JP2017082259A - Manufacturing method of solvent-added metal powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of metal powder that enables easy dry classification without causing an adverse effect when made into a paste-like state, through adhering a solvent to be used in a conductive paste onto metal powder, and also to provide a dry classification method using the metal powder.SOLUTION: The manufacturing method is of solvent-added metal powder having, on a surface thereof, a solvent I configured to form a conductive paste. The metal powder is formed through an adhesion process of adhering the solvent I on the surface of the metal powder by using a solvent II having a flash point lower than a flash point of the solvent I. When the metal powder at least having adhesion of the solvent I is dried, the residual amount of the solvent I present on the surface of metal powder after the drying is 0.5-10 mass%.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a metal powder used for a conductive paste used for wiring layers and electrodes of circuit boards, electrodes of electronic components, and the like.

  Metal powder is used as a material for a conductive paste for producing a thick film conductor. This thick film conductor is used for the formation of wiring layers and electrodes of circuit boards, and electrodes of multilayer ceramic components such as multilayer ceramic capacitors and multilayer ceramic substrates.

The conductive paste used for this thick film conductor is manufactured as follows.
The conductive paste is produced by kneading a metal powder, a vehicle containing a resin such as ethyl cellulose, and an organic solvent such as terpineol or dihydroterpineol together with a minute amount of additives for adjusting dispersibility and viscosity.

As an example of a thick film conductor using a conductive paste, an internal electrode of a multilayer ceramic capacitor using nickel powder as a metal powder will be described.
First, a conductive paste is screen printed on a dielectric green sheet. Next, a dielectric green sheet is placed on the printed conductive paste, and the screen printing of the conductive paste on the surface is laminated so as to be alternately overlapped, and then the laminate is formed by pressure bonding. Thereafter, the laminate is cut into a predetermined size, and after removing the binder in a weakly oxidizing atmosphere in order to burn and remove the resin such as ethyl cellulose used as the organic binder, it is 1300 ° C. in a reducing atmosphere. A ceramic body is produced by firing at a high temperature. An external electrode is attached to the produced ceramic body to obtain a multilayer ceramic capacitor.

In the multilayer capacitor, the metal powder in the conductive paste that becomes the internal electrode is mainly a base metal such as nickel rather than the noble metal. Therefore, the binder removal treatment of the multilayer body is to prevent the nickel powder from being oxidized as much as possible. And in an atmosphere containing a very small amount of oxygen or water vapor.
In recent years, high integration of electric circuits, miniaturization of electronic components, and large capacity have been demanded. For example, in multilayer ceramic capacitors, both internal electrodes and dielectrics have been made thinner, while in circuit boards, wiring layers have a narrow pitch and thin films. Is being promoted.

Under such circumstances, for example, the average particle diameter of nickel powder used for the internal electrode of the multilayer ceramic capacitor is mainly 0.3 μm class or less, and in the future, the atomization is further progressing and 0.2 μm or less is mainly used. It is estimated that
Such nickel powder for internal electrodes does not have to have a desired average particle diameter, but is one of the important characteristics that there are few or no coarse particles about 3 to 5 times the average particle diameter. Studies on removal methods of coarse particles by wet or dry classification have been actively conducted.

  In the examination of such classification methods, a method in which a powder mixed with a liquid auxiliary such as an alcohol such as ethanol or an ether such as diethylene glycol monomethyl ether is put into a heated air stream and classified while vaporizing the liquid auxiliary. Has been proposed (see Patent Documents 1 to 3).

  When using an alcohol with a low flash point such as ethanol, if the pretreatment is performed at room temperature to mix the auxiliary agent and nickel powder, the alcohol will evaporate, making it difficult to maintain the mass ratio of nickel powder and alcohol at a constant level. The resulting effect varies and is limited. For these reasons, pre-treated products using alcohol with a low flash point are unsuitable for mass production processes where large quantities are stored and crushed and classified in a heated air stream.

On the other hand, when using ethers with a relatively high flash point, such as diethylene glycol monomethyl ether, diethylene glycol ether is largely vaporized and removed from nickel powder by classification in a heated air stream, but a small amount remains. .
As mentioned earlier, pastes containing nickel powder for internal electrodes of multilayer ceramic capacitors are precisely designed by mixing vehicles with solvents such as terpineol and dihydroterpineol and a small amount of additives. If ethers such as monomethyl ether remain, there may be a problem that the dispersibility and viscosity of the nickel powder in the paste cannot be maintained.

