JP4490754B2 - Method for producing nickel powder mixed with ceramic powder, and method for producing nickel paste mixed with ceramic powder - Google Patents

Description

The present invention relates to a method for producing a nickel powder mixed with ceramic powder , for example, which is a material for an internal electrode of a multilayer ceramic electronic component, and a method for producing a nickel paste mixed with ceramic powder .

Nickel is widely used as a material for internal electrodes of multilayer ceramic electronic components. As a multilayer ceramic electronic component having an internal electrode mainly composed of nickel, for example, a multilayer capacitor described in Patent Document 1 is known. This type of multilayer ceramic electronic component is extremely demanded for miniaturization and thinning (multilayering).
JP-A-11-354374

  In order to reduce the thickness of the multilayer ceramic electronic component, it is important to reduce the thickness of the internal electrode and the dielectric layer. In order to reduce the thickness of the dielectric layer, it is necessary to reduce the particle size of the nickel powder contained in the internal electrode. For this reason, a nickel paste is produced from nickel powder having a small particle size, and the internal electrode is formed using the nickel paste. It is necessary to produce. For example, a commercially available nickel powder has an average particle size of about 0.4 μm, but may contain particles having a maximum particle size of 1 μm due to particle size variation.

  When nickel powder is used as a material for an internal electrode of a multilayer ceramic electronic component, if the particles of nickel powder are too large relative to the thickness of the dielectric layer, the particles of nickel powder may penetrate the dielectric layer. In order to avoid this, when the nickel powder having the average particle diameter of 0.4 μm is used, the thickness of the dielectric layer cannot be set to 1 μm or less. Thus, when a commercially available nickel powder is used, the thinning of the dielectric layer is restricted, and the thinning of the multilayer ceramic electronic component is restricted. For this reason, a nickel powder having a smaller particle size than the above nickel powder has been desired.

The present invention has been made in order to solve the above-described problems, and the production of nickel powder having a small particle size mixed with ceramic powder , and nickel mixed with ceramic powder , including nickel powder having a small particle size. For the production of pastes.

In order to solve the above problems, the method for producing nickel powder mixed with ceramic powder according to the present invention was obtained by roasting a mixed solution of nickel nitrate and ceramic powder having properties that are less likely to be reduced than nickel oxide . A step of obtaining a pulverized product by mixing and pulverizing nickel oxide and the ceramic powder, and a step of reducing the pulverized product, wherein the nickel oxide has an average particle size of 0.2 μm in the step of obtaining the pulverized product. It is characterized by crushing so as to be the following.

  Since nickel oxide has lower ductility than metallic nickel, it can be pulverized more finely than metallic nickel. For this reason, nickel oxide and ceramic powder are mixed and pulverized to obtain a pulverized product containing finely pulverized nickel oxide. Subsequently, the nickel oxide in the pulverized product is reduced by the reduction treatment to produce nickel. At this time, since the nickel oxide is made fine by pulverization, the particle diameter of the nickel after reduction is also reduced. Furthermore, the ceramic powder mixed in the pulverized product inhibits the aggregation of the produced nickel. For this reason, it is suppressed that nickel aggregates and a particle size becomes large, and, as a result, nickel powder with a small particle size is obtained.

The nickel powder production method of the present invention is obtained by roasting nickel oxide and a mixed solution of nickel salt and ceramic powder . By this step, nickel oxide can be obtained efficiently.

In the nickel powder manufacturing method, the nickel salt is nickel nitrate. Since nickel nitrate is easily dissolved in water, handling in the step of obtaining the above nickel oxide becomes easy.

Also, the method for producing a nickel paste mixed with ceramic powder according to the present invention comprises the step of roasting a mixed solution of nickel nitrate and a ceramic powder having properties that are less likely to be reduced than nickel oxide and the ceramic. A step of mixing and pulverizing powder to obtain a pulverized product, a step of reducing the pulverized product to obtain a reduced product, a step of adding a binder and a solvent to the reduced product, and a step of dispersing the reduced product And in the step of obtaining the pulverized product, the nickel oxide is pulverized so as to have an average particle size of 0.2 μm or less.

