Copper powder, paste, sintered body, composite, low-temperature co-fired ceramic substrate and multilayer ceramic capacitor

Abstract

The present invention is a copper powder with a surface treatment layer, and contains a Si compound with Si-O bonds, an amphoteric metal X, and an alkaline earth metal Y, wherein the amount of Si α (mol), the amount of the amphoteric metal X β (mol), and the amount of the alkaline earth metal Y γ (mol) satisfy formula (I): α / β ≥ 0.8, formula (II): γ / β ≥ 0.4, and formula (III): 4α ≥ 2.4β + 1.6γ.

Description

Technical Field

[0001] This manual describes copper powder, paste, sintered bodies, composites, low-temperature co-fired ceramic substrates, and multilayer ceramic capacitors. Background Technology

[0002] In recent years, in order to achieve miniaturization or high functionality of electronic devices, there has been a demand for miniaturization, smoothing, and densification of wiring in electronic substrates or components such as low-temperature co-fired ceramic (LTCC) substrates or multi-layer ceramic capacitors (MLCCs). It is believed that using fine copper powder in the wiring formation is an effective way to meet these requirements.

[0003] In this application, copper powder is sometimes pre-mixed with organic substances such as solvents or organic binders to form a paste. In this case, the paste is printed into a specific pattern using screen printing or the like, and then fired to remove the organic substances from the paste and sinter the copper powder. This forms a wiring network that is a sintered body of copper powder.

[0004] Furthermore, in order to produce such fine copper powder, there may be a slurry containing self-dispersed cuprous oxide powder, using chemical reduction or disproportionation methods.

[0005] As a related technology, for example, in Patent Document 1, the subject of the invention is "copper powder for conductive paste for external electrodes with excellent oxidation resistance and sintering properties". The invention proposes "a copper powder for conductive paste for external electrodes with excellent oxidation resistance and sintering properties, characterized in that: the copper powder used as a conductive filler in the conductive paste contains less than 5% by weight of Si, which is substantially entirely coated on the surface of copper particles in the form of a SiO2-based gel coating, and the SiO2-based gel coating contains at least one glass-forming component".

[0006] [Existing Technical Documents] [Patent Literature] [Patent Document 1] Japanese Patent Application Publication No. 2008-101276. Summary of the Invention

[0007] [The problem that the invention aims to solve] In the manufacture of LTCC substrates, a paste is applied to a blank containing ceramic powder, and the blank is fired simultaneously, so that the ceramic powder in the blank and the copper powder in the paste are sintered together.

[0008] Here, during firing, the temperature ranges of the shrinkage behavior of ceramic powder and copper powder may differ. In this case, the stress accompanying their shrinkage difference may lead to wire peeling or cracking. Furthermore, ceramic powder generally has a higher sintering temperature, while metal powder tends to be easier to sinter at lower temperatures with smaller particle sizes. Therefore, when using a certain degree of fine copper powder in the manufacture of LTCC substrates, the aforementioned shrinkage difference is more significant.

[0009] Furthermore, during the manufacturing of LTCC substrates or MLCCs, sintering is performed to thoroughly remove organic matter contained in the paste, etc. This often involves heating in an environment containing water vapor, causing the decomposition products of the organic matter to separate in gaseous form. If the copper powder is sintered at a relatively low temperature, there is a possibility that the gas generated inside the sintered copper powder will not be released to the outside, resulting in noticeable voids (so-called blistering) within the resulting wiring. These voids within the wiring can become a risk factor for reduced product reliability, such as the infiltration of plating solution.

[0010] It is argued that the purpose of Patent Document 1 is to provide a copper powder that can be sintered at a lower temperature (see paragraphs 0005, 0007 and 0025, etc.), which completely ignores the viewpoints mentioned above.

[0011] This specification discloses copper powder, paste, sintered body, composite, low-temperature co-fired ceramic substrate and multilayer ceramic capacitor. The copper powder is sintered at a certain high temperature to become a sintered body with relatively high density after sintering.

[0012] [Technical means to solve the problem] The copper powder disclosed in this specification has a surface treatment layer and contains a Si compound with Si-O bonds, an amphoteric metal X, and an alkaline earth metal Y. The amount of Si α (mol), the amount of the amphoteric metal X β (mol), and the amount of the alkaline earth metal Y γ (mol) satisfy Equation (I): α / β ≥ 0.8, Equation (II): γ / β ≥ 0.4, and Equation (III): 4α ≥ 2.4β + 1.6γ.

[0013] The paste disclosed in this specification contains the aforementioned copper powder.

[0014] The sintered body disclosed in this specification is a sintered body of copper powder, and the copper powder includes the aforementioned copper powder.

[0015] The composite disclosed in this specification comprises a sintered body of ceramic powder and a sintered body of the aforementioned copper powder formed on the sintered body of the ceramic powder.

[0016] The low-temperature co-fired ceramic substrate disclosed in this specification is a low-temperature co-fired ceramic substrate having the above-mentioned composite.

[0017] The multilayer ceramic capacitor disclosed in this specification is a multilayer ceramic capacitor having the above-described composite.

[0018] [The effects of the invention] The copper powder mentioned above is sintered at a certain high temperature, resulting in a copper powder with a relatively high density after sintering. Detailed Implementation

[0019] The following describes in detail the implementation schemes of the aforementioned copper powder, paste, sintered body, composite, low-temperature co-fired ceramic substrate, and multilayer ceramic capacitor.

[0020] One embodiment of the copper powder has a surface treatment layer. The copper powder mainly contains a Si compound having Si-O bonds (hereinafter also referred to as "Si compound"), an amphoteric metal X, and an alkaline earth metal Y in the surface treatment layer. Typically, at least a portion of the amphoteric metal X can be contained therein in the form of an amphoteric metal X compound (hereinafter also referred to as "X compound"), and at least a portion of the alkaline earth metal Y can be contained therein in the form of an alkaline earth metal Y compound (hereinafter also referred to as "Y compound"), but the form of the amphoteric metal X and the alkaline earth metal Y in the copper powder is not limited. Furthermore, when measuring the amounts α, β, and γ of Si (silicon), amphoteric metal X, and alkaline earth metal Y in copper powder with this surface treatment layer, the amounts α (mol) of Si, β (mol) of amphoteric metal X, and γ (mol) of alkaline earth metal Y satisfy equation (I): α / β ≥ 0.8, equation (II): γ / β ≥ 0.4, and equation (III): 4α ≥ 2.4β + 1.6γ.

[0021] It is believed that when copper powder with a surface treatment layer containing Si compounds, amphoteric metal X, and alkaline earth metal Y is heated, a glass network mainly composed of oxides containing Si, amphoteric metal X, alkaline earth metal Y, and oxygen is formed on the surface of the copper powder at a certain temperature. If this glass network contains Si, amphoteric metal X, and alkaline earth metal Y in a specific amount or ratio, it exists between the copper powder particles at low temperatures, effectively inhibiting the sintering of the copper powder. On the other hand, at high temperatures, it can be removed as a glass network with moderate fluidity. More specifically, when the above formulas (I), (II), and (III) are satisfied, it is not easy to form a tricluster with a structure of three tetrahedra bonded to one oxygen atom. Thus, it is expected to suppress the glass transition inhibition caused by the tricluster and the density reduction of the sintered copper powder caused by the tricluster. The tricluster is considered as a type of ceramic, namely aluminum-rich andalusite (3Al2O3). 2SiO2 or 2Al2O3 The "nuclei" of SiO2 play a functional role. If aluminum-rich andalusite is formed on the surface of copper powder due to the formation of three clusters during the sintering of copper powder, it is presumed that aluminum-rich andalusite will remain on the surface of copper powder even after sintering due to its low fluidity. Therefore, it is believed that the formation of three clusters will lead to a decrease in the density of the sintered copper powder body.