  For this reason, when a classification method for vaporizing and removing the auxiliary agent in a heated air stream is used for the nickel powder for a multilayer ceramic capacitor, it is optimal to use a solvent such as terpineol or dihydroterpineol used in the paste as an auxiliary agent. However, when nickel powder and terpineol or dihydroterpineol are simply mixed, since the viscosity is high, the nickel powder cannot be distributed with a small amount of addition, and the desired effect cannot be obtained by classification in a heated air stream. On the other hand, when the addition amount is increased, it may become a clay state instead of a powder and may not be supplied into the classifier.

WO2010-047175 WO2012-124453 publication WO2011-132301 gazette

  It is an object of the present invention to provide a method for producing a metal powder that does not adversely affect the paste when it is made into a paste by attaching a solvent used for the conductive paste to the metal powder and can be easily dry-classified. . Another object of the present invention is to provide dry classification using this metal powder.

  A first invention of the present invention is a method for producing a metal powder with a solvent having a solvent I constituting a conductive paste on its surface, and the solvent I is used by using a solvent II having a flash point lower than the flash point of the solvent I. The residual amount of the solvent I present on the surface of the metal powder after drying is at least 0.5 to 10% by mass, which is obtained by performing a drying treatment on the metal powder formed through the adhesion process to be adhered to the surface of the metal powder. It is a manufacturing method of the metal powder with a solvent characterized by being.

  In the second invention of the present invention, at least the solvent I adheres to the surface by stirring the mixture B formed by mixing the mixture A of the metal powder and the solvent II and the solvent I in the adhesion step in the first invention. It is a manufacturing method of the metal powder with a solvent characterized by forming metal powder.

  In the third invention of the present invention, at least the solvent I adheres to the surface by stirring the mixture C formed by mixing the metal powder and the mixed solvent of the solvent I and the solvent II in the attaching step in the first invention. It is a manufacturing method of the metal powder with a solvent characterized by forming metal powder.

  According to a fourth invention of the present invention, the adhering step in the first invention is performed by stirring a mixture E formed by mixing a mixed solvent of the solvent I and the solvent II with a mixture D of the metal powder and at least the solvent I. A method for producing a metal powder with a solvent, characterized in that a metal powder having at least a solvent I adhered to the surface is formed.

  According to a fifth aspect of the present invention, there is provided a metal powder with a solvent, characterized in that the drying temperature of the drying treatment in the first to fourth aspects is not lower than the flash point of the solvent II and lower than the flash point of the solvent I. It is a manufacturing method.

  A sixth invention of the present invention is a method for producing a metal powder with a solvent, wherein the atmosphere of the drying treatment in the first to fifth inventions is carried out in an inert gas atmosphere or a reduced pressure atmosphere.

  According to a seventh aspect of the present invention, the residual amount of the solvent II attached to the dried metal powder after the drying treatment in the first to sixth aspects is less than 0.5% by mass. It is a manufacturing method of metal powder.

  The eighth invention of the present invention is the method for producing a metal powder with a solvent, wherein the solvent I in the first to seventh inventions is at least one selected from terpineol and dihydroterpineol.

  A ninth invention of the present invention is the production of a metal powder with a solvent, wherein the solvent II in the first to eighth inventions is at least one selected from acetone, methanol, ethanol, and 2-propanol Is the method.

  In a tenth aspect of the present invention, the metal powder according to the first to ninth aspects is from a metal group selected from zinc, lead, cadmium, tin, copper, nickel, cobalt, aluminum, silver, palladium, platinum, and gold. A method for producing a metal powder with a solvent, which is an alloy of at least one metal or a plurality of metals selected from the metal group.

  The eleventh aspect of the present invention is characterized in that the average particle size obtained from the observation image of the scanning electron microscope (SEM) of the metal powder in the first to tenth aspects is 0.05 μm to 5 μm. It is a manufacturing method of metal powder with a solvent.

  A twelfth aspect of the present invention is a method for producing a metal powder with a solvent, characterized in that the dried metal powder in the first to eleventh aspects is crushed and classified using a dry classifier.

  A thirteenth aspect of the present invention is a method for producing a metal powder with a solvent, wherein the dry classifier in the twelfth aspect is a fluid classifier.

  According to a fourteenth aspect of the present invention, the crushing and classification in the fluid classifier according to the thirteenth aspect are performed by supplying the swirling air flow chamber with the metal powder after drying together with the gas medium. A method for producing metal powder with a solvent, characterized in that the temperature of the medium is heated to a temperature not lower than the flash point of solvent I and not higher than flash point + 200 ° C.

  A fifteenth aspect of the present invention is a method for producing a metal powder with a solvent, wherein the gas medium according to the fourteenth aspect is air or an inert gas.

