JP3653447B2 - Coated metal powder and method for producing the same, coated metal powder paste and ceramic laminated part - Google Patents

Description

【００３７】
【表２】

【００３８】
【表３】

【００３９】
【発明の効果】
本発明の被覆金属粉末は上記のように構成したので、表１、表２及び表３から判るように、大気中酸化特性や非酸化雰囲気中収縮特性に優れ、これを使用した積層セラミックコンデンサもクラックやデラミネーションがなく、ショート不良率も極めて低く、各種電子部品の製造に有利に使用されることができる。
【図面の簡単な説明】
【図１】本発明の実施例１により製造された被覆金属粉末のＩＲ測定チャートである。
【図２】比較例１のＩＲ測定チャートである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coated metal powder and a production method thereof, a coated metal powder paste, and a ceramic laminated electronic component. The electronic component has an internal conductor, and includes, for example, a ceramic capacitor, a resonator, a filter, an inductor, and a substrate.
[0002]
[Prior art]
In recent years, the development of electronic equipment has been remarkable, and there is a growing demand for downsizing, high reliability and compounding of electronic components to be incorporated in response to the development of new products. Multilayer ceramic capacitors have also been actively reduced in size and increased in capacity as existing products have been upgraded, and dielectric layers have been made thinner and multilayered. Conventionally, Pd, which is a noble metal, has been used as an internal electrode for a barium titanate-based dielectric in a high dielectric constant multilayer ceramic capacitor.
[0003]
However, since an expensive noble metal is used, an increase in the number of internal electrode layers due to the multilayering causes an increase in cost, making it difficult to meet the demand for lower prices. Therefore, cheaper base metal Ni has been widely used for the internal electrode.
In general, Ni paste for Ni internal electrodes consists of Ni powder as an electrode forming component, a resin such as cellulose resin and acrylic resin, and an organic binder component consisting of trimethylbenzene, terpineol and the like as solvents thereof. Is kneaded by a mechanical kneading means such as a three roll mill and mixed and dispersed.
[0004]
Next, manufacturing of the ceramic capacitor using the Ni paste described above will be described. First, a dielectric green sheet composed of a dielectric powder represented by barium titanate (BaTiO ₃ ) and an organic binder such as polyvinyl butyral is applied to the dielectric green sheet. Ni paste is printed in a predetermined pattern and dried.
Next, the dielectric green sheets on which the Ni paste is printed are laminated so that the internal metal electrodes are alternately overlapped, and thermocompression bonded. Next, the laminate is cut, debindered by heating at a temperature of 500 ° C. or lower in an oxidizing atmosphere, and then heated to a temperature of about 1300 ° C. in a reducing atmosphere so that the Ni internal electrode is not oxidized. Then, the internal electrode and the dielectric are sintered. After that, an external electrode paste is applied to the side surface of the fired chip so as to be connected to the internal electrode and fired again. Finally, Ni plating or the like is applied on the external electrode to complete the ceramic capacitor.
[0005]
As described above, the ceramic capacitor can be obtained by simultaneously firing the ceramic dielectric and the metal internal electrode. At that time, it is important to match the shrinkage characteristics by firing the dielectric and the electrode. In particular, in the binder removal step in an oxidizing atmosphere, Ni powder is oxidized and expanded, whereas the dielectric green sheet has almost no dimensional change.
Therefore, the larger the oxidative expansion of the Ni powder, the greater the stress generated between the dielectric green sheet and the electrode layer, causing cracks in the chip and destruction of the laminated structure (hereinafter this phenomenon will be referred to as delamination). Problem) occurs.
[0006]
Also, in the firing process in a reducing atmosphere, shrinkage of the internal electrode due to the reduction reaction of Ni powder and firing shrinkage at a high temperature occur. At this time, if the shrinkage behavior of the electrode layer and the shrinkage behavior of the dielectric are significantly different, Stress is generated at the interface between the layer and the dielectric layer, and cracks and delamination are generated as in the previous binder removal step. In general, when an internal electrode using pure Ni powder obtained by a conventional method is used in the production of a ceramic capacitor, shrinkage due to firing of the dielectric sheet occurs at about 1100 ° C., whereas shrinkage due to firing of the internal electrode. Is said to start around 700 ° C. on the lower temperature side.