  In this manufacturing method, nickel oxide having low ductility is mixed and pulverized with ceramic powder, and a pulverized product containing finely pulverized nickel oxide is obtained. Subsequently, the nickel oxide in the pulverized product is reduced by the reduction treatment to produce nickel. At this time, since the nickel oxide is made fine by pulverization, the particle diameter of the nickel after reduction is also reduced. Furthermore, the ceramic powder mixed in the pulverized product inhibits the aggregation of the produced nickel. For this reason, it is suppressed that the particle size of nickel becomes large, and nickel powder with a small particle size is obtained as a result. By adding a binder and a solvent to the reduction product of the nickel powder and ceramic powder thus obtained and dispersing the reduction product, a nickel paste containing nickel powder and ceramic powder having a small particle size can be obtained. .

The method for producing a nickel paste mixed with ceramic powder according to the present invention is a method for producing a nickel paste for forming an internal electrode disposed in a ceramic fired body, comprising nickel nitrate and the ceramic fired body. and nickel oxide obtained by roasting a mixture of ceramic powder having at least Tsuo含hard property is reduced than seen nickel oxide of the main component, the ceramic powder, the mixed pulverized to pulverized product A step of obtaining a reduced product by reducing the pulverized product, and a step of adding a binder and a solvent to the reduced product to disperse the reduced product, thereby obtaining the pulverized product. In the step, the nickel oxide is pulverized so as to have an average particle size of 0.2 μm or less.

  In this manufacturing method, nickel oxide having low ductility is mixed and pulverized with ceramic powder, and a pulverized product containing finely pulverized nickel oxide is obtained. Subsequently, the nickel oxide in the pulverized product is reduced by the reduction treatment to produce nickel. At this time, since the nickel oxide is made fine by pulverization, the particle diameter of the nickel after reduction is also reduced. Furthermore, the ceramic powder mixed in the pulverized product inhibits the aggregation of the produced nickel. For this reason, it is suppressed that the particle size of nickel becomes large, and nickel powder with a small particle size is obtained as a result. By adding a binder and a solvent to the reduction product of the nickel powder and ceramic powder thus obtained and dispersing the reduction product, a nickel paste containing nickel powder and ceramic powder having a small particle size can be obtained. . The ceramic powder contained in the nickel paste contains the main component of the ceramic fired body. For this reason, if this nickel paste is used to form an internal electrode disposed on the ceramic fired body, the above main component functions as a common material for the internal electrode.

Moreover, the manufacturing method of the nickel paste of this invention is obtained by baking nickel oxide and the mixed solution of nickel salt and ceramic powder. By this step, nickel oxide can be obtained efficiently.

In the nickel paste manufacturing method, the nickel salt is nickel nitrate. Since nickel nitrate is easily dissolved in water, handling in the step of obtaining the above nickel oxide becomes easy.

According to the present invention, it is possible to perform the production of small nickel powder particle size ceramic powder is mixed, and the particle size including small nickel powder, the manufacture of the ceramic powder is mixed nickel paste.

According to the present invention, a method of manufacturing the nickel powder ceramic powder are mixed, and, for embodiments of the method for manufacturing a nickel paste which ceramic powder is mixed is described. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

(First embodiment)
1st Embodiment of the manufacturing method of the nickel paste which concerns on this invention is described. FIG. 1 is a flowchart showing a method for producing a nickel paste. In this manufacturing method, first, liquid nickel nitrate is prepared, introduced into a roasting furnace, and roasted in air at 500 to 900 ° C. for 30 to 120 minutes (roasting step: S102). By this roasting treatment, nickel nitrate is oxidized to obtain nickel oxide. The nickel oxide thus obtained is a powder having an average particle size of about 0.3 μm.

