JPH03218615A - Formation of electrode and laminated chip component using same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for forming electrodes used in laminated chip components and to a laminated chip component using the same.

BACKGROUND OF THE INVENTION With the demand for miniaturization of electronic components, laminated chip components have come into widespread use. As the electrode material,
Traditionally gold. Silver, platinum. Precious metals such as palladium are used, but internal electrodes account for a large proportion of the material cost of laminated chip parts, and in order to reduce costs, consideration has been given to replacing precious metals with base metal materials or reducing the amount used. ing.

Regarding total replacement with base metal materials, copper and nickel are currently used. However, since base metals generally have a low equilibrium oxygen partial pressure, when fired at high temperatures,
Since oxides are formed and conductivity decreases, there is a problem in that the firing atmosphere must be controlled. moreover,
For multilayer chip parts, the ceramic material and the internal electrode material must be fired simultaneously, and then the external electrode must be coated and baked. The formation of this external electrode also requires atmosphere control, resulting in lower yields and increased manufacturing costs. The problem arises.

On the other hand, in order to reduce the amount of precious metals used, attempts have been made to use base metals as a base material and coat them with precious metals (for example, Japanese Patent Publication No. 46-40593, Japanese Patent Application Laid-Open No. 60-60
-100679). However, in this method, when baking the precious metal coating at high temperatures, it is impossible to completely suppress heat diffusion from the base material to the coating metal, so the same problem as the above-mentioned full replacement with base metals may occur. can be easily considered. In addition, silicon oxide,
aluminum oxide, zirconium oxide, titanium dioxide,
Alternatively, methods using oxides such as barium titanate are being considered, but since these are all insulators, the thickness of the coating must be increased in order to maintain conductivity as an electrode material. Significant cost reductions cannot be expected.

Furthermore, when firing multilayer chip components, the internal electrodes exposed at the edges retreat from the surface due to evaporation or shrinkage, resulting in poor connection between the internal and external electrodes, and in the case of capacitors, the electrode area decreases. Problems arise such as a decrease in capacitance and, in the case of an inductor, an increase in resistance.

Problems to be Solved by the Invention Particles for electrode materials using base metal materials having the above-described structure, and furthermore, particles for electrode materials in which base metals or oxides are coated with noble metals, can be oxidized by high-temperature heat treatment or combined materials. In order to prevent interaction with the metal and the resulting decrease in conductivity, the thickness of the coating must be increased, which increases the amount of precious metal used, making it impossible to significantly reduce the cost of electrode materials. There is.

Further, in the conventional firing process, there is a problem that a connection failure between the internal electrode and the external electrode occurs during firing.

The present invention was made with the aim of significantly reducing electrode formation costs and providing highly reliable laminated chip parts when forming various laminated chip parts using inexpensive transition metal oxides. It is.

Means for Solving the Problems In order to solve the above problems, the method for forming an electrode of the present invention is as follows:
First, nickel oxide, copper oxide, and iron oxide were used as particles for internal and external electrode materials. The particle surface of a transition metal oxide powder such as cobalt oxide is coated with 5.0 to 15.0% by weight of a noble metal based on the base material. Furthermore, an electrode paste similar to that of the internal electrode is applied to the unfired chip as an electrode for external extraction, and after co-firing the laminate having the internal electrode and the external electrode in air, it is reduced in a hydrogen atmosphere. It is characterized by this.

Here, the reason why the amount of the noble metal coated is 5.0 to 15.0% by weight of the base material is that it is necessary to reduce the amount of noble metal used as much as possible in order to reduce costs. Note that the coating noble metal does not need to uniformly cover the entire base material. In other words, it is only necessary that the diffusion of the base substance is suppressed to the extent that it does not affect the properties of the multilayer chip component, and if an appropriate frit is used and the sintering temperature is lowered, even 5.0% by weight can be practically sufficient diffusion. A preventive effect can be obtained. Furthermore, if the amount of noble metal coated exceeds 15.0% by weight, the effect of reducing the amount used becomes small.

Note that there is no upper limit to the reduction temperature as long as it does not affect the electrical properties of the material fired together with the electrode.

Function: With the above-described configuration, the present invention can suppress thermal diffusion of the transition metal oxide, which is the base material, during firing in air. Furthermore, by using a transition metal material, the cost of electrode materials and, by extension, the cost of laminated chip components can be significantly reduced. Furthermore, since the electrodes are formed by hydrogen reduction after firing the internal and external electrodes at the same time, there is no need for complicated atmosphere control, and the system is inexpensive and highly reliable, with no connection failures between the internal and external electrodes. A transition metal electrode can be obtained.

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

(Example 1) Commercially available iron oxide and cobalt oxide powders with a particle size of 0.5 μm were each immersed in an activation solution containing neutral type palladium ions, and the powders were activated. Separately, a palladium plating solution was prepared by dissolving palladium chloride in concentrated ammonia water and adding hydrochloric acid to the solution to adjust the pH to 8.5. Hydrazine was added to this palladium plating solution, and the activated powder was added and stirred to plate the powder surface with palladium. After the plating treatment, the plate was washed with water by decantation and dried to obtain a palladium-coated powder. The weight ratio of the base material and palladium in the powder thus obtained was 90/10.

Ethyl cellulose (45 cps) was used as a binder in an amount of 1.0% by weight based on 5.0 g of the above palladium-coated powder.
, TVNOL 1. as solvent. 1 cc was added and thoroughly kneaded using a triple roll to prepare an electrode paste. Further, as comparative samples, electrode pastes were similarly prepared using iron oxide and cobalt oxide without palladium coating.

