpm or higher, the copper compound can be uniformly reduced, resulting in more uniform copper particles, which is therefore preferable.

[0211] The dispersion containing copper particles obtained in this process can be aged as needed.

[0212] The maturation conditions can be appropriately set. For example, the maturation temperature is preferably 40°C or higher and 120°C or lower, more preferably 40°C or higher and 100°C or lower, even more preferably 60°C or higher and 100°C or lower, and particularly preferably 60°C or higher and 95°C or lower. The maturation time is preferably 1 minute or higher and 2.0 hours or lower, more preferably 5 minutes or higher and 2.0 hours or lower. Furthermore, during maturation, a known mixer can be used for stirring. The stirring speed is not limited, and 50 rpm or higher is sufficient. Preferably, the stirring speed is 100 rpm or higher.

[0213] The dispersion containing copper particles obtained in this process can be subjected to solid-liquid separation as needed.

[0214] Solid-liquid separation can be achieved using well-known methods. For example, pressure filtration devices such as industrial rotary presses and filter presses, vacuum filtration devices such as Nutz filters and vacuum leaf filters, and centrifugation are commonly used. Decanting is also a suitable method.

[0215] The solid components obtained after the solid-liquid separation can be cleaned using known methods.

[0216] The solid components obtained after the solid-liquid separation can be dried using known methods. For example, heating equipment such as dryers, ovens, and electric furnaces, or desiccators, vacuum dryers, and vacuum dryers controlled at a specified temperature can be used.

[0217] When a desiccator is used in the drying process, the desiccator is controlled at a specified temperature and under a vacuum atmosphere, thereby enabling the solid components to dry. A vacuum pump can be used to achieve a vacuum atmosphere inside the desiccator. For example, a ULVAC G-20DA vacuum pump can be used.

[0218] The drying conditions can be appropriately set. For example, the drying temperature is preferably 20°C or higher and 120°C or lower, and the drying time is more preferably 0.5 hours or higher and 10 hours or lower. From the viewpoint of more effectively suppressing the oxidation of copper particles, the drying atmosphere is preferably under a stream of inactive gas such as nitrogen or argon, or under a vacuum atmosphere.

[0219] By employing the manufacturing method including the above-described steps A and B, carboxylic acid-coated copper particles with an average particle size of 100 nm or more and 600 nm or less can be obtained. These carboxylic acid-coated copper particles are used as raw materials in the manufacture of the composite copper particles of the present invention.

[0220] <Copper Ointment>

[0221] The copper paste of the present invention contains the composite copper particles of the present invention and a solvent for paste preparation.

[0222] There are no particular limitations on the solvent used for pastes; any organic solvent can be used. For example, protic polar solvents and aprotic solvents can be used, and a combination of various solvents can be appropriately used.

[0223] In this invention, alcohol solvents, glycol solvents, glycol ether solvents, and ester solvents have high affinity for polymeric dispersants and carboxylic acids with acid values, and are therefore preferred to be used.

[0224] Examples of alcohol solvents include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, modified alcohols, or aromatic alcohols such as benzyl alcohol, menthol, and terpineol (α, β, γ, δ).

[0225] As a diol solvent, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, etc. can be used.

[0226] As glycol ether solvents, there are ethylene glycol ethers and propylene glycol ethers.

[0227] Examples of ethylene glycol ethers include ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether (ethyl carbitol), diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether (hexyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, triethylene glycol monohexyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, ethylene glycol diacetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate, and ethylene glycol phenyl ether.

[0228] Examples of propylene-based ethylene glycol ethers include propylene glycol monomethyl ether, propylene glycol dimethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol monohexyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monohexyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, tripropylene glycol monohexyl ether, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, propylene glycol diacetate, propylene glycol monobutyl ether acetate, dipropylene glycol monobutyl ether acetate, and propylene glycol phenyl ether.

[0229] Examples of ester solvents include methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, and n-propyl acetate.

[0230] In the copper paste of the present invention, the solvent used for the paste may be one type or two or more. The type and ratio can be arbitrarily set, taking into account the required properties of the copper paste, the required properties of the bonding components, the required properties of the conductive material, and the compatibility with other compounding components. For example, a combination of dipropylene glycol and hexylcarbidol can be used as a combination of various paste solvents.

[0231] The copper paste of the present invention may contain various additives as needed. Examples of additives include various commonly used reducing agents, dispersants, emulsifiers, antifreeze agents, pH adjusters, thickeners, defoamers, film-forming aids, etc.

[0232] When the copper paste of the present invention contains the above-mentioned reducing agent, the reducing agent that can be used includes, for example, monoethanolamine, diethanolamine, triethanolamine, dimethylaminoethanol, N-methyldiethanolamine, hydrazine, formic acid, etc.

[0233] Furthermore, the copper paste of the present invention may contain copper particles other than the composite copper particles of the present invention. Specifically, it may contain micro-copper particles with an average particle size of 1 μm to 50 μm or nano-copper particles with an average particle size of 100 nm or less. The shape of the micro-copper particles and nano-copper particles is not particularly limited, and for example, any shape such as spherical, blocky, needle-like, sheet-like, substantially spherical, irregular, polyhedral, spindle-shaped, flat, etc., as well as aggregates of these shapes, can be listed. The average particle size of the micro-copper particles and nano-copper particles can be measured in the same manner as the average particle size of the composite copper particles described above.

