JP2004007015A - Electronic part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic part in which debinding is allowed at a temperature lower than 400°C, preventing cracking or delamination. <P>SOLUTION: The electronic part comprises an internal conductor in a dielectrics. The internal conductor is composed of a matrix 1 comprising an alloy of base metal and palladium and a dispersed phase 2 of palladium. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to electronic components such as multilayer ceramic capacitors.

Generally, a multilayer ceramic capacitor has a structure in which dielectric layers and internal electrode layers are alternately stacked, and each dielectric layer is sandwiched between the internal electrode layers. Here, the dielectric layer is formed by firing an unfired ceramic green sheet at a high temperature and sintered, and the internal electrode layer is formed by firing a conductive paste at a high temperature to form a conductive metal thin film.

In recent years, the demand for lighter and smaller electronic components has become more stringent, and in order to satisfy the demand, the sheet thickness per layer has been reduced, the number of layers has been further increased, and multilayer ceramic capacitors have been required. In order to achieve a smaller size and a larger capacity, a dielectric material having a high relative dielectric constant is used, and the sheet thickness is further reduced.

In addition, when the internal electrode layer is formed of a conductive paste for internal electrodes containing a noble metal such as Pd as a main component, the cost of forming the electrodes is significantly increased with an increase in the number of layers. Has been developed, and a multilayer ceramic capacitor having an internal electrode layer formed with the paste has been put to practical use. When a base metal such as Ni is used as the internal electrode layer, the base metal generally has a low equilibrium oxygen partial pressure, so that there is a problem that an oxide is formed when firing at a high temperature and the conductivity is reduced. . Therefore, firing must be performed in a non-oxidizing atmosphere in which Ni is not oxidized, and the dielectric material naturally requires reduction resistance.

A conventional multilayer ceramic capacitor having Ni as an internal electrode layer generally includes a non-sintered laminate in which a plurality of ceramic green sheets each having a surface coated with a conductive paste for an internal electrode layer are laminated on the air to reduce the firing cost. It has been manufactured by performing binder removal treatment at 400 ° C. or higher (hereinafter referred to as de-buying) and sintering and unifying in a nitrogen atmosphere having a very low oxygen partial pressure or a non-oxidizing atmosphere such that the internal electrode layer is not oxidized. .

導電 It is necessary to select a conductive paste or a porcelain material for the internal electrode layer used in such an integrated firing method that has close heat shrinkage characteristics in the firing process, otherwise delamination and cracks are likely to occur.

Conventionally, in order to make the heat shrinkage of the conductive paste close to that of the porcelain, means for covering the base metal surface with Pd, or containing the same or similar porcelain material powder as the green sheet, which is called a co-material, in the conductive paste have been proposed. ing.
JP-A-6-96997 JP-A-54-14096 JP-A-57-30308

However, in the conventional manufacturing method, although the internal electrode layer is hardly oxidized in the firing step, the internal electrode layer is deoxidized at 400 ° C. or higher in the air. There has been a problem that delamination and cracks sometimes occur in the laminate. As a result, there is a problem that delamination and cracks occur in the obtained capacitor.

On the other hand, if the debuying is performed at a temperature lower than 400 ° C. in order to prevent the oxidative expansion of the internal electrode layer, the debuying cannot be performed completely and remains as carbon, causing oversintering during firing. Ni melts. As a result, there is a problem in that Ni on the end face blows out to the outside, the capacity is lost, and the capacity is reduced. Further, there is a problem that voids are generated in the sintered body due to the residual carbon, and cracks are generated in the sintered body.

That is, although de-buying is performed in the air in terms of sintering cost and the like, when de-buying is performed in the air, the organic binder used for the green sheet and the organic binder used for the conductive paste are completely scattered. It is difficult to remove, it is not possible to obtain the capacity as designed, voids are generated in the sintered body, cracks are generated in the sintered body, or the internal electrode layer is oxidized and expanded and laminated Problems such as delamination and cracks have occurred in ceramic capacitors.