  By attaching a conductive paste solvent such as terpineol or dihydroterpineol to the metal powder, it does not adversely affect the viscosity fluctuation during storage of the conductive paste, and the metal powder does not adhere to the equipment during dry classification and can be easily crushed. , It becomes possible to classify. By crushing and classifying using this metal powder, coarse particles are removed, and it can be used for wiring layers of circuit boards and electronic component electrodes that are highly integrated, miniaturized, and increased in capacity.

The present invention is a method for producing a solvent-attached metal powder having a solvent I contained in a conductive paste on its surface, and is subjected to an adhesion step in which the solvent I is adhered to the surface of the metal powder using a solvent II having a flash point lower than that of the solvent I. The metal powder to which at least the solvent I and the solvent II are deposited is dried to vaporize and remove the solvent II to produce a metal powder with a solvent having the solvent I on the surface.
By the way, the solvent I in the adhering process adheres to the surface of the metal powder together with the solvent II, and the solvent II having a low flash point is vaporized and removed in the next drying treatment, and the solvent I is left on the surface of the metal powder, thereby the metal powder with solvent. Is formed.

  Here, the solvent I is a solvent constituting the conductive paste, and this solvent I has a flash point and a boiling point higher than room temperature and is easy to handle at the time of manufacturing the paste, and is vaporized and removed before heating and entering the binder removing step. It is desirable that it has a characteristic that it is easy to obtain desired characteristics at the time of printing, and is preferably at least one selected from terpineol and dihydroterpineol.

  On the other hand, the solvent II used together with the solvent I has a flash point lower than that of the solvent I and can be removed by vaporization while leaving the solvent I on the surface of the metal powder in the drying process. The solvent I can be dispersed and used together with the solvent II having such characteristics. As a result, the solvent I is uniformly present on the surface of the metal powder after the solvent II is vaporized and removed. It also has an effect that can be achieved.

[Metal powder]
The metal powder to be prepared is, for example, nickel powder, gas phase reduction method such as CVD (Chemical Vapor Deposition) method or PVD (Physical Vapor Deposition) method, hydrazine, sodium borohydride and nickel salt mixed in liquid Wet reduction method for precipitating nickel, mixing sodium hydroxide and nickel salt in liquid and precipitating nickel hydroxide, roasting nickel hydroxide to obtain nickel oxide and reducing in a hydrogen gas atmosphere nickel powder However, this method can be used for any of these synthesized methods.
Furthermore, since the nickel powder synthesized by these methods contains impurities, the nickel powder that is a raw material is a nickel powder that is dried after washing with an acidic aqueous solution containing water, an organic acid, an inorganic acid, or carbon dioxide gas, or In addition, the slurry may be a slurry that has been cleaned, or nickel powder that has been vapor-phase treated to include other elements on the surface of the nickel powder in order to control sintering or catalytic activity, or other elements that are nickel. A slurry containing nickel powder that has been wet-treated for inclusion on the powder surface and nickel powder that has been wet-treated to contain other elements on the nickel powder surface may remain as it is, and the same applies to other metal powders. The powder or slurry processed by the method is used.

Although the nickel powder has been described above as an example of the metal powder to be used, it is not limited to the nickel powder, and any metal species may be used as long as it is a metal powder used for the conductive paste.
Preferred metal species are composed of a metal containing at least one element selected from zinc, lead, cadmium, tin, copper, nickel, cobalt, aluminum, silver, palladium, platinum, and gold, or an alloy thereof. Further, a metal powder containing at least one element selected from these listed or an alloy thereof may be coated on the surface of a metal powder made of another metal species.

The average particle size region of the metal powder used in the present invention is suitably 0.05 μm or more.
When the average particle size is smaller than 0.05 μm, it is difficult to obtain a monodispersed dry powder itself, and it is difficult to apply this method.
On the other hand, the upper limit of the average particle diameter is not particularly limited, but since the gist of the present invention is to obtain a metal powder suitable for dry classification, it is preferably applied to a metal powder for dry classification. The average particle size of the metal powder is approximately 5 μm or less. Of course, the use of the present invention for a metal powder having an average particle diameter exceeding 5 μm or a metal powder not subjected to dry classification is not prevented.
In addition, an average particle diameter calculates | requires and calculates the average value of the diameter of each particle | grain calculated | required from the observation image of a scanning electron microscope (SEM). As a method of obtaining this average value, the area and number of particles that can be seen in the entire shape of the particle shape are measured using image analysis software, the diameter of each particle is calculated from these data, and the average value is calculated. May be used. Furthermore, the observation image of SEM should just make magnification 1000 times-30000 times, More preferably, 3000 times-20000 times.

