JPH0374819A - Manufacture of laminated ceramic parts - Google Patents

Abstract

PURPOSE:To enable simultaneous process of debinder sintering and shorten the process, by adopting a sintering process in air which has not been realized except noble metal material, reducing oxide, forming a cobalt electrode and iron metal, making them base metal electrodes, and forming a laminated ceramic parts. CONSTITUTION:Since ceramic material can be sintered at a temperature lower than or equal to the diffusion temperature of cobalt oxide or iron oxide, the diffusion of cobalt and iron into the ceramic material can be practically prevented when baking is performed in air as it is. Since reduction is performed at a temperature at which the ceramic material is not reduced after the ceramic material is sintered, it is possible to transform cobalt oxide into cobalt and form inner electrodes. That is, in the case of cobalt oxide, the melting point is high and 1998 deg.C, and it is stable; reduction is possible at a temperature higher than or equal to 200 deg.C by using hydrogen gas or the like. In the case of iron oxide, the melting point is high and 1538 deg.C, and it is stable; the reduction is possible at 300 deg.C or more. Thereby the sintering of electrodes and the ceramic material is enabled in air.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing laminated ceramic parts.

Conventional technology Multilayer ceramic components are often found in chip capacitors, chip inductors, multilayer wiring boards, etc. In particular, in ceramic capacitors, the technology for laminating electrode materials and dielectric materials is most advanced, and the number of laminated layers ranges from several tens to 100 layers. It is expected that the development of highly laminated technology for various chip components will continue in the future as high-density packaging technology advances. As the number of layers becomes higher and higher, electrode materials become more expensive in terms of material cost, so their weight in the cost will only continue to increase. Electrode materials are important materials in electronic components, and are one of the materials for which cost reduction is most desired.

Dielectric porcelain (generally used for chip capacitors)
For example, barium titanate) has a high sintering temperature, so
The internal electrodes are Pt, Pd, and Au.

Precious metals such as Ag, which have a high melting point and are resistant to oxidation at high temperatures, have been used. However, in recent years, there has been a demand for lower costs, and in response to this demand, BaTiOs-based porcelain dielectrics
The development of low-temperature sintered porcelain dielectric materials that can use Ag-Pd alloys with a high composition ratio of Ag has become active (for example,
(Japanese Unexamined Patent Publication No. 62-20201, etc.). In addition, lead-based dielectrics exhibiting a high dielectric constant are Pb (Mgw3Nb2/z
)03 as the main raw material and is sintered at 900°C to 950°C is already commercially available. However, even though the composition ratio of Ag has increased, expensive Ag-Pd based materials are still used for these dielectric electrodes. At present, for the reasons mentioned above, the cost of electrodes in chip capacitors is still high, and no effective means have been found to reduce the cost of chip capacitors. Therefore, recently, various studies have been made to use base metals such as Cu and Ni, which are much cheaper than Ag, for the internal electrodes (for example, Japanese Patent Laid-Open No. 58-68803). However, these methods also require sintering in nitrogen or a reducing atmosphere to prevent oxidation of the internal electrodes, and the cost of gasification cannot be ignored, and even in a neutral gas atmosphere, sintering is required at high temperatures. As a result, the dielectric material tends to be reduced, causing problems such as insufficient sintering and variations in properties.

Problems to be Solved by the Invention As mentioned above, ceramic materials that can be sintered at low temperatures have been developed, and electrode pastes are being shifted to Ag-Pd or low-cost materials with a high content of Ag. There is a price difference of 10 times compared to Ni, etc., and it accounts for a very high proportion of the cost, such as low-cost, small-sized, large-capacity multilayer ceramic capacitors, ceramic chip inductors, and ceramic multilayer circuit boards that can realize high-density packaging. However, the purpose of obtaining various laminated ceramic parts cannot be satisfied. Also, recently, Japanese Patent Application Publication No. 63-1
Multilayer ceramic capacitors using base metals such as Cu and Ni are being developed as disclosed in Japanese Patent No. 5407, but these methods also require sintering in nitrogen or a reducing atmosphere to prevent oxidation of the internal electrodes. It is necessary to perform firing, and the purity of nitrogen and oxygen concentration during firing must be controlled, and the cost of gasification cannot be ignored. Furthermore, since the dielectric is fired at high temperatures even in a neutral gas atmosphere, the dielectric tends to be reduced, resulting in insufficient sintering, and the base metal material of the internal electrodes diffuses into the dielectric ceramic, causing its characteristics to deteriorate. There are problems such as fluctuations.