[0007]
Various improvements have been made to these solutions.
For example, nickel powder having a composite oxide layer containing La and Ni on at least a part of the surface (Japanese Patent Laid-Open No. 10-324906), at least one of Al, Co, Cr or Mn with respect to 100 mol of Ni Ni powder containing at least 0.01 mol and no more than 1 mol of the above element (Japanese Unexamined Patent Publication No. 11-21644), Ni powder having a composite oxide layer represented by formula (1) on at least a part of its surface . _{A x B y O (x +} 2y) ( provided that one or more elements wherein A is Ca, Sr and Ba, B is a .x representing one or two elements of Ti and Zr y represents a number satisfying the following formula: 0.5 ≦ y / x ≦ 4.5) (Japanese Patent Laid-Open No. 11-124602) and the like have been proposed.
[0008]
[Problems to be solved by the invention]
However, in these Ni powders, it was necessary to control the heat shrinkage behavior during sintering to some extent by mixing 20-30% of a complex oxide such as barium titanate as an electrode paste. In multilayer capacitors, dielectric layers with a thickness of 3 μm or less and hundreds of layers are manufactured, and as a result, the thickness of one internal electrode layer is 1 μm or less, so the Ni powder is fine. Must be micronized to 0.2 μm. Along with this, the mixed oxide to be mixed must also be micronized, but if it becomes particles of 0.1 μm or less, it tends to be agglomerated powder, and even if this is mixed with Ni powder, the electrode layer becomes thicker. There was a problem. In addition, since the composite oxide is mixed non-uniformly, there is a case where the dielectric and the shrinkage behavior are inconsistent during the sintering process, resulting in delamination.
As a result of intensive studies in view of the above problems, the present inventors have found that Ni particles coated with a certain type of complex oxide are completely coated with a complex oxide layer, so that in the initial stage of sintering. Since there was no contact between Ni, it was found that the sintering rate between Ni particles could be relaxed and a dense internal electrode layer could be formed, and the present invention was completed.
[0009]
[Means for Solving the Problems]
That is, in the first aspect, the present invention is a coated metal powder in which at least a part of the surface of the metal powder is coated with an inorganic compound, the metal powder is Ni particles, and the inorganic compound to be coated is And the following formula:
ABO _{3-X / 2} (OH) _X
(In the formula, A represents one or more elements selected from Mg, Ca, Sr, and Ba, B represents one or more elements selected from Ti, Zr, and Hf. X represents the formula. The present invention provides a coated metal powder characterized by being a compound represented by the following formula: 0 <x <6 .
[0010]
Furthermore, in the second aspect of the present invention, the element A and the element B are added to the aqueous suspension of the metal powder, and the inorganic compound is deposited on the surface of the metal powder. A feature of the present invention is to provide a method for producing a coated metal powder.
[0011]
Furthermore, in the third aspect of the present invention, there is provided a coated metal powder paste comprising the above coated metal powder and a resin binder.
[0012]
Furthermore, in the fourth aspect of the present invention, there is provided a ceramic laminated electronic component characterized by using the above coated metal powder.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The coated metal powder of the present invention is a coated metal powder that is at least partially coated with an inorganic compound on the surface of the metal powder, and the coated inorganic compound has an OH group in the compound. To do.
As the inorganic compound to be coated, ABO _{3−X / 2} (OH) _x (wherein A is one or more elements selected from Mg, Ca, Sr, Ba, B is Ti, Zr, 1 or 2 or more elements selected from Hf, and x is a compound represented by the formula 0 <x <6. A preferred combination of A and B is Ti and Ba.
The inorganic compound to be coated has OH groups in order to deposit on the surface in an aqueous solution of metal powder. For example, when the OH group is baked at a temperature of 300 ° C. or higher, the OH group cannot be confirmed, but the OH group is confirmed by the presence or absence of a peak in the infrared absorption spectrum (IR).
In other words, the fact that the OH group cannot be confirmed is that the absorption peak on the infrared absorption spectrum diagram does not exist with respect to the spectrum base, or the peak is slightly broadened with respect to the baseline even if there is a peak. Are also included.
