JP4150638B2 - Inorganic oxide-coated metal powder and method for producing the inorganic oxide-coated metal powder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention according to the present application relates to an inorganic oxide-coated metal powder and a method for producing the inorganic oxide-coated metal powder. An object of the present invention is to provide an inorganic oxide-coated metal powder that is particularly suitable for ceramic materials.
[0002]
[Prior art]
Conventionally, copper powder and silver powder have been widely used as raw materials for copper paste and silver paste and low-temperature fired ceramic substrates. Due to the ease of handling, the former metal paste has been used to easily form a conductor circuit in a wide range from the use for experimental purposes to the use in the electronics industry. For example, for sample preparation of an electron microscope, routing of a conductor circuit of a printed wiring board, formation of an interlayer conductive conductor as an alternative to a through hole for obtaining interlayer conduction of a multilayer printed wiring board, electrode formation of a ceramic capacitor, and the like. Among various applications, especially when used for a low-temperature fired ceramic substrate, dimensional stability when processed into a green sheet and sintered is an important issue.
[0003]
The production of such metal powder for low-temperature fired ceramics can be broadly classified and classified into a dry production method and a wet production method. It is appropriate to consider the latter wet manufacturing method as a method of manufacturing by directly depositing metal powder from a solution containing a target metal element. Therefore, the former dry production method includes not only a pulverization method using a completely mechanical method but also an atomization method using a molten metal.
[0004]
As a feature of the metal powder obtained by these methods, the metal powder obtained by the former dry production method has a crystallite diameter of 40 to 50 nm and is relatively large, and the metal powder is fired on a low-temperature fired ceramic substrate. In this case, it has an advantage of excellent oxidation resistance and shrinkage resistance. In contrast, the metal powder produced by the wet production method generally has a crystallite diameter of 35 nm or less and is smaller than the metal powder obtained by the dry production method, and is resistant to oxidation during firing of a low-temperature fired ceramic substrate. It has a disadvantage that it is inferior in resistance and shrinkage resistance. Shrinkage resistance is said to depend on the size of the metal powder crystallites. That is, the larger the crystallite diameter, the smaller the shrinkage when heated at a high temperature and the better the shrinkage resistance.
[0005]
The metal powder as used in the present specification is used for the production of a metal powder-containing slurry, and is mainly used for use as a low-temperature fired ceramic by processing into a green sheet of low-temperature fired ceramic and firing. Therefore, the metal powder which is easily oxidized and inferior in oxidation resistance greatly changes the quality of the low-temperature fired ceramic. Furthermore, when the crystallite diameter is small, the metal powder has a large shrinkage ratio and poor shrinkage resistance. When the binder of the slurry containing the metal powder is fired to remove the binder, the shrinkage behavior becomes large and the dimensional accuracy of the low-temperature fired ceramic. It is difficult to maintain a good state. As far as these things are considered, it seems desirable to use metal powder produced by a dry production method.
[0006]
[Patent Document 1]
US Pat. No. 5,126,915 [0007]
[Problems to be solved by the invention]
However, as a characteristic of the powder obtained by the dry production method, there is a defect that the particle size distribution is broad and it is difficult to produce a fine powder with high accuracy. In recent years, the requirements for the finishing accuracy of the surface of low-temperature fired ceramics have become more and more strict, and the weight cumulative particle size D ₅₀ by the laser diffraction scattering type particle size distribution measurement method is 10 μm or less, and the metal powder has a narrow particle size distribution. Therefore, the demand for metal powder having excellent dispersibility has become remarkable.
[0008]
Moreover, even in the case of such fine metal powders, it is desired in the market that the powder be excellent in oxidation resistance during firing of a low-temperature fired ceramic and in shrinkage resistance with small shrinkage behavior during firing. It has come. In order to satisfy this requirement, it is desirable to satisfy these requirements using a metal powder having a fine particle size and a sharp particle size distribution obtained by a wet manufacturing method.