[0234] The content of the aforementioned composite copper particles in the copper paste of the present invention can be appropriately adjusted according to the application. The content of copper particles in the copper paste can, for example, be confirmed by thermogravimetric analysis.

[0235] The copper paste of the present invention is prepared by mixing the aforementioned raw materials. In this mixing process, a known mixer can be used. Examples include commonly used industrial mixers such as twin-shaft mixers, three-roll mills, sand mills, and planetary mixers. Alternatively, for laboratory-scale applications, a mixer, hybrid mixer, homogenizer, and shaker can be used. Materials can also be mixed without using a mixer. Mixing also includes the contact and coexistence of materials with each other.

[0236] The mixer can use pulverizing media as needed. For example, it can use materials such as glass, alumina, zirconium oxide, and zirconium silicate.

[0237] Degassing can be performed as needed during or after the mixing process.

[0238] The atmosphere for the mixing process can be air, an inert gas, or a vacuum. From the viewpoint of more effectively suppressing the performance degradation caused by the oxidation of copper particles, an inert gas and a vacuum are preferred.

[0239] <Jointing Components>

[0240] The composite copper particles of the present invention, or copper paste containing the composite copper particles of the present invention, can be used as bonding components, which can effectively bond a substrate and a substrate. Furthermore, they can also be used for bonding three-dimensional stacked integrated circuits (3D-ICs). The composite copper particles of the present invention can, for example, be used directly as bonding components, or they can be made into copper paste and then used as bonding components.

[0241] When the copper paste is used in the bonding component, it is preferable that the copper paste contains the aforementioned composite copper particles in a manner that is 80% or more and 98% or less by mass relative to the total amount of the copper paste, and more preferably 85% or more and 96% or less by mass.

[0242] The copper paste, by containing more than 80% by mass of the composite copper particles, can more effectively suppress the occurrence of voids during heating and further improve the bonding strength, and is therefore preferred. Furthermore, by containing less than 98% by mass, it can more effectively prevent the aggregation of the composite copper particles in the paste, and significantly improve the spreadability of the paste.

[0243] The joining component may contain additives depending on its intended use. Examples of such additives include those mentioned above.

[0244] The substrate and the material to be bonded can be the same material or different materials. The material to be bonded is not particularly limited. Examples include various metallic materials, semiconductor materials (e.g., chips), ceramic materials, or resin materials.

[0245] The surfaces of the substrate and the material to be joined can be ground as needed.

[0246] When the material is metallic, grinding methods include wheel grinding, fine grinding, polishing, tumbling, and electrolytic grinding. The abrasives and grinding media used in grinding can be made from well-known materials. Examples of abrasive materials include diamond, alumina, silicon carbide, and cubic boron nitride.

[0247] When the material is a semiconductor, chemical mechanical polishing (CMP) is used. Examples of abrasive particles include inorganic metal oxides such as cerium oxide and silicon dioxide.

[0248] When the material is ceramic or resin, mechanical and chemical grinding can be used as an example.

[0249] The surfaces of the substrate and the material to be joined can be plated as needed.

[0250] The type of metal used for plating can be selected appropriately according to the intended application. Examples include gold plating, silver plating, copper plating, nickel plating, chromium plating, and alloy plating of various metals. When performing alloy plating, the composition of the plating can also be adjusted appropriately according to the intended application.

[0251] As a plating method, known methods can be adopted. For example, dry plating such as physical vapor deposition and chemical vapor deposition, and wet plating such as displacement plating, electroplating, and electroless plating can be listed.

[0252] Specific examples of the substrate include semiconductor substrates such as silicon substrates, metal substrates such as copper substrates, lead frames, metal-bonded ceramic substrates (e.g., Direct Bonded Copper: DBC), semiconductor element mounting substrates such as LED (Light-Emitting Diode) packages, power supply components such as copper strips, metal blocks, and terminals, heat sinks, and water-cooled plates.

[0253] The joining method using the joining member of the present invention involves providing a joining member on a substrate, placing a material to be joined on the opposite side of the substrate of the joining member to obtain a laminate, and joining the substrate and the material to be joined by heating the laminate. However, the joining method using the joining member of the present invention is not limited to the above-described joining method, as long as the purpose of the present invention can be achieved.

[0254] Methods for coating bonding components onto a substrate include screen printing, transfer printing, offset printing, letterpress printing, gravure printing, photogravure printing, stencil printing, soft lithography, inkjet printing, dispensing, comma blade coating, slot coating, die coating, gravure coating, bar coating, spray coating, spin coating, and electrophoretic coating.

[0255] The substrate coated with the bonding components can be dried as needed. The drying conditions can be appropriately set. By drying the substrate before sintering, the flow of the bonding components and the occurrence of voids during sintering can be better suppressed.

[0256] As for the drying conditions, the drying atmosphere can be, for example, an oxygen-free atmosphere, an inactive atmosphere, or a reducing atmosphere. The drying pressure can be at atmospheric pressure or under reduced pressure. The drying temperature is not particularly limited, as long as the composite copper particles contained in the bonding component do not sinter.

[0257] The copper paste and bonding component of the present invention can achieve a sintered body with high bonding strength through heating and sintering alone, and therefore can be applied to pressureless bonding methods. Of course, the copper paste and bonding component of the present invention can also be applied to pressure bonding methods.