It is an object of the present invention to solve the above-mentioned problems, and to provide a method for manufacturing laminated ceramic parts that uses inexpensive electrode materials, saves on gasification in terms of process, and has less variation in properties. It is something.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention forms internal electrodes with a paste containing cobalt oxide or iron oxide as a main component on a raw sheet containing a ceramic material, an organic binder, and a plasticizer. a step of stacking a plurality of materials to form a laminate; a step of debinding and firing the laminate in air to form a sintered body; and a step of heating the sintered body with hydrogen or a mixed gas containing hydrogen. A multilayer ceramic component is obtained by a step of heat-treating the cobalt oxide layer or iron oxide layer to form an internal electrode, and a step of forming an external terminal electrode electrically connected to the internal electrode outside the laminate. It is something to do.

Effects According to the method of the present invention as described above, the ceramic material can be sintered at a temperature lower than the temperature at which cobalt oxide or iron oxide diffuses. However, diffusion of cobalt and iron into ceramic materials can be practically prevented. After the ceramic material is sintered, the ceramic material is reduced at a temperature at which it is not reduced, thereby converting the cobalt oxide into cobalt to form the internal electrode. In the case of cobalt oxide, it is a thermally stable material with a high melting point of 1998°C, and
It is known that metallic cobalt can be obtained by reduction with a reducing gas such as hydrogen gas or ammonia gas at the above temperature. In this way, the reduced cobalt can be used to form internal electrodes to form a multilayer ceramic component. Similarly, iron oxide has a melting point of 1
It is a material that is thermally stable at a high temperature of 538°C, and is known to become metallic iron by being reduced with a reducing gas such as hydrogen gas or ammonia gas at a temperature of 300°C or higher. Therefore, in the present invention, since the electrode and the ceramic material can be sintered in air, there is no need to sinter the electrode in a neutral gas atmosphere such as nitrogen or in a reducing atmosphere such as hydrogen, and the steps that require atmospheric treatment are After sintering, only the process of reducing cobalt oxide to cobalt or iron oxide to iron is required, which greatly reduces gas costs and eliminates the variation in properties that occurs when firing in a neutral or reducing atmosphere. Benefits will be obtained.

Example Examples of the present invention will be specifically described below.

<Example 1> First, a high dielectric constant dielectric material containing barium titanate as a main component was used as a dielectric material, and its average particle size was 0.
Dielectric powder material with a distribution of 2 μm was placed in each polypot.
00g was collected and 20g of polyvinyl butyral was added to each.
, butylbenzyl phthalate 9g, toluene 150cc
After adding and stirring 80 cc of ethanol, the mixture was mixed in a ball mill for 16 hours to prepare a slurry. Next, this slurry was used to form a film on an organic film using a doctor blade method to obtain a green sheet with a thickness of 40 μm. Next, the average particle diameter is 0.5 μm and 1.0 μm.

Each Log of 1.5 μm cobalt oxide (Coo) and 3 cc of a vehicle in which polybutyl methacrylate (PBMA) was dissolved in terpineol were added and kneaded with a three-stage roll to prepare a nickel oxide paste. This conductor paste was screen printed on the processed raw sheet to form an electrode pattern.

The electrode-formed raw sheets produced in the same manner were stacked so that the electrode on the raw sheet was configured as a counter electrode with the raw sheet interposed therebetween. Here, the thickness per layer of raw sheet is 40
The effective area acting as a μm capacitor was 2.4-2, and it was a 5-layer laminate. Next, heat press at 70℃ 250
After laminating and compression molding the sheet at a pressure of kg/cd, it was cut into predetermined dimensions. In this way, a chip stack of dielectric material and cobalt oxide was prepared. FIG. 1 shows a cross section after lamination, where 1 is a dielectric green sheet containing a barium titanate compound, and 2 is a cobalt oxide internal electrode.

