Copper paste for bonding

Abstract

The present invention addresses the problem of providing a copper paste for bonding, which has excellent low-temperature sinterability and excellent bonding strength with respect to an object to be bonded. This copper paste for bonding, which solves the problem, contains a solvent, an additive, and a copper powder. The solvent has a boiling point of 100°C to 300°C inclusive. The additive contains an amine-based organic compound that has a mass average molecular weight of 1,000 or less. The copper powder has a number average particle diameter of 30 nm to 180 nm inclusive as calculated from a circle equivalent diameter, and is coated with a surface coating material with which an organic material that satisfies specific conditions (1) and (2) is detected when organic materials present on the surface of the copper powder are detected by gas chromatography mass spectrometry. The distance between the Hansen solubility parameter of the copper powder coated with a surface coating material and the Hansen solubility parameter of the amine-based organic compound is 7 or less, and the distance between the Hansen solubility parameter of the copper powder coated with the surface coating material and the Hansen solubility parameter of the solvent is 7.1 or less.

Description

Copper paste for bonding 【0001】 This invention relates to a copper paste for bonding. 【0002】 Copper powder is used as a bonding material to join materials together due to its excellent conductivity and heat transfer properties. For example, copper powder is used as a material for bonding copper paste to join materials in electronic components. In recent years, with the miniaturization and increased capacity of electronic components, the copper powder used in the above-mentioned bonding copper paste is required to be finer. Unlike ordinary particles of submicron size or larger, metal nanoparticles with a particle size of submicron or less have a lower firing temperature, and their application to low-temperature firing pastes and other applications is being considered. 【0003】 Metal powders that sinter at low temperatures have the advantage of not only requiring less thermal load during sintering and less residual stress during cooling, but also being able to exist stably after sintering without melting down to the bulk metal melting point. For low-temperature sintering of copper powder, as with other metal powders, it is effective to increase the surface energy by making the particles finer. However, finer particles are more susceptible to oxidation, and surface oxidation worsens sinterability. Therefore, an oxide-resistant film (antioxidant film) is necessary on the surface of the copper powder, and furthermore, this oxide-resistant film itself must decompose at low temperatures so as not to hinder sintering. Low-temperature sintering of copper powder requires two things: fine particles and an oxide-resistant film that does not inhibit low-temperature sintering. 【0004】 Furthermore, several techniques have been reported regarding low-temperature sinterability and bonding strength with the materials to be joined using copper paste for bonding. 【0005】 For example, Patent Document 1 discloses a copper paste technology aimed at providing a paste with high bonding strength to a workpiece, comprising copper powder and a liquid medium, wherein the liquid medium contains polyethylene glycol, the copper particles constituting the copper powder have an average primary particle size of 0.03 μm or more and 1.0 μm or less, a fatty acid having 6 to 18 carbon atoms is applied to their surface, and the crystallite size of the (111) plane is 50 nm or less, and the mass ratio of copper powder in the copper paste is 50% or more and 99% or less. 【0006】Furthermore, Patent Document 2 discloses a technology for a paste-like metal microparticle composition characterized by mixing (A) heat-sinterable metal microparticles having an average particle size of 0.005 μm to 0.2 μm and whose surface is coated with an organic substance having 3 to 24 carbon atoms and polar groups, (B) a polymer dispersant having acidic and basic functional groups, and (C) a volatile dispersion medium having a boiling point of 70°C to 300°C, followed by aging at -50°C to +25°C for an aging time of the following formula, and then (D) heat-sinterable metal particles having an average particle size greater than 0.2 μm and less than or equal to 10 μm. (Formula) Aging time (h) = -(temperature (°C)) + 48 【0007】 Furthermore, Patent Document 3 discloses a bonding composition that, in bonding of metal nanoparticles, exhibits excellent bonding properties by firing at low temperatures, can produce a bonded body that has high bonding strength even after being stored for a certain period of time, and the resulting bonded body exhibits excellent heat resistance when maintained for a long period of time in an environment of 250°C. The composition contains copper nanoparticles A, monocarboxylic acid B, and organic solvent C, wherein the monocarboxylic acid B has 5 to 12 carbon atoms, and the monocarboxylic acid B has one or more functional groups or bonds selected from the group consisting of hydroxyl groups, ketotic carbonyl groups, and ether bonds. 【0008】 Japanese Patent Publication No. 2020-053404, Japanese Patent Publication No. 2014-111800, International Publication No. 2024 / 111095, Japanese Patent Publication No. 2024-084994 【0009】 Copper pastes used for joining require excellent low-temperature sinterability and bonding strength with the objects to be joined. However, the technologies disclosed in Patent Documents 1 to 3 had room for improvement in terms of low-temperature sinterability and bonding strength. In other words, conventional copper pastes used for joining require further improvement in terms of low-temperature sinterability and bonding strength. 【0010】 Therefore, the present invention aims to provide a copper paste for joining that exhibits excellent low-temperature sinterability and bonding strength with the objects to be joined. 【0011】According to an aspect of the present invention, there is provided a copper paste for bonding, which contains a solvent, an additive, and copper powder. The additive contains an amine-based organic compound having a mass average molecular weight of 1000 or less. The solvent has a boiling point of 100°C or higher and 300°C or lower. The copper powder has a number average particle size calculated from the equivalent circle diameter of 30 nm or more and 180 nm or less, and the surface is coated with a surface coating containing an organic substance that satisfies the following conditions (1) and (2). The distance between the Hansen solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the amine-based organic compound is 7 or less, and the distance between the Hansen solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the solvent is 7.1 or less. Condition (1) When the organic substance present on the surface of the copper powder is detected by gas chromatography-mass spectrometry, H(−O−CH ２ −CH ２ ). ｎ −OH (where n is an integer of 1 or more and 4 or less), HOOC−CH ２ (−O−CH ２ −CH ２ ). ｍ −OH (where m is an integer of 1 or more and 3 or less), HOOC−CH ２ (−O−CH ２ −CH ２ ). ｌ −O−CH ２ −COOH (where l is 1 or 2), H(−C ３ H ６ O). ｓ −OH (where s is an integer of 1 or more and 4 or less), HOOC−CH(CH ３ )(−C ３ H ６ O). ｔ −OH (where t is an integer of 1 or more and 3 or less), HOOC−CH(CH ３ )(−C ３ H ６ O). ｕ −O−CH(CH ３One or more substances selected from the group consisting of )-COOH (where u is 1 or 2) are detected. Condition (2) When organic matter present on the surface of copper powder is detected by liquid chromatography-mass spectrometry, it is a chain-like organic substance with a molecular weight of 210 to 1000, and each of the ends of the chain-like organic substance has a functional group that can coordinate to copper ions, such as a carboxyl group (-COOH), a hydroxyl group (-OH), or an amino group (-NH). ２ ), aldehyde group (-CHO), nitro group (-NO ２ ), thiol group (-SH), sulfo group (-SO ３ H), phosphate group (-PO ４ H ２ A chain-like organic substance having one or more selected from the group consisting of a cyanide group (-CN), a chloro group (-Cl), a bromo group (-Br), and an iodine group (-I) is detected. 【0012】 Furthermore, the copper paste for joining according to the embodiment of the present invention may have a composition in which the solvent is 0.1% to 19% by mass, the additive is 0.5% to 19% by mass, and the copper powder is 80% to 92% by mass relative to the copper paste for joining. Furthermore, the copper powder may have an average flatness of 0.2 to 0.4. Furthermore, the copper powder may have a coefficient of variation (CV value), which is an indicator of particle size distribution, of 50% or less. Furthermore, the amine-based organic compound may have an amino group and a hydroxyl group. Furthermore, the amine-based organic compound may not have an acidic functional group. Furthermore, the solvent may have a boiling point of 150°C to 200°C. Furthermore, the solvent may contain a monohydric alcohol. Furthermore, the copper paste for joining may contain a metal stearate salt or calcium phosphate. Furthermore, in measuring the thermal shrinkage rate based on the thickness of the compact at 25°C when a compact obtained by pressure molding copper powder is heated from 25°C in an inert atmosphere, the configuration may be such that the temperature at which the thermal shrinkage rate becomes 1% is 230°C or lower. Also, in measuring the thermal shrinkage rate based on the thickness of the compact at 25°C when a compact obtained by pressure molding copper powder is heated from 25°C in both an inert and a reducing atmosphere, the configuration may be such that the temperature difference between the temperature at which the thermal shrinkage rate becomes 3% in an inert atmosphere and the temperature at which the thermal shrinkage rate becomes 3% in a reducing atmosphere is less than 10°C. 