[0009]
In order to improve the shrinkage resistance, when trying to increase the crystallite diameter of the metal powder obtained by the wet method, the metal powder can be heated to grow the grain size inside the powder grain. That's fine. Therefore, it is considered that the metal powder obtained by the wet method may be simply heated.
[0010]
However, simply heating in the normal metal powder state will oxidize the surface of the metal powder, forming an oxide film on the surface, and the agglomerated state will proceed significantly. The properties are significantly impaired. If such a powder is used for the production of a low-temperature fired ceramic, the resulting low-temperature fired ceramic has a rough surface. Therefore, by simply heating ordinary copper powder, it is possible to provide metal powder having a small particle size with a sharp particle size distribution, having excellent oxidation resistance and shrinkage resistance as well as ensuring dispersibility of the particles. It was difficult.
[0011]
[Means for Solving the Problems]
Therefore, as a result of earnest research, the inventors of the present invention can obtain a metal powder having a large crystallite diameter by previously coating copper powder or silver powder obtained by a wet manufacturing method with an inorganic oxide layer. I came up with something. The present invention will be described below.
[0012]
In the claim, “inorganic oxide coated metal powder having an inorganic oxide layer on the surface of copper powder or silver powder, the inorganic oxide layer being 0.1% by mass of the weight of the inorganic oxide coated metal powder. It is composed of any one of silicon oxide, aluminum oxide, magnesium oxide, zirconium oxide and zinc oxide having a converted mass thickness of 10% by mass , and the crystallite diameter of copper powder or silver powder is 50 nm or more. The characteristic inorganic oxide-coated metal powder. " That is, the inorganic oxide layer is provided on the surface of the powder of copper powder or silver powder having a crystallite diameter of 50 nm or more. The shrinkage resistance can be improved by making the crystallite diameter larger than the crystallite diameter of the metal powder obtained by the conventional wet manufacturing method.
[0013]
The metal powder at this stage is not particularly limited as long as it is a metal material that can be used for low-temperature fired ceramics. However, considering the powder characteristics required for metal powders used in the production of low-temperature fired ceramics in recent years, it is preferable to use either copper powder or silver powder obtained by a wet manufacturing method.
[0014]
In addition, any one of silicon oxide, aluminum oxide, magnesium oxide, zirconium oxide, and zinc oxide is used for the inorganic oxide layer. Among these, it is preferable to use any one of silicon oxide, aluminum oxide, and magnesium oxide. Zinc oxide is particularly preferable when silver powder is used as the core material. Silicon oxide, aluminum oxide, and magnesium oxide are easily fixed uniformly on the surface of copper powder or silver powder. At the same time, considering that the firing temperature of the low-temperature fired ceramic is generally 900 ° C. or more, it functions most effectively as a barrier layer for preventing the aggregation of copper powder or silver powder as the core material. .
[0015]
However, it is difficult to physically indicate the thickness of the inorganic oxide layer as a gauge thickness because of the nature of a metal powder that is an aggregate of fine particles. Therefore, the present inventors decided to express the thickness of the inorganic oxide layer as a converted mass thickness. The reduced mass thickness, and displays in mass% as a proportion of the inorganic oxide layer in the inorganic oxide coated metal powder mass. Strictly, when considering the converted mass thickness, it is necessary to consider the particle size of the metal powder. As the quality of the metal powder is constant, if the presence of a metal powder and the particle size diameter is small and a large metal powder, larger in specific surface area of the former, the particulate with the same amount of inorganic oxide surface This is because if the coating is performed, the former inorganic oxide layer of the metal powder becomes thinner.
[0016]
Therefore, the present inventors considered the particle size of copper powder or silver powder required in the current low-temperature fired ceramics, and the value of the weight cumulative particle size D ₅₀ by the laser diffraction scattering particle size distribution measurement method is 0.1 μm. The equivalent mass thickness of the inorganic oxide layer when copper powder or silver powder of 10 μm is targeted is that the inorganic oxide coating amount of the inorganic oxide-coated metal powder is 0.1% by mass to 10% by mass. It is revealed.