Next, this laminate was held in air at 1250° C. for 2 hours at a temperature increase/decrease rate of 100° C./hr to perform binder removal and sintering simultaneously. After firing, the sintered body was heat-treated at 250° C. for 2 hours in a 100% hydrogen atmosphere furnace to reduce cobalt oxide to cobalt. After reduction, in order to attach the external electrode, a metallic cobalt paste was applied and heated for 600 minutes in a nitrogen atmosphere.
A multilayer ceramic capacitor was manufactured by baking at a temperature of 0.degree. C. and providing an external electrode conductive to the internal electrode 2 outside the multilayer body.

FIG. 2 shows a manufacturing process diagram according to the method of the present invention.

In order to compare the characteristics of the multilayer ceramic capacitors obtained in this way, electrical characteristics such as capacitance, dielectric loss, and edge resistance were measured. In order to compare the characteristics of the method of the present invention and the conventional method (a multilayer ceramic capacitor configured with a palladium electrode as an internal electrode and manufactured under the same conditions including the number of laminated layers), a multilayer ceramic capacitor manufactured using the conventional method was compared. Served. Table 1 below shows the results of characteristics such as capacitance, dielectric loss, and insulation resistance (IR).

As is clear from Table 1, it can be seen that the method of the present invention provides sufficiently satisfactory chip capacitor characteristics compared to the conventional method. In addition, the electrode material cost is overwhelmingly cheaper than palladium, and although the process includes a reduction process, the reduction temperature is low and hydrogen concentration control is not strict, making it possible to process chip capacitors in large quantities. Therefore, the manufacturing cost can be reduced to about 1/10 in consideration of process cost and material cost.

<Example 2> First, a high dielectric constant dielectric material containing barium titanate as a main component was used as a dielectric material, and its average particle size was 0.
Dielectric powder material with a distribution of 2 μm was placed in each polypot.
00g was collected and 20g of polyvinyl butyral was added to each.
, butylbenzyl phthalate 9g, toluene 150oc
After adding 80 oc of ethanol and stirring, the mixture was mixed in a ball mill for 16 hours to prepare a slurry. Next, this slurry was used to form a film on an organic film using a doctor blade method to obtain a green sheet with a thickness of 40 μm. Next, the average particle diameter is 1.0 μm and 1.5 μm.

Each Log of iron oxide (Fe203) of 2.0 μm and a vehicle 3ω in which polybutyl methacrylate (PBMA) was dissolved in terpineol were added and kneaded with a three-stage roll to prepare a nickel oxide paste. This conductor paste was screen printed on the processed raw sheet to form an electrode pattern.

The electrode-formed raw sheets produced in the same manner were stacked so that the electrode on the raw sheet was configured as a counter electrode with the raw sheet interposed therebetween. Here, the thickness per layer of raw sheet is 40
μm, effective area that acts as a capacitor is 2.4m2
A 5-layer laminate was obtained.

Next, the sheets were laminated using a hot press at a pressure of 70° C. and 250 kg/c and compression molded, and then cut into predetermined dimensions. In this way, a chip stack of dielectric material and iron oxide was prepared. Next, this laminate was heated to 100°C in air.
Hold at 1250 °C for 2 hours at a temperature increase/decrease rate of / hr,
Binder removal and sintering were performed simultaneously. After firing, the sintered body was heat treated at 400° C. for 2 hours in a 100% hydrogen atmosphere furnace to reduce iron oxide to iron. After reduction, in order to attach external electrodes, apply copper paste and heat at 600°C in a nitrogen atmosphere.
A multilayer ceramic capacitor was fabricated by baking the multilayer ceramic capacitor with an external electrode connected to the internal electrode outside the multilayer body. In order to compare the characteristics of the multilayer ceramic capacitors obtained in this way, we measured the capacitance.

Electrical properties such as dielectric loss and insulation resistance were measured.