[0022] The result is that the copper powder is coated with a high-molecular-weight, highly fluid glass network, thus becoming copper powder that is sintered at a certain high temperature. Furthermore, due to the increased sintering temperature, gases from the decomposition products of organic matter contained in the paste are fully expelled during the process before reaching that temperature, thus reducing the likelihood of bubbling. Additionally, as the reduced fluidity of the glass network is suppressed, the glass network is easily expelled to the outside during the copper powder sintering process. These results in the production of high-density sintered bodies or wiring where the formation of voids is suppressed.

[0023] (Copper powder) Copper powder contains Cu (copper), and in most cases, it is predominantly composed of Cu. The Cu content (excluding copper oxide) in copper powder can be, for example, 99.0% by mass or higher, typically 99.5% by mass or higher. The presence of Cu in copper powder or its Cu content can be confirmed and determined by X-ray diffraction (XRD).

[0024] The BET specific surface area of ​​copper powder is 0.13 m². 2 / g or more, preferably 0.22 m 2 / g or more, and preferably 0.67m 2 / g or more. Furthermore, the BET specific surface area of ​​the copper powder is 15 m². 2 / g or less, preferably 10 m 2 / g or less, and preferably 5 m 2 / g or less. Even with such a large specific surface area and relatively small particle size, copper powder in this embodiment can increase the sintering temperature by forming a specific surface treatment layer. Furthermore, the smaller the BET specific surface area, in other words, the larger the particle size of the copper powder, the higher the sintering temperature of the copper powder tends to be, and the higher the density of the sintered body tends to be. On the other hand, the larger the BET specific surface area, in other words, the smaller the particle size of the copper powder, the more likely it is to form fine wiring. The BET specific surface area mentioned here refers to the value obtained by measuring copper powder that has been surface-treated and has a surface treatment layer formed.

[0025] The BET specific surface area of ​​copper powder can be determined according to JIS Z8830:2013, using microarray. The experiment was conducted using Bell's BELSORP-mini II. More specifically, for a 3 g sample of copper powder, after degassing at 70°C for 5 hours in a vacuum with an absolute pressure of less than 10 Pa, the nitrogen adsorption isotherm was determined using the static volumetric method, and the BET method was used to analyze the results obtained, thereby calculating the BET specific surface area.

[0026] The copper powder has a surface treatment layer. More specifically, the copper powder is composed of surface treatment particles (also simply referred to as "particles") having a core particle, namely a copper particle, and a surface treatment layer that typically covers almost the entire surface of the copper particle. The surface treatment layer contains a Si compound with Si-O bonds, an amphoteric metal X, and an alkaline earth metal Y, thereby including the Si compound with Si-O bonds, the amphoteric metal X, and the alkaline earth metal Y in the copper powder. At least a portion of the amphoteric metal X may be in the form of an X compound. At least a portion of the alkaline earth metal Y may be in the form of a Y compound. By including the above-mentioned Si compound, amphoteric metal X, and alkaline earth metal Y, a glass network that raises the sintering temperature can be effectively formed during the heating of the copper powder.

[0027] Furthermore, in the copper powder of this embodiment, the amount of Si α (mol), the amount of amphoteric metal X β (mol), and the amount of alkaline earth metal Y γ (mol) contained in the copper powder due to the aforementioned surface treatment layer, etc., satisfy Equation (I): α / β≧0.8, Equation (II): γ / β≧0.4, and Equation (III): 4α≧2.4β+1.6γ.

[0028] If at least one of equations (I), (II), and (III) above is not satisfied, there is a concern that the formation of triclusters may hinder vitrification, resulting in a glass network that is difficult to flow. This is because the mass of the amphoteric metal X (β) and / or the mass of the alkaline earth metal Y (γ) is excessive relative to the mass of Si (α), or the mass of the amphoteric metal X (β) is excessive relative to the mass of the alkaline earth metal Y (γ). If the fluidity of the glass network decreases, it may remain inside the sintered copper powder, potentially leading to a decrease in its density.

[0029] The closer the value of α / β is to 1.0, the closer the value of γ / β is to 0.5, and the closer the value of 4α is to 3β + 2γ, the more preferred the latter is. It is believed that in this case, the ratio of non-crosslinked oxygen is sufficiently reduced, and the softening temperature of the glass network is increased. When copper powder begins to sinter at high temperature due to contact between exposed copper particles, if the softening temperature, which approximates the glass transition temperature, is increased, sintering can be effectively suppressed by coating the copper particles with the glass composition up to the high temperature; in other words, the sintering initiation temperature of the copper powder can be increased. The copper powder preferably has a mass ratio of α and β satisfying formula (I'): α / β ≦ 3.0, more preferably satisfying formula (I''): α / β ≦ 2.0, and particularly preferably satisfying formula (I'''): α / β ≦ 1.6. Furthermore, the copper powder preferably has a content of β and γ satisfying formula (II'): γ / β ≦ 2.0, more preferably satisfying formula (II''): γ / β ≦ 1.0, and particularly preferably satisfying formula (II'''): γ / β ≦ 0.7. Additionally, the copper powder preferably has a content of α, β, and γ satisfying formula (III'): 4α ≦ 3.6β + 2.4γ, and more preferably satisfying formula (III''): 4α ≦ 3.3β + 2.2γ.

[0030] From the viewpoint of sufficiently increasing the sintering initiation temperature, the content of Si, the content of amphoteric metal X, and the content of alkaline earth metal Y in the copper powder are each preferably 0.01 atomic% or more, more preferably 0.05 atomic% or more, and even more preferably 0.10 atomic% or more. Furthermore, it is also considered that the components of the surface treatment layer of the copper powder in this embodiment are not formed in the form of a surface treatment layer as described above, but rather added separately to the paste in the form of a glass frit. However, considering that when added in the form of a glass frit, compared to the case of forming a surface treatment layer, the amount required to increase the sintering temperature would be greater, which might lead to a lower density of the sintered body. Therefore, this embodiment has the advantage of being able to form an effective surface treatment layer with a relatively small amount. On the other hand, if the content of Si, the content of amphoteric metal X, and the content of alkaline earth metal Y in the copper powder are too high, there are concerns that the resistivity of the sintered copper powder may increase, or the density of the sintered body may not be able to increase to a certain extent. Therefore, the content of Si, the content of the amphoteric metal X, and the content of the alkaline earth metal Y are each preferably 5.0 atomic% or less, more preferably 3.0 atomic% or less, and especially preferably 1.5 atomic% or less.

[0031] The Si compounds contained in copper powder are Si compounds containing Si-O bonds, and typically exist in a gel state. The gel-state Si compounds form a SiO2 network, therefore, when coated on the surface of copper particles in a gel state, they may exhibit higher oxidation resistance compared to non-gel-state Si compounds.

