JPS58163102A - Conductive paste - 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 The present invention primarily relates to a conductive paste suitable as an internal electrode material for a ceramic capacitor.

The most well-known type of ceramic capacitor with an internal electrode structure is the multilayer ceramic capacitor, but there are also other types, such as single-layer ceramic capacitors in which one or both electrodes are buried inside dielectric ceramic. type has also been proposed recently. These ceramic capacitors with an internal electrode structure are small, have large capacity, have high insulation properties, exhibit excellent frequency characteristics up to a high frequency range, and generally have a monolithic moisture-proof structure, so they can be used as chip components without an exterior cover. It has features such as high reliability, and the circuit thickness is l.
As an important component that plays a part in the development and modularization of electronic devices, they are becoming widely used in various electronic devices such as electronic computers, communication devices, television receivers, radio receivers, electronic clocks, and calculators.

This type of porcelain capacitor is made by mixing a suitable dielectric porcelain powder, binder, and solvent into a paste and forming it into a sheet by means such as a doctor blade method, roll coater method, or screen printing method. After coating and printing a conductive paste that will become internal electrodes on the green sheet, stack these in order according to the required number of layers, and then heat this laminate in a natural atmosphere with a
After firing at a temperature of 400° C., the sintered body is generally manufactured by providing end electrodes that are electrically connected to the internal electrodes on the end faces of the sintered body.

In this case, the conductive paste used is a base material obtained by uniformly dispersing metal powder in an organic vehicle. The condition is to use a metal material that has a melting point and does not oxidize or react upon contact with the dielectric ceramic even when fired at a temperature of 1250 to 1400°C in a natural atmosphere. Conventionally, platinum, gold, palladium, an alloy thereof, or an alloy of these and silver has been used as a metal powder satisfying this condition.

However, because the shrinkage ratio between these metals and dielectric porcelain is extremely different, delamination occurs at the interface between the dielectric porcelain and the electrode made of the metal during firing, resulting in a large change in the obtained capacity. However, simultaneous firing was difficult because it impairs practicality. Further, there is a problem in that the metal particles grow abnormally during firing, resulting in voids, cracks, and the like.

As a solution to this drawback, a method has been proposed in which a conductive paste is prepared by adding several to ten-odd percent of dielectric ceramic particles as a co-material together with metal particles.

According to this conventional technology, it is possible to suppress the occurrence of delamination, but since the common material is an insulator, the amount of the common material is increased to the extent that the delamination suppressing effect is improved. The quality as a ceramic capacitor deteriorates, and the electrical characteristics as a ceramic capacitor deteriorate.

The problem was that it turned into something.

The present invention suppresses the above-described abnormal grain growth of metal particles to suppress the occurrence of voids and electrode breakage, and also suppresses the occurrence of delamination by combining the shrinkage ratio of the electrode and the shrinkage ratio of the dielectric ceramic. An object of the present invention is to provide a conductive paste that can be simultaneously fired without deteriorating its quality and electrical characteristics.

In order to achieve the above object, the conductive paste according to the present invention is characterized in that it contains conductive powder in which the surfaces of particles made of metal oxide or metalloid oxide are coated with a conductor.

That is, in the present invention, when preparing a conductive paste containing a noble metal powder such as platinum, gold, palladium, an alloy thereof, or an alloy of these with silver as a conductive component, a co-material is used together with the noble metal powder. As shown in FIG. 1, a conductive powder in which the surface of particles 1 made of a metal oxide or a metalloid oxide is coated with a conductor 2 is made to coexist in an organic vehicle.

The metal oxide particles 1 have the same composition as the dielectric ceramic used as the ceramic capacitor, for example, BaTio3°TiO2, A, which is generally used as a ceramic capacitor.
It is made of insulating oxide such as l2O3, ZrO2, SiO2, etc. Further, the semimetal oxide particles 1 are used when obtaining a semiconductor ceramic capacitor, and
It is composed of valence-controlled semiconductor ceramics, carbon, silicon, antimony, bismuth, etc. After pre-calcining these metal oxides or metalloid oxides,
The particles 1 are obtained by pulverization. In this case, the particles 1 have a particle size of 1 gm or less, ideally 0.5 to 0.8 pL.
It is desirable to classify into about m.