[0017]
When the coating amount is less than 0.1% by mass, it does not serve as a barrier layer for preventing the agglomeration of particles due to heating during firing of the low-temperature fired ceramic. On the other hand, when the thickness exceeds 10% by mass, the dispersibility of the obtained inorganic oxide-coated metal powder is deteriorated. By forming an inorganic oxide layer having such a uniform thickness, the inorganic oxide-coated metal powder according to the present invention does not have electrical conductivity by itself. Furthermore, it is more preferable to employ 1% by mass to 10% by mass in order to eliminate the variation in production to ensure stable non-conductivity and to stabilize the obtained shrinkage resistance. By adopting the coating amount of the inorganic oxide as described above, the crystallite diameter can be adjusted by performing sufficient heat treatment for the first time.
[0018]
The production of the inorganic oxide-coated metal powder described above is performed by the following method. Method of producing an inorganic oxide coated metal powder for the conductor circuit formed according to the present invention, the granular surface of the copper powder or silver powder, the inorganic oxide to the granular surface by affixing at Mekanokemika Le techniques The crystallite diameter of copper powder or silver powder is adjusted to 50 nm or more by forming an inorganic oxide layer and performing heat treatment. That is, it is possible to set the heat treatment temperature high by coating the surface of copper powder or silver powder with an inorganic oxide layer. As a result, the crystallite diameter can be made equal to or larger than the crystallite diameter of the copper powder or silver powder obtained by the dry production method.
[0019]
And at this manufacturing method, "the particulate surface of the copper powder or silver powder, is fixed by Mekanokemika Le techniques inorganic oxide" and, the powder of the inorganic oxide to be fixed to the copper powder or silver powder and its surface the door, or by stirring and mixing, and the like using a media mill method, and than to fix the inorganic oxide particulate surface of the copper powder or silver powder, copper powder or silver powder particulate and inorganic oxide powder A device capable of mixing and colliding with powder particles is sufficient, and no special equipment is required. As the inorganic oxide powder used at this time, a powder having a specific surface area of 50 m ² / g or more is preferably used. This specific surface area depends mainly on the particle diameter of the inorganic oxide powder, and it can be said that the particle diameter decreases as the specific surface area increases.
[0020]
And heat processing is performed under the following conditions. Strictly speaking, the condition is changed according to the type of metal powder. This heat treatment is to promote so-called recrystallization and increase the crystallite diameter. However, this heat treatment should not promote the aggregation of the surface of the copper powder or silver powder itself so as not to change the quality of the inorganic oxide-coated metal powder.
[0021]
In consideration of these, when using copper powder, it is desirable to perform the heat treatment in a reducing atmosphere or an inert gas atmosphere at 500 ° C. to 1000 ° C. Heating at a temperature of less than 500 ° C. makes it difficult to recrystallize the copper powder crystals obtained by the wet manufacturing method. On the other hand, when heating at a temperature exceeding 1000 ° C., the aggregation of the copper powder, which is the core material, progresses and the copper powder itself is softened even if an inorganic oxide layer is present. Is going to get worse. And since copper itself tends to oxidize very easily, it is preferable to employ a reducing atmosphere or an inert gas atmosphere as the heating atmosphere.
[0022]
Moreover, at the case of using the silver powder at a temperature of the heat treatment is 350 ° C. to 900 ° C., it is desirable to perform in the atmosphere, either a reducing atmosphere or an inert gas atmosphere atmosphere. This heat treatment is performed for the purpose of adjusting the crystallite diameter, and vaporizing organic impurities contained in the silver powder and causing heat expansion, and degassing treatment. Therefore, when heating at a temperature of less than 350 ° C., the degassing treatment of impurities cannot be performed satisfactorily, and it becomes difficult to recrystallize the silver powder crystals obtained by the wet manufacturing method. On the other hand, when heating is performed at a temperature exceeding 900 ° C., even if an inorganic oxide layer is present, oxidation progresses to the surface of the silver powder as the core material, and the silver powder itself softens. This is because the shape of the powder particles is deteriorated. And in the case of silver, since it is hard to oxidize compared with copper, it is possible to use an air atmosphere as a heating atmosphere, and naturally adopting a reducing atmosphere or an inert gas atmosphere can also improve the safety of quality. This is preferable.