[0032] Examples of amphoteric metals X contained in copper powder that can form glass networks include Al (aluminum), zinc (Zn), tin (Sn), and lead (Pb). Among these, copper powder preferably contains Al as the amphoteric metal X. This is because Al-containing aluminosilicate glasses have good thermal stability and mechanical properties, making them suitable for use as substrate glass in liquid crystal displays or cover glass in smartphones. Furthermore, their high glass transition temperature, close to the softening temperature, helps improve sintering delay.

[0033] The compounds of zwitterionic metal X may include, for example, at least one selected from the group consisting of hydroxycarboxylic acid salts, carboxylic acid salts (preferably basic carboxylic acid salts), and compounds having an XO bond. The hydroxycarboxylic acid or basic carboxylic acid of zwitterionic metal X is water-soluble and does not readily evaporate; therefore, it is easy to form a uniform surface treatment layer, resulting in an expected improvement in sintering delay. Furthermore, since they are water-soluble, there is no need to use environmentally burdensome solvents such as organic solvents.

[0034] In particular, the compound of zwitterionic metal X preferably contains at least one of the group consisting of lactate, citrate and tartrate selected from hydroxycarboxylate salts, and additionally or alternatively contains basic formate and / or basic acetate salts from the carboxylate salt group. These compounds, due to their shorter carbon chains, can suppress the generation of decomposition gases or residues that might hinder the increase in sintering density.

[0035] Compounds containing XO bonds are typically generated by the hydrolysis of alkoxides used in surface treatment, and thus contained in the surface treatment layer, and subsequently in the copper powder. If the alkoxides are hydrolyzed, alcohols are generated as byproducts in addition to the compounds containing XO bonds. Since alcohols have low boiling points, they can be easily removed by heating and drying, and are less likely to remain on the copper powder surface as carbon components. From this perspective, it is preferable, for example, to use alkoxides having an alkoxy group having 4 or fewer carbon atoms for surface treatment. Examples of such alkoxides include: methyl oxide, ethoxide, n-propoxide, isopropoxide, n-butoxide, sec-butoxide, tert-butoxide, etc. In this case, the compounds containing XO bonds, as decomposition products from the hydrolysis of such alkoxides, are contained in the copper powder. The presence of compounds containing XO bonds can be confirmed by mass spectrometry analysis as described below.

[0036] The alkaline earth metal Y is preferably at least one selected from the group consisting of Ca, Ba, and Sr, including Ca (calcium), Ba (barium), Sr (strontium), and Ra (radium). Ca, Ba, and Sr have relatively high softening temperatures, and including at least one of these allows for an increase in the sintering initiation temperature of the copper powder. Ca is particularly preferred, and Ba is even more preferred.

[0037] Compounds of alkaline earth metal Y may include, for example, at least one selected from the group consisting of hydroxides, carboxylates, hydroxycarboxylates, nitrates, and compounds having YO bonds. Hydroxides or carboxylates of alkaline earth metal Y are preferred in that they do not readily produce corrosive gases during thermal decomposition. Hydroxides that produce H₂O as a decomposition byproduct are particularly preferred.

[0038] In particular, the compounds of alkaline earth metal Y preferably contain formate and / or acetate in carboxylates, and additionally or alternatively contain lactate in hydroxycarboxylates. These compounds, due to their shorter carbon chains, can suppress the generation of decomposition gases or residues that might hinder the increase in sintering density.

[0039] Compounds containing YO bonds are typically formed by the hydrolysis of alkoxides used in surface treatment. During the hydrolysis of alkoxides, alcohols are generated as byproducts. Since alcohols have low boiling points, they can be easily removed by heating and drying, and are less likely to remain on the copper powder surface as carbon components. From this perspective, it is preferable, for example, to use alkoxides having an alkoxy group having four or fewer carbon atoms for surface treatment. Examples of such alkoxides include: methyl oxide, ethoxide, n-propoxide, isopropoxide, n-butoxide, sec-butoxide, tert-butoxide, etc. In this case, the compound containing YO bonds, which is a decomposition product of the hydrolysis of such alkoxide, is contained in the copper powder.

[0040] Once the presence of Si-O bonds in the copper powder is confirmed, the copper powder can be placed into an Al sample container (manufactured by Hitachi Advanced Scientific Corporation, GAA-0068, Al open sample container). The tablets (5.2 H2.5 mm) were placed in a container at half capacity and pressed under pressure while still containing the drug-coated paper to form tablets. The tablets were then analyzed using X-ray photoelectron spectroscopy (XPS) on a PHI 5000 Versa Probe II manufactured by ULVAC-PHI Corporation. The X-ray source was monochromatic AlKα rays (X-ray energy: 1486.6 eV), with an output of 25 W, a beam diameter of 100 μm, an X-ray incident angle of 90 degrees, and a photoelectron extraction angle of 45 degrees. Measurements were performed under conditions of electron and Ar ion irradiation for charge neutralization. MultiPak Version 9.5.0.8 was used for data analysis, and Cu2p was used for spectral charge correction. 3 / 2 The peak was corrected to the one at 932.7 eV. Subsequently, for Si2p and Ca2p... 3 / 2 Ca2p 1 / 2 Ba3d 5 / 2 Sr3d 5 / 2 Sr3d3 / 2 The background intensity of the peaks was calculated and peak fitting was performed using the iterative Shirley method, and the peak apex of each obtained spectrum was taken as the binding energy. The Si2p peak was used to evaluate the presence or absence of Si-O bonds. The position of the Si2p peak varies depending on the bonding state of Si, and Si-O bonds are detected at 102 eV to 104 eV. The presence of Si-O bonds is determined by detecting peaks in this range.

[0041] Furthermore, the presence of YO bonds in the copper powder can be confirmed through the XPS analysis described above. The peak positions vary depending on the bonding state of the alkaline earth metal Y, with Ca-O bonds at Ca2p. 3 / 2 The binding energy was detected at 345–350 eV, indicating that the Sr-O bond is located in Sr3d. 5 / 2 The binding energy was detected at a peak of 132–137 eV, indicating that the Ba-O bond is located at Ba3d. 5 / 2 The binding energy was 778–783 eV, and a peak was detected. The presence of YO bonds was determined by detecting peaks in this range. As an example, in the case of copper powder containing calcium lactate, the binding energy was [missing information - likely related to Ca2p]. 3 / 2 The binding energy was detected at a peak of 347.2–348.2 eV. Furthermore, in the case of copper powder containing barium acetate, the binding energy of Ba3d... 5 / 2 The binding energy was 780.6–781.6 eV, and a peak was detected.

[0042] In addition, the presence of compound X or compound Y in copper powder can be confirmed as follows: Add 5 mL of pure water to 1 g of copper powder and irradiate with ultrasound for 20 minutes (frequency: 24, 31 Hz, output 110 W, temperature: 20℃~40℃). After centrifugation, recover the supernatant, mix it with 3 mL of acetonitrile, and filter it through an injection filter (Rephile Syringe Filter (material: hydrophilic PTEF, pore size: 0.22 μm)). Collect the filtrate. Add 0.5 mL of 0.1% formic acid aqueous solution to 0.5 mL of this solution. Use this liquid as the sample liquid for mass spectrometry analysis. The mass spectrometry analysis device can be a liquid chromatography-Orbitrap mass spectrometer (Orbitrap Exploris240 mass spectrometer manufactured by Thermo Fisher Scientific), with a scan range of 50-500 (m / z) and a resolution of 60000. For sample ionization, NanoMate manufactured by Advion Interchim Scientific can be used. The spray voltage can be set to 1.4 kV, the gas type can be set to nitrogen, and the gas pressure can be set to 0.3 psi.