[Adhesion process]
Next, the prepared metal powder and the solvent I and the solvent II are mixed. Here, when the solvent I to be adhered to the surface of the metal powder is composed of a plurality of solvents, all kinds of solvents I to be adhered are mixed.
When using a slurry containing metal powder that has been washed or surface-treated with water or an aqueous solution, decantation is repeated using solvent II to obtain a slurry from which the solvent component (water) has been removed during washing or surface treatment. Alternatively, after removing the solvent component at the time of washing and surface treatment as much as possible by performing solid-liquid separation, the decantation is repeated using the solvent II to obtain a slurry from which the solvent component at the time of washing and surface treatment is removed. .
Thus, it is preferable to make it a substantially non-aqueous slurry.

  The solvent II that forms the slurry with the metal powder generally uses terpineol, dihydroterpineol, or both as the solvent I that constitutes the conductive paste, so that acetone, methanol, ethanol, 2-propanol, butanol, etc. Alcohol is good, and acetone, methanol, ethanol, or 2-propanol is preferable, and ethanol or acetone is more preferable.

The mixing of the metal powder, the solvent I, and the solvent II in the present invention may be any method other than the method of mixing only the solvent II after mixing the metal powder and the solvent I.
The reason is that when the solvent I and the metal powder are first mixed, the solvent I is locally adsorbed on the surface of the metal powder, and even if the solvent II is subsequently mixed, the solvent I is evenly distributed on the surface of the metal powder. This is because it cannot be distributed.
As a desirable mixing method, first, the method of mixing the solvent I after the formation of the mixture A in which the metal powder and the solvent II are mixed (formation of the mixture B) (method of claim 2), and the second is the solvent I and the solvent. A method of mixing the mixed solvent of II and the metal powder (formation of the mixture C) (method of claim 3), and thirdly, after forming the mixture D of the mixed metal powder and the solvent I, Any one of the methods of adding a mixed solvent and mixing (forming the mixture E) (the method according to claim 4) is employed.

  Addition amount of solvent I represented by terpineol and dihydroterpineol is quantitatively processed in a feeder which is quantitatively supplied to a processing machine that is crushed and classified in a heated air stream after vaporizing and removing solvent II. What is necessary is just the grade which can be set in the state which can be supplied to a machine, 0.5 mass%-10 mass% are preferable with respect to metal powder, Furthermore, 1.0 mass%-5 mass% are preferable. When the added amount of the solvent I is more than 10% by mass, it becomes a clay state in the feeder during the treatment, and it becomes difficult to supply into the apparatus machine from the supply port of the heated airflow apparatus. Further, the amount of the solvent I remaining in the metal powder after processing in a heated air current increases, and the degree of freedom in paste design is limited. When the amount of the solvent I added is less than 0.5% by mass, the metal powder adheres to the inner wall of the classifier, and the distribution rate to the coarse powder side including the coarse particles increases, and the desired fine powder yield is obtained. May decrease.

  The addition amount of the solvent II represented by acetone or alcohol may be an amount that can maintain the fluidity that can be stirred when the metal powder and the solvent I are mixed. Adding a larger amount of solvent II only increases the time for vaporization and removal.

[Drying process]
As the next step, a slurry in which metal powder, terpineol or dihydroterpineol as the solvent I, and acetone or alcohol as the solvent II are mixed, is subjected to a flash point of the solvent II in a reduced-pressure atmosphere or an inert gas atmosphere. The drying treatment is performed at a temperature lower than the flash point of the solvent I as described above. By setting the drying temperature within the above range, the solvent II is vaporized and removed preferentially during the drying process, and the solvent I remains on the surface of the metal powder.
The drying temperature is more preferably a temperature range close to the flash point of the solvent II to be vaporized and removed in order not to vaporize the solvent I to be left.

The atmosphere of the drying process may vaporize and remove the solvent II in an air atmosphere, but in order to consider safety and avoid the oxidation of metal powder as much as possible, the drying process may be performed in an inert gas atmosphere or a reduced pressure atmosphere. preferable.
The inert gas used is preferably nitrogen gas or argon gas, and the reduced-pressure atmosphere is preferably 90 kPa or less.

In this drying treatment, either standing or stirring may be used, and the drying time may be appropriately selected. The residual amount of the vaporized removal solvent as the solvent II in the metal powder after the drying treatment is 0.5 mass% or less is good.
The reason for this is that if alcohol or acetone remains on the surface of the metal powder, in the case of nickel powder, problems such as causing a sheet attack phenomenon after lamination may occur.

[Dry classification process]
By carrying out the drying treatment, the solvent II is removed by evaporation, and the metal powder in which the solvent I remains is subjected to dry classification, whereby the coarse particles are removed.
The dry classifier used is preferably a fluid classifier that supplies metal powder together with the gas medium pressurized in the swirling airflow chamber. By using this apparatus, crushing and classification are performed simultaneously.
The metal powder is heated by the swirling air flow chamber itself, and is put into the swirling air flow chamber in which the heated gas medium is flowing to be processed. The gas medium is preferably air or an inert gas, and the inert gas is preferably nitrogen gas or argon gas.