[0023]
By adopting such a production method, the progress of the aggregation of the inorganic oxide-coated metal powder is prevented, and “the average particle diameter D ₅₀ by the laser diffraction scattering type particle size distribution measuring method and the standard deviation SD of the particle size distribution are determined. than it is possible so as not to exacerbate the coefficient of variation CV value "that you express in relation SD _{/ D 50} × 100. The “standard deviation SD” is a standard deviation obtained from the particle size distribution of the powder obtained as a result of measurement using the laser diffraction / scattering particle size distribution measuring method, and the value of this CV value is small. It means that the particle size of the particles is uniform, the dispersibility is excellent, and there is no large variation.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the present invention through an embodiment while comparing with a comparative example.
[0025]
1st Embodiment: The manufacturing method of the copper powder first used as a core material is demonstrated. 4 kg of copper sulfate (pentahydrate) and 120 g of aminoacetic acid were dissolved in water to prepare an 8 L (liter) copper salt aqueous solution having a liquid temperature of 60 ° C. While stirring this aqueous solution, 5.75 kg (1.15 equivalents) of 25 wt% sodium hydroxide solution was quantitatively added over about 30 minutes, and stirring was performed at a liquid temperature of 60 ° C. for 60 minutes. The cupric oxide was produced by aging until the color was completely black. Thereafter, the mixture was allowed to stand for 30 minutes, 1.5 kg of glucose was added, and the cupric oxide was reduced to cuprous oxide by aging for 1 hour. Furthermore, 1 kg of hydrated hydrazine was quantitatively added over 5 minutes to reduce cuprous oxide to form metallic copper, thereby producing a copper powder slurry.
[0026]
Then, the obtained copper powder slurry was filtered, sufficiently washed with pure water, filtered again, and dried to obtain copper powder. The weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method of a copper powder is 0.93 .mu.m, C V value is 0.22, and the crystallite diameter was 32.2nm. As a result of measuring the thermal expansion coefficient, the shrinkage rate at 900 ° C. was 13.0%.
[0027]
In addition, the measurement of the crystallite diameter in the present specification is obtained by calculating the average crystallite diameter using RINTKU V made by RIGaku and using the crystallite analysis software. The crystallite diameter in the present specification is the average crystal diameter. It is a child diameter. The shrinkage rate was measured by putting 20 g of powder used for measurement into 20 g of a solution of 95 wt% terpineol C and 5 wt% ethyl cellulose, kneading with a three roll, and then at a temperature of 80 ° C. for 1 hour. It was dried and put into a powder state again. Then, the thermal expansion coefficient is continuously measured while heating the obtained powder in a predetermined atmosphere using a thermomechanical analyzer (TMA / SS6000 manufactured by Seiko Denshi Kogyo Co., Ltd.) at a heating rate of 10 ° C./min. The thermal shrinkage rate when the ambient temperature was 900 ° C. was measured.
[0028]
Then, a copper powder 1kg and an inorganic oxide and a silicon oxide powder 0.05 kg, using hybrida homogenizer, at a rotational speed of 6000 rpm, perform mechanochemical fixation for 5 minutes, the silicon oxide-coated copper powder Manufactured. The coating amount of silicon oxide coated on the surface of the silicon oxide-coated copper powder at this stage was 5% by mass. Weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method of the silicon oxide-coated copper powder before the heating is 0.94 .mu.m, C V value is 0.25, and the crystallite diameter in the 28.2nm there were. As a result of measuring the thermal expansion coefficient, the shrinkage rate at 900 ° C. was 6.3%. In other words, the copper powder is subjected to mechanochemical processing, so the crystallite diameter is smaller than the copper powder obtained by the original wet manufacturing method, but the thermal expansion due to the presence of the oxide coating layer. Although the shrinkage rate at that time was also small, it was not enough to fall within the range required by the market.
