JPS58178903A - 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 mainly relates to the composition of a conductive paste for forming external electrodes of chip capacitors and the like.

When forming external electrodes, such as end electrodes, of chip capacitors of laminated type or internal electrode structure type, conventionally Ag
It has been common practice to use a conductive paste containing 10 to 30% Pd powder based on the powder, and to configure Ag-Pd baking as an electrode. The reason why Pd powder is included in Ag powder is to improve compatibility with the internal electrode, which is mainly composed of Pd, and to improve the soldering heat resistance during soldering and prevent the phenomenon of electrode solder being eaten away. This is to do so. However, since the soldering heat resistance is generally greatly influenced by the Pd content, the higher the soldering heat resistance is, the more Pd is used, resulting in a disadvantage that the cost of forming the external electrodes becomes extremely high. Moreover, even if the above-mentioned method is used, the soldering heat resistance is insufficient, and a metal layer such as Ni is formed on the intermediate layer of the external electrode by means such as plating, thereby improving the soldering heat resistance. We had to take measures to improve this. In any case, conventionally,
In order to improve the soldering heat resistance of external electrodes, expensive P
Since it was necessary to add a large amount of d or to perform plating treatment, the drawback of high product cost was unavoidable.

An object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide a conductive paste that can form external electrodes with excellent solder heat resistance and solder wettability at a very low cost.

In order to achieve the object L, the conductive paste according to the present invention is characterized in that it contains conductive particles whose surfaces are coated with a conductive material and metal particles.

Namely, 1. The conductive paste according to the present invention, as shown in FIG. It is dispersed in

The core particles l have the same composition as the dielectric ceramic that becomes the magnetic capacitor, for example, BaTi0B, T i02 , which are commonly used as magnetic capacitors.
When obtaining reduction-reoxidation type semiconductor ceramic capacitors using metal oxides such as AI, oJ, ZrO2, S+02, etc., it is common to construct them using valence-controlled semiconductor ceramics, which are semimetal oxides. In addition to this, Ni,
Cr, Go, A1. It can also be made of base metals or semimetals such as Fe, Pb, Sn, alloys thereof, carbon, conductive ceramics, and the like. In this case, the core particle 1 has a particle size of 1 g.
It is desirable to classify the particles to 0.5-0.81 Lm or less, ideally about 0.5-0.81 Lm.

Then, conductive particles are obtained by coating the conductive material 2 on the surface of the particles l classified into a predetermined particle size as described above. The conductive material 2 is basically composed of at least one of noble metals such as Pt, Au, Pd, and Ag, or alloys thereof, and may include Ni, Cr, Go, AI, Fe,
It may also be made of base metals such as Pb and Sn. As a method for coating the core particles 1 with these metals, a metal electroless method, a solution reduction method, a vapor phase deposition method, etc. are suitable.

Further, the metal particles used together with the conductive particles serve as a conductive component, and are metal materials that have good compatibility with the internal electrodes and have excellent solder heat resistance, such as Pt, Au,
It is made of at least one of noble metals such as Pd and Ag, or alloys thereof.

The conductive paste according to the present invention having the above-mentioned composition can be applied to a ceramic substrate or the like by a dip method, a roll coater method, or a brush coating method, and then baked, in the same way as conventional conductive pastes. , forming external electrodes such as end electrodes. Baking is done at 400°C to 900°C in the air.
Perform the test under the following temperature conditions.

In this case, since the conductive paste according to the present invention contains conductive particles whose surfaces are coated with a conductive material on the surface of the core particles and metal particles, expensive metal particles such as Pd that serve as the conductive component It is possible to drastically reduce the amount of oxide used, thereby achieving a significant cost reduction while forming an external electrode with excellent soldering heat resistance. Moreover, the temperature is 400℃ in the atmosphere.
Since the electrode can be formed by baking at temperatures ranging from 900° C. to 900° C., the electrode forming process becomes simple. Next, the present invention will be explained in more detail with reference to Examples.