Here, in order to compare the characteristics of the method of the present invention and the conventional method (a multilayer ceramic capacitor configured with a palladium electrode as an internal electrode), a multilayer ceramic capacitor manufactured by the conventional method was used for comparison. Table 2 below shows the results of characteristics such as capacitance, dielectric loss, and insulation resistance.

(Margins below) As is clear from Table 2, it can be seen that according to the present invention, fully satisfactory chip capacitor characteristics can be obtained compared to the conventional method. In addition, the electrode material cost is overwhelmingly cheaper than palladium, and although the process includes a reduction process, the reduction temperature is low and hydrogen concentration control is not strict, making it possible to process chip capacitors in large quantities. Therefore, it is possible to reduce the manufacturing cost to about 1/10 in consideration of process cost and material cost.

<Example 3> In order to produce a multilayer wiring board, the main component was Al2O3, and 2w of lead borosilicate glass was used as the frit.
200g of each of two types of insulating materials with t% added and having average particle diameters distributed between 0.5 μm and 2 μm were collected in a polypot, and the same procedure as in Example 1 was carried out to obtain two types of 40 μm raw sheets. Next, 10 g each of cobalt carbonate, cobalt hydroxide, and cobalt nitrate with an average particle size of 1.0 to 2.3 μm and a vehicle 3ω containing polybutyl methacrylate (PBMA) dissolved in terpineol were added and kneaded with a three-stage roll. A cobalt compound paste was prepared. The multilayer wiring board is a three-dimensional arrangement of sheets on which wiring circuits are constructed, and the manufacturing method is almost the same as in Example 1, except that a through-hole process is added, such as printing, laminating, It is obtained by repeating the through-hole process, cutting and firing each circuit block. After firing, the sintered body is placed in an atmosphere furnace containing 50% hydrogen and 50% nitrogen for 25 minutes.
Reduction treatment was carried out at 0° C. for 4 hours, and the cobalt compound, which had been changed into cobalt oxide by firing in air, was reduced to metallic cobalt. The cobalt in the thus obtained multilayer wiring board had a resistance value sufficiently low for practical use and was an electrode with excellent migration, and the Al2O3 layer as an insulating layer showed excellent electrical properties such as insulation resistance.

In this example, only materials mainly composed of Al2O3 were used as the insulating layer, but ceramic insulator materials that sinter at a temperature below the melting point of cobalt oxide (for example, forsterite, steatite, magnesia, titania-based insulator materials) may also be used.
If so, it goes without saying that the method of the present invention can be applied.

<Example 4> In order to produce a multilayer wiring board, the main component was Al2O3, and 2wt% lead borosilicate glass was used as the frit.
200g of each of two kinds of insulating materials added with average particle diameters distributed at 0.5 μm and 2 μm were collected in a polypot, and the same procedure as in Example 1 was carried out to obtain two kinds of raw sheets of 40 μm. Next, iron carbonate with an average particle size of 1.5 μm, 2.0 am
Iron hydroxide of 1.3 μm, iron nitrate of 1.3 μm, and Vehicle 3 in which polybutyl methacrylate (PBMA) was dissolved in terpineol were added and kneaded with a three-stage roll to prepare a cobalt compound paste. The multilayer wiring board is one in which sheets each having a wiring circuit are arranged three-dimensionally, and the manufacturing method is similar to that of Example 1 except that a through-hole process is added. It is obtained by repeating printing, laminating, and through-hole processes, and then cutting and firing each circuit block. After firing, the sintered body is heated with hydrogen 8
A reduction treatment was performed at 400° C. for 5 hours in an atmospheric furnace containing 0% nitrogen and 20% nitrogen, and iron oxide, which had been oxidized and changed from an iron compound to iron by firing in air, was reduced to metallic iron.

In the multilayer wiring board thus obtained, the iron as the electrode had a sufficiently low resistance for practical use and had excellent migration, and the Al2O3 layer as the insulating layer showed excellent electrical properties such as insulation resistance.

In this example, only materials mainly composed of Al2O3 were used as the insulating layer, but ceramic insulator materials that sinter at a temperature below the melting point of cobalt oxide (for example, forsterite, steatite, magnesia, titania-based insulator materials) may also be used.
If so, it goes without saying that the method of the present invention can be applied.

