JPH07130573A - Ceramic powder coated with conductive metal - Google Patents

Abstract

PURPOSE:To provide ceramic particles which are coated with conductive metal material such as silver or palladium used as electrode material and can be used in place of silver or palladium keeping at high as silver or palladium in electrical properties so as to lessen silver or palladium in consumption quantity. CONSTITUTION:Conductive metal material-coated ceramic fine particles are formed through such manner that ceramic particles (ceramic component ranges from 90 to 10wt.% of metal-coated ceramic particle) of average grain diameter below 5mum, preferably below 1.5mum are coated with coating layer substantially formed of conductive metal material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive metal-coated ceramic powder which can be advantageously used for manufacturing electrodes.

[0002]

2. Description of the Related Art Conventionally, a substrate with an electrode layer having a unit structure composed of a substrate and an electrode layer provided on the substrate has been used as a component of various electric and electronic devices.
Such a substrate with an electrode layer is used, for example, for a ceramic capacitor, a thermistor, a varistor, various resistors, a CR
It is used for composite parts, IC boards, and conductive patterns for printed wiring.

The most commonly used conductive materials for the electrode layers for these purposes are noble metals such as silver, gold, palladium and platinum, or alloys thereof. These noble metals have high conductivity and are excellent as materials for electrodes, but they are extremely expensive, which is a major obstacle to reduction in manufacturing cost of electrodes.

For this reason, a measure which uses an inexpensive base metal instead of a noble metal as a material for electrodes, or a noble metal-coated powder obtained by coating fine-particle base metal or ceramic powder with a noble metal is used. Measures such as reducing the amount of precious metal used by using a paint have been conventionally studied.

Copper as a material for electrodes instead of precious metal,
The former measure using a base metal such as nickel has been put to practical use in the manufacture of, for example, ceramic capacitors and IC substrates. However, when using these base metals, it is necessary to carry out the baking work on the substrate in an inert atmosphere such as a nitrogen atmosphere in order to prevent oxidation. Therefore, the atmosphere was controlled for the implementation. There is a problem that a special firing furnace is required.

[0006] Furthermore, recently, a multilayer capacitor, which is rapidly becoming popular, and a multilayer varistor manufactured by a similar method,
In manufacturing a laminated coil, a multilayer IC package, etc., a method for simultaneously firing a capacitor substrate, a varistor substrate, etc. and an electrode material at a high temperature is employed, so that the electrode material is stable even under high temperature conditions. Is required. Generally, a base metal is unstable at a high temperature unless it is placed in a special atmosphere. Therefore, an electrode for manufacturing an electronic component including a co-firing process of such an electrode material and a substrate is included in the electrode. Material (conductive metal material)
As a general rule, expensive platinum, palladium,
Noble metals such as silver and alloys of these are used.

Further, when the powder of the noble metal is used, the same is true, but when the powder of the base metal is applied to the ceramic substrate in the form of the conductive paint and the simultaneous firing is carried out, the gap between the metal and the ceramic is obtained. The problem is that various structural defects occur due to differences in the expansion and contraction curves of the powder, or differences in the sintering start temperature, and the electrical characteristics and mechanical strength of the resulting electrodes are often reduced. There is.

On the other hand, the amount of precious metal used is reduced by using a conductive paint made of precious metal-coated powder obtained by coating fine-particle base metal or ceramic powder with precious metal as described above, instead of precious metal. Measures have also been studied and announced. However, in a method such as a chemical plating method which is a conventionally known powder coating method, there is a problem that a noble metal coating layer to be formed is partially mixed with a base metal or ceramic component serving as a core portion. Therefore, the electrode layer produced by firing a conductive coating material using such coated particle powder on the surface of the substrate,
The conductivity will be much lower than that of the noble metal used, and it cannot be practically used as an electrode for electronic parts.

[0009]

SUMMARY OF THE INVENTION The present invention provides a substrate having an electrode layer capable of reducing the amount of the conductive metal material used without deteriorating the electrical characteristics of the conductive metal material used as the electrode material. The main object is to provide a conductive metal-coated ceramic powder that is particularly effective for manufacturing.

INDUSTRIAL APPLICABILITY The present invention is particularly effective for producing a substrate having an electrode layer having improved mechanical properties and solder resistance without deteriorating the electrical properties of a conductive metal material used as an electrode material. It is also an object of the present invention to provide such a conductive metal-coated ceramic powder.