On the other hand, in order to process the dielectric material whose main component is BaTiO3 into a green sheet, for 200 g of dielectric powder, 15 g of polyvinyl petyral, 9 g of butylbenzyl phthalate, 120 cc of luene, 70 cc of ethanol
After stirring, the mixture was mixed in a ball mill for 16 hours to prepare a slurry.

Next, using the slurry obtained as described above, a film was formed on an organic film by a doctor blade method to obtain a green sheet with a thickness of about 40 microns. Next, the four types of electrode material particles made into a paste were screen printed on the processed green sheet to form an electrode pattern. Then, similarly produced sheets with electrodes formed thereon were laminated so that the electrodes on the sheets constituted counter electrodes with the green sheet interposed therebetween.

Next, this laminate was laminated using a heat press, cut to a predetermined size, and the electrode paste was applied as an external electrode to the end face where the electrode was exposed, and the electrode paste was placed in the air at 1250 degrees for 2 hours. After baking at 350℃-4
The internal electrode was reduced in pure hydrogen for an hour. The permittivity of the chip capacitors obtained in this way was ε = 12,000 for those coated with palladium, but for those without palladium coating, part of the electrode material was a dielectric. The dielectric constant is ε=9000 for iron oxide and ε=10000 for cobalt oxide.
The effectiveness of palladium coating was confirmed.

(Example 2) Example 1 was added to a commercially available copper oxide powder having a particle size of 0.5 μm.
Palladium coating was applied in the same manner as above to prepare an electrode paste.

On the other hand, magnesium lead niobate [Pb(M g l/
3N b 2/3) 03], 8 parts by weight of polyvinyl butyral resin, 4 parts by weight of dibutyphthalate, 40 parts by weight of trichloroethane, and 25 parts by weight of butyl acetate were added, and the mixture was milled in a ball mill. The mixture was kneaded for 20 hours. The dielectric slurry thus obtained was formed into a sheet with a thickness of 40 μm using a reverse roll method.

Next, the electrode paste is printed in a desired pattern on the dielectric sheet, and this is laminated to create a laminate in which electrodes and dielectrics are alternately laminated, and then cut into desired dimensions. Then, apply the above electrode paste as an external electrode to the end surface where the electrode is exposed, and heat it at 1100°C for 2 hours.
After baking for an hour, hydrogen reduction was performed at 200°C for 5 hours. The capacitance value of the multilayer chip capacitor obtained in this way agrees well with the design value calculated from the dielectric constant (ε=12000), confirming the practicality of the electrode formation method according to the present invention. Ta.

(Example 3) Nickel oxide powder having a particle size of 0.5 μm was immersed in an activation solution containing neutral type palladium ions for activation treatment. Separately, a plating solution consisting of platinum chloride, aqueous ammonia, and hydrochloric acid was prepared, and hydrazine and activated powder were added to this plating solution and stirred to plate the powder surface with platinum. After plating, it was washed with water by decantation and dried to obtain a platinum-coated powder. The weight ratio of the base material and platinum in the powder thus obtained was 90/10. Then, using this platinum-coated powder, an electrode paste was produced in the same manner as in Example 1.

Next, Ni-Zn ferrite powder having a particle size of 1 to 3 μm is made into a paste using the above method to obtain a magnetic paste. Thereafter, the thus obtained magnetic paste and electrode paste were alternately printed to form an electrode in a spiral shape. That is, the structure is such that a spiral electrode is embedded with magnetic particles.

This was cut into desired dimensions, and the above electrode paste was applied as an external electrode to the end face of the resulting laminate where the internal electrodes were exposed, and after baking in air at 1200°C for 2 hours,
Reduction was carried out in pure hydrogen at 250°C for 4 hours.

It was confirmed that the inductor component thus obtained had an inductance of 100 μH.

It goes without saying that in addition to this embodiment, the electrode forming method according to the present invention can also be applied to piezoelectric actiniators, laminated varistors, and the like. Furthermore, as for the base material, it goes without saying that not only nickel oxide, steel oxide, iron oxide, and cobalt oxide mentioned in this example, but also reaction products thereof can be used. Furthermore, although the oxide powder used in this example had a particle size in the range of 0.5 μm, the particle size and shape are not particularly defined.

Furthermore, in addition to the above embodiments, gold, silver, rhodium, iridium, ruthenium, and alloys thereof, which can be plated electrolessly, can be used as the noble metal to be coated. Furthermore, when coating with noble metals, it is also possible to coat with two or more types of noble metals.

Effects of the Invention As described above, the electrode forming method according to the present invention coats the surface of nickel oxide, copper oxide, iron oxide, cobalt oxide, or a reaction product thereof with a noble metal, and simultaneously exposes the inner electrode and the outer electrode to air. After firing, hydrogen reduction is performed. Therefore, heat diffusion during firing in air is suppressed, and it is possible to significantly reduce electrode material costs and electrode formation costs.Furthermore, by preventing poor connections between internal and external electrodes, it is possible to reduce costs. Accordingly, it is possible to provide a highly reliable and high-performance multilayer chip component.

Claims (3)

[Claims] (1) For internal electrodes and external electrodes, particles for electrode material in which the particle surface of transition metal oxide powder is coated with 5.0 to 15.0% by weight of noble metal of the base material are used, and the ceramic layer and the above internal electrode are used. A method for forming an electrode, which comprises simultaneously performing sintering of a laminate formed by laminating layers and baking the electrode for external extraction in air, and then performing a reduction treatment in a hydrogen atmosphere. (2) The method for forming an electrode according to claim 1, wherein the reduction is performed in a hydrogen atmosphere at 200° C. or higher. (3) A laminated chip component in which electrodes are formed by the method according to claim 1.