[0029]
Therefore, the silicon oxide-coated copper powder obtained as described above is heated at 500 ° C., 700 ° C., and 900 ° C. for 1 hour in a nitrogen gas atmosphere with a hydrogen concentration of 1 wt% to reduce the crystallite diameter. Three types of adjusted silicon oxide-coated copper powder were obtained. As a result, (i) when the temperature of 500 ° C. is adopted, the weight cumulative particle diameter D ₅₀ of the laser diffraction scattering type particle size distribution measurement method of the heated silicon oxide-coated copper powder is 0.92 μm, and the crystallite diameter Is 52.6 nm , and the CV value is 0.24. (Ii) Weight cumulative particles of a laser diffraction scattering type particle size distribution measurement method of silicon oxide-coated copper powder after heating when a temperature of 700 ° C. is adopted The diameter D ₅₀ is 0.93 μm, the crystallite diameter is 58.4 nm , the CV value is 0.25, and (iii) silicon oxide-coated copper powder after heating when a temperature of 900 ° C. is adopted the weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method is 0.94 .mu.m, crystallite size 66.8nm, C V value was 0.24.
[0030]
From this result, the crystallite diameter is the same as the copper powder obtained by the dry manufacturing method when temperatures of 500 ° C. and 700 ° C. are adopted, and when heated at a temperature of 900 ° C., the dry crystal type is obtained. It can be seen that a crystallite size larger than the copper powder obtained by the production method is obtained. Moreover, even if it heats at any temperature, it turns out that it has not deteriorated greatly seeing from the CV value of the copper powder before forming an inorganic oxide layer.
[0031]
Furthermore, as a result of measuring the coefficient of thermal expansion by the same method as described above using three types of silicon oxide-coated copper powder, the shrinkage rate at 900 ° C. employed (i) a heating temperature of 500 ° C. In the case, the shrinkage rate of the silicon oxide-coated copper powder after heating is 2.5%, and (ii) the shrinkage rate of the silicon oxide-coated copper powder after heating is 2.0% when a heating temperature of 700 ° C. is adopted. (Iii) When the heating temperature of 900 ° C. was adopted, the shrinkage ratio of the silicon oxide-coated copper powder after heating was 1.2%, and all were within the shrinkage ratio of 3%, which is said to be ideal. .
[0032]
2nd Embodiment: Since the copper powder used by this embodiment used what was obtained with the same manufacturing method as used in 1st Embodiment, in order to avoid the overlapping description, description here is abbreviate | omitted. That is, the weight cumulative particle diameter D _{50 of} the laser diffraction scattering type particle size distribution measurement method is 0.93 μm , the CV value is 0.22, the crystallite diameter is 32.2 nm, and the shrinkage rate at 900 ° C. is 13.0%. Copper powder was used as the core material.
[0033]
Then, the oxide and aluminum powder 0.03kg a copper powder 1kg and an inorganic oxide, with hybrida homogenizer, at a rotational speed of 6000 rpm, perform mechanochemical fixation for 5 minutes, the aluminum oxide-coated copper powder Manufactured. The coating amount of the aluminum oxide coated on the surface of the aluminum oxide-coated copper powder at this stage was 3% by mass. Weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method of the aluminum oxide coated copper powder before the heating is 0.92 .mu.m, C V value is 0.25, and the crystallite diameter in the 27.8nm there were. As a result of measuring the thermal expansion coefficient, the shrinkage rate at 900 ° C. was 4.2%. In other words, the copper powder is subjected to mechanochemical processing, so the crystallite diameter is smaller than the copper powder obtained by the original wet manufacturing method, but the thermal expansion due to the presence of the oxide coating layer. Although the shrinkage rate at that time was also small, it was not enough to fall within the range required by the market.
[0034]
Therefore, the aluminum oxide-coated copper powder obtained as described above was heated at 900 ° C. for 1 hour in a reducing atmosphere with a hydrogen concentration of 1 wt% to adjust the crystallite diameter. As a result, the weight cumulative particle diameter D ₅₀ of the aluminum oxide-coated copper powder after heating was 0.93 μm, the crystallite diameter was 68.0 nm , and the CV value was 0.26. Met. It can be seen that this crystallite size is larger than the copper powder obtained by the dry production method. Furthermore, as a result of measuring the thermal expansion coefficient by the same method as described above using the above-described aluminum oxide-coated copper powder, the shrinkage rate at 900 ° C. is 0.6%, and the shrinkage rate is within 3%. It was settled in.