[0011]

DISCLOSURE OF THE INVENTION The present invention is directed to fine-grained ceramic powder having an average particle size of 5 μm or less, which is covered with a coating layer formed substantially only of a conductive metal material (provided that ceramics are used). The weight of the parts is in the range of 90 to 10% by weight based on the whole coating powder).

In the present invention, "a coating layer formed substantially only of a conductive metal material" means that the surface of the coating layer has electrical properties such as conductivity, which are used for forming the coating layer. It means that the amount of the ceramic powder and / or the ceramic component that is obviously changed from the electrical characteristics of the conductive metal material itself is not exposed or present.

The high-purity metal-coated powder such as the conductive powder of the present invention cannot be manufactured by a coating method such as a chemical plating method which has been conventionally known. It can be easily produced by utilizing the reaction for forming a coating layer via

The following methods can be mentioned as typical methods utilizing the reaction for forming the coating layer via the gelled state. (A) Fine-grained ceramic powder that exists in a uniformly dispersed state, (B) a conductive metal salt that forms a coating layer that exists in a uniformly dispersed state, and (C) a coating layer that exists in a dissolved state After forming a conductive metal coating layer on the surface of the finely divided ceramic powder by adding a reducing agent such as hydrazine to an aqueous suspension containing conductive metal ions, which forms a. Method of collecting and drying.

Alternatively, as another method of utilizing the reaction for forming the coating layer which similarly goes through the gelled state, the following method can be mentioned. An aqueous gelling solution containing a conductive metal ion and a supersaturated amount of a conductive metal chelate compound, in an amount sufficient to reduce both the conductive metal ion and the conductive metal chelate compound into a conductive metal simple substance. By mixing hydrogen peroxide and an aqueous dispersion containing the finely divided ceramic powder in a uniformly dispersed state, and an alkalizing agent, the gel state of the aqueous gelling liquid is eliminated and at the same time, the finely divided ceramic powder A method in which a conductive metal simple substance is deposited on the surface to form a conductive metal coating layer, which is then collected and dried.

Further, as another method of utilizing the reaction for forming the coating layer which similarly goes through the gel state, the following method can also be mentioned. Stirring the reducing agent in a dispersion liquid in which fine-grained ceramic powder is uniformly dispersed in a gel-like aqueous solution of pH 5-10 containing a conductive metal compound, non-metallic ammonium (such as ammonium chloride) and aqueous ammonia. In addition to eliminating the gel state of the aqueous gelling solution, a conductive metal simple substance is deposited on the surface of the fine-grained ceramic powder to form a conductive metal coating layer, which is then collected and dried. How to make.

The method for producing a high-purity metal-coated powder as described above is a method invented by the present inventor prior to the present invention. Further detailed points of these production methods can be found in the present application. Japanese Patent Application Nos. 55-51516 and 55-
116482, 56-133314, and 56-1.
It is disclosed in the patent application specification of 33315.

Examples of the metal used as the conductive metal material in the present invention include noble metals such as platinum, gold, silver and palladium, molybdenum, nickel and cobalt.
Mention may be made of base metals such as iron, copper, zinc, tin, antimony, tungsten, manganese, titanium, vanadium, chromium, etc., which can exist in air in a substantially stable manner. These metals can be used alone or in the form of an alloy.

Examples of finely divided ceramic powder used in the present invention include oxide-based ceramics such as silicon dioxide, zirconium oxide, aluminum oxide, titanium dioxide, ferric oxide, calcium oxide and barium titanate, or Examples of the powder include non-oxide ceramics containing at least two kinds of atoms such as tungsten carbide, silicon carbide, and titanium nitride and having an average particle size of 5 μm or less. However, in order to bring the electrical properties and mechanical strength of the obtained electrode layer to a particularly excellent level, it is preferable to select a powder having an average particle size of 1.5 μm or less. Further, depending on the purpose, it may be preferable to use finely divided ceramic powder having an average particle diameter of 1 micron or less.

Uniform and high-purity coating of such a powder having a particularly small average particle size is actually impossible by a conventional coating method such as chemical plating, but it goes through the gelled state. By using the coating method, it is possible to form a uniform and high-purity coating layer.

The weight ratio of the ceramic powder forming the core of the high-purity metal-coated powder of the present invention to the high-purity metal forming the coating layer is 90:10 to 10:90, preferably 75. : 25 to 25:75.