【0013】 The copper paste for joining according to an aspect of the present invention exhibits excellent bonding strength with the objects to be joined. 【0014】 This is an explanatory diagram of the process used to evaluate the bonding strength in the examples. This is a cross-sectional SEM image of the sintered film using the bonding copper paste of Example 3. This is a cross-sectional SEM image of the sintered film using the bonding copper paste of Comparative Example 1. This is a cross-sectional SEM image of the sintered film using the bonding copper paste of Comparative Example 2. This is a graph showing the results of the bonding strength test of Example 3. This is a graph showing the results of the bonding strength test of Comparative Example 1. This is a graph showing the results of the bonding strength test of Comparative Example 2. This is a surface photograph of the bonding copper paste after sintering of Example 34. This is a surface photograph of the bonding copper paste after sintering of Example 39. This is a surface photograph of the bonding copper paste after sintering of Comparative Example 4. 【0015】 The following describes specific embodiments of the present invention in detail. However, the present invention is not limited to the embodiments described below, and can be modified as appropriate without altering the essence of the invention. Furthermore, in the following description, "A to B" means "A or greater and B or less." 【0016】 [Copper Paste for Bonding] The copper paste for bonding in this embodiment (sometimes referred to as copper paste) contains a solvent, an additive, and copper powder. The components are described below. 【0017】 (Copper powder) The copper paste for bonding in this embodiment contains specific copper powder. The copper powder will be described below. 【0018】(Particle size and particle size distribution of copper powder) In this specification, the particle size of copper powder is calculated by the equivalent diameter of a circle. The number-average particle size (sometimes abbreviated as number-average particle size or particle size) calculated from the equivalent diameter of a circle of copper powder may be 30 nm to 180 nm, 30 nm to 100 nm, or 30 nm to 80 nm. For example, the number-average particle size of copper powder can be within the range of any two of the values ​​of 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm and the values ​​shown in the examples. When the number-average particle size of copper powder is within the above range, the bonding strength of the bonding copper paste can be improved. When the number-average particle size of copper powder is 195 nm or more (see Comparative Examples 1 and 2), the bonding strength of the bonding copper paste decreases. The method for measuring (calculating) the equivalent diameter of a circle in copper powder is the method described in the Examples section. 【0019】 Furthermore, while the particle size distribution of the copper powder is not particularly limited, it is preferable that the coefficient of variation (CV value) is 50% or less, and may be 40% or less, or 35% or less. When the particle size distribution of the copper powder is within the above range, the rheological properties of the paste become easier to control, and the printability and leveling properties during paste application are improved. In addition, the sintering of metal particles during bonding can be made uniform. The lower limit of the coefficient of variation (CV value) is not particularly limited, but may be, for example, 10% or more, or 20% or more. Note that the number average particle size and particle size distribution of the copper powder in this embodiment are values ​​measured by the method described in the example. The number average particle size and particle size distribution of the copper powder can be controlled by known methods, for example, by the manufacturing method described in International Publication No. 2023 / 163083. 【0020】 (Surface coating of copper powder) The surface of the copper powder is coated with organic matter (surface coating). The surface of the copper powder is coated with a surface coating containing organic matter that satisfies the following conditions (1) and (2). When the surface of the copper powder is coated with a surface coating containing organic matter that satisfies the following conditions (1) and (2), the bonding strength of the copper paste for bonding can be improved. [Condition (1)] When organic matter present on the surface of the copper powder is detected by gas chromatography-mass spectrometry, H(-O-CH) ２ -CH ２) ｎ -OH (where n is an integer between 1 and 4), HOOC-CH ２ (-O-CH ２ -CH ２ ) ｍ -OH (where m is an integer between 1 and 3), HOOC-CH ２ (-O-CH ２ -CH ２ ) ｌ -O-CH ２ -COOH (where l is 1 or 2), H (-C ３ H ６ O) ｓ -OH (where s is an integer between 1 and 4), HOOC-CH(CH ３ ) (-C ３ H ６ O) ｔ -OH (where t is an integer between 1 and 3), HOOC-CH(CH ３ ) (-C ３ H ６ O) ｕ -O-CH(CH ３ One or more selected from the group consisting of )-COOH (where u is 1 or 2) is detected. [Condition (2)] When organic matter present on the surface of copper powder is detected by liquid chromatography-mass spectrometry, it is a chain-like organic substance with a molecular weight of 210 to 1000, and each end of the chain-like organic substance has a functional group that can coordinate to copper ions, such as a carboxyl group (-COOH), a hydroxyl group (-OH), or an amino group (-NH). ２ ), aldehyde group (-CHO), nitro group (-NO ２ ), thiol group (-SH), sulfo group (-SO ３ H), phosphate group (-PO ４ H ２ A chain-like organic substance having one or more selected from the group consisting of a cyanide group (-CN), a chloro group (-Cl), a bromo group (-Br), and an iodine group (-I) is detected. 【0021】(Gas chromatograph mass spectrometry) Among the organic substances shown in "Condition (1)" above, it is more preferable that one or more are selected from the group consisting of the organic substances shown in (Chemical Formula 1) to (Chemical Formula 8) below. These organic substances are, for example, organic substances derived from polyol solvents. 【0022】 (Chemical Formula 1) Triethylene glycol (H(-O-CH) ２ -CH ２ ) ３ -OH) (Molecular weight: 150), (Chemical formula 2) Tetraethylene glycol (H(-O-CH) ２ -CH ２ ) ４ -OH) (Molecular weight: 194), (Chemical formula 3) 2-[2-(2-hydroxyethoxy)ethoxy]acetic acid (HOOC-CH ２ (-O-CH ２ -CH ２ ) ２ -OH) (Molecular weight: 164), (Chemical formula 4) 2-[2-[2-(2-hydroxyethoxy)ethoxy]ethoxy]acetic acid (HOOC-CH ２ (-O-CH ２ -CH ２ ) ３ -OH) (Molecular weight: 208), (Chemical formula 5) Ethylenedioxydiacetic acid (HOOC-CH ２ -O-CH ２ -CH ２ -O-CH ２ -COOH) (Molecular weight: 178), (Chemical formula 6) [oxybis(ethyleneoxy)]diacetic acid (HOOC-CH ２ (-O-CH ２ -CH ２ ) ２ -O-CH ２ -COOH) (Molecular weight: 222), (Chemical formula 7) Tripropylene glycol (H(-C) ３ H ６ O) ３ -OH) (Molecular weight: 192, either atactic polymer, isotactic polymer, or syndiotactic polymer), (Chemical formula 8) Tetrapropylene glycol (H(-C) ３ H ６ O) ４-(OH) (Molecular weight: 250, any of atactic polymer, isotactic polymer, syndiotactic polymer) 【0023】 Since GC / MS is a measurement method for gasifying and detecting organic substances, it can be said that the specific organic substances detected by the GC / MS are organic substances with relatively small molecular weights and easy to gasify. In addition, the method for detecting the organic substances by GC / MS in this embodiment is the method described in the examples. 【0024】 (Liquid chromatography-mass spectrometry) Among the chain-like organic substances shown in the above "condition (2)", those with a molecular weight of 210 or more and 700 or less are more preferable. Further, it is more preferable that the chain-like organic substance has a carboxy group or a hydroxy group at each end of the molecule, and it is more preferable that both ends have a carboxy group or a hydroxy group. 【0025】 Examples of such chain-like organic substances include those shown in the following (Chemical formula 9) to (Chemical formula 15). These organic substances are also preferable because they can be easily purchased. (Chemical formula 9) Dodecanedioic acid (HOOC-(CH ２ ) １０ -COOH) (Molecular weight: 230), (Chemical formula 10) Tetradecanedioic acid (HOOC-(CH ２ ) １２ -COOH) (Molecular weight: 258), (Chemical formula 11) Hexadecanedioic acid (HOOC-(CH ２ ) １４ -COOH) (Molecular weight: 286), (Chemical formula 12) Octadecanedioic acid (HOOC-(CH ２ ) １６ -COOH) (Molecular weight: 314), (Chemical formula 13) Eicosanedioic acid (HOOC-(CH ２ ) １８ -COOH) (Molecular weight: 342), (Chemical formula 14) Poly(ethylene glycol) bis(carboxymethyl) ether (HOOC-CH ２ -(O-CH ２ -CH ２ ) ｎ -O-CH ２-COOH, n=1-4) (average molecular weight 250), (Chemical formula 15) poly(ethylene glycol) bis(carboxymethyl) ether (HOOC-CH ２ - (O-CH ２ -CH ２ ) ｎ -O-CH ２ -COOH, n=9-12) (average molecular weight 600), 【0026】 The copper powder in this embodiment has low-temperature sinterability. Although the mechanism by which the copper powder in this embodiment exhibits low-temperature sinterability has not been fully elucidated, the specific organic substances detected by GC / MS and the specific organic substances detected by LC / MS have a small proportion of functional groups capable of coordinating with copper ions in their long chain molecules. Therefore, even when the copper powder surface is evenly coated with the organic substances, the density of bonds with the copper powder surface via functional groups is low, which may facilitate detachment from the copper powder surface due to heat. 【0027】 Furthermore, the organic matter detected by GC / MS may also be detected by LC / MS, and the organic matter detected by LC / MS may also be detected by GC / MS. The organic matter present on the surface of the copper powder in this embodiment, the organic matter detected by GC / MS, and the organic matter detected by LC / MS may all include other substances such as other organic matter or compounds, without departing from the spirit of the present invention. Such other substances may, for example, be substances derived from polyols used in the polyol process used in copper production. 