At that time, the heated gas medium and the swirling airflow chamber can be efficiently processed by setting the temperature to be higher than the flash point of the solvent I represented by terpineol or dihydroterpineol and lower than the boiling point.
When the heated gas medium enters and the swirling air flow chamber itself is also processed in the heated chamber, the metal powder adheres to the wall surface of the swirling air flow chamber as the solvent I present on the metal powder surface is vaporized. In such a situation, the agglomeration of the metal powder is difficult to occur, and pulverization and classification are performed.

  When the heating temperature at that time is below the flash point of the solvent I, the vaporization of the solvent I is insufficient, and the metal powder may adhere to the wall surface of the swirling air flow chamber or the metal powder may be aggregated. In order to avoid an explosion due to ignition, the amount of gas when the solvent I is gasified and the amount of the heated gas medium must be taken into consideration and adjusted to be outside the explosion range.

Next, although an example and a comparative example are given and the present invention is explained, the present invention is not limited to these examples.
Hereinafter, evaluation items and methods thereof will be described.

[Measuring method of average particle diameter of metal powder]
Using a scanning electron microscope (SEM), an SEM image with a magnification of 10,000 times is obtained.
Using the image analysis software (Mac View, manufactured by Mountec Co., Ltd.), the SEM image was measured for the area and number of particles in which the entire shape of the particles was visible, and from these, the diameter of each particle was determined, and the average value was obtained. Calculated by

[Confirmation of solvent residue in metal powder]
The metal powder containing the solvent was set in TG-DTA, heated in a nitrogen atmosphere from room temperature to the boiling point of the solvent II at 2 ° C./min, held for 1 hour, and the weight decreased until that time, It was defined as the residual amount of solvent II. Thereafter, the temperature was raised to the boiling point of the solvent I at 2 ° C./min and held for 1 hour, and the weight decreased from the time when the residual amount of the solvent II was defined until the end of the holding time was defined as the residual amount of the solvent I.

  In the case of metal powder containing only solvent I, the metal powder is set in TG-DTA, heated from room temperature to the boiling point of solvent I at 2 ° C./min in a nitrogen atmosphere, and held for 1 hour. The weight reduced to that point was defined as the residual amount of solvent I.

[Confirmation of equality between solvent I and metal powder]
For samples using solvent II, after the drying treatment, for samples using only solvent I, after mixing with solvent I, the color unevenness of the metal powder is visually confirmed. If there is no color unevenness, solvent I is the metal powder. It was judged that they existed evenly.

[Confirmation of operation status during classification processing]
The operation status was confirmed by checking the state of the metal powder in the feeder that feeds powder into the swirling airflow chamber, the supply status into the classifier, and the adhesion status in the classifier.
Visually confirm that the metal powder is not in the clay state in the supply feeder, that the metal powder is continuously supplied from the feeder into the classifier, and that the metal powder is not attached to the machine after the classification. did.

[Observation of surface condition of paste dry film]
A conductive paste was prepared by mixing and stirring 4 g of a solvent-containing metal powder obtained by this method, 20 g of ethyl cellulose and 4 g of terpineol mixed with 80 g of terpineol, and 7 g of terpineol with a self-revolving mixer.
The conductive paste was printed and applied to a glass plate with a thickness of 2 μm with an FOG gauge and dried at 120 ° C. for 1 hour to produce a dry film.
With a laser microscope, it was confirmed whether or not projections (aggregates of metal powder) were present on the surface of the printed surface.

  Weigh 1000 g of nickel powder with an average particle size of 0.2 μm as metal powder and 400 g of ethanol (flash point: 18 ° C.) as solvent II in a beaker, and stir and mix with a stirrer to prepare an ethanol slurry of nickel powder (mixture A). Produced. Thereafter, terpineol (flash point: 82 ° C.) as solvent I was added to 0.8 mass% with respect to the nickel powder, stirred with a glass rod, mixed (mixture B), and maintained at 40 ° C. in a nitrogen atmosphere. And dried for 48 hours.

  The nickel powder after drying obtained by the drying process is a swirling airflow jet mill (made by POWREC Co., Ltd.) that has the effect of crushing and classifying using centrifugal force and centripetal force after confirming the solvent residual state and color unevenness of the metal powder. ), The swirling air flow chamber is kept at 120 ° C. with a ribbon heater, air heated to 150 ° C. is supplied at a pulverization pressure of 0.50 MPa and a supply pressure of 0.55 MPa, and dry classification treatment is performed with a powder supply amount of 50 g / min. .