[0014]
The inorganic compound coated on the surface of the metal powder is a composite oxide deposited coating as shown by ABO _{3-X / 2} (OH) _X , but this ABO _{3-X / 2} (OH) _X The molar ratio is A / B = 0.5 to 1.5, preferably 0.8 to 1.2. Such a structure can be confirmed by an X-ray diffraction spectrum.
Such a coated inorganic compound layer is coated in an aqueous solution, but is crystallized at the time of coating, forms a pseudo cubic perovskite structure, and contains a hydroxyl group in the compound.
The core of the coated metal powder is Ni particles or Ag—Pd particles. Ni particles are preferred, but in any case, they are not particularly limited as long as they are industrially available for ceramic laminated electronic parts.
Specifically, the average particle size is 0.1 to 0.5 μm, the BET specific surface area is about 1 to 4 m ² / g, the purity is 99.9% or more, and the shape is spherical, but is limited thereto. It is not a thing.
[0015]
Furthermore, the coated metal powder of the present invention is such that a composite oxide represented by ABO _{3-X / 2} (OH) _X is uniformly coated on the particle surface, and its particle size is basically a raw material. Depending on the shape of some Ni particles or Ag-Pd particles, the properties of Ni particles or Ag-Pd particles can be used.
The degree of coating of the present invention is represented by the ratio of the particle size ratio (Z = X / Y) between the average particle size (X) measured by SEM photograph observation and the average particle size (Y) calculated from the BET specific surface area. Is done.
In order to obtain a sufficient antioxidant effect in the Ni powder, this ratio is 3 or more and at least 2 or more.
[0016]
The particle diameter measured from the electron micrograph is preferably as large as the number of particles to be measured. However, it is sufficient that the number of particles is 200 or more in the measurement with the photograph.
The average particle diameter measured from such an electron micrograph is 0.1 to 1.0 μm, but the maximum particle diameter of the particles to be measured is preferably 4 times or less of the average particle diameter. When the average particle size is 1 μm, for example, the maximum particle size is 4 μm or less.
This is because the thickness of the internal electrode layer exceeds the thickness of particles having a maximum particle size of 4 or more.
[0017]
The particle diameter derived from the BET specific surface area is calculated by the following equation (1).
Particle diameter by BET specific surface area = 6 / (density × specific surface area) (1)
[0018]
In the production method of the present invention, an A-element compound and a B-element compound are added to an aqueous suspension of metal powder, and ABO _{3-X / 2} (OH) _X is deposited on the surface of the metal powder. It is.
The compound of element A to be used is one or more selected from oxides, hydroxides, alkoxides and the like of element A. Specifically, oxides or hydroxides such as Mg, Ca, Sr and Ba, and alkoxides. Of these, barium hydroxide is preferred.
In addition, the B element compound used is one or more selected from B element oxides, hydroxides, alkoxides, and the like. Specifically, oxides such as Ti, Zr, and Hf, hydroxides, and alkoxides. Of these, titanium alkoxide is preferable.
However, when a hydroxide is used for the compound of element A, or when NaOH, KOH, or LiOH is used as an alkali, other raw materials may be chloride, nitrate, or acetate.
[0019]
The production method of the present invention will be described more specifically. A metal powder is placed in a suspension, and an element A compound and an element B compound or a solution thereof are continuously added to the solution and reacted. Although reaction temperature is not specifically limited, Usually, it is about 20-100 degreeC. Moreover, although reaction time is not specifically limited, Usually, it is about 0.5 to 24 hours.
After completion of the reaction, the solution is filtered by a predetermined method, washed and dried to obtain the coated metal powder of the present invention.
The coated metal powder according to the present invention can be used for screen printing using a paste used when forming an internal electrode, which is one of the manufacturing processes of a multilayer ceramic capacitor.
Such a paste is a slurry in which the coated metal powder of the present invention is dispersed in an organic binder. As the organic binder used, various resins are used in a state dissolved in an organic solvent. Typical organic binders are acrylic resin, phenol resin, alkyd resin, rosin ester, various celluloses and the like. Organic solvents include alcohols, hydrocarbons, ethers, and esters.
[0020]
As other additives, waxes, surfactants, ceramic powder, organic bentonite and the like are used.