【0028】Furthermore, in this embodiment, when the copper powder is pressure-molded at 100 MPa to form a compact, and heated in an inert atmosphere from 25°C at a heating rate of 10°C / min, it is preferable that the temperature at which the thermal shrinkage rate becomes 1% is 230°C or lower when the thermal shrinkage rate is measured based on the thickness of the compact at 25°C. The temperature at which the thermal shrinkage rate of the compact becomes 1% is the temperature at which the copper powder begins to shrink in volume due to the sintering phenomenon, and can also be expressed as the temperature at which sintering begins. For example, in the copper powder of this embodiment, the temperature at which the thermal shrinkage rate becomes 1% is within the range of any two of the values ​​of 220°C, 215°C, 210°C, 205°C, 200°C, and 195°C. 【0029】 Furthermore, in this embodiment, when the copper powder is compressed at 100 MPa to form a compact, and heated from 25°C at a heating rate of 10°C / min under both an inert and a reducing atmosphere, the thermal shrinkage rate is measured based on the thickness of the compact at 25°C. Preferably, the temperature difference between the temperature at which the thermal shrinkage rate becomes 3% under an inert atmosphere and the temperature at which the thermal shrinkage rate becomes 3% under a reducing atmosphere is less than 10°C. In this case, since the sintering behavior does not change significantly between an inert atmosphere and a reducing atmosphere, the constraints on the selection of the firing atmosphere due to the difficulty of sintering the copper powder are relaxed. Moreover, the temperature at which the thermal shrinkage rate of the compact becomes 3% is the temperature at which volume shrinkage due to the sintering phenomenon of the copper powder has progressed to a certain extent. This not only serves as an indicator of the sinterability of the copper powder, but also allows for the estimation of the presence or absence of an oxide film that inhibits sintering by comparing the results under both an inert and a reducing atmosphere. In other words, a temperature difference of less than 10°C between the temperatures at which the thermal shrinkage rate of the compacted material is 3% under an inert atmosphere and under a reducing atmosphere means that no oxide film that could inhibit sintering is formed on the surface of the copper powder. For example, in the copper powder of this embodiment, the temperature difference between the temperature at which the thermal shrinkage rate is 3% under an inert atmosphere and the temperature at which the thermal shrinkage rate is 3% under a reducing atmosphere can be, for example, 8°C or less, 6°C or less, or 5°C or less. 【0030】Specifically, if the temperature at which the thermal shrinkage rate of a compacted material reaches 3% under a reducing atmosphere is 10°C or more lower than the temperature at which it reaches 3% under an inert atmosphere, it is thought that the surface of the copper powder used for thermal shrinkage measurement was covered with a thin oxide film, and the oxide film was reduced by the reducing gas, making it easier to sinter (sintering was inhibited by the oxide film under an inert atmosphere). On the other hand, if the thermal shrinkage rate is measured under a reducing atmosphere under conditions where there is an even greater amount of oxide on the surface of the copper powder used for thermomechanical analysis, a large amount of water vapor is generated by reduction, and the expansion of the compacted material due to water vapor exceeds the amount of shrinkage due to sintering of the copper powder, and a tendency for the thermal shrinkage behavior in the thermomechanical analysis profile to shift to the higher temperature side is observed. This corresponds to the case where the temperature at which the thermal shrinkage rate of a compacted material reaches 3% under a reducing atmosphere is 10°C or more higher than the temperature at which it reaches 3% under an inert atmosphere. 【0031】 Although the mechanism by which copper powder has the effect of preventing the formation of oxide films as described above has not been fully elucidated, the specific organic substances detected by GC / MS and the specific organic substances detected by LC / MS are combinations of organic substances with different molecular lengths, and since they can efficiently and evenly coat the surface of the copper powder, it is possible that they have a high function as an antioxidant film. 【0032】 (Shape of copper powder) The shape of the copper powder is not particularly limited, but for example, it is preferable that the average flatness is 0.2 or more and 0.4 or less. The flatness of the copper powder was calculated by the method described in the examples. A higher flatness than a perfectly spherical shape of copper powder is advantageous for bonding because it increases the number of contact points that one particle can make with other particles. However, if the flatness is 0.4 or more, the particles are elongated, which can easily lead to the formation of voids during filling, and if it is 0.2 or less, the particles are almost perfectly round, resulting in fewer contact points between particles, which can hinder sintering during pressurized heating. 【0033】(Method for producing copper powder) The copper powder described above is not particularly limited, but can be produced, for example, using the polyol method, or by adjusting the reaction conditions as appropriate to have the above properties using the method described in International Publication No. 2023 / 163083. The copper powder can be produced, for example, using the method described in the examples. 【0034】 (Additives) The copper paste for bonding according to this embodiment includes additives. The additives include amine-based organic compounds. Additives containing amine-based organic compounds, for example, act as dispersants to improve the dispersibility of copper powder dispersed in the solvent and maintain the stability of the dispersion state. Furthermore, when the additives include amine-based organic compounds, the bonding strength can be improved. 【0035】 Furthermore, the mass-average molecular weight of the amine-based organic compound is 1000 or less, preferably 500 or less, and more preferably 300 or less. The lower limit of the mass-average molecular weight of the amine-based organic compound is not particularly limited, but may be, for example, 50 or more, or 60 or more. 【0036】 Furthermore, the amine-based organic compound preferably has an amino group, and more preferably has both an amino group and a hydroxyl group. When the amine-based organic compound has both an amino group and a hydroxyl group, the bonding strength can be further improved. The amino group can interact with the organic film on the surface of the copper powder and act as a dispersant for the copper powder. In addition, the hydroxyl group exhibits reducing properties when heated and can play a role in promoting the sintering of the copper powder. 【0037】 Furthermore, amine-based organic compounds do not necessarily have to contain acidic functional groups. Acidic functional groups typically have dissociable protons. Examples of acidic functional groups include carboxyl groups (-COOH) and sulfo groups (-SO). ３ H), sulfate group (-OSO ３ These include H, thiol groups (-SH), etc. If the amine-based organic compound contains an acidic functional group, the copper powder may aggregate. 【0038】Furthermore, amine-based organic compounds may consist of hydrocarbon chains other than amino groups and hydroxyl groups, and some of the carbon atoms in the hydrocarbon chains may be substituted with oxygen. Also, amine-based organic compounds may have two or more hydroxyl groups. The number of carbon atoms in the amine-based organic compound may be, for example, 2 to 70, 2 to 20, or 2 to 10. 【0039】 Examples of amine-based organic compounds include 2-amino-2-ethyl-1,3-propanediol, triethanolamine, DL-2-amino-1-butanol, 2-(methylamino)ethanol, 2-(dimethylamino)ethanol, 1-amino-2-propanol, diethanolamine, 2-aminoethanol, and 2-amino-2-methyl-1-propanol. Among the above amine-based organic compounds, 2-amino-2-ethyl-1,3-propanediol is preferred. 【0040】 Furthermore, for amine-based organic compounds (additives), the distance between the Hansen solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the amine-based organic compound (additive) is 7 or less, and is generally preferable to be smaller. For example, the distance between the Hansen solubility parameter of the amine-based organic compound (additive) and the Hansen solubility parameter of the copper powder coated with the surface coating can be 7.0 or less, 6.0 or less, 5.0 or less, 4.0 or less, 3.2 or less, and the values ​​and ranges shown in the examples. When the distance between the Hansen solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the amine-based organic compound (additive) is 7 or less, the copper powder can be dispersed uniformly, and this also contributes to improving the bonding strength. (Hereinafter, the "Hansen solubility parameter" will be referred to as the "HSP value," and the distance between "Hansen solubility parameters" will be referred to as the "HSP distance.") In this embodiment, the copper paste for bonding can have high bonding strength even if the distance between the solubility parameters is 1 or more, 2 or more, or 3 or more. 