[0258] In this application, the term "pressureless bonding method" refers to a method of heating a laminate in which a bonding member is disposed between a substrate and a material to be bonded, with the bonding member and the material to be bonded disposed in the direction of the substrate's own weight, or under an applied load of 0.01 MPa or less.

[0259] In this application, the term "pressure bonding method" refers to a method of heating a laminate in which a bonding member is disposed between a substrate and a material to be bonded, under a load greater than 0.01 MPa.

[0260] The heating atmosphere for the laminated body using the non-pressurized bonding method or the pressurized bonding method can be an oxygen-free atmosphere, an inactive atmosphere, or a reducing atmosphere. However, from the viewpoint of more effectively avoiding the large-scale manufacturing equipment for sintered bodies, an inactive atmosphere is preferred.

[0261] Preheating can be performed before the laminate of the pressureless bonding method is fully sintered. The preheating temperature is preferably 150°C or lower, more preferably 140°C or lower. From the viewpoint of solvent evaporation rate, 130°C or lower is even more preferred. Alternatively, preheating may be omitted by keeping the heating rate applied to the laminate at 10°C / min or lower. Copper particles may or may not sinter during preheating. The preheating conditions can be appropriately set according to the desired bonding characteristics.

[0262] The heating temperature of the laminated body using either pressureless or pressure-bonded bonding is preferably 100°C or higher and 400°C or lower, more preferably 150°C or higher and 300°C or lower. If the sintering temperature is 300°C or lower, it can be said that the bonding member of the present invention can be sintered at a sufficiently low temperature.

[0263] From the viewpoints of ensuring sufficient evaporation of the solvent contained in the bonding component and ensuring sufficient sintering of the composite copper particles contained in the bonding component, the heating time of the laminate in the pressureless bonding method is preferably 1 minute or more and 120 minutes or less. Conversely, the heating time of the laminate in the pressure bonding method is preferably 1 minute or more and 60 minutes or less.

[0264] The bond strength of sintered bodies obtained by pressureless bonding or pressure bonding is measured by the method described in the examples.

[0265] The bonding strength of the sintered body obtained by the pressureless bonding method is preferably 20 MPa or more, more preferably 25 MPa or more, and even more preferably 27 MPa or more. If the sintered body has such bonding strength, it can be determined that the bonding is sufficient, confirming that the bonding member of the present invention is applicable to pressureless bonding pastes. Furthermore, as described, the atmosphere for pressureless bonding is preferably an inactive atmosphere, but the bonding strength of the sintered body obtained by pressureless bonding under other atmospheres (e.g., a reducing atmosphere) can also be determined to be sufficient as long as it is within the above range.

[0266] Furthermore, the bonding strength of the sintered body obtained by the pressure bonding method is preferably 20 MPa or more, more preferably 25 MPa or more, and even more preferably 27 MPa or more. If the sintered body has such bonding strength, it can be determined that it is sufficiently bonded. In addition, it can also be determined that the bonding member of the present invention is applicable to pressure bonding paste.

[0267] <Conductive Materials>

[0268] The composite copper particles of the present invention, or copper paste containing the composite copper particles of the present invention, can be used as conductive materials. For example, the composite copper particles of the present invention can be used directly as conductive materials, or they can be made into copper paste and then used as conductive materials. Specifically, the copper paste can be used as a material for conductive films, electrodes, wiring, etc.

[0269] When the copper paste of the present invention is used as a material for conductive films, electrodes, and wiring, it can be applied to a substrate. Methods for applying the paste include screen printing, transfer printing, offset printing, letterpress printing, gravure printing, photogravure printing, stencil printing, inkjet printing, soft lithography, dispensing, comma blade coating, slot coating, die coating, gravure coating, rod coating, spray coating, spin coating, and electrophoretic coating.

[0270] When the copper paste is used as the conductive material, the concentration of the composite copper particles contained in the copper paste can be appropriately adjusted according to the coating method described above.

[0271] There is no particular limitation on the thickness of the coating layer, but it is preferably 0.1 μm or more and 100 μm or less. In this case, the coating can cover the entire surface of the substrate, or it can be coated in a patterned or textured manner. Depending on the coating method and the intended use, additives may be appropriately included. Various additives mentioned above can be listed as examples.

[0272] Specific examples of the substrate include semiconductor substrates such as silicon substrates, metal substrates such as copper substrates, lead frames, metal-bonded ceramic substrates (e.g., Direct Bonded Copper: DBC), semiconductor element mounting substrates such as LED (Light-Emitting Diode) packages, power supply components such as copper strips, metal blocks, and terminals, heat sinks, water-cooled plates, and glass. Additionally, organic materials such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), acrylic resins such as polypropylene, polycarbonate, and polymethyl methacrylate, vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers, epoxy resins, polyarylates, polysulfones, polyethersulfones, polyimides, fluororesins, phenoxy resins, polyolefin resins, nylon, styrene resins, and ABS resins can be used. Depending on the application, these materials can be appropriately selected as either thin-film flexible substrates or rigid substrates. Furthermore, there are no restrictions on the size of the substrate, and it can be any shape such as disc, card, or sheet. The surface of the substrate does not need to be flat; it can also be a shape with concave or convex surfaces or curves.