The conductive powder produced by the production method of the present invention can be particularly advantageously used for producing a substrate with an electrode layer from a ceramic substrate and an electrode layer provided on the substrate.

The ceramic substrate contains, as a main component, oxide ceramics such as silicon dioxide, zirconium oxide, aluminum oxide, titanium dioxide, ferric oxide, calcium oxide, barium titanate, or the like, or It is a substrate formed mainly of non-oxide ceramics such as tungsten carbide, silicon carbide and titanium nitride. The main ones of these ceramic substrates are already ceramic capacitors, thermistors, varistors, various resistors, CR composite components, IC substrates, electronic components such as conductive patterns for printed wiring, and multilayer capacitors, multilayer varistors, multilayer coils, Multi-layer IC
It has been used as a substrate for electronic parts such as packages, or its use has been attempted.

That is, the electrode layer can be formed by baking the high-purity metal-coated powder of the present invention produced by the above method on a ceramic substrate in the form of a conductive paint.

The conductive paint can be prepared by a method similar to the conventional method for preparing a conductive paint using a single conductive metal. That is, an appropriate additive, solvent, etc. are added to the high-purity coating powder to prepare a conductive paint.

The electrodes can be formed on the ceramic substrate by, for example, applying a conductive coating material to the ceramic substrate by a method such as screen printing and then firing it in a firing furnace. The firing method, firing conditions and the like can be determined according to the method and conditions when firing a conductive coating material made of the same metal as the metal forming the coating layer.

When the electrode layer is formed by using the high-purity coated particles of the present invention, the ceramic material of the ceramic substrate and the ceramic material of fine-grained ceramic powder present inside the electrode layer are the same. Is advantageous. That is, in the conventional method of baking the conductive paint on the substrate, since the expansion coefficient of the metal of the conductive paint and the material of the substrate are different, before firing,
It has been a general practice to apply a conductive coating material to the fired substrate and then fire it. However, when the high-purity coated particles of the present invention are used, the main component of the ceramic material of the ceramic substrate and the ceramic material of the fine particulate ceramic powder present inside the electrode layer are the same or of the same type (for example, both are oxidized). If you select such a material, apply the conductive paint directly to the unfired ceramic substrate and fire it as it is. It is possible to perform the operation, that is, the simultaneous firing.

[0028]

INDUSTRIAL APPLICABILITY The conductive metal-coated ceramic powder of the present invention can be particularly advantageously utilized for manufacturing various kinds of electric parts, electronic parts, electric appliances, substrates with electrode layers incorporated in electronic parts. For example, a substrate with an electrode layer obtained by using the conductive metal-coated ceramic powder of the present invention is an electronic component in a form in which a lead wire is provided in an electronic component including a ceramic substrate and an electrode layer provided on the substrate. The electronic component may be in a variety of forms, such as an electronic component in which these electronic components are stacked and an electronic component in which the stack has a spiral shape. Examples of specific products are ceramic capacitors, thermistors, varistors,
Various resistors, CR composite parts, IC boards, electronic parts such as conductive patterns for printed wiring, and multilayer capacitors,
Multilayer varistor, Multilayer coil, Multilayer IC package, BL
A ceramic capacitor etc. can be mentioned.

By manufacturing the above-mentioned electronic component using the conductive metal-coated ceramic powder of the present invention, the conductive metal material can be used without deteriorating the electrical characteristics of the conductive metal material used as the electrode material. It is possible not only to reduce the amount used, but also to improve its mechanical properties and various properties such as solder resistance.

For example, there is a phenomenon called delamination (delamination) among the structural characteristics that greatly affect the mechanical strength of electronic components. This delamination is caused by the difference in the expansion / contraction curve between the conductive material and the ceramic substrate used when the substrate with an electrode layer is manufactured by the co-firing method, or the difference in the sintering start temperature between them and the conductivity. Between the electrode layer and the substrate due to the ignition phenomenon caused by the reaction between the conductive material, the binder, the solvent, the ceramic substrate, etc., and the change in the electrode volume due to the oxidation and reduction of the electrode material. This is a phenomenon in which a tear occurs. It is known that when this delamination occurs, the characteristics of the electronic component, particularly the mechanical strength, are significantly reduced. In a substrate with an electrode layer obtained by using the conductive metal-coated ceramic powder of the present invention, this delamination hardly occurs, and therefore, a substrate with an electrode layer obtained by using the conductive metal-coated ceramic powder of the present invention Shows particularly high mechanical strength.