Next, 20 parts by weight of ceramic powder is added to and mixed with 100 parts by weight of the obtained nickel oxide powder. Here, barium titanate (BaTiO ₃ ) powder is used as the ceramic powder. This mixed powder is introduced into a pulverizer and pulverized (pulverization step: S104). A ball mill or a bead mill using a medium can be used as the pulverizer here. Here, in a ball mill, pulverization is performed at 40 to 100 rpm for 15 to 24 hours using a medium having a diameter of 2 mm.

  Here, since nickel oxide has very low ductility compared to metallic nickel, it can be pulverized to a finer particle size than the particle size of nickel powder obtained by pulverizing metallic nickel. Therefore, in this pulverization step S104, the nickel oxide is finely pulverized and the average particle size becomes 0.2 μm or less. The mixed barium titanate is also finely pulverized at the same time. Thus, a pulverized product in which nickel oxide powder having an average particle size of 0.2 μm or less and barium titanate powder are mixed is obtained.

  Next, the obtained pulverized product is subjected to a treatment for reducing by a thermal reduction method or a solution reduction method (reduction step: S106). In the thermal reduction method, the obtained pulverized product is introduced into a reduction furnace and heated at 300 to 800 ° C. for 30 to 120 minutes while being placed in a hydrogen atmosphere by a predetermined atmosphere control means. In the solution reduction method, the obtained pulverized product is put into a solvent hydrazine together with an alkaline reducing agent. And it is made to react on the conditions of 25-70 degreeC, and the obtained suspension solution is filtered and powder is obtained.

  By this reduction treatment, nickel oxide in the pulverized material is reduced to produce nickel. Since nickel oxide is more easily reduced than barium titanate, barium titanate in the pulverized product is not reduced in this reduction treatment.

  Since the average particle diameter of nickel oxide was reduced to 0.2 μm or less in the pulverization step S104, nickel having a small particle size is generated by the reduction reaction in the reduction step S106. Aggregation of the produced nickel is inhibited by the ceramic powder (here, barium titanate powder) mixed in the pulverized product. For this reason, it is suppressed that the produced | generated nickel aggregates and a particle size becomes large. As a result, the particle size of the nickel powder obtained by the reduction treatment is uniform and the particle size is reduced. In this way, a reduction product is obtained in which a nickel powder having an average particle size of 0.2 μm or less and a small particle size and a small variation in particle size is mixed with a barium titanate powder having an average particle size of about 0.2 μm. . Here, since the barium titanate mixed in the reduction product functions as a co-material in the internal electrode of the multilayer ceramic capacitor 1 (described later), without isolating the nickel powder in the reduction product, The reduction product can be used for the production of nickel paste.

  A predetermined amount of a binder and a solvent are added to the reduction product while adjusting the viscosity, and the mixture is stirred. Here, ethyl cellulose is used as the binder and terpineol is used as the solvent. Thus, the nickel powder and the barium titanate powder are dispersed in the solvent (dispersing step: S108). At this time, the nickel powder and the barium titanate powder are efficiently dispersed in the solvent because the particle size is small. Then, a nickel paste in which a nickel powder having an average particle size of 0.2 μm or less and a small particle size and a small variation in particle size and a barium titanate powder are dispersed in a solvent is completed.

(Second Embodiment)
Next, a second embodiment of the nickel paste manufacturing method according to the present invention will be described. The manufacturing method of this embodiment is different from the first embodiment in steps until a pulverized product in which nickel oxide powder and barium titanate powder are mixed is obtained.

  First, 20 parts by weight of ceramic powder is mixed with 100 parts by weight of the prepared nickel nitrate powder, and water is added. Then, the nickel nitrate powder and the ceramic powder are dissolved to obtain a mixed aqueous solution. Here, barium titanate powder is used as the ceramic powder. This mixed aqueous solution is introduced into a roasting furnace and subjected to a roasting treatment in air at 500 to 900 ° C. for 30 to 120 minutes, whereby nickel nitrate is oxidized to become nickel oxide. In this roasting process, barium titanate does not change. Thus, a powder in which nickel oxide powder and barium titanate powder are mixed is obtained.