Check the operation status during the classification process with respect to the state of nickel powder in the feeder that feeds powder into the swirling airflow chamber, the supply status of nickel powder into the swirling airflow chamber, and the adhesion status of nickel powder in the swirling airflow jet mill. did.
Furthermore, the nickel powder after the classification treatment was made into a paste, printed on a glass plate, applied and dried to produce a dry film, and the surface was observed.
These results are shown in Table 1.

A nickel powder was produced after drying under the same conditions as in Example 1 except that the terpineol of the solvent I was added to 10% by mass with respect to the nickel powder. After confirming the solvent residual state of the produced nickel powder and the color unevenness of the nickel powder, classification treatment was performed in the same manner as in Example 1 to confirm the operation status during the classification treatment. Further, the classified nickel powder was made into a paste, printed on a glass plate, coated and dried to produce a dried film, and the surface was observed.
These results are shown in Table 1.

A nickel powder was produced after drying under the same conditions as in Example 1 except that the terpineol of solvent I was dihydroterpineol (flash point: 90 ° C.). After confirming the solvent residual state of the produced nickel powder and the color unevenness of the nickel powder, classification treatment was performed in the same manner as in Example 1, and the operation status during the classification treatment was confirmed. Further, the classified nickel powder was made into a paste, printed on a glass plate, coated and dried to produce a dried film, and the surface was observed.
These results are shown in Table 1.

A nickel powder was produced after drying under the same conditions as in Example 2 except that the terpineol of solvent I was dihydroterpineol. After confirming the solvent residual state of the produced nickel powder and the color unevenness of the nickel powder, classification treatment was performed in the same manner as in Example 1 to confirm the operation status during the classification treatment. The classified nickel powder was made into a paste, printed on a glass plate, applied and dried to produce a dry film, and the surface was observed.
These results are shown in Table 1.

A nickel powder was produced after drying under the same conditions as in Example 1 except that the solvent II ethanol was acetone (flash point: −20 ° C.). After confirming the solvent residual state of the produced nickel powder and the color unevenness of the nickel powder, classification treatment was performed in the same manner as in Example 1 to confirm the operation status during the classification treatment. The classified nickel powder was made into a paste, printed on a glass plate, applied and dried to produce a dry film, and the surface was observed.
These results are shown in Table 1.

A nickel powder was produced after drying under the same conditions as in Example 2 except that the solvent II ethanol was acetone. After confirming the solvent residual state of the produced nickel powder and the color unevenness of the nickel powder, classification treatment was performed in the same manner as in Example 1 to confirm the operation status during the classification treatment. The classified nickel powder was made into a paste, printed on a glass plate, applied and dried to produce a dry film, and the surface was observed.
These results are shown in Table 1.

A solution in which 1000 g of nickel powder having an average particle size of 0.2 μm as metal powder, terpineol as solvent I weighed to be 0.8 mass% with respect to nickel powder, and ethanol as solvent II weighed 400 g are mixed. Were mixed with a stirrer.
Then, it dried at 48 degreeC by hold | maintaining at 40 degreeC by nitrogen atmosphere. The nickel powder obtained by the drying treatment was subjected to a classification treatment in the same manner as in Example 1 after confirming the solvent residual state and the color unevenness of the nickel powder, and the operation status during the classification treatment was confirmed. Further, the classified nickel powder was made into a paste, printed on a glass plate, coated and dried to produce a dried film, and the surface was observed.
These results are shown in Table 1.

As a metal powder, 1000 g of nickel powder having an average particle diameter of 0.2 μm and terpineol, which is solvent I, weighed so as to be 0.4 mass% with respect to the nickel powder were mixed. Thereafter, a premixed mixture of terpineol and nickel powder, and a solution obtained by mixing terpineol as solvent I measured to be 0.4% by mass with respect to the nickel powder and ethanol as solvent II measured at 400 g, Stir and mix with a stirrer.
Then, it dried at 48 degreeC by hold | maintaining at 40 degreeC by nitrogen atmosphere. The nickel powder obtained by the drying treatment was subjected to a classification treatment in the same manner as in Example 1 after confirming the solvent residual state and the color unevenness of the nickel powder, and the operation status during the classification treatment was confirmed. Further, the classified nickel powder was made into a paste, printed on a glass plate, coated and dried to produce a dried film, and the surface was observed.
These results are shown in Table 1.

A silver powder was produced after drying under the same conditions as in Example 1 except that the metal powder was a silver powder having an average particle diameter of 1.5 μm. After confirming the solvent residual state of the produced silver powder and the color unevenness of the silver powder, classification treatment was performed in the same manner as in Example 1 to confirm the operation status during classification. Further, the classified silver powder was pasted, printed on a glass plate, applied and dried to produce a dry film, and the surface thereof was observed.
These results are shown in Table 1.