[0273] <Conductor>

[0274] The conductor of the present invention contains the aforementioned conductive material. Alternatively, the conductor can be obtained by heating the conductive material. A lower volume resistivity (also referred to herein as "specific resistivity") is preferred for the conductor. For example, the volume resistivity (specific resistivity) is preferably 100 μΩ·cm or less, or 50 μΩ·cm or less. If within such a range, the conductor of the present invention can be used for practical applications (e.g., conductive films, electrodes, wiring). Furthermore, the volume resistivity of the conductor is measured using the method described in the embodiments.

[0275] There are no particular limitations on the heating method. Examples of heating methods include resistance heating, electron beam heating, laser heating, flash heating, plasma heating, dielectric heating, induction heating, and heating using a heat source such as a burner.

[0276] The heating temperature can be adjusted appropriately according to the substrate. For example, when using a semiconductor substrate such as a silicon substrate, a metal substrate such as a copper substrate, polyimide, or glass as the substrate, the heating temperature can be below 300°C. Alternatively, when using PET or PEN as the substrate, the heating temperature can be below 150°C.

[0277] The heating atmosphere can be an oxygen-free atmosphere, an inactive atmosphere, or a reducing atmosphere, but from the viewpoint of more effectively avoiding the large-scale manufacturing equipment, an inactive atmosphere is preferred.

[0278] The heating time being between 1 minute and 60 minutes is sufficient.

[0279] Example

[0280] The present invention has been described in detail with reference to embodiments and comparative examples, but the present invention is not limited thereto.

[0281] (Measurement of the average particle size of copper particles)

[0282] A scanning electron microscope (Hitachi High Technology Co., Ltd.: S4800) with a magnification set to 50,000x was used to photograph copper particles manufactured in the example, and scanning electron microscope images were taken. For 50 primary particle sizes in the scanning electron microscope images, the Feret diameter was measured, and their arithmetic mean was calculated as the average particle size.

[0283] (Thermal decomposition characteristics of polymeric dispersants)

[0284] The thermal decomposition characteristics of the polymeric dispersants used in the embodiments and comparative examples of this application were measured using a thermogravimetric differential thermal analysis apparatus (Rigaku Corporation: TG-DTA8122) under the conditions shown below. The mass reduction rate was calculated based on the mass difference between 30°C and 250°C.

[0285] ○ Measurement conditions

[0286] Atmosphere being measured:

[0287] Atmosphere flow rate: 100 mL / min

[0288] Measurement temperature range: 25℃~1000℃

[0289] Heating rate: 10℃ / min

[0290] (Measurement of weight-average molecular weight of polymeric dispersants)

[0291] The weight-average molecular weight of the polymeric dispersants used in the examples and comparative examples of this application was measured using gel permeation chromatography (Tosoh Corporation: HLC-8420GPC) under the conditions shown below. The control of the apparatus, data collection, calculation, and report generation were performed using the dedicated software EcoSEC Elite.

[0292] ○ Measurement conditions

[0293] Sample concentration: 1 mg / mL (Dissolve 5 mg of polymeric dispersant in 5 mL of tetrahydrofuran, filter using a membrane filter, and adjust to the concentration stated above.)

[0294] Sample injection volume: 10 μL

[0295] Chromatographic column: TSKgel SuperHZM-M (manufactured by Tosoh Corporation, substrate: styrene-divinylbenzene, particle size: 3μm and 5μm, column size: inner diameter 4.6mm × 15cm × 2 columns)

[0296] Column temperature: 40℃

[0297] Detector: Differential refractive index meter (RI detector)

[0298] Solvent: Tetrahydrofuran (THF)

[0299] Flow rate: 0.35 mL / min

[0300] The analytical results of the above-mentioned polymeric dispersants are shown in Table 1. The acid value and amine value of the polymeric dispersants are also listed. Furthermore, the effective component of all polymeric dispersants is 100%.

[0301] Table 1

[0302]

[0303] (Manufacturing Example 1)

[0304] A 10L four-necked glass flask was placed in an oil bath. 2L of 1-propanol (manufactured by Kishida Chemical Co., Ltd.), 637.6g of copper oxide (manufactured by Nisshin Chemical Co., Ltd.: N-300), 96.0g of acetic acid (manufactured by Fujifilm and Wako Pure Chemical Co., Ltd.), and 82.7g of decanoic acid (manufactured by Fujifilm and Wako Pure Chemical Co., Ltd.) were added as solvents. The mixture was stirred at 250 rpm at room temperature. This constant stirring speed was maintained in subsequent steps.

[0305] In addition, 127.0g of 2-aminoethanol (manufactured by Tokyo Chemical Industry Co., Ltd.) was added within 10 minutes, and stirring was continued to prepare a mixture containing copper compounds.

[0306] The copper compound-containing mixture was heated to 50°C in an oil bath. 80g of 60% hydrazine hydrate (manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a reducing agent was added dropwise over 3 minutes and 45 seconds, followed by stirring for 40 minutes. Next, the process of adding 80g of 60% hydrazine hydrate dropwise over 3 minutes and 45 seconds and stirring for 15 minutes was repeated three times (i.e., a total of 240g of 60% hydrazine hydrate was added in this process). Here, 680g of 60% hydrazine hydrate was added dropwise over 30 minutes. In this process, the total amount of reducing agent added was 1000g, and the addition time was 130 minutes. Furthermore, the oil bath temperature was set to 50°C during the addition of the reducing agent.

[0307] After adding the full amount of reducing agent, the mixture is heated to 90°C and stirred for 2 hours to obtain a dispersion containing copper particles.