[0043] As an example, the m / z values ​​of compounds X and Y used in the experiments described in the following embodiments are shown below in single isotopic mass mode in positive ion detection mode. The single isotopic mass of an element refers to the precisely calculated mass of the isotope with the highest natural abundance for each element. Aluminum lactate has a m / z value of approximately 295.061 [M+H]. + The peak was detected in ionic form, with aluminum citrate showing a peak around 223.040 as [M+H]. + The peak was detected in ionic form; aluminum tartrate showed a peak around 498.973 as [M+H]. + The peak was detected in the form of ions, with basic aluminum formate showing a peak around 250.956 as [M+H]. + The peak was detected in the form of ions, with basic aluminum acetate showing a peak around 307.019 as [M+H]. + The peak was detected in ionic form, with calcium hydroxide showing a peak around 74.976 as [M+H]. + The peak was detected in ionic form, with calcium formate showing a peak around 130.966 as [M+H]. + The peak was detected in ionic form; calcium acetate showed a peak around 158.997 as [M+H]. + The peak was detected in ionic form, with calcium lactate showing a peak around 219.018 as [M+H]. + The peak was detected in ionic form; calcium citrate showed a peak around 498.903 as [M+H]. + The peak was detected in ionic form; calcium tartrate showed a peak around 188.971 as [M+H]. + The peak was detected in ionic form; calcium nitrate showed a peak around 164.946 as [M+H]. + The peak was detected in ionic form, with strontium hydroxide showing a peak around 122.919 as [M+H]. + The peak was detected in ionic form, with strontium formate showing a peak around 178.909 as [M+H]. + The peak was detected in ionic form, with strontium acetate showing a peak around 205.932 as [M+H]. + The peak was detected in ionic form, with strontium lactate showing a peak around 266.961 as [M+H]. + The peak was detected in ionic form, with strontium citrate showing a peak around 642.732 as [M+H]. + The peak was detected in ionic form; strontium tartrate showed a peak around 236.914 as [M+H]. + The peak was detected in ionic form; strontium nitrate showed a peak around 212.889 as [M+H]. + The peak was detected in ionic form, with barium hydroxide showing a peak around 172.919 as [M+H]. + The peak was detected in ionic form, with barium formate showing a peak around 228.908 as [M+H].+ The peak was detected in ionic form, with barium acetate showing a peak around 256.940 as [M+H]. + The peak was detected in ionic form, with barium lactate showing a peak around 316.961 as [M+H]. + The peak was detected in ionic form, with barium citrate showing a peak around 792.731 as [M+H]. + The peak was detected in ionic form, with barium tartrate showing a peak around 286.914 as [M+H]. + The peak was detected in ionic form; barium nitrate showed a peak around 262.889 as [M+H]. + Peaks are detected in ionic form. "Nearby" means within ±0.1%.

[0044] The so-called [M+H] + The ion is defined as an ion formed by the addition of a proton to the molecule of the compound in question.

[0045] Furthermore, it may be impossible to detect a peak at the m / z value under a single isotopic mass. In this case, peaks containing organic acids from compound X and amphoteric metal X, or peaks containing organic acids from compound Y and alkaline earth metal Y, may be detected.

[0046] As an example, in the case of copper powder containing aluminum lactate ([CH3CH(OH)COO]3Al), the following may occur: a peak is not detected near the single isotopic mass of 295.061, but a peak is detected near the calculated value of 205.0293 for the structure [CH3CH(OH)COO]2Al, which is equivalent to aluminum lactate without one lactic acid moiety [CH3CH(OH)COO], or a peak is detected near the calculated value of 179.0136 for the structure [CH3CH(OH)COO(CO2H)]Al, which is equivalent to aluminum lactate without two lactic acid moiety moiety [CH3CH(OH)COO] and with formic acid added. The latter can be considered as the addition of formic acid used as a pretreatment for mass spectrometry analysis.

[0047] Based on the results of this mass spectrometry analysis, it can also be confirmed that the compound of the amphoteric metal X is a type of hydroxycarboxylate, namely lactate.

[0048] That is, by detecting the peaks containing organic acids from compound X and amphoteric metal X, or the peaks containing organic acids from compound Y and alkaline earth metal Y, it is possible to confirm that the compound containing amphoteric metal X or alkaline earth metal Y is the aforementioned compound.

[0049] The amount of Si, α, or content in copper powder is determined as follows: Copper powder is alkali-fused using sodium peroxide and sodium carbonate. The resulting melt is dissolved in hydrochloric acid and then purified to a certain volume using ultrapure water. The solution is analyzed using ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy) to determine the mass (μg) of Si relative to the unit mass (g) of copper powder. Specifically, it is determined using an ICP-OES instrument (Hitachi Advanced Scientific Corporation): PS3500UVDDII. After establishing a calibration curve for Si concentration using a standard solution, the sample solution adjusted to the range of the calibration curve is measured. More specifically, JCSS standard solution for chemical analysis (silicon standard solution (Si1000), specifications: for atomic absorption spectrometry and ICP analysis) manufactured by Kanto Chemical Co., Ltd. was added to a solution composed of sodium peroxide, sodium carbonate, and hydrochloric acid. Solutions with Si concentrations adjusted to 0.1 μg / mL and 1.0 μg / mL, and a solution with a Si concentration of 0 μg / mL without the aforementioned JCSS standard solution were prepared as standard solutions to establish the calibration curve. The sodium peroxide, sodium carbonate, and hydrochloric acid in the standard solutions were adjusted to have the same molar concentrations as those in the sample solution. The sample solution was prepared by setting the collection volume to 0.5 g, and adjusting the Si concentration of the sample solution to be within the calibration curve range. A wavelength with no spectroscopic interference was selected for measurement, and off-peak background correction was applied. Furthermore, the crucible used during alkali fusion should be made of a material that will not leach the element being measured and will not form poorly soluble substances with the crucible components. For example, a zirconium crucible can be used.

[0050] Furthermore, the amount or content of the amphoteric metal X in copper powder is determined as follows: Copper powder can be alkali-fused using sodium peroxide and sodium carbonate, the resulting melt is dissolved in hydrochloric acid, and then purified to a certain volume using ultrapure water. The solution is then analyzed using ICP-OES (in μg) to determine the mass of the amphoteric metal X relative to the unit mass (g) of copper powder. Specifically, this is determined using an ICP-OES instrument manufactured by Hitachi Advanced Scientific Corporation: PS3500UVDDII. After establishing a calibration curve for the concentration of X with a standard solution, the sample solution adjusted to the range of the calibration curve is measured. More specifically, standard solutions for chemical analysis manufactured by Kanto Chemical Co., Ltd. (Aluminum standard solution (Al 1000), Zinc standard solution (Zn 1000), Tin standard solution (Sn 1000), Lead standard solution (Pb 1000), specifications: for atomic absorption spectrometry and ICP analysis) corresponding to the metal being measured were added to a solution composed of sodium peroxide, sodium carbonate, and hydrochloric acid. Solutions with X concentrations adjusted to 0.1 μg / mL and 1.0 μg / mL, and a solution with an X concentration of 0 μg / mL without the aforementioned standard solutions were prepared and used as standard solutions to establish the calibration curve. The sodium peroxide, sodium carbonate, and hydrochloric acid in the standard solutions were adjusted to have the same molar concentrations as those in the sample solution. The sample solution was collected at a volume of 0.5 g and adjusted so that the X concentration of the sample solution fell within the calibration curve range. The measurement wavelength should be selected at a wavelength without spectral interference, and the measurement should be performed using off-peak background correction. Furthermore, the crucible used during alkali fusion should be made of a material that will not leach the element being measured and will not form insoluble substances with the crucible components; for example, a zirconium crucible can be used.