[0035]
3rd Embodiment: Since the copper powder used by this embodiment used what was obtained with the same manufacturing method as used in 1st Embodiment, in order to avoid the overlapping description, description here is abbreviate | omitted. That is, the weight cumulative particle diameter D _{50 of} the laser diffraction scattering type particle size distribution measurement method is 0.93 μm , the CV value is 0.22, the crystallite diameter is 32.2 nm, and the shrinkage rate at 900 ° C. is 13.0%. Copper powder was used as the core material.
[0036]
Then, a copper powder 1kg and an inorganic oxide and a magnesium oxide powder 0.03 kg, using hybrida homogenizer, at a rotational speed of 6000 rpm, perform mechanochemical fixation for 5 minutes, the magnesium oxide-coated copper powder Manufactured. The coating amount of magnesium oxide coated on the surface of the magnesium oxide-coated copper powder at this stage was 3% by mass. Weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method of this heating before the magnesium oxide coating copper powder is 0.92 .mu.m, C V value is 0.28, and the crystallite diameter in the 28.2nm there were. As a result of measuring the thermal expansion coefficient, the shrinkage rate at 900 ° C. was 5.8%. In other words, the copper powder is subjected to mechanochemical processing, so the crystallite diameter is smaller than the copper powder obtained by the original wet manufacturing method, but the thermal expansion due to the presence of the oxide coating layer. Although the shrinkage rate at that time was also small, it was not enough to fall within the range required by the market.
[0037]
Therefore, the magnesium oxide-coated copper powder obtained as described above was heated at a temperature of 900 ° C. for 1 hour in a reducing atmosphere with a hydrogen concentration of 1 wt% to adjust the crystallite diameter. As a result, a weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method of the magnesium oxide-coated copper powder after heating is 0.93 .mu.m, the crystallite diameter 60.6 nM, C V value, 0.26 Met. It can be seen that this crystallite size is larger than the copper powder obtained by the dry production method. Furthermore, as a result of measuring the thermal expansion coefficient by the same method as described above using the above-described aluminum oxide-coated copper powder, the shrinkage rate at 900 ° C. was 1.1%, and the shrinkage rate was within 3%. It was settled in.
[0038]
4th Embodiment: The manufacturing method of the silver powder first used as a core material is demonstrated. Here, 300 g of silver nitrate is added to 360 ml of ion-exchanged water in a reaction vessel and completely dissolved, and then 300 ml of 25 wt% ammonia water is added and stirred to prepare an ammine silver complex aqueous solution. The temperature was adjusted. Then, the ammine silver complex aqueous solution was added in about 3 seconds, and the mixture was stirred for about 3 minutes to complete the reduction precipitation of silver particles. Thereafter, silver particles were collected by filtration, sufficiently washed with pure water, and dried to obtain silver powder.
[0039]
The weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method of silver is 1.51 .mu.m, C V value is 0.34, and the crystallite diameter was 7.7 nm. As a result of measuring the thermal expansion coefficient, the shrinkage rate at 900 ° C. was 16.0%. The thermal expansion coefficient was measured by the same method as described in the first embodiment.
[0040]
Then, a silicon oxide powder 0.05kg is this silver powder 1kg and an inorganic oxide, with hybrida homogenizer, at a rotational speed of 6000 rpm, perform mechanochemical fixation treatment for 5 minutes to produce a silicon oxide coating silver . The coating amount of silicon oxide coated on the surface of the silicon oxide-coated silver powder at this stage was 5% by mass. Weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method of the silicon oxide coated silver powder before the heating is 1.30 .mu.m, C V value is 0.27, and the crystallite diameter 6.8nm met It was. As a result of measuring the thermal expansion coefficient, the shrinkage at 900 ° C. was 7.0%. That is, the silver powder is subjected to mechanochemical processing, so that the crystallite diameter is smaller than the silver powder obtained by the original wet manufacturing method, but the oxide coating layer exists, Although the shrinkage rate is small, the shrinkage rate is within the range required by the market.