[0308] The dispersion containing copper particles was stirred and naturally cooled to below 50°C. After standing for 30 minutes, 30g of solid components were weighed and recovered through solid-liquid separation.

[0309] As a cleaning step, the solid component and 75 mL of 2-propanol (Wako Pure Chemical Industries, Ltd.) were stirred in a mixer (Defoaming Rentaro AR-250, manufactured by Shin-Gei Corporation) at 2000 rpm for 10 minutes. Afterwards, the solid component was obtained by solid-liquid separation using a centrifuge (Beckman Coulter Allegra X-30R) at 400 G for 5 minutes.

[0310] The above cleaning process was repeated to obtain the carboxylic acid-coated copper particles of Manufacturing Example 1. The average particle size of the carboxylic acid-coated copper particles of Manufacturing Example 1 was 297 nm.

[0311] (Example 1)

[0312] A 75 mL treatment solution was prepared by mixing octanoic acid (manufactured by Fujifilm and Wako Pure Chemical Industries, Ltd.), a polymeric dispersant (BYK-LP C 24365), and 2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.). Here, in the treatment solution, octanoic acid was 6% by mass and BYK-LPC 24365 was 2% by mass.

[0313] The carboxylic acid-coated copper particles obtained in Manufacturing Example 1 were mixed with the treatment liquid and stirred at 2000 rpm for 10 minutes using a mixer (Defoaming Rentaro AR-250, manufactured by Shinki Corporation).

[0314] Subsequently, a centrifuge was used to separate the solid and liquid components for 5 minutes with a centrifugal force of 400G, and the solid components were recovered.

[0315] The recovered solid components were allowed to stand in a desiccator, and the pressure inside the desiccator was reduced using a vacuum pump (ULVAC G-20DA). The desiccator was then subjected to vacuum drying at 1.3 Pa and 25°C for 300 minutes to obtain the composite copper particles of Example 1.

[0316] (Example 2)

[0317] Except for changing the octanoic acid in Example 1 from 6% by mass to 12% by mass and the BYK-LP C 24365 from 2% by mass to 4% by mass, the composite copper particles of Example 2 were obtained in the same manner as in Example 1.

[0318] (Example 3)

[0319] Except for changing BYK-LP C 24365 in Example 1 from 2% by mass to 0.5% by mass, the composite copper particles of Example 3 were obtained in the same manner as in Example 1.

[0320] (Example 4)

[0321] Except for replacing octanoic acid (8 carbons) in Example 1 with decanoic acid (10 carbons), the composite copper particles of Example 4 were obtained in the same manner as in Example 1.

[0322] (Comparative Example 1)

[0323] Except for the absence of BYK-LP C 24365 as in Example 1, the copper particles of Comparative Example 1 were obtained in the same manner as in Example 1.

[0324] (Comparative Example 2)

[0325] Except for the absence of octanoic acid as in Example 1, the copper particles of Comparative Example 2 were obtained in the same manner as in Example 1.

[0326] (Comparative Example 3)

[0327] Except for changing BYK-LP C 24365 in Example 1 to BYK-LP C 22124, the copper particles of Comparative Example 3 were obtained in the same manner as in Example 1.

[0328] (Comparative Example 4)

[0329] Except for changing BYK-LP C 24365 in Example 1 to BYK-LP C 22146, the copper particles of Comparative Example 4 were obtained in the same manner as in Example 1.

[0330] (Comparative Example 5)

[0331] Except for changing BYK-LP C 24365 in Example 1 to BYK-LP C 22435, the copper particles of Comparative Example 5 were obtained in the same manner as in Example 1.

[0332] (Comparative Example 6)

[0333] Except for changing the octanoic acid in Example 1 from 6% by mass to 30% by mass and the BYK-LP C 24365 from 2% by mass to 10% by mass, the copper particles of Comparative Example 6 were obtained in the same manner as in Example 1.

[0334] (Comparative Example 7)

[0335] Except for changing the octanoic acid in Example 1 from 6% by mass to 0.6% by mass and the BYK-LP C 24365 from 2% by mass to 0.2% by mass, the copper particles of Comparative Example 7 were obtained in the same manner as in Example 1.

[0336] (Manufacturing Example 2)

[0337] A 10L glass four-necked flask was placed in an oil bath, and 1L of ethyl carbitol (manufactured by Kishida Chemical Co., Ltd.), 159.1g of copper oxide (manufactured by Nisshin Chemical Co., Ltd.), and 13.9g of hexanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) were added as solvents. The mixture was stirred at 200 rpm at room temperature to prepare a mixture containing copper compounds.

[0338] The mixture containing the copper compound is heated to 90°C. At the stage of reaching 90°C, 200g of hydrazine hydrate (Wako Pure Chemical Industries Co., Ltd.) as a reducing agent is added to the mixture within 30 seconds.

[0339] After adding the reducing agent, the mixture was stirred at 90°C for 20 minutes to obtain a dispersion containing copper particles.

[0340] The dispersion containing copper particles was naturally cooled to below 50°C and allowed to stand for 30 minutes. Then, 30g of the solid component was weighed and recovered through solid-liquid separation.

[0341] As a cleaning step, the solid component and 75 mL of 2-propanol (Wako Pure Chemical Industries, Ltd.) were stirred in a mixer (Defoaming Rentaro AR-250, manufactured by Shin-Gei Corporation) at 2000 rpm for 10 minutes. Afterwards, the solid component was obtained by solid-liquid separation using a centrifuge (Beckman Coulter Allegra X-30R) at 400 G for 5 minutes.