[0051] Furthermore, the amount or content of alkaline earth metal Y in copper powder is determined as follows: Copper powder can be dissolved using hydrochloric acid and nitric acid, and then purified to a certain volume using ultrapure water. The solution is then analyzed using ICP-OES to determine the mass (μg) of alkaline earth metal Y relative to the unit mass (g) of copper powder. Specifically, this is determined as follows: Using an ICP-OES instrument manufactured by Hitachi Advanced Scientific Corporation: PS3500UVDDII, a calibration curve for the concentration of Y is prepared with a standard solution, and the sample solution adjusted to the range of the calibration curve is measured. More specifically, standard solutions for chemical analysis manufactured by Kanto Chemical Co., Ltd. (calcium standard solution 1 (Ca 1000), strontium standard solution (Sr 1000), and barium standard solution (Ba 1000), specifications: for atomic absorption spectrometry and ICP analysis) corresponding to the metals being measured were added to a solution composed of hydrochloric acid and nitric acid. Solutions with Y concentrations adjusted to 1 μg / mL and 10 μg / mL, and a solution with a Y concentration of 0 μg / mL without the aforementioned standard solutions were prepared and used as standard solutions to establish the calibration curve. The hydrochloric acid and nitric acid in the standard solutions were adjusted to the same molar concentrations as those in the sample solution. The sample solution was collected at a volume of 0.5 g and adjusted so that the Y concentration of the sample solution fell within the calibration curve range. A wavelength with no spectroscopic interference was selected for measurement, and off-peak background correction was applied.

[0052] The carbon (C) content in the copper powder is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 1.0% by mass or less. Furthermore, the oxygen (O) content in the copper powder is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less. If the C or O content is too high, copper oxide (CuO) or cuprous oxide (Cu2O) is easily formed. Copper oxide or cuprous oxide tends to remain in the sintered body without being reduced in a steam environment. As a result, the resistivity of the sintered body may increase, or the density of the sintered body may decrease. On the other hand, a lower C or O content does not have a particularly adverse effect, as the copper powder in this embodiment generally contains C or O from compounds derived from the surface treatment layer.

[0053] The carbon (C) content of copper powder is determined using a high-frequency induction heating furnace combustion-infrared absorption method. Specifically, a LECO CS844 carbon-sulfur analyzer can be used. The sample collection amount is set to 0.2 g and adjusted to fall within the intensity range of the calibration curve. The combustion aid is LECO CEL II and Fe shavings, and a steel needle is used as a standard material for the calibration curve to determine the C content of the copper powder. Alternatively, when the sample is placed in an alumina crucible for measurement, the alumina crucible can be pre-treated before being used to determine the carbon content of the copper powder. This pre-treatment involves heating the sample in air at a certain rate from room temperature to 1000°C for 2 hours, and then maintaining the temperature at 1000°C for 2 hours.

[0054] The oxygen content of copper powder was determined using an inactive gas melting-infrared absorption method. Specifically, a LECO TC600 isoxonitric analyzer was used, with the sample size set to 0.02 g to 0.05 g, adjusted to fall within the intensity range of the calibration curve. A steel needle, serving as a certification standard, was used for the calibration curve, and the copper powder was placed into a nickel capsule for measurement. Furthermore, to prevent oxidation by atmospheric oxygen, the measurement was performed immediately after opening the capsule.

[0055] The copper powder is preferably measured to shrink by 2% at a temperature of 500°C or higher, and more preferably 700°C or higher, when heated from room temperature to 1000°C in an environment containing nitrogen and water vapor at a vapor pressure of 3.6 kPa, during thermomechanical analysis (TMA). This higher 2% shrinkage temperature makes it easier for the shrinkage behavior of the copper powder during LTCC substrate manufacturing to match that of the ceramic powder, thus suppressing wire stripping or cracking. Furthermore, when the copper powder is sintered as a paste, sintering is less likely to occur until the decomposition products of the organic matter are fully released in gaseous form, thus suppressing blistering.

[0056] Furthermore, in thermomechanical analysis, when copper powder is heated from room temperature to 1000°C in an environment containing nitrogen and water vapor at a vapor pressure of 3.6 kPa, the minimum value of its linear expansion rate is preferably 95% or more of the theoretical ideal linear expansion rate, and more preferably 96% or more. This theoretical ideal linear expansion rate is calculated based on the true density and thermal expansion rate of copper at the temperature at which this minimum linear expansion rate is obtained. This means that the copper powder is sintered more densely, thereby suppressing the formation of voids in the sintered body, and thus reducing the risk of reduced product reliability, such as the infiltration of plating solution.

[0057] Specifically, the thermomechanical analysis described above was performed as follows: Copper powder (approximately 0.3 g) was placed into a particle mold with a 5 mm diameter hole and compressed with a force of 1 kN to create cylindrical copper powder particles (height: approximately 3 mm, diameter: approximately 5 mm). The height was measured using a micrometer (e.g., Coolant Purf Micrometer MDC-25MX, maximum permissible error ±1 μm) and used as the initial particle height. The particles were then placed in a thermomechanical analysis apparatus (e.g., NETZSCH TMA4000SE), and after evacuating to a gauge pressure below -0.1 MPa, nitrogen gas was introduced to create an inactive environment. Subsequently, a water vapor generator (NETZSCH HC9800) was connected to the thermomechanical analysis apparatus, and nitrogen gas containing water vapor with a dew point temperature of 30°C was flowed at a flow rate of 300 mL / min. Subsequently, the flow rate of nitrogen gas flowing into the thermomechanical analyzer was changed to 50 mL / min. Gas flow was maintained at this state for 15 minutes to stabilize the measurement environment. While the gas flow was maintained between the steam generator and the thermomechanical analyzer, a 10 g load was applied, and the temperature was increased from room temperature (25°C) to 1000°C at a rate of 10°C / min. During this heating process from room temperature to 1000°C, the particle height was measured once per second, and the temperature at which the particle height shrank by 2% relative to the initial height was taken as the 2% shrinkage temperature.

[0058] Furthermore, the linear expansion rate is calculated as follows: the particle height of the copper powder at the time of heating, obtained through the thermomechanical analysis described above, is divided by the initial particle height. The obtained value is then subtracted by 1, and multiplied by 100. Since the particle height decreases with heating, the linear expansion rate becomes negative. Moreover, the copper powder particles shrink as they heat up, and correspondingly, the linear expansion rate changes with temperature. The point where the linear expansion rate becomes minimum during the heating process from room temperature to 1000°C can be considered as the copper powder particles undergoing sintering and shrinking to the maximum extent. When this minimum linear expansion rate is close to the "theoretical ideal linear expansion rate of bulk copper at the temperature at which this minimum value is obtained," the copper powder can be considered to be a copper powder that becomes a high-density sintered body after sintering. The theoretical ideal linear expansion rate can be determined based on the true density of copper (8.96 g / cm³). 3 ) and coefficient of thermal expansion (1.77×10 -5 ( / K), calculate the linear expansion rate of copper powder with the same size and shape as the copper powder particles, and then calculate the value that varies with temperature.