Example 1 (I) Preparation of silver-coated barium titanate powder An aqueous solution prepared by dissolving 10 g of silver nitrate in 50 ml of water and an aqueous solution prepared by dissolving 15 g of ethylenediaminetetraacetic acid (EDTA) disodium salt in 200 ml of water. And were mixed with stirring to obtain a gelling solution. In order to reduce the viscosity of this gel state, 50 ml of water was further added, and then 100 ml of an aqueous hydrogen peroxide solution (30% aqueous solution) was added to the gelling solution.
Was added.

Separately, barium titanate powder (average particle size:
1.4 μ) 6 g was added to 150 ml of water to uniformly prepare a dispersion liquid, and this dispersion liquid was added to a gelling liquid (containing hydrogen peroxide) and stirred sufficiently. When the obtained gelling liquid was vigorously stirred and 100 ml of an aqueous sodium hydroxide solution (NaOH 5 g / 25 ml water) was added thereto, the gel state was resolved, and silver was deposited on the surface of the barium titanate powder. To this reaction system was further added 150 ml of a hydrogen peroxide aqueous solution (30% aqueous solution) to complete the reaction.

The obtained silver-coated barium titanate powder was taken out by filtering, washing with water and drying.
It shows a light gray color after drying, the yield is 11.7 g (theoretical yield 12 g), and the barium titanate / silver weight ratio in the powder is 5
It was 0/50. According to the observation with a scanning electron microscope, the surface coating layer of this silver-coated barium titanate powder was formed only of silver, and no non-uniformity due to mixing or exposure of ceramic powder was observed.

(II) Ceramic Capacitor Electrode A mixture having the following composition containing the silver-coated barium titanate powder obtained in (I) above was prepared. Silver-coated barium titanate powder 10 g Lead borosilicate glass frit 0.2 g Ethyl cellulose 1.0 g Ethyl cellosolve 2.5 g Butyl carbitol 2.5 g This mixture was well kneaded using a three-roll type kneading device, and used for electrodes. The conductive paint of

The obtained conductive paint was screen-printed on both sides of a sintered barium titanate ceramic capacitor (diameter 13.0 mm, thickness 0.5 mm) element (substrate), and 800 Firing was performed at ° C. Table 1 shows the results of measurement of electrical properties, mechanical properties and solder resistance properties of this fired product (silver-coated powder electrode). Further, for comparison, the same measurement was performed for a silver electrode produced by using the same amount of silver simple substance powder as the silver-coated powder instead of the silver-coated powder and firing the same. The results are also shown in Table 1.

Table 1 Characteristics Silver coated powder electrode Silver electrode Electrical characteristics εs 6500 6420 tan δ (%) 1.5 1.6 Lead wire tensile strength 2.5 kg 1.8 kg Solder erosion without erosion Peripheral area erosion Solderability Same as left

The above measurement was carried out as follows.
Capacitance (εs) and dissipation factor (tan δ) are 25 ℃
And YHP Digital LCR Meter Model 4274A
Using, measuring voltage 1.0Vrms, measuring frequency 1.0K
It was measured under the condition of Hz.

The lead wire tensile strength is determined by baking the electrode and then pre-melting the solder (S manufactured by Senju Metal Co., Ltd.).
-356, containing 3.5% of Ag) and having a diameter of 0.
5mm solder-plated annealed copper wire (MLT manufactured by Kyowa Electric Cable Co., Ltd.)
-122) was attached, and the measurement was performed with an Intesco universal material testing machine).

As for the solder erosion and solderability, the temperature was controlled at 230 ° C. (S-made by Senju Metal Co., Ltd.
356, containing 3.5% Ag), and a magnification of 20
It was judged by observing with a stereoscopic microscope.

Example 2 (I) Production of Silver-Coated Ferric Oxide Powder Instead of barium titanate powder, ferric oxide (average particle size:
A silver-coated ferric oxide powder was produced in the same manner as in Example 1 except that 1.5 g) 6 g was used. Yield is 1
1.6 g (12 g theoretical yield) of ferric oxide in powder /
The silver weight ratio was 50/50. According to the observation with a scanning electron microscope, the surface coating layer of this silver-coated ferric oxide powder was formed only of silver, and no non-uniformity due to mixing or exposure of the ceramic powder was observed.