[0342] The above cleaning process was repeated to obtain the carboxylic acid-coated copper particles of Manufacturing Example 2. The average particle size of the carboxylic acid-coated copper particles of Manufacturing Example 2 was 80 nm.

[0343] (Comparative Example 8)

[0344] Unlike Example 1, the copper particles of Comparative Example 8 were obtained in the same manner as in Example 1, except that the copper particles of Comparative Example 8 were obtained using the carboxylic acid-coated copper particles obtained in Manufacturing Example 2.

[0345] (Measurement of composite copper particles and the crystal state of copper particles before and after atmospheric exposure)

[0346] Using an X-ray diffraction (XRD) apparatus (Rigaku Corporation: SmartLab SE), the X-ray diffraction patterns of the composite copper particles of Examples 1 to 4 and the copper particles of Comparative Examples 1 to 8 before and after atmospheric exposure were measured under the following conditions. The oxidation state before and after atmospheric exposure was confirmed based on the obtained diffraction patterns. The apparatus control, data collection, calculation, and report generation were performed using dedicated software, SmartLab Studio II.

[0347] Figure 1 The image shows X-ray diffraction patterns of the composite copper particles of Example 1 before and after atmospheric exposure. According to... Figure 1 Both before and after atmospheric exposure, only peaks from metallic copper can be observed. Here, the Cu(111) surface is confirmed near 2θ = 43.3°, and the Cu(200) surface is confirmed near 2θ = 50.4°.

[0348] ○ Measurement conditions

[0349] X-ray tube: CuKα

[0350] Tube voltage: 40kV

[0351] Tube current: 40mA

[0352] Measurement range: 30°~70°

[0353] Step size: 0.01°

[0354] Speed: 5° / min

[0355] (Observations of composite copper particles and lattice fringes of copper particles before and after atmospheric exposure)

[0356] The composite copper particles of Examples 1 to 4 and the copper particles of Comparative Examples 1 to 8 before and after atmospheric exposure were observed using a transmission electron microscope (TEM (Hitachi High Technology Co., Ltd.: H-9000)). The oxidation state of copper was confirmed based on the arrangement of atoms in the crystal (lattice fringes). Here, the lattice spacing of the (111) plane of metallic copper was 2.1 Å (0.21 nm).

[0357] Figure 2 The image shows a TEM image of the composite copper particles of Example 1 before atmospheric exposure. Figure 3 The image shows TEM images of the composite copper particles of Example 1 after atmospheric exposure. In both the TEM images before and after atmospheric exposure, only a lattice spacing of 0.21 nm from the (111) plane of metallic copper was observed on the surface of the copper particles; no copper oxidation was observed. Furthermore, regarding the composite copper particles of Example 1, in… Figure 4 The paper also shows its SEM images before atmospheric exposure for reference.

[0358] (Measurement of organic content)

[0359] Using a thermogravimetric differential thermal analysis apparatus (Rigaku Corporation: TG-DTA8122), the mass reduction of the composite copper particles of Examples 1 to 4 and the copper particles of Comparative Examples 1 to 8 was measured under the following conditions. In the obtained spectra, the mass reduction rate in the temperature range from 30°C to 200°C represents the mass of the carboxylic acid, the mass reduction rate in the temperature range from 200°C to 350°C represents the mass of the polymeric dispersant, and the mass reduction rate in the temperature range from 30°C to 350°C represents the mass of the organic components in the treated copper particles.

[0360] Based on these results, the mass of the composite copper particles and the carboxylic acid (octanoic acid or decanoic acid) contained in the copper particles, as well as the ratio of carboxylic acid to polymeric dispersant, are shown in Table 2.

[0361] ○ Measurement conditions

[0362] Measurement atmosphere: Nitrogen (purity: 99.995%)

[0363] Atmosphere flow rate: 500 mL / min

[0364] Measurement temperature range: 30℃~500℃

[0365] Heating rate: 10℃ / min

[0366] Table 2

[0367]

[0368] Table 3

[0369]

[0370] (The preparation of copper paste)

[0371] As part of the overall proportion of the copper paste, the composite copper particles of Examples 1-4 and the copper particles of Comparative Examples 1 and 3-7 were mixed in the following proportions: 92.5% by mass, dipropylene glycol 3.6% by mass, hexylcarbidol 3.6% by mass, and triethanolamine 0.3% by mass. The mixture was then kneaded for 4 minutes at 2000 rpm using a mixer (Defoaming Rentaro AR-250, manufactured by Shinki Co., Ltd.).

[0372] Subsequently, the samples were degassed at 2200 rpm for 2 minutes to obtain copper paste for samples 1-4, 6-9 and 12-13.

[0373] Furthermore, the paste containing copper particles from Comparative Example 8, prepared by the above method, did not reach a coatable viscosity and could not be evaluated (not recorded in the table).

[0374] In the preparation of the copper paste, the paste was mixed in the following proportions as in Example 1: 92.5% by mass of copper particles, 3.75% by mass of dipropylene glycol, and 3.75% by mass of hexylcarbidol. Otherwise, the copper paste of Sample 5 was obtained by the same method.