【0041】In this specification, the "Hansen solubility parameter (HSP value)" and the "distance between Hansen solubility parameters (HSP distance)," such as the Hansen solubility parameter of the copper powder coated with the surface coating, the Hansen solubility parameter of the amine-based organic compound (additive), the Hansen solubility parameter of the solvent, the distance between the solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the additive, and the distance between the solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the solvent, were calculated as described in the following paragraphs and examples. 【0042】 The Hansen solubility parameter is one of the indicators of a substance's solubility, and it represents solubility as a three-dimensional vector. This three-dimensional vector typically includes a dispersion term (δ ｄ ), polar term (δ ｐ ), hydrogen bond term (δ ｈ ) can be expressed as follows. The closer the Hansen solubility parameter distance (HSP distance), the higher the compatibility can be evaluated. In this specification, the HSP distance can be calculated using the HSP values ​​of substances registered in the database of the Hansen Solubility Parameter in Practice (HSPiP) software. In this invention, for substances registered in the HSPiP version 6 database, those values ​​are used, and for solvents not registered in the database, values ​​estimated from the "Y-MB method" installed in HSPiP version 6 are used. The Y-MB method is a method that uses a neural network algorithm to automatically decompose molecular identifiers such as SMILES (Simplified Molecular Input Line Entry Specification) and InChI (International Chemical Identifier) ​​into atomic groups, and estimates the HSP value from the number of atomic groups. In the case of a mixture of multiple types of substances, the HSP value is calculated by multiplying the HSP value of each individual substance in the mixture (each component of a three-dimensional vector) by its volume ratio in the mixture, and then adding these together. 【0043】Furthermore, Patent Document 4 (Japanese Patent Application Publication No. 2024-084994) discloses a conductive ink or conductive paste comprising metal nanoparticles, water or a hydrophilic solvent having a vapor pressure of 10 hPa or more, and an additive solvent, wherein the distance Ra between the Hansen solubility parameter of the metal nanoparticles and the Hansen solubility parameter of the additive solvent is in the range of 2.5 to 13, and the distance Rb between the Hansen solubility parameter of the water or hydrophilic solvent and the Hansen solubility parameter of the additive solvent is 35 or less. However, Patent Document 4 does not consider bonding strength, nor does it consider the relationship between HSP distance and bonding strength. 【0044】 The amine-based organic compound (additive) is preferably 0.5% to 19% by mass, more preferably 1.0% to 15% by mass, and even more preferably 2.0% to 10% by mass, based on the total amount of the copper paste for bonding. The additive may or may not contain components other than the amine-based organic compound. Furthermore, the additive may contain the amine-based organic compound as its main component, and the amine-based organic compound may constitute 50% or more by mass, 70% or more by mass, 90% or more by mass, or 95% or more by mass of the additive. The amine-based organic compound (additive) can be in the values ​​and ranges shown above and in the examples. 【0045】 The total amount of additives is preferably 0.5% to 19% by mass, more preferably 1.0% to 15% by mass, and even more preferably 2.0% to 10% by mass, based on the total amount of copper paste for bonding. The total content of solvent and additives is preferably 8.0% to 20% by mass, based on the total amount of copper paste for bonding. Furthermore, the total amount of additives can be within the values ​​and ranges shown above and in the examples. 【0046】(Solvent) The copper paste for bonding according to this embodiment contains a solvent. The solvent is an organic solvent. The solvent is a dispersion medium for copper powder. The solvent has a boiling point of 100°C to 300°C, preferably 150°C to 250°C, and more preferably 150°C to 200°C. Including the above solvent can improve bonding strength. The boiling point of the solvent can be the values ​​and ranges shown above and in the examples. 【0047】 Furthermore, the solvent is preferable to have a distance of 7.1 or less between the Hansen solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the solvent, and is generally preferable to have a smaller value. For example, the solvent can have a distance of 7.0 or less, 6.0 or less, and the values ​​and ranges shown in the examples. Note that the solvent is not limited as long as it satisfies the boiling point and HSP distance described above. When the distance between the Hansen solubility parameter of the surface coating and the Hansen solubility parameter of the solvent is within the above range, the bonding strength can be improved. Note that in the copper paste for bonding of this embodiment, the above solubility parameter distance may be 1 or more, 2 or more, 3 or more, or even 3.5 or more, and high bonding strength can be obtained. 【0048】 The solvent can be, for example, an alcohol-based solvent (a solvent having an OH group), an ester-based solvent, etc. As the alcohol-based solvent, glycol-based solvents and monohydric alcohol-based solvents can be used, with glycol-based solvents and monohydric alcohol-based solvents being preferred, and monohydric alcohol-based solvents being preferred. When the solvent is a glycol-based solvent, for example, it exhibits excellent sintering properties due to the reducing power of hydroxyl groups. In addition, the alcohol-based solvent may consist of linear or cyclic hydrocarbons other than the hydroxyl groups, or it may consist of linear hydrocarbons, and some of the carbon atoms in the hydrocarbon chain may be substituted with oxygen. Furthermore, the number of carbon atoms in the solvent may be, for example, 2 to 20 or 2 to 10. 【0049】Specific examples of solvents include alcohol-based solvents such as 1-pentanol and cyclopentanol; and glycol-based solvents such as 1,2-butanediol, propylene glycol, ethylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, 1,2-pentanediol, 1,2-hexanediol, and 2-methyl-2,4-pentanediol. 【0050】 The solvent content is preferably 0.1% to 19% by mass, more preferably 0.5% to 15% by mass, and even more preferably 1% to 10% by mass, relative to the total amount of copper paste for bonding. The solvent content can also be within the values ​​and ranges shown above and in the examples. 【0051】(Other Components) The copper bonding paste of this embodiment may contain other components as needed. For example, the copper bonding paste may contain metal stearate or calcium phosphate as other additives. Copper bonding paste is usually used to bond metal members together, and since it is sandwiched between the metal members, the surface of the sintered copper bonding paste is rarely exposed. However, when bonding a small metal member to a plate-shaped metal member, the surface of the sintered copper bonding paste will be exposed. In such cases, containing metal stearate or calcium phosphate can suppress cracking of the surface of the copper bonding paste after sintering, resulting in a smooth surface. This is thought to be because copper has a high affinity for metal stearate or calcium phosphate, thus suppressing cracking while maintaining bonding strength. Furthermore, the inclusion of metal stearate or calcium phosphate also contributes to improving bonding strength. As metal stearate, magnesium stearate, calcium stearate, zinc stearate, etc. can be used. As calcium phosphate, tricalcium phosphate, monocalcium phosphate, dicalcium phosphate, etc. can be used. The amount of metal stearate or calcium phosphate is preferably 0.5% to 10% by mass, more preferably 1% to 8% by mass, and even more preferably 1% to 7% by mass, relative to the total amount of copper paste for bonding. The content of metal stearate or calcium phosphate can be within the values ​​and ranges shown above and in the examples. Additionally, silane coupling agents, viscosity modifiers, etc., can be used as needed. 【0052】 (Method for manufacturing copper paste for bonding) The method for manufacturing the copper paste for bonding according to this embodiment will now be described. The copper paste for bonding according to this embodiment can be manufactured, for example, by stirring and kneading each of the above components. Stirring and kneading can be done using conventionally known methods, such as a three-roll mill, a ball mill, or a mixer. For the method for manufacturing copper powder, for example, the method described in International Publication No. 2023 / 163083 can be used. 【0053】(Characteristics of the Bonding Copper Paste) The bonding copper paste can be suitably used for joining objects to be joined. By applying pressure and heating, the copper powder in the bonding copper paste is sintered to form a sintered body (sometimes abbreviated as a sintered body). For example, after applying the bonding copper paste to the objects to be joined, applying pressure and heating can form a joined body (sometimes abbreviated as a joined body) in which the sintered body formed by the sintering of copper powder is joined to the objects to be joined. Alternatively, after applying the bonding copper paste between a first object to be joined and a second object to be joined, applying pressure and heating can form a joined body (sometimes abbreviated as a joined body) in which the first object to be joined and the second object to be joined are joined by the sintered body. 【0054】 The pressure applied to the bonding copper paste can be, for example, 1 MPa to 10 MPa. The temperature at which the bonding copper paste is heated can be, for example, 180°C to 300°C. Conventional known devices can be used for pressurizing and heating the bonding copper paste. In the bonding copper paste, the material of the objects to be bonded is not particularly limited, but can be, for example, copper, silicon, silicon carbide, PET resin, etc. 