Further, when the base metal surface is coated with Pd, Pd becomes palladium oxide from around 400 ° C. when debuying at 400 ° C. or more in the atmosphere in the air, and oxidizes the base metal particles which are the nuclei of the particles. There has been a problem that resistance increases and delamination and cracks occur in the multilayer ceramic capacitor. On the other hand, at a temperature lower than 400 ° C., the de-buying could not be completely performed as described above.

Further, when the above-mentioned co-material is contained in the conductive paste, although the heat shrinkage can be adjusted, the base metal is oxidized and the internal electrode layer expands when the de-buying temperature is 400 ° C. or more as described above, and the There is a fear that cracks may occur in the laminated body during the pass, and at a temperature lower than 400 ° C., the pass can not be completely removed. Further, in the capacitor after firing, the connection portion between the dielectric layers increases (the portion where the upper and lower dielectric layers are connected via the common material of the holes formed in the internal electrode layer increases), and the continuity of the internal electrode layer increases. There is a problem that the property is reduced.

An object of the present invention is to provide an electronic component which can be removed at a temperature lower than 400 ° C. and can prevent cracks and delamination.

電子 The electronic component of the present invention is an electronic component having an internal conductor in a dielectric, wherein the internal conductor is composed of a matrix composed of an alloy of a base metal and palladium and a dispersed phase composed of palladium. In particular, a multilayer ceramic capacitor in which dielectric layers and internal electrode layers are alternately stacked, wherein the internal electrode layers are composed of a matrix composed of an alloy of a base metal and palladium and a dispersed phase composed of palladium. desirable.

In the conductive paste of the present invention, since the surface of the base metal is coated with palladium oxide, the organic binder is formed by oxygen in the air and oxygen of the palladium oxide even in the de-buying treatment at a temperature lower than 400 ° C. in the air. Can be effectively oxidized and removed.

In addition, since the base metal particle surface is coated with palladium oxide and there is no contact between the base metal particles, the sintering temperature of the internal conductor can be delayed depending on the amount (thickness) of the coating palladium oxide. The contraction curve can be made closer to the dielectric, and delamination and cracks can be prevented. Since the palladium oxide covering the base metal surface is reduced to metal palladium by firing in a non-oxidizing atmosphere, the thickness of the internal conductor is reduced due to the volume reduction, and delamination and cracks can be prevented. In addition, the thickness of the internal conductor can be reduced.

In addition, the air can be removed at a temperature lower than 400 ° C. in the air, and the palladium oxide is reduced to metal palladium in firing in a non-oxidizing atmosphere, and almost all of the internal base metal is alloyed. Does not increase, and the characteristics of the dielectric are not adversely affected. In addition, since the base metal and palladium are alloyed, it is difficult to be oxidized as compared with the case where the base metal is formed. Therefore, even when reoxidation treatment is performed under a low oxygen partial pressure after firing, oxidation is not performed, and reliability is improved. Can be.

That is, if the surface of the base metal particles is coated with palladium oxide, the amount of carbon remaining after manufacturing a multilayer ceramic capacitor or the like can be reduced even if the debuying is performed at a temperature lower than 400 ° C. in the atmosphere, and cracks and debris can be reduced. Lamination can be prevented, and the internal electrode layer can be made thinner.

In the conventional conductive paste, there were problems such as starting sintering at a lower temperature than the green sheet, and also having a large shrinkage rate, a strong spherical property, and a mesh shape. Regarding such a problem as well, since the surface of the base metal particles is coated with palladium oxide, Ni and Pd are alloyed, so that the temperature at which sintering is started can be delayed, and grain growth of the base metal can be suppressed. Further, palladium oxide is reduced to metallic palladium, and the volume is reduced, so that a continuous internal electrode layer can be formed.