[0375] In the preparation of the copper paste, the paste was mixed in the following proportions as in Comparative Example 1: 92.5% by mass of copper particles, 3.5% by mass of dipropylene glycol, 3.5% by mass of hexylcarbidol, 0.3% by mass of triethanolamine, and 0.2% by mass of BYK-LP C 24365. Otherwise, the copper paste of Sample 10 was obtained by the same method.

[0376] In the preparation of the copper paste, the paste was mixed in the following proportions as in Comparative Example 2: 92.5% by mass of copper particles, 3.35% by mass of dipropylene glycol, 3.35% by mass of hexylcarbidol, 0.3% by mass of triethanolamine, and 0.5% by mass of octanoic acid. Otherwise, the copper paste of sample 11 was obtained by the same method.

[0377] In addition, in the preparation of the copper paste, the composite copper particles or copper particles are exposed to the atmosphere (temperature 28°C, humidity 60%) for 1 hour. Otherwise, the copper paste is prepared by the same method, and the changes in bonding strength and resistivity caused by atmospheric exposure are confirmed.

[0378] Furthermore, the copper particles in Comparative Example 8, after being exposed to the atmosphere (temperature 28°C, humidity 60%) for 1 hour, exhibited exothermic oxidation and smoke, thus making it impossible to produce a paste (not recorded in the table).

[0379] Table 4

[0380]

[0381] (Preparation of sintered bodies)

[0382] On a substrate with a diameter (ϕ) of 10 mm, a thickness of 5 mm, and a surface roughness (Ra: arithmetic mean roughness) from 0.1 to 0.2 μm, a metal mask with an opening of ϕ 5 mm and a thickness of 0.1 mm is provided, and copper paste obtained according to the above procedure is applied to the opening as a bonding component.

[0383] The metal mask is removed, and a copper sheet (batter copper, alloy number C1100) with a thickness of 5 mm and a surface roughness (Ra: arithmetic mean roughness) ranging from 0.1 μm to 0.2 μm is placed on the coated bonding component area to obtain a laminate. Furthermore, the surface roughness is the average Ra value measured by laser microscopy for three randomly selected test pieces from 100 test pieces.

[0384] The laminate was placed in a fixture with 10.5 mm space on three sides, and nitrogen (99.995% purity) was passed through it at 100 mL / min. The laminate was then placed on a heating plate heated to 200°C and held for 30 minutes. After that, it was allowed to cool naturally to 50°C to obtain a sintered body.

[0385] (Measurement of bond strength)

[0386] The sintered body was placed on a strength testing machine (JSL-1KN, manufactured by Japan Measurement Systems Co., Ltd.), and a shear force was applied from the substrate side at a rate of 1 mm / s in a direction parallel to the bonding surface. The bonding strength was calculated based on the load applied to the substrate and the copper sheet at the moment of peeling.

[0387] (Fabrication of conductive film)

[0388] Copper paste obtained according to the above procedure is applied to a 100 μm thick polyimide film substrate using a coater.

[0389] The substrate coated with copper paste was placed in a tubular furnace (JTEKT Thermal Systems, KTF-035N1).

[0390] Nitrogen (99.995% purity) was flowed through a tubular furnace at a rate of 100 mL / min, and the temperature was increased from 25°C to 150°C at a rate of 5°C / min, and held for 60 minutes. Afterward, the temperature was allowed to cool naturally to 50°C to obtain the conductive film.

[0391] (Measurement of electrical conductivity)

[0392] The surface resistivity of the above conductive film was measured using a low resistivity meter (Loresta-GX MCP-T700, manufactured by Nitto Seiko Analytical Technology Co., Ltd.).

[0393] The thickness of the conductive film was then measured using a film thickness gauge (Mitutoyo Corporation, ID-C112X), and the volume resistivity (specific resistivity) was obtained by multiplying it by the surface resistivity.

[0394] The bonding strength of the sintered body and the volume resistivity of the conductive film, measured by the above method, are shown in Table 5.

[0395] Table 5

[0396]

[0397] Samples 1 to 5 containing the composite copper particles of the present invention exhibit sufficient bonding strength (above 20 MPa) before and after atmospheric exposure. Furthermore, the resistivity of samples 1 to 5 remains at the micrometer level, below 100 μΩ·cm, before and after atmospheric exposure, making them suitable for conductive applications. Moreover, since their resistivity is also below 50 μΩ·cm, they are even more suitable for conductive applications.

[0398] Sample 6, which used copper particles from Comparative Example 1 (copper particles manufactured using a treatment solution without polymeric dispersants), showed a bonding strength of 10.2 MPa after atmospheric exposure, which was not the desired bonding strength.

[0399] In addition, sample 10, which also used copper particles from Comparative Example 1 and added a polymeric dispersant during paste preparation, had a bonding strength of 10.7 MPa after atmospheric exposure, which was not the desired bonding strength.

[0400] This can be understood as meaning that in order to remain suitable for bonding applications after atmospheric exposure, the composite copper particles need to contain a polymeric dispersant. Furthermore, the polymeric dispersant needs to be applied to the copper particles during the manufacturing process, rather than during the paste preparation.

[0401] Using the copper particles of Comparative Example 2 (copper particles manufactured using a treatment solution that does not contain carboxylic acid), the sample 11 in which carboxylic acid (octanoic acid) was added during the preparation of the paste did not obtain sufficient bonding strength, regardless of whether it was before or after exposure to the atmosphere.