The internal electrode can be formed by a screen printing method, and can be obtained by a conventional method, for example, a known method of forming through a baking process such as printing, drying, binder removal, and main baking.
Furthermore, the coated metal powder paste of the present invention can be used as a ceramic laminated electronic component. The electronic component has an internal conductor, and includes, for example, a ceramic capacitor, a resonator, a filter, an inductor, and a substrate.
[0021]
【Example】
Hereinafter, the present invention will be further described by way of examples, but is not limited thereto.
(Example 1)
Add 120 g of nickel powder having an average particle size of 0.51 μm, specific surface area (1.27 m ² / g) and 50 g of barium hydroxide to 1 liter of ion-exchanged water, and stir well at 80 ° C. Subsequently, 40 g of tetrabutyl titanate was added in 30 minutes and aged for 8 hours. After separating this slurry, it was dried at 120 ° C. in a vacuum dryer and pulverized. When this powder was subjected to XRD measurement, IR measurement, and SEM imaging, it was confirmed that the powder was a nickel powder whose entire surface was coated with a barium titanate containing a hydroxyl group. FIG. 1 is an IR measurement chart of this powder.
In FIG. 1, the OH group can be confirmed with a peak at 3500 cm ⁻¹ .
The specific surface area was 12.81 m ² / g and the density was 7.92 g / cc. The nickel powder was subjected to thermogravimetric analysis (TG) and thermomechanical analysis (TMA) to evaluate atmospheric oxidation characteristics and shrinkage characteristics in a non-oxidizing atmosphere. The results are shown in Tables 1 and 2.
[0022]
In addition, a multilayer ceramic capacitor was produced by the following procedure.
(Preparation of conductive paste)
First, 50% by weight of the above-described coated nickel powder and 50% by weight of the vehicle (ethyl cellulose 5% and α-terpineol 95%) were mixed and dispersed by a three-roll mill to prepare a conductive paste.
[0023]
(Production of ceramic green sheets)
An organic solvent was used as a dispersion medium for the dielectric powder containing barium titanate as a main component, an organic binder and a plasticizer were added, and wet-mixed sufficiently to prepare a slurry.
Using the slurry, sheet molding was performed by a doctor blade method to obtain a dielectric ceramic green sheet and dried.
[0024]
(Production of laminate)
A conductive paste was printed on a plurality of internal electrode patterns on one surface of the obtained green sheet, and after drying, a plurality of green sheets were laminated, pressure-bonded, and cut to prepare a laminate.
[0025]
(Production of sintered body)
The laminate was heated in air at 330 ° C. for 5 hours to remove the binder, and then calcined at 1250 ° C. for 2 hours in a reducing gas flow with a H ₂ / N ₂ volume ratio of 2/100. A sintered body was produced.
[0026]
(Reoxidation, terminal electrode mounting)
Next, in order to make up for the oxygen deficient by the firing, the terminal electrode is formed by applying and baking Cu paste on both ends of the sintered body after firing at 800 ° C. for 4 hours in an air atmosphere and reoxidizing. The multilayer ceramic capacitor was formed.
The thickness of the internal electrode of the multilayer ceramic capacitor was 1.5 μm, the thickness of the dielectric layer was 5 μm, and the number of dielectric layers was 50. The external dimensions are 3.2 mm × 1.6 mm × 1.2 mm.
[0027]
The multilayer ceramic capacitor obtained as described above was solidified with 100 samples of each sample and polished, and observed under a microscope at a magnification of 400 times to inspect for cracks and delamination. Further, a DC voltage of 10 V was applied to the multilayer ceramic capacitor, and a withstand voltage failure rate (short-circuit failure rate) test was conducted in which the insulation resistance after 30 seconds was 100 MΩ or less. The results are shown in Tables 2 and 3.