【0055】 The bonding strength of the joint formed by the copper bonding paste (referred to as the bonding strength of the joint) can be, for example, 10 MPa or more. For example, the bonding strength of the joint can be 10 MPa or more, 20 MPa or more, 30 MPa or more, 40 MPa or more, or 50 MPa or more, as shown in the examples. In this specification, the bonding strength of the joint is the value measured in the bonding strength test shown in the examples. 【0056】 The copper paste for bonding has low-temperature sinterability. For example, the sintering start temperature of the copper paste for bonding can be set to, for example, 180°C or higher, preferably 200°C or higher. 【0057】 In the copper paste for bonding, the viscosity when rotated at 1 rpm can be between 1 mPas and 1000 mPas. In the bonded body and sintered body produced by the copper paste for bonding, the thermal conductivity can be 100 W / (m·K) or higher. 【0058】 As described above, the copper paste for joining according to this embodiment is a copper paste for joining that comprises a solvent, an additive, and copper powder, wherein the additive comprises an amine-based organic compound with a mass-average molecular weight of 1000 or less, the solvent has a boiling point of 100°C or more and 300°C or less, the copper powder has a number-average particle size calculated from the equivalent circle diameter of 30 nm or more and 180 nm or less, and the surface is coated with a surface coating containing organic matter that satisfies the following conditions (1) and (2): the distance between the Hansen solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the amine-based organic compound (additive) is 7 or less, and the distance between the Hansen solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the solvent is 7.1 or less. [Condition (1)] When organic matter present on the surface of the copper powder is detected by gas chromatography-mass spectrometry, H(-O-CH ２ -CH ２ ) ｎ -OH (where n is an integer between 1 and 4), HOOC-CH ２ (-O-CH ２ -CH ２ ) ｍ -OH (where m is an integer between 1 and 3), HOOC-CH ２ (-O-CH ２ -CH ２ ) ｌ -O-CH ２ -COOH (where l is 1 or 2), H (-C ３ H ６ O) ｓ -OH (where s is an integer between 1 and 4), HOOC-CH(CH ３ ) (-C ３ H ６ O) ｔ -OH (where t is an integer between 1 and 3), HOOC-CH(CH ３ ) (-C ３ H ６ O) ｕ -O-CH(CH ３One or more selected from the group consisting of )-COOH (where u is 1 or 2) is detected. [Condition (2)] When organic matter present on the surface of copper powder is detected by liquid chromatography-mass spectrometry, it is a chain-like organic substance with a molecular weight of 210 to 1000, and each end of the chain-like organic substance has a functional group that can coordinate to copper ions, such as a carboxyl group (-COOH), a hydroxyl group (-OH), or an amino group (-NH). ２ ), aldehyde group (-CHO), nitro group (-NO ２ ), thiol group (-SH), sulfo group (-SO ３ H), phosphate group (-PO ４ H ２ A chain-like organic substance having one selected from the group consisting of a cyanide group (-CN), a chloro group (-Cl), a bromo group (-Br), and an iodine group (-I) is detected. 【0059】 The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited in any way by the examples. 【0060】 The methods for measuring the physical properties in the examples and comparative examples are as follows: (1) Average particle size, particle size distribution, and flatness The number-average particle size and particle size distribution of copper powder were determined by image analysis of the particle shape using an SEM (scanning electron microscope). SEM images with a magnification of 700 to 1200 particles per field of view were used, and the equivalent circle diameter and number-average particle size of the copper powder were calculated using MIPAR image analysis software manufactured by Lightstone. In addition, the flatness of each copper powder particle "(major axis - minor axis) / major axis" was determined by analyzing the SEM image of the copper powder, and the average value of the flatness was calculated by averaging the multiple values ​​obtained. 【0061】(2) Analysis of organic matter on the copper powder surface For the organic components on the copper powder surface, 10 mg of copper powder was immersed in 70 μl of a 1 wt% tetramethylammonium hydroxide-methanol solution to extract the organic matter from the surface. After drying at 50°C for 10 minutes, the organic components were gasified in a pyrolysis furnace (Frontier Labs PY-3030D) at 300°C for 30 seconds, and detected in the range of m / z = 33 to 550 by GC / MS (Shimadzu Corporation GC section: GC-2010Plus, MS section: QP-2010Ultra). <Gas chromatograph conditions> Column: Frontier Labs UltraALLOY ＋ -5 30m x 0.25mm inner diameter Carrier gas: Helium Temperature program: 50-350°C, 10°C / min Injection method: Split (split ratio 20:1) Inlet temperature: 300°C 【0062】 In parallel, 0.5 g of copper powder was immersed in 10 ml of 0.5 N sodium hydroxide aqueous solution to extract organic matter from the surface. The supernatant after centrifugation was used as an evaluation sample and detected by LC / MS (Agilent Technologies, LC unit: Agilent 1290 Infinity 2, MS unit: Agilent 6530). Qualitative analysis of organic components was performed based on the data obtained. <Liquid Chromatography Conditions> Column: Waters ACQUITY UPLC BEH C18 1.7 μm × 150 mm Column temperature: 40°C Flow rate: 0.2 ml / min Injection volume: 5 μl Eluent: Pure water / acetonitrile mixture: Between 0 and 22.5 min…99.5 / 0.5, Between 22.51 and 30 min…0 / 100, Between 30.01 and 35 min…99.5 / 0.5 <Mass Spectrometry Conditions (for LC)> Polarity: Positive Measured mass range: m / z = 70 to 1700 Ionization method: ESI Gas temperature, flow rate: 280°C, 12 L / min Nebulizer pressure: 55 psi Sheath gas temperature, flow rate: 350°C, 12 L / min Fragmenter: 100 V Scan speed: 3 spec / sec 【0063】(3) Measurement of Thermal Shrinkage Behavior (TMA) The thermal shrinkage behavior of the obtained copper powder was measured using thermomechanical analysis (TMA) (TMA4000SA, BRUKER Corporation). Approximately 0.3 g of copper powder was weighed and filled into a mold having a cylindrical hole with an inner diameter of 5 mm. A load of 100 MPa was applied to a press machine for 1 minute to form a compact with a diameter of 5 mm and a height of 2 mm to 4 mm. The shrinkage rate in the thickness (height) direction of the compact was measured when heated from 25°C under the following conditions, and the temperatures at which the thermal shrinkage rate was 1% and 3% based on the thickness of the compact at 25°C were determined. • Heating rate: 10°C / min • Temperature range: Room temperature to 800°C • Applied load: 98 mN • Atmosphere: Pure nitrogen (inert atmosphere) or 2 vol%-H ２ +98 capacity%-N ２ (Reducing Atmosphere) In all of the copper powders used in Examples 1 to 40, the temperature difference between the temperature at which the thermal shrinkage rate was 3% under the inert atmosphere and the temperature at which the thermal shrinkage rate was 3% under a reducing atmosphere was less than 10°C. In addition, in all of the copper powders used in Examples 1 to 40, when the compact obtained by pressure molding the copper powder was heated from 25°C under an inert atmosphere, the temperature at which the thermal shrinkage rate was 1% was 230°C or lower, based on the thickness of the compact at 25°C. 【0064】 (4) Calculation of HSP value and HSP distance The method for evaluating the HSP value of copper powder is described below, but in reality, it is the HSP value of organically coated copper powder using the method described in the Examples and Comparative Examples, and not the HSP value of copper itself. 10 mL each of the 30 solvents listed below was taken into a screw bottle of about 10 mL in size. Approximately 0.1 g of copper powder whose HSP value was to be evaluated was taken, placed in the prepared screw bottle, the lid was closed, and dispersed using an ultrasonic cleaner. After that, it was left to stand overnight, and the dispersed particles and those that had settled were visually determined. The determination results were entered into the HSPiP (version 6) software, and a program was executed to find a sphere with the smallest radius such that the solvent with good dispersion was on the inside of the sphere and the solvent with poor dispersion was on the outside of the sphere. The center of the sphere obtained by executing this program was taken as the HSP value of the organically coated copper powder. 【0065】The solvents used to evaluate the HSP value of copper powder are as follows: acetone, acetonitrile, acetophenone, aniline, 1-bromonaphthalene, butanol, γ-butyrolactone, chlorobutane, cyclohexane, diacetone alcohol, diethylenetriamine, dimethyl sulfoxide, dipropylene glycol, ethanol, ethanolamine, ethyl acetate, ethylene glycol, formamide, n-hexane, methanol, methyl ethyl ketone, methyl isobutyl ketone, N-methyl-2-pyrrolidone, morpholine, 2-phenoxyethanol, propylene carbonate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, 1,2,3,4-tetrahydronaphthalene, and toluene. The method for calculating the HSP value of substances other than the organically coated copper powder is as described above. 【0066】 (Calculation of HSP distance) For the two components whose HSP distance we want to evaluate, the HSP value of component 1 is (δ ｄ１ , δ ｐ１ , δ ｈ１ ), the HSP value of component 2 (δ ｄ２ , δ ｐ２ , δ ｈ２ Assuming this is the case, the HSP distance Ra is defined as shown in (Equation 1) below. In this case, based on this definition, we calculated the "HSP distance between the copper powder surface coating and the additive (amine-based organic compound)" and the "HSP distance between the copper powder surface coating and the solvent". 