[0402] This can be understood as the copper particles in Comparative Example 2, although treated with a polymeric dispersant, have reduced sinterability because the treatment solution does not contain carboxylic acid. Furthermore, sufficient bonding strength cannot be obtained by treating the copper particles solely with a polymeric dispersant; therefore, it is clear that they cannot be used for bonding applications after atmospheric exposure.

[0403] Sample 7, which used copper particles from Comparative Example 3 (copper particles treated with a polymeric dispersant having an acid value of more than 60 mg KOH / g and a mass reduction rate of less than 70%), showed a decrease in bond strength from 7.7 MPa to 0 MPa after atmospheric exposure.

[0404] This can be understood as a polymeric dispersant used to treat the copper particles of Comparative Example 3. Because the mass reduction rate at 250°C is small (specifically, the mass reduction rate = 53.4%), the bonding strength of sample 7 before atmospheric exposure is low.

[0405] Alternatively, it can be understood that the polymeric dispersant used to treat the copper particles in Comparative Example 3 has a low weight-average molecular weight (weight-average molecular weight = 553) and a bonding strength of 0 MPa after atmospheric exposure. Therefore, atmospheric exposure causes the organic components of the treated copper particles to detach, resulting in copper oxidation.

[0406] Sample 8, which used copper particles from Comparative Example 4 (copper particles treated with a polymeric dispersant having an amine value but no acid value and a mass reduction rate of less than 70%), showed a significant decrease in bond strength from 34.0 MPa to 7.4 MPa (a decrease of approximately 78%) after atmospheric exposure. This demonstrates that atmospheric exposure has a very significant impact on performance degradation.

[0407] Sample 9, which used copper particles from Comparative Example 5 (copper particles without acid value and amine value, and with a mass reduction rate of less than 70% for the polymeric dispersant), showed a bonding strength of 10.8 MPa after atmospheric exposure, which was not the desired bonding strength.

[0408] Sample 12, which used copper particles from Comparative Example 6 (copper particles with excessive organic content), had an organic content of 7.16% by mass in the treated copper particles. The bonding strength after atmospheric exposure was 18.6 MPa, which was not the desired bonding strength.

[0409] Sample 13, which used copper particles from Comparative Example 7 (copper particles with insufficient organic content), had a treated copper particle organic content of 0.22% by mass. The bonding strength after atmospheric exposure was significantly reduced to 2.1 MPa.

[0410] Industrial availability

[0411] The composite copper particles of the present invention are suitable for bonding applications (e.g., bonding components) not only before atmospheric exposure but also after atmospheric exposure. Furthermore, due to their low resistivity, they can also be used for conductive applications (e.g., conductive materials). Additionally, bonding components containing the composite copper particles of the present invention can yield sintered bodies with sufficient bonding strength even without pressure bonding. The manufacturing process of the composite copper particles of the present invention is not limited and can be easily manufactured.

Claims

1. A composite copper particle, comprising copper particles and organic components, wherein, The composite copper particles, with an average particle size measured by scanning electron microscopy, have a value of 100 nm or more and 600 nm or less. The organic component comprises at least a carboxylic acid or its salt and a polymeric dispersant, and the content of the organic component is more than 0.3% by mass and less than 6.0% by mass relative to the total composite copper particles. The polymeric dispersant has an acid value of 60 mg KOH / g or higher, and its mass reduction rate in the atmosphere is 70% or higher when heated from 30°C to 250°C at a heating rate of 10°C / min using a thermogravimetric differential thermal analysis device.

2. The composite copper particles according to claim 1, wherein, The polymeric dispersant, as measured by a thermogravimetric differential thermal analysis device, has an exothermic peak temperature below 300°C.

3. The composite copper particles according to claim 1 or claim 2, wherein, The carboxylic acid or its salt has 2 or more but less than 20 carbon atoms.

4. The composite copper particles according to claim 1 or claim 2, wherein, The organic component, as the mass ratio of the carboxylic acid or its salt to the polymeric dispersant, has a value of 1.0 or more and 12.0 or less.

5. The composite copper particles according to claim 1 or claim 2, wherein, The carboxylic acid or its salt is coated on the surface of the copper particles.

6. A copper paste comprising the composite copper particles of claim 1 and a paste solvent.

7. A joining component comprising composite copper particles or copper paste, wherein, The composite copper particles are those described in claim 1. The copper paste contains the composite copper particles as described in claim 1 and a solvent for the paste.

8. A conductive material, comprising composite copper particles or copper paste, wherein, The composite copper particles are those described in claim 1. The copper paste contains the composite copper particles as described in claim 1 and a solvent for the paste.

9. A sintered body comprising the joining component of claim 7 as a raw material.

10. A conductor comprising the conductive material of claim 8.

11. A method for manufacturing composite copper particles, wherein, The process includes mixing copper particles coated with carboxylic acid, carboxylic acid or its salt, a polymeric dispersant, and a solvent.

12. The method for manufacturing composite copper particles according to claim 11, wherein, The process includes mixing carboxylic acid-coated copper particles with a treatment liquid containing carboxylic acid or its salt, a polymeric dispersant, and a solvent.

13. The method for manufacturing composite copper particles according to claim 11 or claim 12, wherein, The process includes mixing carboxylic acid-coated copper particles with a treatment liquid containing carboxylic acid or its salt, a polymeric dispersant and a solvent, and then drying the mixture.

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