[0059] The surface treatment layer of copper powder may also contain polypropylene glycol, polyethylene glycol, polyoxyethylene alkyl ethers, or alkyl carboxylic acids. This can improve the dispersibility of copper powder in the paste.

[0060] (Manufacturing method) The aforementioned copper powder can be manufactured by performing specific surface treatments on untreated copper powder. The term "untreated copper powder" here refers to copper powder that has undergone specific surface treatment, but it can also refer to copper powder that has undergone other surface treatments besides the specific surface treatment.

[0061] While untreated copper powder for specific surface treatments can be obtained through purchase or other means, it can also be produced by generating copper particles through liquid-phase methods such as chemical reduction or disproportionation.

[0062] In chemical reduction methods, for example, when using copper salt solutions such as copper sulfate as raw material solutions, the pH is adjusted by adding other bases such as sodium hydroxide, followed by the addition of a reducing agent such as hydrazine. Based on the reduction reaction 4CuSO4 + N2H4 + 8NaOH → 2Cu2O + 4Na2SO4 + 6H2O + N2, cuprous oxide powder is generated in the slurry. Subsequently, the slurry is heated, and while adjusting the pH, hydrazine is added again. For example, through the reaction 2Cu2O + N2H4 → 4Cu + 2H2O + N2, cuprous oxide is reduced to copper, generating copper particles in the liquid.

[0063] In the disproportionation method, for example, an aqueous solution containing dispersants such as gum arabic, gelatin, and collagen peptides is mixed with a slurry containing cuprous oxide powder, and sulfuric acid is added to it. Thus, copper particles are generated in the liquid by the disproportionation reaction Cu2O + H2SO4 → Cu↓ + CuSO4 + H2O.

[0064] In a specific surface treatment of the aforementioned untreated copper powder, the untreated copper powder is added to a liquid surface treatment agent containing at least SiO2, or a glass precursor, glass-forming intermediate oxide precursor, or glass-forming modified oxide precursor that generates SiO2 through thermal decomposition, polymerization, condensation, etc., and stirred to bring it into contact with the surface treatment agent. The contact between the untreated copper powder and SiO2 or the glass precursor, glass-forming intermediate oxide precursor, and glass-forming modified oxide precursor can be performed simultaneously by at least two of them, or sequentially in any order.

[0065] In surface treatment agents, glass precursors can be, for example, compounds represented by Si(OC2H5)4, such as tetraethoxysilane (TEOS) or tetraethyl orthosilicate. Glass-forming intermediate oxide precursors are those containing amphoteric metal X; specific examples include aluminum lactate, aluminum citrate, aluminum tartrate, basic aluminum formate, basic aluminum acetate, zinc acetate, tin acetate (tin diacetate, tin tetraacetate), lead acetate, etc. These specific examples of compounds can be thermally decomposed to generate Al2O3, ZnO, SnO, or PbO. Glass-forming modified oxide precursors are those containing alkaline earth metal Y; specific examples include calcium acetate, barium acetate, etc. These specific examples of compounds can be thermally decomposed to generate CaO or BaO.

[0066] Untreated copper powder is brought into contact with a surface treatment agent and then dried to obtain copper powder with a surface treatment layer.

[0067] (paste) The paste contains the aforementioned copper powder and can also be called a conductive paste. In some cases, the paste may contain adhesive resin and solvent in addition to copper powder.

[0068] Examples of adhesive resins include: cellulose resins, acrylic resins, alkyd resins, polyvinyl alcohol resins, polyvinyl acetal, ketone resins, urea resins, melamine resins, polyesters, polyamides, and polyurethanes.

[0069] As solvents, for example, the following can be used: alcohol solvents (e.g., one or more selected from the group consisting of terpineol, dihydroterpineol, isopropanol, butyl carbitol, terpineoxyethanol, and dihydroterpineoxyethanol), glycol ether solvents (e.g., butyl carbitol), and acetate solvents (e.g., one or more selected from the group consisting of butyl carbitol acetate, dihydroterpineol acetate, dihydroterpineol acetate, carbitol acetate, linalool acetate, and terpineol acetate). ketone solvents (e.g., methyl ethyl ketone), hydrocarbon solvents (e.g., one or more selected from the group consisting of toluene and cyclohexane), cellosols (e.g., one or more selected from the group consisting of ethyl cellosols and butyl cellosols), diethyl phthalate, or propionate ester solvents (e.g., one or more selected from the group consisting of dihydroterpineol propionate, dihydrocarvate propionate, and isobornyl propionate), etc.

[0070] (LTCC substrate and MLCC) In the manufacture of LTCC substrates and MLCCs, for example in the co-firing process, the following process may be carried out: the above-mentioned paste is applied to a blank containing ceramic powder by means of printing or other methods, and the paste and blank are alternately deposited and heated at the same time to fire.

[0071] The heating at this time may be carried out in an oxygen-containing environment, typically an environment containing water vapor, to remove organic matter such as binder resins and solvents that may be contained in the paste or blank. In this case, the gas generated inside the copper powder contained in the paste and undergoing sintering can be released to the outside. Here, because the copper powder in the above embodiment has a higher sintering temperature, the gas inside is fully released to the outside until the end of sintering. Therefore, the generation of bubbling can be effectively suppressed, and the copper powder can form a wiring that is a sintered body with high density after firing.

[0072] Furthermore, because of its high sintering temperature, this copper powder shrinks during firing in a manner similar to that of the ceramic powder in the blank. As a result, the formation of wire peeling or cracking caused by differential shrinkage can be effectively suppressed after firing.

[0073] The LTCC substrate or MLCC manufactured in this manner has a sintered body of ceramic powder and a sintered body of copper powder formed on the sintered body of ceramic powder.

[0074] [Example] Next, the aforementioned copper powder was tested and its properties were confirmed, and will be described below. However, this description is for illustrative purposes only and is not intended to be limiting.

[0075] (Adjustment of the surface treatment agent aqueous solution) Tetraethoxysilane (TEOS) and 0.25% by weight citric acid aqueous solution are mixed in any weight ratio and stirred at room temperature for more than 2 hours to prepare TEOS aqueous solution.

[0076] Aluminum lactate and pure water are mixed in any weight ratio and stirred at room temperature for more than 2 hours to prepare an aluminum lactate aqueous solution.

[0077] DL-calcium lactate pentahydrate is mixed with pure water in any weight ratio and stirred at room temperature for more than 2 hours to prepare an aqueous solution of calcium lactate.

[0078] Barium acetate and pure water are mixed in any weight ratio and stirred at room temperature for more than 2 hours to prepare a barium acetate aqueous solution.

[0079] Calcium acetate and pure water are mixed in any weight ratio and stirred at room temperature for more than 2 hours to prepare a calcium acetate aqueous solution.

[0080] Polypropylene glycol and pure water are mixed in any weight ratio and stirred at room temperature for more than 2 hours to prepare a polypropylene glycol aqueous solution.

[0081] (Example 1) The prepared BET specific surface area value is 2.0 m². 2 20 g of untreated copper powder was mixed with 4.5 g of 5% TEOS aqueous solution, 4.8 g of 5% aluminum lactate aqueous solution, and 3.1 g of 5% calcium lactate aqueous solution, followed by a small amount of pure water. The mixture was then kneaded using a rotary mixer (model: ARE-310, manufactured by Sinkie Co., Ltd.) at a rotation speed of 2000 rpm, a rotation speed of 800 rpm, and a kneading time of 5 minutes. The kneaded sample was then dried using a vacuum dryer (model: AVO-250-SB) at 70°C for 5 hours at a gauge pressure below -0.1 MPa. After vacuum drying, the temperature was checked for drop, and the sample was restored to atmospheric pressure. The sample was then removed and pulverized using a mortar to obtain the surface-treated copper powder of Example 1.