A copper powder was produced after drying under the same conditions as in Example 1 except that the metal powder was a copper powder having an average particle size of 0.5 μm. After confirming the solvent residual state of the produced copper powder and the color unevenness of the copper powder, classification treatment was performed in the same manner as in Example 1 to confirm the operation status at the time of classification. Further, the classified copper powder was made into a paste, printed on a glass plate, applied and dried to produce a dry film, and the surface was observed.
These results are shown in Table 1.

(Comparative Example 1)
A nickel powder was produced after drying under the same conditions as in Example 1 except that the content was 0.3% by mass of terpineol. After confirming the solvent residual state of the produced nickel powder and the color unevenness of the nickel powder, classification treatment was performed in the same manner as in Example 1 to evaluate the operating conditions during the classification treatment.
These results are shown in Table 1.

(Comparative Example 2)
A nickel powder was produced after drying under the same conditions as in Example 1 except that the content was 15% by mass of terpineol. After confirming the solvent residual state of the produced nickel powder and the color unevenness of the nickel powder, classification treatment was performed in the same manner as in Example 1 to evaluate the operating conditions during the classification treatment.
These results are shown in Table 1.

(Comparative Example 3)
1000 g of nickel powder having an average particle size of 0.2 μm was placed in a stainless steel container placed in a water bath heated to 70 ° C., and added and mixed little by little so that terpineol was 0.8 mass%.
After confirming the solvent residual state and the color unevenness of the metal powder, uniformly mixed nickel powder is used with a swirling airflow type jet mill (manufactured by POWREC Co., Ltd.) that has the effect of crushing and classifying using centrifugal force and centripetal force. The swirling air flow chamber was kept at 120 ° C. with a ribbon heater, and air heated to 150 ° C. was supplied at a pulverization pressure of 0.50 MPa and a supply pressure of 0.55 MPa, and processed at a powder supply amount of 50 g / min.

Check the operation status during the classification process with respect to the state of nickel powder in the feeder that feeds powder into the swirling airflow chamber, the supply status of nickel powder into the swirling airflow chamber, and the adhesion status of nickel powder in the swirling airflow jet mill. did.
These results are shown in Table 1.

(Comparative Example 4)
Nickel powder was prepared by mixing under the same conditions as in Comparative Example 3 except that the amount of terpineol added to the nickel powder was 10% by mass. After confirming the solvent residual state of the produced nickel powder and the color unevenness of the nickel powder, classification treatment was performed in the same manner as in Example 1, and the operating conditions during the classification treatment were evaluated.
These results are shown in Table 1.

(Comparative Example 5)
Nickel powder was prepared by mixing under the same conditions as in Comparative Example 3 except that the amount of terpineol added to the nickel powder was 20% by mass. After confirming the solvent residual state of the produced nickel powder and the color unevenness of the nickel powder, classification treatment was performed in the same manner as in Example 1 to evaluate the operating conditions during the classification treatment.
These results are shown in Table 1.

(Comparative Example 6)
1000 g of nickel powder having an average particle diameter of 0.2 μm was placed in a stainless steel container placed in a water bath heated to 70 ° C., and diethylene glycol monomethyl ether was added little by little so as to be 5% by mass.
After confirming the solvent residual state and the color unevenness of the metal powder, uniformly mixed nickel powder is used with a swirling airflow type jet mill (manufactured by POWREC Co., Ltd.) that has the effect of crushing and classifying using centrifugal force and centripetal force. The swirling air flow chamber was kept at 120 ° C. with a ribbon heater, and air heated to 150 ° C. was supplied at a pulverization pressure of 0.50 MPa and a supply pressure of 0.55 MPa, and processed at a powder supply amount of 50 g / min.
Check the operation status during the classification process: the state of nickel powder in the feeder that feeds powder into the swirling air chamber, the supply status of nickel powder into the swirling air chamber, and the operating status of nickel powder in the swirling air jet mill did. The classified nickel powder was made into a paste, printed on a glass plate, applied and dried to produce a dry film, and the surface was observed.
These results are shown in Table 1.

(Comparative Example 7)
A silver powder was prepared by mixing under the same conditions as in Comparative Example 3 except that the metal powder was a silver powder having an average particle diameter of 1.5 μm. After confirming the solvent residual state of the produced silver powder and the color unevenness of the silver powder, classification treatment was performed under the same conditions as in Example 1 to evaluate the operating conditions during the classification treatment.
These results are shown in Table 1.