[0041]
Therefore, the silicon oxide-coated silver powder obtained as described above was heated in the air at a temperature of 450 ° C. for 1 hour to obtain a silicon oxide-coated silver powder having an adjusted crystallite diameter. As a result, the weight-cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method of the silicon oxide coated silver powder after heating is 1.32 .mu.m, crystallite size 60.0nm, C V value is 0.33 there were.
[0042]
From this result, the crystallite diameter is larger than the silver powder obtained by the dry production method (the crystallite diameter of the silver powder obtained by the dry production method is generally 30 to 40 nm). I understand that. Moreover, even after heating, it can be seen that the CV value of the silver powder before forming the inorganic oxide layer is not significantly deteriorated.
[0043]
Furthermore, as a result of measuring the thermal expansion coefficient by the same method as described above using the silicon oxide-coated silver powder after heating, the shrinkage rate at 900 ° C. is 2.1%, which is 5% which is said to be ideal. It was within the shrinkage rate.
[0044]
Fifth Embodiment: Since the silver powder used in this embodiment is the same as that used in the fourth embodiment, it is not described here to avoid duplicate description. That is, the weight cumulative particle diameter D _{50 of} the laser diffraction scattering particle size distribution measurement method is 1.51 μm , the CV value is 0.34, the crystallite diameter is 7.7 nm, and the shrinkage rate at 900 ° C. is 16.0%. Silver powder was used as the core material.
[0045]
Then, the oxide and aluminum powder 0.05kg is this silver powder 1kg and an inorganic oxide, with hybrida homogenizer, at a rotational speed of 6000 rpm, perform mechanochemical fixation treatment for 5 minutes to produce an aluminum oxide coating silver . The coating amount of the aluminum oxide coated on the surface of the aluminum oxide-coated silver powder at this stage was 5% by mass. Weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method of the aluminum oxide coated silver powder before the heating is 1.33, C V value is 0.27, and the crystallite diameter 6.3nm met It was. As a result of measuring the thermal expansion coefficient, the shrinkage rate at 900 ° C. was 6.5%. That is, the silver powder is subjected to mechanochemical processing, so that the crystallite diameter is smaller than the silver powder obtained by the original wet manufacturing method, but the oxide coating layer exists, Although the shrinkage rate is small, the shrinkage rate is within the range required by the market.
[0046]
Therefore, the aluminum oxide-coated silver powder obtained as described above was heated at 450 ° C. for 1 hour in the air atmosphere to adjust the crystallite diameter. As a result, the weight-cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method of the aluminum oxide coated silver powder after heating is 1.31 .mu.m, crystallite size 68.0nm, C V value is 0.32 there were. It can be seen that the crystallite size is larger than the silver powder obtained by the dry production method. In addition, even after heating, it can be seen that the value is rather good when viewed from the CV value of the silver powder after forming the inorganic oxide layer before heating. Furthermore, as a result of measuring the thermal expansion coefficient by the same method as described above using the above-mentioned aluminum oxide coated silver powder, the shrinkage rate at 900 ° C. was 1.8%, and the shrinkage rate was within 5%. It was settled.
[0047]
Sixth Embodiment: Since the silver powder used in this embodiment is the same as that used in the fourth embodiment, the silver powder used is not described here to avoid redundant description. That is, the weight cumulative particle diameter D _{50 of} the laser diffraction scattering particle size distribution measurement method is 1.51 μm , the CV value is 0.34, the crystallite diameter is 7.7 nm, and the shrinkage rate at 900 ° C. is 16.0%. Silver powder was used as the core material.