Also, by containing 0.5 to 12% by weight of palladium oxide in all metals in terms of metal palladium, oxidation of the base metal particles at the time of de-buying is prevented, alloying of palladium and nickel is optimized, and the internal conductor The sintering temperature is reduced, and oversintering of the internal conductor can be suppressed.

For example, in a multilayer ceramic capacitor manufactured using the conductive paste of the present invention, the internal electrode layer is composed of a matrix made of an alloy of a base metal and palladium, and a dispersed phase made of palladium, and cracks and delamination occur. Can be prevented, the size and thickness can be reduced, and the variation in capacity can be reduced.

As described above, according to the conductive paste and the electronic component containing a base metal whose surface is coated with palladium oxide as a main component, for example, in a multilayer ceramic capacitor, the binder is removed at a temperature lower than 400 ° C. in the air atmosphere. No cracking or delamination occurs in any case after binder removal and after firing even after performing, and by coating the surface of the base metal particles with palladium oxide, the sinterability of Ni can be delayed, and palladium oxide Is reduced to palladium, the volume is reduced, and a thinner inner conductor can be achieved.

導電 The conductive paste of the present invention contains base metal particles whose surface is coated with palladium oxide as a main component. Examples of the base metal include Ni, Co, Cu, and alloys of two or more of them. Ni is preferable because the firing temperature of the metal matches the firing temperature of a general dielectric material and the cost is low. . The shape of these base metal particles is spherical, flake-like, protruding or irregular, and is not particularly limited. The average particle diameter of the base metal particles is desirably 0.05 to 0.8 μm as a value determined by the specific surface area diameter from the viewpoint of reducing the thickness of the internal electrode layer and reducing the thickness variation.

The coating thickness of the palladium oxide coating the surface of the base metal particles is desirably 10 to 100 nm. When the coating thickness is 100 nm or more, aggregation of the particles is likely to occur, dispersibility of the particles is reduced, or a binder solution for dispersing the base metal particles. Use amount increases.

On the other hand, if the coating thickness is 10 nm or less, the base metal particles serving as nuclei may be oxidized. In order to coat the base metal surface with palladium oxide, the base metal is immersed in an aqueous solution containing stannic chloride and hydrochloric acid and then in an aqueous solution of palladium chloride, followed by filtration, washing and drying. Further, it is obtained by surface treatment in an oxygen atmosphere at a high temperature.

In addition, the conductive paste contains a base metal as a main component, and in order to improve the adhesion with the ceramic green sheet when, for example, manufacturing a multilayer ceramic capacitor, the same raw material as the ceramic green sheet is used as a common material. A predetermined amount of powder may be added. Further, in order to prevent the occurrence of a short circuit between the electrodes due to agglomeration or poor dispersion of particles, it is desirable that the powder used is sufficiently dispersed. Therefore, various resins and dispersants are used in various combinations as organic additives.

Examples of the resin include a cellulose resin, a rosin resin, a polyvinyl resin, a butyral resin, a polyester resin, an acrylic resin, an epoxy resin, a polyamide resin, a polyurethane resin, an alkyd resin, and a maleic acid resin. Amide resins, petroleum resins and the like, and these resins can be used alone or in combination. As a resin that suppresses agglomeration of particles and improves dispersion, a cellulose-based resin is preferable because of its compatibility with other resins and solvents.

分散 Also, as the dispersant, any surfactant generally used for preparing a paste can be used, but a polymer surfactant is desirable from the viewpoint of stabilizing the paste.

The solvent is not particularly limited as long as it is compatible with the organic additive to be used.For example, ethanol, carbitol, toluene, acetate, alcohols such as xylene, hydrocarbons, esters, Ether alcohols, ketones, chlorinated hydrocarbons and the like can be used.

Further, when preparing a homogeneous solution of a desired amount of organic additives and a solvent, a surfactant, a plasticizer, an antistatic agent, an antifoaming agent, an antioxidant, a lubricant, a curing agent, and the like may be used as necessary. It can be used as appropriate.