[0028]
(Example 2)
120 g of nickel powder having an average particle size of 0.51 μm, a specific surface area (1.27 m ² / g) and 25 g of barium hydroxide are added to 1 liter of ion-exchanged water and stirred well at 80 ° C. Subsequently, 20 g of tetrabutyl titanate was added in 30 minutes and aged for 8 hours. After separating this slurry, it was dried at 120 ° C. in a vacuum dryer and pulverized. When this powder was subjected to XRD measurement, IR measurement, and SEM imaging, it was confirmed that it was nickel powder whose entire surface was coated with barium titanate. The specific surface area was 7.92 m ² / g, and the density was 8.33 g / cc. The nickel powder was subjected to thermogravimetric analysis (TG) and thermomechanical analysis (TMA) to evaluate atmospheric oxidation characteristics and shrinkage characteristics in a non-oxidizing atmosphere.
A multilayer ceramic capacitor was produced by the same method as in Example 1, and the same test was performed. The respective results are shown in Tables 2 and 3.
[0029]
(Example 3)
120 g of nickel powder having an average particle size of 0.51 μm, specific surface area (1.27 m ² / g) and 50 g of barium hydroxide are added to 1 liter of ion-exchanged water and stirred well at 80 ° C. Subsequently, 23.0 g of a slurry of metatitanic acid (TiO (OH) ₂ ) (408 g / L in terms of TiO ₂ ) was added and aged for 8 hours. This slurry was separated, dried at 120 ° C. in a vacuum dryer, and pulverized. When this powder was subjected to XRD measurement, IR measurement, and SEM imaging, it was confirmed that it was nickel powder whose entire surface was coated with barium titanate. The specific surface area was 4.31 m ² / g and the density was 7.98 g / cc. Using this nickel powder, the oxidation characteristics in the air and the shrinkage characteristics in the non-oxidizing atmosphere were evaluated.
A multilayer ceramic capacitor was produced by the same method as in Example 1, and the same test was performed. The respective results are shown in Tables 2 and 3.
[0030]
(Example 4)
120 g of nickel powder having an average particle diameter of 0.25 μm and a specific surface area (2.62 m ² / g) and 50 g of barium hydroxide are added to 1 liter of ion-exchanged water and stirred well at 80 ° C. Subsequently, 40 g of tetrabutyl titanate was added in 30 minutes and aged for 8 hours. This slurry was separated, dried at 120 ° C. in a vacuum dryer, and pulverized. When this powder was subjected to XRD measurement, IR measurement, and SEM imaging, it was confirmed that it was nickel powder whose entire surface was coated with barium titanate. The specific surface area was 15.64 m ² / g and the density was 7.98 g / cc. Using this nickel powder, the oxidation characteristics in the air and the shrinkage characteristics in the non-oxidizing atmosphere were evaluated.
A multilayer ceramic capacitor was produced by the same method as in Example 1, and the same test was performed. The respective results are shown in Tables 2 and 3.
[0031]
(Example 5)
120 g of nickel powder having an average particle size of 0.51 μm, specific surface area (1.27 m ² / g) and 50 g of barium hydroxide are added to 1 liter of ion-exchanged water and stirred well at 80 ° C. Subsequently, 40 g of tetrabutyl titanate was added in 30 minutes and aged for 8 hours. After separating this slurry, it was dried at 120 ° C. in a vacuum dryer and pulverized. When this powder was subjected to XRD measurement, IR measurement, and SEM imaging, it was confirmed that the powder was a nickel powder whose entire surface was coated with a barium titanate containing a hydroxyl group. The specific surface area was 12.81 m ² / g and the density was 7.92 g / cc. The nickel powder was subjected to thermogravimetric analysis (TG) and thermomechanical analysis (TMA) to evaluate atmospheric oxidation characteristics and shrinkage characteristics in a non-oxidizing atmosphere.
A multilayer ceramic capacitor was produced by the same method as in Example 1, and the same test was performed. The respective results are shown in Tables 2 and 3.
[0032]
(Comparative Example 1)
Using nickel powder having an average particle size of 0.51 μm and a specific surface area (1.27 m ² / g), the oxidation characteristics in air and the shrinkage characteristics in reducing atmosphere were evaluated.
FIG. 2 is an IR measurement chart of this powder. In FIG. 2, the peak of the OH group near 3500 cm ⁻¹ is not observed.
A multilayer ceramic capacitor was produced by the same method as in Example 1, and the same test was performed. The respective results are shown in Tables 2 and 3.