(II) Varistor Electrode A mixture having the following composition containing the silver-coated ferric oxide powder obtained in (I) above was prepared. Silver-coated ferric oxide powder 10 g Lead borosilicate glass frit 0.2 g Ethyl cellulose 1.0 g Ethyl cellosolve 2.5 g Butyl carbitol 2.5 g This mixture was further thoroughly kneaded using a three-roll type kneading device, and an electrode was prepared. A conductive paint for use was obtained.

The obtained conductive paint was screen-printed to obtain a sintered varistor element (Fe ₂ O ₃ 85 mol%.
La ₂ O ₃ 5 mol% · CaO 10 mol%, diameter 13.0
mm, thickness 0.5 mm) Print on both sides of (substrate),
Firing was performed at 0 ° C. Table 2 shows the results of measuring the electrical properties, mechanical properties, and solder resistance of this fired product (silver-coated powder electrode). For comparison,
The same measurement was performed for a silver electrode produced by using the same amount of silver simple substance powder as the silver-coated powder instead of the silver-coated powder and firing the same. The results are also shown in Table 2.

Table 2 Characteristics Silver coated powder electrode Silver electrode Electrical characteristics α 5 5 E ₁₀ 12V 12V Lead wire tensile strength 2.6kg 2.0kg Solder bite not bite peripheral part bite solderability Full surface solder wettability Same as left

The voltage non-linearity coefficient α and the terminal voltage E ₁₀ at the time of energizing 10 mA are 25 ° C., and the model 592C manufactured by Mechatronics and the VO manufactured by Iwasaki Tsushinki Co., Ltd., respectively.
It was measured using AC757. The lead wire tensile strength, solder erosion, and solderability were measured and judged in the same manner as in Example 1.

Example 3 (I) Production of Palladium-Coated Barium Titanate Powder Palladium solution (50 g of palladium metal and 700 m of aqua regia)
(dissolved in 1) ammonium chloride 12 in 700 ml
0 g (1.2 equivalent times with respect to palladium) was added to obtain a dark gel solution. By adding 450 ml of ammonia water (25% aqueous solution) to this solution, the solution became a pink gel solution and the pH of the solution became about 7.

To this solution, 50 g of barium titanate powder (average particle size: 1.5 μ) was added, and with sufficient stirring, an aqueous solution of sodium borohydride (0.75% by weight) was added to 10 parts.
When 00 ml was added, the gel state was resolved and a black powder was produced. The liquid phase was removed by decantation, washing was performed 10 times each with water and hot water by the same decantation operation, and then dried at 65 ° C. to produce a palladium-coated barium titanate powder.
The yield was 99 g (theoretical yield 100 g), and the barium titanate / palladium weight ratio in the powder was 50/50.
Observation with a scanning electron microscope revealed that the surface coating layer of this palladium-coated barium titanate powder was formed only of palladium, and no non-uniformity due to mixing or exposure of the ceramic powder was observed.

(II) Multilayer Capacitor Internal Electrode A mixture having the following composition containing the palladium-coated barium titanate powder obtained in (I) above was prepared. Palladium (Pd) -coated barium titanate powder 45 g Ethyl cellulose 3.8 g Dibutyl phthalate 3.8 g Butyl carbitol 42.5 g This mixture was well kneaded using a three-roll type kneading device to obtain a conductive paint for electrodes. Obtained.

Using the obtained conductive paint and barium titanate-based element (substrate), a multilayer capacitor [35 layers, electrode spacing 16 μm (after firing)] was manufactured by the simultaneous firing method. Table 3 shows the results of measuring the electrical characteristics and structural characteristics of this multilayer capacitor. Further, for comparison, the same measurement was carried out for a Pd electrode manufactured by using the same amount of palladium (Pd) simple substance powder as the Pd coated powder instead of the palladium (Pd) coated powder and firing the same. The results are also shown in Table 3.