パ ラ ジ ウ ム Also, the palladium oxide covering the base metal particles is desirably contained in an amount of 0.5 to 12% by weight based on the total metal in terms of metal palladium. That is, the weight ratio of palladium oxide when the total amount of the base metal and palladium oxide is 1 is determined, and the value obtained by converting palladium oxide to metal palladium is preferably 0.5 to 12% by weight.

This is because if the amount of palladium oxide is less than 0.5% by weight of the total metal in terms of metal palladium, the coated Ni particles are easily oxidized at the time of de-buying, which may cause cracks. If the content is more than 10% by weight, palladium and nickel are alloyed and the sintering temperature is lowered, so that the internal electrode may be over-sintered and may be cracked or delaminated in a ball shape. Because there is. Since palladium oxide reduces palladium in a reducing atmosphere and alloys Ni and Pd, it is desirable that the content of palladium oxide be 1 to 5% by weight in all metals in terms of metal palladium.

In the electronic component of the present invention, for example, in a multilayer ceramic capacitor, a dielectric layer and an internal electrode layer are alternately laminated, and the internal electrode layer is made of an alloy of a base metal and palladium as shown in FIG. And a dispersed phase 2 made of palladium. In FIG. 1, reference numeral 3 denotes an internal electrode layer, and reference numeral 4 denotes a dielectric layer.

The electronic component may be any component having an internal conductor in a dielectric, such as a multilayer ceramic capacitor, a resonator, and an actuator, and includes a substrate having an internal conductor.

In the conventional case in which the surface of the Ni particles is coated with palladium, Ni and palladium are completely solid-solved at the time of debuying and firing, but in the conductive paste of the present invention, the base metal particles are coated with palladium oxide. Therefore, since there is a step of reducing palladium oxide to metal palladium, the solid solution step of Ni and palladium is delayed, and some palladium which cannot be alloyed exists, and the matrix 1 composed of an alloy of base metal and palladium is present. Thus, the dispersed phase 2 made of palladium comes to exist.

(4) A method for manufacturing a multilayer ceramic capacitor using the conductive paste of the present invention will be described. First, a ceramic green sheet having a predetermined composition is manufactured by a pulling method, a doctor blade method, a reverse roll coater method, a gravure coater method, a screen printing method, a gravure printing method or the like. The thickness of the green sheet is desirably 0.5 to 50 μm from the viewpoint of miniaturization and large capacity.

Further, the conductive paste is formed on the ceramic green sheet by a screen printing method, an extrusion method, a gravure printing, an offset printing method, or another method, and the thickness thereof is 2 μm or less, particularly 1 μm from the viewpoint of miniaturization and high reliability. It is desirable that:

Then, a plurality of green sheets to which the conductive paste is applied are laminated, and the laminated molded body is deburied at a temperature lower than 400 ° C. in the air, for example, 350 ° C. It is obtained by firing for up to 3 hours. Further, after firing, if necessary, reoxidation is performed at 900 to 1100 ° C. for 3 to 10 hours under a low oxygen partial pressure of about 10 ⁻⁶ to 10 ⁻¹⁰ to obtain a multilayer ceramic capacitor.

First, Ni powder was immersed in an aqueous solution containing stannic chloride and hydrochloric acid, then immersed in a palladium chloride solution, filtered, washed and dried. Ni powder coated with palladium oxide after surface treatment was obtained. As a result of observation by a transmission electron microscope and a crystal structure analysis, it was confirmed that the surface layer of the base metal particles was covered with palladium oxide. At this time, the average particle diameter of the Ni powder was 0.2 μm.

Next, a conductive paste was prepared by kneading 45% by weight of the base metal powder, 5.5% by weight of ethylcellulose and 55% by weight of a vehicle composed of 94.5% by weight of α-terpineol with a three-roll mill.