[0082] (Example 2) The prepared BET specific surface area value is 2.0 m². 2 50 g of untreated copper powder (at a concentration of 1 / g) was mixed with 11.1 g of 5% TEOS aqueous solution, 12.0 g of 5% aluminum lactate aqueous solution, and 7.7 g of 5% calcium lactate aqueous solution, followed by a small amount of pure water. Subsequent steps were performed in the same manner as in Example 1 to obtain the surface-treated copper powder of Example 2.

[0083] (Example 3) The prepared BET specific surface area value is 2.0 m². 2 30 g of untreated copper powder (at a concentration of 1 g / g) was mixed with 11.4 g of 5% TEOS aqueous solution, 11.7 g of 5% aluminum lactate aqueous solution, and 6.3 g of 5% barium acetate aqueous solution, followed by a small amount of pure water. Subsequent steps were performed in the same manner as in Example 1 to obtain the surface-treated copper powder of Example 3.

[0084] (Example 4) The prepared BET specific surface area value is 2.0 m². 2 30 g of untreated copper powder (at a concentration of 1 g / g) was mixed with 1.7 g of 5% TEOS aqueous solution, 1.0 g of 5% aluminum lactate aqueous solution, and 1.7 g of 5% barium acetate aqueous solution, followed by a small amount of pure water. Subsequent steps were performed in the same manner as in Example 1 to obtain the surface-treated copper powder of Example 4.

[0085] (Example 5) Prepare a specific surface area of ​​1.6 m², comprising 45.6% by mass. 2A slurry of untreated copper powder was prepared by adding 50.6 g of 20% TEOS aqueous solution, 224.2 g of 5% aluminum lactate aqueous solution, 21.0 g of 20% calcium acetate aqueous solution, and 16.5 g of 20% polypropylene glycol aqueous solution per 1 kg of untreated copper powder. The slurry was dried under nitrogen atmosphere and then pulverized to obtain the surface-treated copper powder of Example 5.

[0086] (Example 6) Prepare a specific surface area of ​​1.6 m², comprising 46.1% by mass. 2 A slurry of untreated copper powder was prepared by adding 50.6 g of 20% TEOS aqueous solution, 224.2 g of 5% aluminum lactate aqueous solution, 30.4 g of 20% barium acetate aqueous solution, and 16.5 g of 20% polypropylene glycol aqueous solution per 1 kg of untreated copper powder. The slurry was dried under nitrogen atmosphere and then pulverized to obtain the surface-treated copper powder of Example 6.

[0087] (Comparative Example 1) Its BET specific surface area is 2.0 m². 2 / g of untreated copper powder.

[0088] (Comparative Example 2) The prepared BET specific surface area value is 2.0 m². 2 20 g of untreated copper powder ( / g) was mixed with 0.74 g of 10% TEOS aqueous solution, followed by a small amount of pure water. Subsequent steps were performed in the same manner as in Example 1 to obtain the surface-treated copper powder of Comparative Example 2.

[0089] (Comparative Example 3) The prepared BET specific surface area value is 2.0 m². 2 20 g of untreated copper powder (at a concentration of 1 / g) was mixed with 12.6 g of 5% TEOS aqueous solution, 6.2 g of 5% aluminum lactate aqueous solution, and 2.5 g of 5% calcium lactate aqueous solution, followed by the addition of a small amount of pure water. Subsequent steps were performed in the same manner as in Example 1 to obtain the surface-treated copper powder of Comparative Example 3.

[0090] (Comparative Example 4) The prepared BET specific surface area value is 2.0 m². 2 20 g of untreated copper powder was mixed with 1.7 g of 5% TEOS aqueous solution, 34.1 g of 5% aluminum lactate aqueous solution, and 1.6 g of 5% calcium lactate aqueous solution, followed by the addition of a small amount of pure water. Subsequent steps were performed in the same manner as in Example 1 to obtain the surface-treated copper powder of Comparative Example 4.

[0091] (Comparative Example 5) The prepared BET specific surface area value is 2.0 m². 2 20 g of untreated copper powder was mixed with 1.9 g of 5% TEOS aqueous solution, 4.2 g of 5% aluminum lactate aqueous solution, and 1.0 g of 5% barium acetate aqueous solution, followed by the addition of a small amount of pure water. Subsequent steps were performed in the same manner as in Example 1 to obtain the surface-treated copper powder of Comparative Example 5.

[0092] (Comparative Example 6) The prepared BET specific surface area value is 2.0 m². 2 20 g of untreated copper powder was mixed with 0.8 g of 5% TEOS aqueous solution, 0.7 g of 5% aluminum lactate aqueous solution, and 1.9 g of 5% barium acetate aqueous solution, followed by the addition of a small amount of pure water. Subsequent steps were performed in the same manner as in Example 1 to obtain the surface-treated copper powder of Comparative Example 6.

[0093] (Comparative Example 7) The prepared BET specific surface area value is 2.0 m². 2 20 g of untreated copper powder was mixed with 4.5 g of 5% TEOS aqueous solution and 4.8 g of 5% aluminum lactate aqueous solution, followed by the addition of a small amount of pure water. Subsequent steps were performed in the same manner as in Example 1 to obtain the surface-treated copper powder of Comparative Example 7.

[0094] [Table 1] (evaluate) Following the method described above, the BET specific surface area and the contents of C, O, Si, Al, Ca, and Ba were determined for each copper powder from Examples 1-6 and Comparative Examples 1-7. Here, Al corresponds to the amphoteric metal X, and Ca and Ba correspond to the alkaline earth metal Y. The remaining amount was presumed to be Cu. The results are shown in Table 2.

[0095] Based on the contents of Si, Al, Ca, and Ba mentioned above, using the molar mass of Si (28.09 g / mol), Al (26.98 g / mol), Ca (40.08 g / mol), and Ba (137.33 g / mol), their molar masses α, β, and γ, as well as the values ​​of α / β, γ / β, 4α, and 2.4β + 1.6γ, were calculated. These results are also shown in Table 2.

[0096] Furthermore, according to the above method, Si-O bonds were confirmed to exist in the copper powder of Examples 5 and 6. Additionally, YO bonds, containing either compound X or compound Y, were confirmed to exist in the copper powder of Examples 5 and 6 according to the above method. As a result, in mass spectrometry analysis, peaks containing organic acids from aluminum lactate and aluminum were detected in Examples 5 and 6; peaks containing organic acids from calcium acetate and calcium were detected in Example 5; and peaks containing organic acids from barium acetate and barium were detected in Example 6.

[0097] Based on these results, it is highly likely that the copper powders of Examples 1-4, which underwent the same surface treatment as the copper powders of Examples 5-6 with respect to Si, X, and Y compounds, also contain Si-O bonds, YO bonds, and peaks containing organic acids and aluminum from aluminum lactate, organic acids and calcium from calcium acetate, or organic acids and barium from barium acetate.