Example A dielectric ceramic was used as a core particle, and a conductive material made of Pd was coated on the surface of the ceramic particle so that the ratio of the ceramic particle to the ceramic particle was 1=1 to obtain conductive particles. A solution reduction method was used for Pd coating. Then, this conductive particle powder was mixed with 80% A
Pd powder and 20% Pd powder are added at a ratio of 5% by weight, and this is dispersed together with a glass frit in a #1 quality vehicle. A conductive paste was prepared. The conductive paste thus prepared was adhered to both ends of a chip capacitor by a dipping method and fired at a temperature of 750 to 850°C to produce a chip capacitor.

Figure 2 shows a comparison of the solder heat resistance of the chip capacitor obtained in the above example with that of a conventional chip capacitor using Ag-Pd electrodes, and Figure 3 also compares the solder wettability. FIG.

As is clear from Fig. 2, the conventional type using Ag-Pd based conductive paste has a solder erosion rate of 1.30%, but the solder erosion rate of the electrode of the present invention is only about 10%. It is suppressed to about half of the conventional level. Moreover, in the embodiment, Ag
The ratio of Pd powder to the powder is about 22.5% by weight, which is significantly smaller than the conventional amount.

Furthermore, as shown in FIG. 3, solder wettability almost equivalent to that of the conventional method can be ensured. Conventionally, the h method, in which base metal powder such as N1 is added to Ag-Pd-based conductive paste, has been known as a means of improving soldering heat resistance.
In this conventional method, the tenacity of the solder is extremely reduced, making it impractical. In the conductive paste according to the present invention, the core particles are composed of an oxide or the like that acts as an element for solder penetration, but since the surface is coated with a metal such as Pd, there is no reduction in solder wettability. It can defend by 1 point.

The main use of the conductive paste according to the present invention is as a conductive paste for forming external electrodes of ceramic capacitors, such as in the case of multi-layered conductive pastes, but it goes without saying that there are various other uses as well.

As described below, the conductive paste according to the present invention is characterized by containing conductive particles whose surfaces are coated with a conductive material on the surface of core particles and metal particles, and therefore has good soldering heat resistance. Furthermore, it is possible to provide a conductive paste that can form external electrodes with excellent solder wettability at a very low cost.

[Brief Description of the Drawings] Figure 1 is a cross-sectional view modeling the structure of the conductive paste according to the present invention, and Figure 2 is a comparison of the soldering heat resistance of the conductive paste according to the present invention with that of conventional pastes. FIG. 3 is a diagram showing the solder wettability of the conductive paste according to the present invention in comparison with that of a conventional paste. l... Core particle 2... Conductive material Figure 1 PL shaft Material FIA product

Claims (8)

[Claims] (1) A conductive paste characterized by containing conductive particles whose surfaces are coated with a conductive material and metal particles. (2) The conductive material is PL, Au, Pd, Ag
The conductive paste according to claim 1, characterized in that the conductive paste is made of one or more noble metals such as or at least one of these alloys. (3) The conductive material may include Ni, Cr, Co, Al.
The conductive paste according to claim 1 or 2, characterized in that it is made of at least one type of base metal such as Fe, Pb, and Sn. (4) The conductive paste according to claim 1, wherein the particles serving as the core are made of at least one type of metal oxide or semimetal oxide. (5) The conductive paste according to claim 1, wherein the core particles have conductivity. (6) The core particles are Ni, Cr, 'Co
The conductive paste according to claim 5, characterized in that the conductive paste is made of at least one of base metals or semimetals of , 'AI, Fe'4, or alloys thereof. (7) The conductive paste according to claim 5, wherein the core particles are made of at least one of carbon and conductive ceramic. (8) The sieve of the patent claim, characterized in that the sieve is fired at 400°C to 900°C in the atmosphere, the turning portions 1 and 2;
The conductive paste according to item 3, 4, 5, '6, or 7.