[0048]
Then, a magnesium oxide powder and 0.05kg is this silver powder 1kg and an inorganic oxide, with hybrida homogenizer, at a rotational speed of 6000 rpm, perform mechanochemical fixation treatment for 5 minutes to produce a magnesium oxide coated silver powder . The coating amount of magnesium oxide coated on the surface of the magnesium oxide-coated silver powder at this stage was 5% by mass. Weight cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method of the magnesium oxide coating silver before the heating is 1.21, C V value is 0.28, and the crystallite diameter 6.5nm met It was. As a result of measuring the thermal expansion coefficient, the shrinkage rate at 900 ° C. was 7.1%. That is, the silver powder is subjected to mechanochemical processing, so that the crystallite diameter is smaller than the silver powder obtained by the original wet manufacturing method, but the oxide coating layer exists, Although the shrinkage rate is small, the shrinkage rate is within the range required by the market.
[0049]
Therefore, the magnesium oxide-coated silver powder obtained as described above was heated in an air atmosphere at a temperature of 450 ° C. for 1 hour to adjust the crystallite diameter. As a result, the weight-cumulative particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method of the magnesium oxide coating silver after heating is 1.23 [mu] m, crystallite diameter 60.6 nM, C V value is 0.33 there were. It can be seen that the crystallite size is larger than the silver powder obtained by the dry production method. In addition, even after heating, it can be seen that the value is rather good when viewed from the CV value of the silver powder after forming the inorganic oxide layer before heating. Furthermore, as a result of measuring the thermal expansion coefficient by the same method as described above using the above-described magnesium oxide-coated silver powder, the shrinkage rate at 900 ° C. was 2.0%, and the shrinkage rate was within 5%. It was settled.
[0050]
【The invention's effect】
The inorganic oxide-coated metal powder according to the present invention is heated at a high temperature because it has a large crystallite diameter while maintaining uniform fineness and excellent dispersibility, which are the advantages of copper powder or silver powder obtained by a wet manufacturing method. It has excellent shrinkage resistance when subjected to By using this inorganic oxide-coated metal powder, it is possible to improve the dimensional stability of a sintered body containing a metal powder such as a low-temperature fired ceramic, and it is possible to dramatically improve the product yield. . In addition, the inorganic oxide coated metal powder uses copper powder, silver powder or the like as a core material and has an inorganic oxide layer on its surface layer, so that the aggregation of copper powder or silver powder of the core material does not proceed. Since high-temperature heating is possible, it is easy to adjust the crystallite diameter of the copper powder or silver powder of the core material, and the above-described unique manufacturing method can be employed.

Claims (5)

An inorganic oxide-coated metal powder comprising an inorganic oxide layer on the surface of copper powder or silver powder,
The inorganic oxide layer is composed of any one of silicon oxide, aluminum oxide, magnesium oxide, zirconium oxide, and zinc oxide having a converted mass thickness of 0.1 mass% to 10 mass% of the weight of the inorganic oxide-coated metal powder. And
And the inorganic oxide coat metal powder characterized by the crystallite diameter of copper powder or silver powder being 50 nm or more. The inorganic oxide-coated metal powder according to claim 1, wherein copper powder or silver powder having a weight cumulative particle diameter D ₅₀ measured by a laser diffraction / scattering particle size distribution measurement method of 0.1 μm to 10 μm is used . It is a manufacturing method of the inorganic oxide coat metal powder according to claim 1 or 2,
Form an inorganic oxide layer on the surface of the powder by fixing the inorganic oxide on the surface of the powder of copper powder or silver powder by a mechanochemical method,
Then, the crystallite diameter of copper powder or silver powder is adjusted to 50 nm or more by heat-treating, The manufacturing method of the inorganic oxide coat metal powder characterized by the above-mentioned.   The method for producing an inorganic oxide-coated metal powder according to claim 3, wherein the heat treatment is performed in a reducing atmosphere or an inert gas atmosphere at 500 ° C to 1000 ° C when using copper powder.   The inorganic oxide coat according to claim 3, wherein when silver powder is used, the heat treatment is performed at a temperature of 350 ° C to 900 ° C in any one of an air atmosphere, a reducing atmosphere, and an inert gas atmosphere. A method for producing metal powder.