Table 3 Characteristics Pd coated powder electrode Pd electrode Electrical Characteristics C 239 nF 234 nF εs 9790 9600 tan δ (%) 0.58 0.51 IR 3.5X10 10 Ω 3.5X10 10 Ω V B 620V 650V temperature characteristic (ΔC / C) MAX (% ) 11. 2 18.0 MIN (%) -72.0 -73.1 Tc (° C) 20 20 Structural characteristics Delamination 0 out of 50 50 out of 50 Cracks, chips 0 out of 50 2 out of 50

Capacitance (εs) and dielectric loss tangent (tan
δ) was measured by the same method as in Example 1. The insulation resistance (IR) was measured with a YHP insulation resistance tester model 4329A at 25V after 1 minute, and the breakdown voltage (V _B ) was measured with a model NS-3150 manufactured by Nissin Electric Co., Ltd. did. The temperature characteristic (ΔC / C) is measured from -25 ° C to 85 ° C, and the maximum value and the minimum value of the capacity change rate during that period are described (reference temperature 25 ° C), and the temperature showing the maximum value is Tc. Described.

Delamination in the structural characteristics was judged by observing the element by polishing the element and using a 20 × stereoscopic microscope, and observing the appearance of cracks and chips using the same 20 × stereoscopic microscope.

Example 4 (I) Production of Molybdenum-Coated Aluminum Oxide Powder 2 l of molybdenum solution (50 g of molybdenum metal dissolved in 2 l of aqua regia) was used instead of the palladium solution, and oxidation was performed instead of the barium titanate powder. A molybdenum-coated aluminum oxide powder was produced by the same method as in Example 3 except that 6 g of aluminum (average particle size: 1.5 μ) was used. The yield was 98 g (theoretical yield 100 g), and the weight ratio of aluminum oxide / molybdenum in the powder was 50/50. According to the observation with a scanning electron microscope, the surface coating layer of this molybdenum-coated aluminum oxide powder was formed only of molybdenum, and no non-uniformity due to mixing or exposure of ceramic powder was observed.

(II) In-Substrate Multilayer Wiring Board A mixture having the following composition containing the molybdenum-coated aluminum oxide powder obtained in (I) above was prepared. Molybdenum (Mo) coating Aluminum oxide powder 45 g Ethyl cellulose 3.8 g Dibutyl phthalate 3.8 g Butyl carbitol 42.5 g This mixture was further well kneaded using a three-roll type kneader to obtain a conductive paint for electrodes. It was

A multilayer wiring board [30 layers, dielectric layer thickness 16 μm (after firing)] was manufactured by the simultaneous firing method using the obtained conductive coating material and aluminum oxide type element (substrate). Table 4 shows the results of measuring the electrical characteristics and structural characteristics of this multilayer wiring board. For comparison, the same measurement was performed on the Mo electrode manufactured by using the same amount of molybdenum (Mo) simple substance powder as the Mo coating powder, instead of the molybdenum (Mo) coating powder, and firing the same. The results are also shown in Table 4.

Table 4 Characteristics Mo coated powder electrode Mo electrode Electrical characteristics C 181.4pF 181.0pF εs 8.8 8.8 Rsq 16mΩ / sq 16mΩ / sq Structural characteristics Delamination 0 out of 50 50 out of 50

The capacitance (εs) and the wiring resistance (Rsq) are 25 ° C., and the YHP digital LCR meter model 42 is used.
74A, measuring voltage and measuring frequency,
1.0Vrms, 100KHz and 1.0Vrms, 10
It was measured under the condition of 0 Hz. The delamination was observed and judged by the same method as in Example 3.

Example 5 (I) Production of Palladium-Coated Titanium Oxide Powder (0.3 μ) Palladium solution (50 g of palladium metal and 700 m of aqua regia)
(dissolved in 1) ammonium chloride 12 in 700 ml
0 g (1.2 equivalent times with respect to palladium) was added to obtain a dark gel solution. By adding 450 ml of ammonia water (25% aqueous solution) to this solution, the solution became a pink gel solution and the pH of the solution became about 7.

Titanium oxide powder (average particle size:
0.3 μ) 50 g, and with sufficient stirring, add an aqueous solution of sodium borohydride (0.75% by weight) to 1000 m
When 1 was added, the gel state was resolved and a black powder was produced. The liquid phase was removed by decantation, washing was performed 10 times each with water and hot water by the same decantation operation, and then dried at 85 ° C. to produce a palladium-coated titanium oxide powder. Yield 99g
(Theoretical yield was 100 g), and the titanium oxide / palladium weight ratio in the powder was 50/50. According to the observation with a scanning electron microscope, the surface coating layer of this palladium-coated titanium oxide powder was formed only of palladium, and no non-uniformity due to the mixing and exposure of the ceramic powder was observed.