【0067】 【0068】(5) Measurement of bonding strength The manufactured bonding copper paste was applied to a plate-shaped Cu substrate (30 mm (length) x 30 mm (width)) in an area of ​​5 mm x 5 mm x 50 μm (length x width x thickness). A 50 μm thick masking tape was attached to the Cu substrate so that a coating area of ​​5 mm x 5 mm x 50 μm (length x width x thickness) was created on the Cu substrate, and the bonding copper paste was applied to the coating area. After applying the bonding copper paste to the coating area, the thickness of the bonding copper paste applied to the coating area was leveled to 50 μm, the thickness of the masking tape, by rubbing it with a glass plate. After the bonding copper paste dried, the masking tape was removed. Next, a plate-shaped Si chip (5 mm x 5 mm (length x width)) was placed on the upper surface of the bonding copper paste applied to the Cu substrate. Figure 1 schematically shows the state after this Si chip (gold-coated silicon chip) was placed. 【0069】 Next, pressure-heat bonding was performed on the Si chip placed on top of the bonding copper paste applied to the Cu substrate. Pressure-heat bonding was carried out using an HTB-MS manufactured by Alpha Design, under the conditions of 60°C / min, 230°C, 125N (5MPa), 10min, and an N2 atmosphere. By performing pressure-heat bonding, a bonded body was obtained in which the Cu substrate, the sintered body formed from the copper powder of the bonding copper paste, and the Si chip were joined together. 【0070】 Next, a joint strength evaluation test was performed on the obtained joints. The joint strength evaluation test was conducted using a bond tester (Nordson Advanced Technologies, DAGE5000) under the conditions of a speed of 700 μm / s and a shear tool height of 5 μm. The evaluation results of the joint strength are shown in the table, with "A" for 30 MPa or more, "B" for 20 MPa or more and less than 30 MPa, "C" for 10 MPa or more and less than 20 MPa, and "D" for less than 10 MPa. 【0071】In the example where the bonding strength was evaluated as 30 MPa or higher (i.e., A), the measured bonding strength was overrange, exceeding the upper limit of the measurement range of the above-mentioned apparatus. When overrange occurred, the size of the bonding copper paste applied to the Cu substrate was changed from 5 mm × 5 mm × 50 μm (length × width × thickness) to 4 mm × 4 mm × 50 μm (length × width × thickness), and the size of the chip placed on the Cu substrate was changed from (5 mm × 5 mm (length × width)) to 4 mm × 4 mm (length × width), and the above measurement was repeated. Figure 5 shows an example of the overrange data. In Figure 5, since it was overrange, the chip size was changed as described above, and the bonding strength was measured again, confirming that the bonding strength was 50 MPa or higher. 【0072】 (6) Evaluation method for sinterability A strip of 20 mm x 5 mm holes was punched out of a masking tape with a thickness of approximately 50 μm and attached to an alumina substrate with a thickness of 30 mm x 30 mm x 1 mm. Each bonding copper paste was applied and scraped with a glass slide to obtain a coating film of 20 mm x 5 mm x 50 μm. The obtained coating film was sintered in a nitrogen reflow oven at 300°C x 30 min. The temperature was lowered to room temperature in the nitrogen reflow oven and the appearance of the obtained sintered film was observed to check for the presence or absence of cracks. 【0073】 (Additives) In this example and comparative example, additives A to K shown in Table 1 below were used. All additives except additive I (2-amino-2-methyl-1-propanol) were liquid at room temperature (25°C). 【0074】 (Solvent) In this example and comparative example, solvents A to K shown in Table 2 below were used. 【0075】[Example 1] (Production of copper powder) 27 g of cuprous oxide powder was placed in a 200 ml separable flask as copper oxide powder. 100 g of propylene glycol (abbreviation: PG, boiling point: 188°C, molecular weight 76) was added as the first polyol solvent. Then, 0.65 g of cis-1,2-cyclohexanedicarboxylic acid (2.71% by mass (1 mol%) relative to the total amount of copper in the cuprous oxide) and 1.21 ml of 25% by mass sodium hydroxide aqueous solution were added for neutralization, and the mixture was mixed to form a uniform slurry. This slurry was heated to 185°C and maintained at that temperature for 45 minutes while stirring to carry out the reduction reaction. After the reaction solution was cooled, the resulting polyol copper powder was centrifuged, washed, and dried. 【0076】 [Heat Treatment Process] 3.2 g of copper powder was separated from the generated polyol copper powder after centrifugation and redispersed in 13.5 g of tetraethylene glycol as the second polyol solvent. Then, 0.1724 g of eicosanedioic acid (5.39% by mass (1 mol%) relative to the total amount of copper in the copper being treated) and 162 μl of 25% by mass sodium hydroxide aqueous solution for neutralization were added and mixed to form a homogeneous slurry. This slurry was heated to 280°C and maintained at that temperature for 10 minutes while stirring to perform the heat treatment. After the reaction solution was cooled, the generated heat-treated polyol copper powder was centrifuged, washed, and dried. 【0077】 (Manufacturing of copper paste for bonding) The obtained copper powder, additives (amine-based organic compounds), and solvent were mixed in the types and proportions (mass%) shown in Table 3, and the mixture was stirred and kneaded to obtain copper paste for bonding. The obtained copper powder and copper paste for bonding were evaluated. Table 3 shows the manufacturing conditions and evaluation results for the copper powder and copper paste for bonding. 【0078】 [Example 2] (Production of copper powder) [Reduction process] Cuprous oxide (Cu) as copper oxide powder ２O) 3.6 g of powder (Chemet, product code: Ultrafine) was placed in a 50 ml tall beaker, and 13.5 g of 1,2-butanediol (abbreviation: 1,2-BDO, boiling point: 194°C, molecular weight 90) was added as the first polyol solvent. Then, 0.302 g of poly(ethylene glycol) bis(carboxymethyl) ether (average molecular weight 600) (abbreviation: PEG600 dibasic acid, manufactured by Sigma-Aldrich) (9.44% by mass (1 mol%) relative to the total amount of copper in cuprous oxide) and 162 μl of 25% by mass sodium hydroxide aqueous solution were added for neutralization, and the mixture was mixed to form a homogeneous slurry. This slurry was heated to 185°C and maintained at that temperature for 45 minutes with stirring to carry out the reduction reaction. After the reaction solution was cooled, the resulting polyol copper powder was centrifuged, washed, and dried. 【0079】 (Manufacturing of copper paste for bonding) The obtained copper powder, additives (amine-based organic compounds), and solvent were mixed in the types and proportions (mass%) shown in Table 3, and the mixture was stirred and kneaded to obtain copper paste for bonding. The obtained copper powder and copper paste for bonding were evaluated. Table 3 shows the manufacturing conditions and evaluation results for the copper powder and copper paste for bonding. 【0080】 [Example 3] (Production of copper powder) The procedure was the same as in Example 1, except that 0.1159 g of dodecanedioic acid (3.63% by mass (1 mol%) relative to the total amount of copper in the copper being treated) was added instead of eicosanedioic acid in the heat treatment step to obtain polyol copper powder after heat treatment. 【0081】 (Manufacturing of copper paste for bonding) The obtained copper powder, additives (amine-based organic compounds), and solvent were mixed in the types and proportions (mass%) shown in Table 3, and the mixture was stirred and kneaded to obtain copper paste for bonding. The obtained copper powder and copper paste for bonding were evaluated. Table 3 shows the manufacturing conditions and evaluation results for the copper powder and copper paste for bonding. 【0082】 [Example 4] (Production of copper powder) The procedure was carried out in the same manner as in Example 2, except that 13.5 g of propylene glycol (abbreviation: PG, boiling point: 188°C, molecular weight 76) was used as the first polyol solvent, to obtain polyol copper powder after heat treatment. 【0083】(Manufacturing of copper paste for bonding) The obtained copper powder, additives (amine-based organic compounds), and solvent were mixed in the types and proportions (mass%) shown in Table 3, and the mixture was stirred and kneaded to obtain copper paste for bonding. The obtained copper powder and copper paste for bonding were evaluated. Table 3 shows the manufacturing conditions and evaluation results for the copper powder and copper paste for bonding. 【0084】 [Example 5] (Production of copper powder) The procedure was carried out in the same manner as in Example 1, except that the amount of PEG600 dibasic acid added was 0.0030 g (0.094% by mass (0.01 mol%) relative to the total amount of copper in cuprous oxide), and 16 μl of a 25% by mass sodium hydroxide aqueous solution was added for neutralization, to obtain polyol copper powder after heat treatment. 【0085】 (Manufacturing of copper paste for bonding) The obtained copper powder, additives (amine-based organic compounds), and solvent were mixed in the types and proportions (mass%) shown in Table 3, and the mixture was stirred and kneaded to obtain copper paste for bonding. The obtained copper powder and copper paste for bonding were evaluated. Table 3 shows the manufacturing conditions and evaluation results for the copper powder and copper paste for bonding. 