Next, a composition in which 0.5 mol part of Y ₂ O ₃ is added to 100 mol part of the main component composed of 97.5 mol% of BaTiO ₃ , 2.0 mol% of CaZrO ₃ and 0.5 mol% of MnO ₃ Was formed on a belt-like carrier film made of a synthetic resin such as polyester or polypropylene by a doctor blade method, and dried to obtain a belt-like ceramic green sheet. Next, the ceramic green sheet was peeled off from the carrier film and punched into a size of 200 mm in length and 200 mm in width. The thickness of the ceramic green sheet was 10 μm.

(4) The above-mentioned conductive paste was printed on one main surface of the obtained ceramic green sheet using a screen printing apparatus. A plurality of ceramic green sheets on which the coating film was formed were laminated to obtain a laminated molded body.

Next, the obtained laminated molded body was heated in the atmosphere at a temperature of 380 ° C. for 2 hours to burn out a binder (organic component). At this time, the appearance of the 100 laminated molded articles after removal of the binder was observed with a binocular microscope to check for cracks and delamination. Thereafter, firing was performed at 1250 ° C. for 2 hours in a reducing atmosphere, and reoxidation was performed at 900 ° C. in a nitrogen atmosphere to obtain a ceramic sintered body. After firing, an indium-gallium paste was applied to each end surface of the obtained ceramic sintered body to form an external electrode electrically connected to the internal electrode layer.

The external dimensions of the multilayer ceramic capacitor thus obtained were 1.6 mm in width, 3.2 mm in length, and 1.0 mm in thickness, and the thickness of the dielectric layer interposed between the internal electrodes was 8 μm. . The effective number of stacked dielectric layers was 50, and the area of the opposed internal electrode per layer was 2.1 mm ² .

(4) The multilayer ceramic capacitor obtained as described above was hardened and polished with resin for each of 100 samples, and observed by a metallographic microscope at a magnification of 400 times to inspect for cracks and delamination. Further, the metal palladium of the surface-coated palladium oxide was almost alloyed with Ni by X-ray diffraction, and it was confirmed that the metal palladium was partially segregated.

と し て As a comparative example, a conductive paste was prepared using Ni powder whose surface was coated with palladium and silver and nickel powder whose surface had not been treated, and the same evaluation was performed. Table 1 shows the number of cracks and delaminations (100 pieces) and the number of cracks and delaminations (100 pieces) after firing at 380 ° C. in the air atmosphere. Shown in

In order to evaluate the sinterability of Ni in the internal electrode layer, the average particle size of nickel or nickel alloy in the fired internal electrode layer was examined by an SEM (scanning electron microscope) and calculated by the intercept method. Described.

Furthermore, H. P (Capacitance was measured by an LCR meter 4284A manufactured by Hewlett-Packard Company, and a coefficient of variation (CV value) of the capacity was calculated by dividing the standard deviation of the capacity by the average value of the capacity. This is also shown in Table 1.

よ り From Table 1, when a conductive paste that has not been subjected to a surface treatment is used, cracks and delaminations occur after de-buying because Ni is oxidized. Similarly, cracks and delaminations occur in the conductive paste using Ni powder coated with Pd and Ag due to oxidation of Ni and oxidation expansion of the coated metal.

On the other hand, the particles of Ni coated with palladium oxide have the smallest average particle diameter, and the particles not subjected to the surface treatment have more advanced grain growth. Further, it was found that the thickness of the internal electrode was smaller when coated with palladium oxide than when the metal was palladium.

Furthermore, it can be seen that the larger the amount of palladium oxide, the smaller the CV value and the smaller the variation in capacitance due to oxidation of the base metal.

FIG. 2 is an explanatory diagram showing a part of the multilayer ceramic capacitor of the present invention in an enlarged manner.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Matrix 2 ... Disperse phase 3 ... Dielectric layer 4 ... Internal electrode layer

Claims (1)

An electronic component having an internal conductor in a dielectric, wherein the internal conductor comprises a matrix made of an alloy of a base metal and palladium and a dispersed phase made of palladium.

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