(II) Multilayer Capacitor Internal Electrode A mixture having the following composition containing the palladium-coated titanium oxide powder obtained in (I) above was prepared. Palladium (Pd) -coated titanium oxide powder 45 g Ethyl cellulose 3.8 g Dibutyl phthalate 3.8 g Butyl carbitol 42.5 g This mixture was further thoroughly kneaded using a three-roll type kneader to obtain a conductive paint for electrodes. It was

A laminated capacitor [35 layers, electrode spacing 16 μm (after firing)] was manufactured by the simultaneous firing method using the obtained conductive paint and barium titanate element (substrate). Table 5 shows the results of measuring the electrical characteristics and structural characteristics of this multilayer capacitor. Further, for comparison, the same measurement was carried out for a Pd electrode manufactured by using the same amount of palladium (Pd) simple substance powder as the Pd coated powder instead of the palladium (Pd) coated powder and firing the same. The results are also shown in Table 5.

Table 5 Characteristics Pd coated powder electrode Pd electrode Electrical characteristics C 236 nF 235 nF εs 9650 9600 tan δ (%) 0.52 0.51 IR 3.5X10 ¹⁰ Ω 3.5X10 ¹⁰ Ω V _B 635V 645V Temperature characteristics (ΔC / C) MAX (%) 12. 1 18.0 MIN (%) -72.0 -73.0 Tc (° C) 20 20 Structural characteristics Delamination 0 out of 50 50 out of 50 Cracks, chips 0 out of 50 2 out of 50

Each characteristic value was measured in the same manner as in Example 3. The obtained multilayer capacitor was hardened with epoxy resin and cut, and its electrode part was observed with a scanning electron microscope at 10,000 times. Palladium formed a continuous layer and ultrafine particles of titanium oxide were uniformly dispersed in the layer. So called,
It was confirmed that a matrix having a sea (Pd) -island (TiO ₂ ) structure was formed.

Comparative Example 1 Palladium solution (50 g of palladium metal dissolved in 700 ml of aqua regia) 700 m
When 50 g of titanium oxide powder (average particle size 0.3 μm) was added to 1 and 50 ml of hydrazine hydrate was added with stirring, instantaneous foaming occurred and black aggregates were formed as a whole. The powder obtained by washing and drying at 65 ° C. was 52 g (theoretical yield 100 g). As a result of the analysis, slightly less than 50 g was Pd, and the remaining 2 g was titanium oxide and titanium hydroxide.

From the above results, it was clarified that titanium oxide was mostly dissolved in the usual palladium solution, and thus the palladium / titanium oxide coprecipitated powder could not be obtained by this method.

Comparative Example 2 (1) Production of Palladium-Coated Titanium Oxide Powder Palladium solution (50 g of palladium metal and 700 m of aqua regia)
(dissolved in 1) ammonium chloride 12 in 700 ml
0 g (1.0 equivalent times with respect to palladium) was added to obtain a dark gel solution. While heating this solution to 60 ° C., 450 m of aqueous ammonia (25% aqueous solution) was added thereto.
When 1 was added and further heated and stirred at 80 ° C. for 1 hour, the solution became a pale yellow solution and the pH of the solution became about 7. To this solution, 50 g of titanium oxide powder (average particle size: 0.3 μ) was added, and 50 ml of hydrazine hydrate was added with sufficient stirring, and the reaction instantly occurred, producing an off-black powder. The liquid phase was removed by decantation, washing was performed 10 times each with water and hot water by the same decantation operation, and then the product was dried at 85 ° C. to produce a palladium / titanium oxide coprecipitated powder. Yield 99
The weight ratio of titanium oxide / palladium in the powder was 50/50. According to observation with a scanning electron microscope, this palladium / titanium oxide coprecipitated powder is in a state in which palladium particles and titanium oxide particles are aggregated, and the surface is formed of palladium exposed portions and titanium oxide exposed portions. It was

(II) Multilayer Capacitor Internal Electrode A mixture having the following composition containing the palladium-coated titanium oxide powder obtained in (I) above was prepared. Palladium (Pd) -coated titanium oxide powder 45 g Ethyl cellulose 3.8 g Dibutyl phthalate 3.8 g Butyl carbitol 42.5 g This mixture was further thoroughly kneaded using a three-roll type kneader to obtain a conductive paint for electrodes. It was

A laminated capacitor [35 layers, electrode spacing 16 μm (after firing)] was manufactured by the simultaneous firing method using the obtained conductive paint and barium titanate-based element (substrate). Table 6 shows the results of measuring the electrical characteristics and structural characteristics of this multilayer capacitor. Further, for comparison, the same measurement was carried out for a Pd electrode manufactured by using the same amount of palladium (Pd) simple substance powder in place of the palladium titanium oxide coprecipitated powder and firing the same. The results are also shown in Table 6.