【0086】[Example 6] (Production of copper powder) [Reduction process] 27 g of cuprous oxide powder was placed in a 200 ml separable flask as copper oxide powder, and 100 g of ethylene glycol (abbreviation: EG, boiling point: 197°C, molecular weight 62) was added as the first polyol solvent. Then, 0.65 g of cis-1,2-cyclohexanedicarboxylic acid (2.71% by mass (1 mol%) relative to the total amount of copper in the cuprous oxide) and 1.21 ml of 25% by mass sodium hydroxide aqueous solution were added for neutralization, and the mixture was mixed to form a uniform slurry. This slurry was heated to 180°C and maintained at that temperature for 45 minutes while stirring to carry out the reduction reaction. After the reaction solution was cooled, the resulting polyol copper powder was centrifuged, washed, and dried. [Heat Treatment Process] 3.2 g of copper powder was separated from the generated polyol copper powder after centrifugation and redispersed in 13.5 g of tetraethylene glycol (abbreviation: TeEG, boiling point: 327°C, molecular weight 194) as the second polyol solvent. Then, 0.302 g of poly(ethylene glycol) bis(carboxymethyl) ether (average molecular weight 600) (PEG600 dibasic acid) (9.44% by mass (1 mol%) relative to the total amount of copper in the copper being treated) and 162 μl of 25% by mass sodium hydroxide aqueous solution for neutralization were added and mixed to form a homogeneous slurry. This slurry was heated to 280°C and maintained at that temperature for 10 minutes while stirring to perform the heat treatment. After the reaction solution was cooled, the generated heat-treated polyol copper powder was centrifuged, washed, and dried. 【0087】 (Manufacturing of copper paste for bonding) The obtained copper powder, additives (amine-based organic compounds), and solvent were mixed in the types and proportions (mass%) shown in Table 3, and the mixture was stirred and kneaded to obtain copper paste for bonding. The obtained copper powder and copper paste for bonding were evaluated. Table 3 shows the manufacturing conditions and evaluation results for the copper powder and copper paste for bonding. 【0088】[Comparative Example 1] (Production of copper powder) [Reduction process] 30 g of copper oxide (CuO) powder (manufactured by Furukawa Chemicals, product number: FCO-M6) was placed in a 200 ml separable flask as copper oxide powder, and 100 g of tetraethylene glycol was added as the first polyol solvent, and the mixture was mixed until a uniform slurry was formed. This slurry was heated to 300°C and maintained at that temperature for 45 minutes while stirring to carry out the reduction reaction. After the reaction solution was cooled, the resulting polyol copper powder was centrifuged, washed, and dried. 【0089】 (Manufacturing of copper paste for bonding) The obtained copper powder, additives (amine-based organic compounds), and solvent were mixed in the types and proportions (mass%) shown in Table 3, and the mixture was stirred and kneaded to obtain copper paste for bonding. The obtained copper powder and copper paste for bonding were evaluated. Table 3 shows the manufacturing conditions and evaluation results for the copper powder and copper paste for bonding. 【0090】 [Comparative Example 2] (Production of copper powder) [Reduction process] The procedure was carried out in the same manner as in Comparative Example 1, except that 100 g of triethylene glycol was used as the first polyol solvent, to obtain polyol copper powder after heat treatment. 【0091】 (Manufacturing of copper paste for bonding) The obtained copper powder, additives (amine-based organic compounds), and solvent were mixed in the types and proportions (mass%) shown in Table 3, and the mixture was stirred and kneaded to obtain copper paste for bonding. The obtained copper powder and copper paste for bonding were evaluated. Table 3 shows the manufacturing conditions and evaluation results for the copper powder and copper paste for bonding. 【0092】 Examples 1 to 6 and Comparative Examples 1 to 2, shown in Table 3 below, were tests conducted by changing the type of copper powder. Figures 2 to 4 show SEM images of the sintered films obtained by sintering the copper bonding paste obtained in Example 3 and Comparative Examples 1 to 2. Figures 5 to 7 show the bonding test results obtained in Example 3 and Comparative Examples 1 to 2. 【0093】 【0094】[Examples 7-11, Comparative Examples 3-4] Examples 7-11 and Comparative Examples 3-4 are tests in which bonding copper paste was manufactured under the same conditions as in Example 2, except that the type of solvent was changed as shown in Table 4 below. Table 4 shows the type of solvent used, evaluation results, etc. For reference, the evaluation results of Example 2 are also shown in Table 4. 【0095】 【0096】 [Examples 12-19, Comparative Examples 5-6] Examples 12-19 and Comparative Examples 5-6 are tests in which bonding copper paste was manufactured under the same conditions as in Example 2, except that the type of additive was changed as shown in Table 5 below. Table 5 shows the types of additives used, evaluation results, etc. For reference, the evaluation results for Example 2 are also shown in Table 5. 【0097】 【0098】 [Examples 20-28, Comparative Examples 7-12] Examples 20-28 and Comparative Examples 7-12 are tests in which bonding copper paste was manufactured under the same conditions as in Example 2, except that the content ratios of copper powder, additives, and solvents were changed. Table 6 shows the content ratios of copper powder, additives, and solvents, as well as the evaluation results. For reference, the evaluation results for Example 2 are also shown in Table 6. 【0099】 【0100】 [Examples 29-31] Examples 29-31 are tests in which bonding copper paste was manufactured under the same conditions as in Example 2, except that the type of solvent was changed as shown in Table 7 below. Table 7 shows the type of solvent used, evaluation results, etc. 【0101】 【0102】[Examples 32-37] Examples 32-37 are tests in which bonding copper paste was manufactured under the same conditions as in Example 2, except that the copper powder obtained in Example 2, the additive (amine-based organic compound), the solvent, and the metal stearate as other components were changed to the proportions shown in Table 8 below. Table 8 shows the copper powder, additive (amine-based organic compound), solvent, other components (metal stearate), proportions, and evaluation results. 【0103】 【0104】 [Examples 38-40] Examples 38-40 are tests in which bonding copper paste was manufactured under the same conditions as in Example 2, except that the copper powder obtained in Example 2, the additive (amine-based organic compound), the solvent, and calcium phosphate as other components were changed to the proportions shown in Table 9 below. Table 9 shows the copper powder, additive (amine-based organic compound), solvent, other components (calcium phosphate), content proportions, and evaluation results. 【0105】 【0106】 (Evaluation Results) As shown in the above examples and Tables 3 to 9, the copper paste for joining in the examples was confirmed to have excellent low-temperature sinterability and excellent bonding strength with the objects to be joined. 【0107】 In Comparative Examples 1 and 2, the copper pastes used for bonding, which were coated with a surface coating that did not contain specific organic compounds and used copper powder with a large particle size, exhibited low bonding strength even when using the same amine-based organic compounds and solvents as in the Examples, as shown in Table 3. 【0108】 Figures 2-4 are SEM images showing the sintered films obtained by sintering the copper bonding pastes obtained in Example 3 and Comparative Examples 1-2. As shown in Figures 2-4, the sintered film of Example 3, in which the copper powder particle size is small, shows that the sintering of the copper powder has progressed, the neck has become larger and denser, and the sintering of the copper powder has progressed more than in Comparative Examples 1-2. 【0109】Furthermore, in the copper pastes used for bonding in Comparative Examples 4 to 6, as shown in Tables 4 and 5, the bonding strength was low because the HSP distance between the copper powder coated with the surface coating and the additive, and the HSP distance between the copper powder coated with the surface coating and the solvent exceeded 7 or 7.1. 【0110】 Furthermore, as shown in Table 6, the copper pastes used for bonding in Comparative Examples 7 to 11 exhibited low bonding strength because they did not contain amine-based organic compounds or solvents. 【0111】 Examples 32 to 37 are examples in which metal stearate salt was included as another component in the copper paste for joining, and as shown in Table 8, they exhibited excellent low-temperature sinterability and excellent bonding strength with the objects to be joined. 【0112】 Examples 38 to 40 are examples in which calcium phosphate was included as another component in the copper paste for joining. As shown in Table 9, these examples exhibited excellent low-temperature sintering properties and superior bonding strength with the objects to be joined. 【0113】 Copper bonding pastes containing metal stearate or calcium phosphate were evaluated using the sinterability evaluation method described above. Figures 7 to 9 are photographs showing the surface of sintered bodies (sintered films) obtained by sintering the copper bonding pastes obtained in Examples 34, 39, and Comparative Example 4. The sintered body shown in Figure 7 is a sintered body of a bonding copper paste containing metal stearate. The sintered body shown in Figure 8 is a sintered body of a bonding copper paste containing calcium phosphate. In the sintered body of Comparative Example 4 shown in Figure 9, many cracks were present on the surface. On the other hand, as shown in Figures 7 and 8, it can be seen that even when the surface is exposed, surface cracking is more suppressed and a smoother surface can be obtained in the sintered bodies of the copper bonding pastes of the examples containing metal stearate or calcium phosphate. 【0114】Furthermore, the technical scope of the present invention is not limited to the embodiments described above. One or more of the requirements described above may be omitted. Also, the requirements described above may be combined as appropriate. In addition, to the extent permitted by law, disclosures of Japanese Patent Application No. 2024-215135 and all documents cited above may be incorporated as part of the description.