(Comparative Example 8)
A copper powder was prepared by mixing under the same conditions as in Comparative Example 3 except that the metal powder was a copper powder having an average particle size of 0.5 μm. After confirming the solvent residual state of the produced copper powder and the color unevenness of the copper powder, classification treatment was performed under the same conditions as in Example 1 to evaluate the operating conditions during the classification treatment.
These results are shown in Table 1.

  About Examples 1-8 which are in the scope of the present invention, there is no problem in the operation state at the time of classification treatment, and no particular change in viscosity is observed even when stored after pasting.

  On the other hand, in Comparative Example 1 where the residual amount of the solvent I after the drying treatment is less than the lower limit of the present invention, nickel powder adheres in the swirling air jet jet mill, and the residual amount of the solvent I after the drying treatment exceeds the upper limit of the present invention. In many Comparative Examples 2, the nickel powder was in a clay state, and the nickel powder could not be fed.

  Further, in Comparative Examples 3 to 5 and Comparative Examples 7 and 8 prepared without using the solvent II, color unevenness was observed when the amount of terpineol charged was small, and adhesion occurred in the swirling airflow jet mill. When the amount of terpineol charged was large, it was in a clay state and could not be fed.

  Further, Comparative Example 6 using diethylene glycol monomethyl ether different from the solvent constituting the conductive paste as the solvent I was good in the classification treatment, but after the classified nickel powder was pasted, a dry film was prepared. As a result of observing the surface, many protrusions were observed. This is considered to be caused as a result of aggregation of the nickel powder in the paste.

Claims (15)

A method for producing a solvent-attached metal powder having a solvent I constituting the conductive paste on its surface,
A dried metal powder obtained by subjecting a metal powder to which at least the solvent I is adhered to the surface of the metal powder to be deposited using the solvent II having a flash point lower than that of the solvent I. A method for producing a metal powder with a solvent, wherein the residual amount of the solvent I present on the surface is 0.5 mass% to 10 mass%.   The adhesion step is characterized in that a mixture A of the metal powder and the solvent II and a mixture B formed by mixing the solvent I are stirred to form a metal powder having at least the solvent I adhered to the surface. The manufacturing method of the metal powder with a solvent of Claim 1 to do.   The adhering step stirs a mixture C formed by mixing the metal powder and a mixed solvent of the solvent I and the solvent II to form a metal powder having at least the solvent I adhered to the surface. The manufacturing method of the metal powder with a solvent of Claim 1.   In the adhering step, the mixture D formed by mixing the mixed powder of the solvent I and the solvent II with the mixture D of the metal powder and at least the solvent I is agitated, and at least the solvent I adheres to the surface. The method for producing a metal powder with a solvent according to claim 1, wherein:   5. The metal powder with solvent according to claim 1, wherein a drying temperature in the drying treatment is a temperature not lower than a flash point of the solvent II and lower than a flash point of the solvent I. 6. Production method.   The method for producing a metal powder with a solvent according to any one of claims 1 to 5, wherein the atmosphere in the drying treatment is an inert gas atmosphere or a reduced pressure atmosphere.   7. The metal powder with a solvent according to claim 1, wherein the residual amount of the solvent II attached to the metal powder after drying after drying is less than 0.5% by mass. Manufacturing method.   The method for producing metal powder with a solvent according to any one of claims 1 to 7, wherein the solvent I is at least one selected from terpineol and dihydroterpineol.   The said solvent II is at least 1 sort (s) chosen from acetone, methanol, ethanol, and 2-propanol, The manufacturing method of the metal powder with a solvent of any one of Claims 1-7 characterized by the above-mentioned.   The metal powder is at least one metal selected from a metal group selected from zinc, lead, cadmium, tin, copper, nickel, cobalt, aluminum, silver, palladium, platinum, gold, or a plurality of metals selected from the metal group It is an alloy, The manufacturing method of the metal powder with a solvent of any one of Claims 1-9 characterized by the above-mentioned.   The average particle diameter calculated | required from the observation image of the scanning electron microscope (SEM) of the said metal powder is 0.05 micrometer-5 micrometers, The metal powder with a solvent in any one of Claims 1-10 characterized by the above-mentioned. Production method.   The method for producing a metal powder with a solvent according to any one of claims 1 to 11, wherein the metal powder after drying is crushed and classified using a dry classifier.   The method for producing metal powder with a solvent according to claim 12, wherein the dry classifier is a fluid classifier. Crushing and classification in the fluid classifier is performed by supplying the dried metal powder together with the gas medium to the swirling airflow chamber,
The temperature of the swirl airflow chamber and the temperature of the gas medium are heated to a temperature not lower than the flash point of the solvent I and not higher than a flash point + 200 ° C. Production method.   The method for producing a metal powder with a solvent according to claim 14, wherein the gas medium is air or an inert gas.