Table 6 Characteristics Pd titanium oxide coprecipitated powder electrode Pd electrode Electrical characteristics C 10 nF 235 nF εs 0.365 9600 tan δ (%) 3.6 0.51 IR 3.5X10 ¹⁰ Ω 3.5X10 ¹⁰ Ω V _B 620V 650V Temperature characteristics (ΔC / C) MAX (%) − 18.0 MIN (%) − −73.0 Tc (° C.) −20 Structural characteristics Delamination 25 out of 50 50 out of 50 Cracks, chips 5 out of 50 2 out of 50

Each characteristic value was measured in the same manner as in Example 3. The obtained multilayer capacitor was hardened with an epoxy resin and cut, and its electrode portion was observed with a scanning electron microscope at a magnification of 10,000 times. As a result, it was found that fine to coarse Pd phases were found in the continuous phase of titanium oxide. It was confirmed to be discontinuous and dispersed.

Comparative Example 3 (I) Production of chemical-plated silver-coated barium titanate powder 46.2 g of the same barium titanate powder (average particle size: 1.5 μ) as used in Example 1 was mixed with hydrochloric acid 1 : After soaking in a solution of 9 parts of water for 3 minutes, thoroughly washing with water, and immersing this for 30 minutes in a plating solution consisting of silver nitrate, 77 g, potassium hydroxide, 40 g, glucose, 70 ammonia water, 90 g, and water (1 liter) for plating treatment. Was done. The obtained silver-coated barium titanate powder was taken out by filtering, washing with water and drying. The obtained powder was incompletely covered with silver, and a portion where barium titanate was exposed was found on the surface of the powder.
The yield of the above powder was 94.14 g, and the yield was 99%.
Is.

(II) Ceramic Capacitor Electrode A conductive paint for electrodes was obtained in the same manner as in Example 1 except that the silver-coated barium titanate powder obtained in (I) above was used. The obtained conductive paint is printed by screen printing on the surface of the same barium titanate-based ceramic capacitor element (substrate) as that used in Example 1,
Firing was performed at 800 ° C.

This fired product (chemical plating silver-coated powder electrode)
Table 7 shows the results of measuring the electrical characteristics, mechanical characteristics, and solder resistance characteristics of the above. However, since solder did not adhere to the fired product, the electrical characteristics were measured in the same manner as in Example 1 with the electrode surface of the fired product sandwiched by the clips. The mechanical strength and solder resistance could not be measured because the solder did not adhere. In Table 7, the measurement results of Example 1 (Table 1) are repeated for comparison.

Table 7 Characteristics Silver coated silver electrode Chemical plating silver powder electrode Coated powder electrode Electrical characteristics εs 6500 6420 10 tan δ (%) 1.5 1.6 40 Lead wire tensile strength (kg) 2.5 1.8 Not measurable Solder erosion Not eroded Peripheral area erosion Not measurable Solderability Solder wetting Same as on left Unmeasurable

From the above results, the silver-coated powder produced by the conventionally used chemical plating method has the internal core material such as ceramics exposed on the surface of the powder, and therefore the silver paste for electrode production is used. It can be seen that it cannot be used as a substitute material for.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01C 7/10 H05K 1/09 A 6921-4E

Claims (4)

[Claims] 1. A fine-particulate ceramic powder having an average particle diameter of 5 μm or less, which is covered with a coating layer formed substantially only of a conductive metal material (however, the weight of the ceramic part is the whole coating powder). 90 to 10% by weight
In the range)). 2. The average particle diameter of the ceramic powder is 1.5.
The conductive metal-coated ceramic powder according to claim 1, which has a size of not more than micron. 3. The conductive metal material is a noble metal.
The conductive metal-coated ceramic powder described. 4. A conductive metal material is precipitated on the surface of the ceramic powder in a gel state from a dispersion liquid composed of an aqueous solution of the conductive metal material in a dissolved state and the ceramic powder dispersed in the solution. The conductive metal-coated ceramic powder according to claim 1, which is obtained by coating.