Claims

1. A copper paste for bonding, comprising a solvent, an additive, and copper powder, wherein the additive contains an amine-based organic compound having a mass average molecular weight of 1000 or less, the solvent has a boiling point of 100°C or higher and 300°C or lower, the copper powder has a number average particle diameter calculated from the equivalent circle diameter of 30 nm or more and 180 nm or less, and is a copper powder coated with a surface coating containing an organic substance whose surface satisfies the following conditions (1) and (2), and the distance between the Hansen solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the amine-based organic compound is 7 or less, and the distance between the Hansen solubility parameter of the copper powder coated with the surface coating and the Hansen solubility parameter of the solvent is 7.1 or less. [Condition (1)] When the organic substance present on the surface of the copper powder is detected by gas chromatography-mass spectrometry, H(−O−CH ２ −CH ２ ) ｎ −OH (where n is an integer of 1 or more and 4 or less), HOOC−CH ２ (−O−CH ２ −CH ２ ) ｍ −OH (where m is an integer of 1 or more and 3 or less), HOOC−CH ２ (−O−CH ２ −CH ２ ) ｌ −O−CH ２ −COOH (where l is 1 or 2), H(−C ３ H ６ O) ｓ −OH (where s is an integer of 1 or more and 4 or less), HOOC−CH(CH ３ )(−C ３ H ６ O) ｔ −OH (where t is an integer of 1 or more and 3 or less), HOOC−CH(CH ３ )(−C ３ H ６ O) ｕ −O−CH(CH ３ One or more substances selected from the group consisting of )-COOH (where u is 1 or 2) are detected. [Condition (2)] When organic matter present on the surface of the copper powder is detected by liquid chromatography-mass spectrometry, it is a chain-like organic substance with a molecular weight of 210 to 1000, and each of the ends of the chain-like organic substance has a functional group that can coordinate to copper ions, such as a carboxyl group (-COOH), a hydroxyl group (-OH), or an amino group (-NH). ２ ), aldehyde group (-CHO), nitro group (-NO ２ ), thiol group (-SH), sulfo group (-SO ３ H), phosphate group (-PO ４ H ２ A chain-like organic substance having one or more selected from the group consisting of a cyanide group (-CN), a chloro group (-Cl), a bromo group (-Br), and an iodine group (-I) is detected.

2. The copper bonding paste according to claim 1, wherein the solvent is 0.1% by mass or more and 19% by mass or less with respect to the copper bonding paste, the additive is 0.5% by mass or more and 19% by mass or less, and the copper powder is 80% by mass or more and 92% by mass or less.

3. The copper paste for joining according to claim 1, wherein the copper powder has an average flatness of 0.2 or more and 0.4 or less.

4. The copper paste for bonding according to claim 1, wherein the copper powder has a coefficient of variation of particle size of 50% or less.

5. The copper bonding paste according to claim 1, wherein the amine-based organic compound has an amino group and a hydroxyl group.

6. The copper bonding paste according to claim 1, wherein the amine-based organic compound does not contain an acidic functional group.

7. The bonding copper paste according to claim 1, wherein the solvent has a boiling point of 150°C or higher and 200°C or lower.

8. The bonding copper paste according to claim 1, wherein the solvent comprises a monohydric alcohol.

9. The bonding copper paste according to claim 1, comprising a metal stearate salt or calcium phosphate.

10. The copper bonding paste according to claim 1, wherein, when the compact obtained by pressure molding the copper powder is heated from 25°C in an inert atmosphere, the temperature at which the thermal shrinkage rate becomes 1% is 230°C or lower, in the measurement of the thermal shrinkage rate based on the thickness of the compact at 25°C.

11. The copper paste for joining according to claim 1, wherein, when a compact obtained by pressure molding the copper powder is heated from 25°C in an inert atmosphere and a reducing atmosphere, the temperature difference between the temperature at which the thermal shrinkage rate becomes 3% in an inert atmosphere and the temperature at which the thermal shrinkage rate becomes 3% in a reducing atmosphere is less than 10°C.

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