<Example 5> Ni-Zn ferrite powder with a particle size of 1.5 μm was prepared as magnetic particles, 200 g was collected in a polypot, and a raw sheet of 40 μm was obtained in the same manner as in Example 1. on the other hand,
A paste is formed using cobalt nitrate as a binder, ethyl cellulose, and α-terpineol as a solvent.

Thereafter, printing, lamination, and through-hole printing are performed alternately on the raw sheet using magnetic sheets and cobalt nitrate paste, thereby forming an electrode configuration in which the printed pattern of cobalt nitrate is formed in a spiral shape. This has a structure in which a spiral electrode is embedded with magnetic particles.

The printed and laminated inductor material is then cut into chip sizes and fired under firing conditions of 1250°C for 2 hours. The inductance component thus sintered is reduced under reducing conditions of 230° C. for 3 hours in an atmosphere of 10% hydrogen, 10% ammonia and 80% nitrogen to form a cobalt luminode. The inductance component thus obtained was a chip inductor having a characteristic of 1 mH.

In the present invention, at least one of cobalt carbonate, cobalt nitrate, and cobalt hydroxide, which become cobalt oxide by heat treatment, may be used as the internal electrode material, and furthermore, cobalt oxide containing cobalt oxide may be used. It goes without saying that the method of the present invention can also be applied to mixed powders. Also, among iron carbonate, iron nitrate, and iron hydroxide, which become iron oxide by heat treatment in the same way,
At least one of these may be used, and the method of the present invention can also be applied to a mixed powder of these containing iron oxide. It is easy to think that the method of the present invention can also be applied to a mixed powder of cobalt oxide and iron oxide.

Effects of the Invention The present invention employs a process of sintering in air, which could only be achieved with precious metal materials, and then reduces oxides to form cobalt electrodes and iron electrodes to form base metal electrodes. It is now possible to form ceramic parts. As a result, the only process that requires complicated firing atmosphere treatment is the process of reducing cobalt oxide to cobalt or iron oxide to iron, and there is no need to fire in a neutral atmosphere such as nitrogen as in conventional methods. Since the binder removal and sintering processes can be performed at the same time, the process is shortened and the gasification process is greatly reduced, resulting in a large cost reduction effect. In addition, since the sintering process, which affects electrical properties such as dielectric properties and magnetic properties, or ceramic properties, can be performed in air, there is no variation in properties that occurs when sintering in a neutral gas atmosphere. . moreover,
By using the method of the present invention, it is possible to achieve low-cost, small-sized, large-capacity sintering at low temperatures, and the use of base metal materials with low resistivity provides excellent migration resistance, among other advantages. It is possible to manufacture laminated ceramic parts with

[Brief explanation of drawings]

FIG. 1 is a diagram showing the constituent countries of a laminated green sheet produced according to the present invention, and FIG. 2 is a diagram showing the manufacturing process for manufacturing a multilayer ceramic capacitor according to the present invention. ■... Raw sheet, 2... Internal electrode.

Claims (1)

[Claims] (1) A step of laminating a plurality of raw sheets containing a ceramic material, an organic binder, and a plasticizer, on which internal electrodes are formed using a paste containing cobalt oxide or iron oxide as a main component, to form a laminate. , a step of removing the binder and firing the laminate in air to form a sintered body, and heat treating the sintered body in hydrogen or a mixed gas containing hydrogen to reduce the cobalt oxide layer or the iron oxide layer. A method for manufacturing a laminated ceramic component, comprising the steps of: forming an internal electrode, and forming an external terminal electrode electrically connected to the internal electrode outside the laminated body. 2. Claim 1, characterized in that at least one of cobalt carbonate, cobalt nitrate, and cobalt hydroxide, which becomes cobalt oxide by heat treatment of the internal electrode material, or a mixed powder thereof containing cobalt oxide is used. A method of manufacturing the described laminated ceramic component. 3. Claim 1, characterized in that at least one of iron carbonate, iron nitrate, and iron hydroxide, which becomes iron oxide by heat treatment of the internal electrode material, or a mixed powder thereof containing iron oxide is used. A method of manufacturing the described laminated ceramic component.