[0098] [Table 2] In addition, thermomechanical analysis (TMA) was performed on each copper powder in the above order and under the above conditions to calculate the temperature at which each shrinkage rate occurred, the density after sintering, and the minimum linear expansion rate and its ratio to the ideal linear expansion rate. The results are shown in Table 3.

[0099] As an example, Example 1 will be described. In Example 1, the initial particle height was 3.303 mm, the diameter was 5.000 mm, and the weight was 0.3014 g. Since the particle was cylindrical, the density was calculated to be 4.65 g / cm³. 3 When the height and diameter of the copper powder particles shrink at the same ratio, the shrinkage to the true density of copper (8.96 g / cm³) will result in the final product being the copper powder. 3 When the linear expansion rate is -19.64%, the calculated height is 2.654 mm, the diameter is 4.018 mm, and the weight is 0.3014 g. These dimensions are taken as those of a fully sintered body at room temperature (25°C). Furthermore, a fully sintered body is defined as a sintered body without voids or impurities such as surface treatment agents, and with a density identical to the true density of copper. Since particles expand thermally, the coefficient of thermal expansion of copper (1.77 × 10⁻⁶) is considered. -5 The particle height of the fully sintered body at the temperature (902℃) where sintering reaches its maximum extent, as determined by the TMA measurements, is calculated as initial length + (initial length × coefficient of thermal expansion × temperature difference), which is 2.695 mm. When the particle height increases from the initial 3.303 mm to the fully sintered body's particle height of 2.695 mm, the linear expansion rate is -18.09%. Therefore, the theoretical ideal linear expansion rate at 902℃ is set to -18.09%.

[0100] [Table 3] According to Table 3, the 2% shrinkage temperature of the copper powders in Examples 1-6 is relatively high. In particular, the 2% shrinkage temperature of the copper powders in Examples 1-3, 5, and 6 is even higher than that of the copper powder in Example 4. This is believed to be because, compared to the copper powder in Example 4, the α / β values ​​of the copper powders in Examples 1-3, 5, and 6 are closer to 1.0, the γ / β values ​​are closer to 0.5, and the 4α value is closer to 3β+2γ. Furthermore, the ratio of linear expansion to theoretical values ​​of the copper powders in Examples 1-4 is relatively high; therefore, they can be considered copper powders that produce sintered bodies with higher density.

[0101] The copper powders in Comparative Examples 1, 2, 4, and 6 had lower 2% shrinkage temperatures. Furthermore, including Comparative Examples 3, 5, and 7, which had higher 2% shrinkage temperatures, the ratio of linear expansion to theoretical values ​​for the copper powders in Comparative Examples 1 to 7 was lower.

[0102] Based on the above, it is implied that the copper powder is sintered at a certain high temperature, resulting in a copper powder with a relatively high density after sintering.

[0103] (Potential contribution to the SDGs) The copper powder described above is sintered at a certain high temperature, resulting in a relatively high-density sintered copper powder. Therefore, it has the potential to suppress wire peeling or cracking, thereby improving the product yield. Improved product yield is related to a stable supply of products or a reduction in the consumption of limited resources, i.e., raw metal materials. Therefore, a copper powder implementation scheme may contribute to UN-led Sustainable Development Goals (SDGs) Goal 9, "Building resilient infrastructure, promoting inclusive and sustainable industrialization and pursuing innovation," or Goal 12, "Ensuring sustainable production and consumption patterns."

Claims

1. A copper powder having a surface treatment layer, and Compounds containing Si with Si-O bonds, amphoteric metal X, and alkaline earth metal Y. The amount of Si, α (mol), the amount of the amphoteric metal X, and the amount of the alkaline earth metal Y, γ (mol), satisfy equation (I): α / β ≥ 0.8, equation (II): γ / β ≥ 0.4, and equation (III): 4α ≥ 2.4β + 1.6γ.

2. The copper powder according to claim 1, wherein, The amphoteric metal X contains Al.

3. The copper powder according to claim 1, having a BET specific surface area of ​​0.13 m². 2 / g or more.

4. The copper powder according to claim 1, in XPS analysis, has at least one of the following peaks: Ca2p with a binding energy in the range of 345–350 eV. 3 / 2 Sr3d with peaks and binding energies in the range of 132–137 eV 5 / 2 Ba3d with peaks and binding energies in the range of 778–783 eV 5 / 2 The peak.

5. The copper powder according to claim 2, wherein it contains at least a portion of the amphoteric metal X in the form of a compound of the amphoteric metal X. The compound of the amphoteric metal X comprises at least one selected from the group consisting of hydroxycarboxylate salts, carboxylate salts, and compounds having XO bonds.

6. The copper powder according to claim 5, wherein, The compound of the amphoteric metal X contains the hydroxycarboxylate. The hydroxycarboxylate comprises at least one selected from the group consisting of lactate, citrate and tartrate.

7. The copper powder according to claim 5, wherein, The compound of the amphoteric metal X includes the carboxylate. The carboxylate comprises basic formate and / or basic acetate.

8. The copper powder according to claim 1, wherein, The alkaline earth metal Y comprises at least one selected from the group consisting of Ca, Ba, and Sr.

9. The copper powder according to claim 8, wherein it contains at least a portion of the alkaline earth metal Y in the form of a compound of the alkaline earth metal Y. The compound of the alkaline earth metal Y comprises at least one selected from the group consisting of hydroxides, carboxylates, hydroxycarboxylates, nitrates, and compounds having YO bonds.

10. The copper powder according to claim 9, wherein, The compound of the alkaline earth metal Y includes the carboxylate. The carboxylates include formate and / or acetate.

11. The copper powder according to claim 9, wherein, The compound of the alkaline earth metal Y includes the hydroxycarboxylate. The hydroxycarboxylic acid salt contains lactate.

12. The copper powder according to any one of claims 1 to 11, wherein, in thermomechanical analysis (TMA), in an environment containing nitrogen and water vapor with a water vapor pressure of 3.6 kPa, the 2% shrinkage temperature when heated from room temperature to 1000°C is above 500°C.

13. The copper powder according to any one of claims 1 to 11, wherein, in thermomechanical analysis (TMA), during the process of heating from room temperature to 1000°C in an environment containing nitrogen and water vapor with a water vapor pressure of 3.6 kPa, the minimum value of the linear expansion rate is more than 95% of the theoretical ideal linear expansion rate, said theoretical ideal linear expansion rate being calculated based on the true density and thermal expansion rate of copper at the temperature at which said minimum linear expansion rate is obtained.

14. The copper powder according to any one of claims 1 to 11, wherein it is used for calcination in an environment containing oxygen atoms.

15. The copper powder according to any one of claims 1 to 11, wherein, The quantities α, β and γ of the substance satisfy equation (I'): α / β≦3.0, equation (II'): γ / β≦2.0, and equation (III'): 4α≦3.6β+2.4γ.

16. The copper powder according to any one of claims 1 to 11, wherein, The content of Si, the content of the amphoteric metal X, and the content of the alkaline earth metal Y are each less than 5.0 atomic%.

17. A paste comprising copper powder according to any one of claims 1 to 11.

18. A sintered body, which is a sintered body of copper powder, wherein the copper powder comprises any one of claims 1 to 11.

19. A composite comprising a sintered body of ceramic powder and a sintered body of copper powder as described in claim 18 formed on the sintered body of the ceramic powder.

20. A low-temperature co-fired ceramic substrate comprising the composite of claim 19.

21. A multilayer ceramic capacitor comprising the composite of claim 19.

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