  Then, the obtained powder is introduced into a pulverizer and pulverized. A ball mill or a bead mill using media can be used as the pulverizer here. Here, in a ball mill, pulverization is performed at 40 to 100 rpm for 15 to 24 hours using a medium having a diameter of 2 mm. By this pulverization treatment, a powder obtained by mixing nickel oxide powder having an average particle diameter of about 0.2 μm and barium titanate powder having an average particle diameter of 0.2 μm or less is obtained.

  The powder thus obtained has the same composition as the pulverized product obtained in the pulverization step S104 of the first embodiment. Therefore, the powder obtained here can be handled in the same manner as the pulverized product in the first embodiment, and becomes a nickel paste through the reduction step S106 and the dispersion step S108. Thus, also by the manufacturing method of this embodiment, the nickel paste containing nickel powder and barium titanate powder having an average particle size of 0.2 μm or less and a small particle size and small variation in particle size is obtained. .

  Examples of the nickel salt from which nickel oxide can be obtained by roasting include nickel nitrate, nickel chloride, nickel sulfate, nickel acetate, nickel hydroxide, nickel carbonate, nickel sulfamate, and the like. In the embodiment, since nickel nitrate which is easily dissolved in water is used, handling in the roasting process becomes easy.

In addition, the ceramic powder mixed in the nickel nitrate in the roasting step S102 or the pulverizing step S104 needs to have a property that is less likely to be reduced than nickel oxide so as not to be reduced in the reducing step S106. Examples of such a ceramic powder material include BaTiO ₃ , CaTiO ₃ , BaO, TiO, MgO, CaO, Y ₂ O ₃ , ZrO ₂ , and SiO ₂ . Among these, a ceramic powder obtained by adding Y ₂ O ₃ to barium titanate is particularly preferable as a ceramic powder mixed in nickel nitrate because of its particularly low reducibility.

  In the first and second embodiments, it is not necessary to isolate the nickel powder from the pulverized product obtained in the reduction step S106, but the nickel powder is isolated from the pulverized product and has an average particle size of 0.2 μm or less. Nickel powder may be obtained.

Next, the multilayer ceramic capacitor 1 will be described.

  As shown in FIG. 2, the multilayer ceramic capacitor 1 includes a ceramic fired body 3 and terminal electrodes 7 and 9. The overall shape of the ceramic fired body 3 is a substantially rectangular parallelepiped, and the terminal electrodes 7 and 9 are provided so as to cover one set of opposing surfaces of the ceramic fired body 3.

  In this ceramic fired body 3, dielectric layers 21, 23, 25 are laminated between four internal electrodes 11, 13, 15, 17 made of nickel, and further the upper surface of the internal electrode 11 and the lower surface of the internal electrode 17. Dielectric layers 27 and 29 are respectively formed in the. The internal electrodes 11 and 15 are connected to the terminal electrode 7, and the internal electrodes 13 and 17 are connected to the terminal electrode 9, whereby the internal electrodes 11 and 13, the internal electrodes 13 and 15, and the internal electrodes 15 and 17 are connected. A capacitor connected in parallel is formed between the two. The dielectric layers 21, 23, 25, 27, and 29 are formed by firing a ceramic green sheet containing barium titanate as a main component.

  The multilayer ceramic capacitor 1 is manufactured as follows. First, an electrode is screen-printed with a nickel paste on a ceramic green sheet mainly composed of barium titanate. This nickel paste is obtained by the above-described nickel paste manufacturing method, and has a mean particle size of 0.2 μm or less, a small particle size and a small variation in particle size, and mixed as a co-material. Barium titanate powder. The electrodes formed of this nickel paste are finally fired to become the internal electrodes 11, 13, 15, 17 of the multilayer ceramic capacitor 1.