[0033]
(Comparative Example 2)
(Method for producing barium titanate)
For slurry of titanium hydrate or metatitanic acid (TiO (OH) ₂ ) produced by hydrolysis of titanyl sulfate (TiOSO ₄ ), which is an intermediate product in sulfuric acid method titanium dioxide production (408 g / L in terms of TiO ₂ ) Add barium hydroxide to 1.2 times mole (Ba (OH) 2.8H2O / TiO2 = 1.2), add 4 times the amount of water of the metatitanic acid slurry and stir at a temperature of 95 ° C. The reaction was continued for 2 hours. Next, solid-liquid separation is performed by a filtration device, and the obtained wet cake is put into a washing device, and excess barium hydroxide is sufficiently washed away with warm water at a temperature of 80 ° C. Subsequently, filtration was performed again, and the obtained crystal powder was dried at 105 ° C.
[0034]
120 g of nickel powder having an average particle size of 0.51 μm and a specific surface area (1.27 m ² / g) and 24 g of barium titanate having an average particle size of 0.1 μm prepared by the above method are placed in 1 liter of ion-exchanged water, and a homomixer For 5 minutes. After separating this slurry, it was dried at 120 ° C. in a vacuum dryer and pulverized. The specific surface area was 2.84 m ² / g and the density was 7.97 g / cc. Using this nickel powder, the oxidation characteristics in the air and the shrinkage characteristics in the non-oxidizing atmosphere were evaluated.
A multilayer ceramic capacitor was produced by the same method as in Example 1, and the same test was performed. The respective results are shown in Tables 2 and 3.
[0035]
(Comparative Example 3)
Nickel powder having a particle size of 0.25 μm and a specific surface area (2.62 m ² / g) was used to evaluate oxidation characteristics in air and shrinkage characteristics in a non-oxidizing atmosphere.
A multilayer ceramic capacitor was produced in the same manner as in Example 1.
[0036]
[Table 1]

[0037]
[Table 2]

[0038]
[Table 3]

[0039]
【The invention's effect】
Since the coated metal powder of the present invention is configured as described above, as can be seen from Tables 1, 2 and 3, it is excellent in atmospheric oxidation characteristics and shrinkage characteristics in a non-oxidizing atmosphere. There are no cracks or delamination, and the short-circuit defect rate is extremely low, so that it can be used advantageously in the manufacture of various electronic components.
[Brief description of the drawings]
FIG. 1 is an IR measurement chart of a coated metal powder produced according to Example 1 of the present invention.
2 is an IR measurement chart of Comparative Example 1. FIG.

Claims (8)

A coated metal powder in which at least a part of the surface of the metal powder is coated with an inorganic compound, the metal powder is Ni particles, and the inorganic compound to be coated is represented by the following formula:
ABO _{3-X / 2} (OH) _X
(In the formula, A represents one or more elements selected from Mg, Ca, Sr, and Ba, B represents one or more elements selected from Ti, Zr, and Hf. X represents the formula. Coated metal powder characterized by being a compound represented by the following formula: 0 <x <6 .   The coated metal powder according to claim 1, wherein the inorganic compound to be coated has a primary particle diameter of 0.1 μm or less.   The particle size ratio (Z = X / Y) between the average particle size (X) obtained by SEM photograph measurement of the coated metal powder and the particle size (Y) calculated from the BET specific surface area is 2 or more. Or the covering metal powder of 2. Coating amount of the inorganic compound to the metal powder is 0.1-50%, coated metal powder according to claim 1. A compound of element A and a compound of element B are added to an aqueous suspension of Ni powder and the following formula:
ABO _{3-X / 2} (OH) _X
(In the formula, A represents one or more elements selected from Mg, Ca, Sr, and Ba, B represents one or more elements selected from Ti, Zr, and Hf. X represents the formula. A method for producing a coated metal powder, characterized by depositing an inorganic compound represented by the following formula: 0 <x <6. The method for producing a coated metal powder according to claim 5 , wherein the compound of element A and the compound of element B are hydroxides or alkoxides. A coated metal powder paste comprising the coated metal powder according to any one of claims 1 to 3 and a resin binder. A ceramic laminated electronic component using the coated metal powder according to any one of claims 1 to 3 .

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