Then, the conductor 2 is coated on the surface of the metal oxide particles or metalloid oxide particles l classified into a predetermined particle size as described above. The conductor 2 is made of the same kind of noble metal as the main component of the conductive paste, that is, platinum,
It is composed of gold, palladium, or an alloy thereof. A solution reduction method is suitable as a coating method for these noble metals. In addition, the ratio of the noble metal conductor 2 and the metal oxide l constituting the conductive powder is 7:3 (weight ratio)
Moderate or preferable.

The conductive paste prepared as described above is printed and coated on the green sheet L in a predetermined pattern by means such as screen printing, in the same way as conventional conductive pastes, and the required number of layers is applied. After stacking and bonding under heat, they are fired by conventional means. In this case, since the conductive paste according to the present invention contains conductive powder in which the surface of metal oxide or metalloid oxide particles l is coated with conductor 2, the shrinkage ratio of the conductive paste and the structure of the ceramic capacitor are There is no difference between the shrinkage ratio of the dielectric ceramic and the occurrence of delamination is suppressed, and at the same time, abnormal grain growth of metal particles and generation of pores are suppressed. Moreover, unlike conventional methods that use dielectric ceramic as a single co-material, the surface of the metal oxide or metalloid oxide particles is coated with a conductive material such as platinum, so the electrode has high conductivity. A ceramic capacitor with good electrical characteristics can be realized.

Figure 2 shows the relationship between the amount of added material and the specific electrode resistance of a ceramic capacitor using the conductive paste according to the present invention and a ceramic capacitor using a conventional conductive paste that uses dielectric ceramic as the sole material. It is a characteristic diagram. Curve L1 is the characteristic when using the conductive paste according to the present invention, and curve L2 is the characteristic when using the conventional conductive paste using dielectric ceramic powder as the sole co-material and dispersing it together with palladium powder in an organic vehicle. The characteristics of each are shown when used.

As is clear from Figure 2, when the conductive paste according to the present invention is used, the specific resistance value is much smaller than when the conventional conductive paste I is used, and the conductivity is extremely high. Excellent. Moreover, when conventional conductive paste is used, as the amount of added acid in the co-material increases, the specific resistance value increases rapidly. Although the formation becomes incapacitated, I
7. When using the conductive finisher according to the present invention,
Despite the increase in the amount of co-material added, the increase in specific resistance value was very small, and even with the amount of co-material added at 30%, it was 9×10 ΩcI.
It exhibits a low specific resistance value of about 11, and can ensure sufficient conductivity for practical use as a capacitor electrode.

As mentioned above, the conductive base according to the present invention is
It is characterized by containing conductive powder in which the surface of particles made of metal oxide or metalloid oxide is coated with a conductor, thereby suppressing abnormal grain growth of metal particles and preventing the occurrence of voids and electrode breakage. At the same time, the shrinkage ratio of the electrode and the shrinkage ratio of the dielectric ceramic are combined to suppress the occurrence of delamination, without deteriorating the quality and electrical characteristics of the electrode.
A conductive paste that can be fired simultaneously can be provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view modeling the structure of the conductive powder constituting the conductive paste according to the present invention, and FIG. FIG. 3 is a diagram showing specific resistance characteristics. l...Metal oxide or metalloid oxide particle 2Φ...Conductor Figure 1

Claims (4)

[Claims] (1) A conductive paste characterized by containing conductive powder in which the surfaces of particles made of metal oxide or metalloid oxide are coated with a conductor. (2) The metal oxide particles are BaTiOB,
T i02. The conductive paste according to claim 1, characterized in that it is made of at least one type of insulating oxide such as Al20B, ZrO2, 5i02, etc. (3) The conductive paste according to claim 1, wherein the metalloid oxide particles are made of at least one of valence-controlled semiconductor ceramics, carbon, silicon, antimony, bismuth, etc. . (4) The conductor is made of at least one kind of noble metal such as platinum, gold, palladium, silver, or an alloy thereof.
Conductive paste as described in section