  Next, the green sheet is formed into a desired size and shape by punching or cutting, and a desired number of layers are stacked, and then pressure forming is performed. Next, the laminated green sheet is formed into a size for each chip by cutting or the like, and then heated at about 300 ° C. for a predetermined time. By this heating, the organic acid, binder, plasticizer, release agent and the like contained in the green sheet or nickel paste are removed by volatilization or decomposition. Thereafter, the ceramic fired body 3 is obtained by firing at about 1250 ° C. At this time, since the electrode formed of the nickel paste contains barium titanate, which is the main component of the ceramic fired body 3, the shrinkage rate during firing of the electrode and the green sheet becomes close, and firing is performed. Generation of cracks in the ceramic fired body 3 at the time is suppressed. Thereafter, terminal electrodes 7 and 9 are provided by baking or the like so as to cover the facing surface of the obtained ceramic fired body 3.

  In the multilayer ceramic capacitor 1 thus obtained, the average particle diameter of the nickel powder contained in the internal electrode 11 or the like is 0.2 μm or less, and there is little variation in the particle diameter. For this reason, the internal electrode 11 and the like can be thinned, and the dielectric layer 21 and the like can be set to a thickness of 1 μm or less so that the dielectric layer 21 and the like are not penetrated by the nickel powder grains. Thus, according to the multilayer ceramic capacitor 1, the internal electrodes 11 and the dielectric layer 21 and the like can be thinned, and as a result, the multilayer ceramic capacitor 1 can be thinned and multilayered.

  In the above embodiment, the present invention is applied to a multilayer ceramic capacitor, but the present invention is not limited to this, and may be applied to an inductor, a varistor, a thermistor, and a filter.

It is a flowchart which shows the manufacturing method of a nickel paste. It is a figure which shows the external shape and cross section of a multilayer ceramic capacitor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor (electronic component), 3 ... Ceramic fired body, 7, 9 ... Terminal electrode, 11, 13, 15, 17 ... Internal electrode, 21, 23, 25, 27, 29 ... Dielectric layer, S102 ... Roasting step, S104 ... grinding step, S106 ... reduction step, S108 ... dispersion step.

Claims (3)

A step of obtaining a pulverized product by mixing and pulverizing nickel oxide obtained by roasting a mixed solution of nickel nitrate and a ceramic powder having properties that are less likely to be reduced than nickel oxide, and the ceramic powder;
A step of reducing the pulverized product,
In the step of obtaining the pulverized product, the nickel oxide is pulverized so as to have an average particle size of 0.2 μm or less. A method for producing nickel powder mixed with ceramic powder . A step of obtaining a pulverized product by mixing and pulverizing nickel oxide obtained by roasting a mixed solution of nickel nitrate and a ceramic powder having properties that are less likely to be reduced than nickel oxide, and the ceramic powder;
Reducing the pulverized product to obtain a reduced product;
Adding a binder and a solvent to the reduction product and dispersing the reduction product,
In the step of obtaining the pulverized product, the nickel oxide is pulverized so as to have an average particle size of 0.2 μm or less. A method for producing a nickel paste mixed with ceramic powder . A nickel paste manufacturing method for forming an internal electrode disposed in a ceramic fired body,
And nickel oxide obtained by roasting a mixture of ceramic powder having a hard property is reduced than at least 1 Tsuo含viewed nickel oxide of the main component of the nitrate nickel ceramic fired body, and the ceramic powder, Mixing and pulverizing to obtain a pulverized product,
Reducing the pulverized product to obtain a reduced product;
Adding a binder and a solvent to the reduction product and dispersing the reduction product,
In the step of obtaining the pulverized product, the nickel oxide is pulverized so as to have an average particle size of 0.2 μm or less. A method for producing a nickel paste mixed with ceramic powder .

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