JPS5925103A - 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 Field of the Invention The present invention relates to a conductive paste used for forming electrodes of ceramic capacitors or external electrodes of leadless components such as chip-shaped multilayer ceramic capacitors and chip-shaped resistors. .

Prior Art Conventionally, as a conductive paste for forming electrodes of ceramic capacitors, a silver paste containing silver as a main component was used, and this was applied to a dielectric ceramic body by means such as screen printing, and then baked. It is common to form the silver-baked electrode as an electrode. Further, external electrodes of leadless components such as chip-shaped multilayer ceramic capacitors and chip-shaped resistors are formed by means such as dipping or transfer.

In this case, in order to reduce the amount of silver used and reduce the cost of forming the electrode, conventionally silver baking was performed to make the electrode as thin as possible.

The disadvantage of the conventional technology is that when silver baking reduces the thickness of the electrode, when the lead wire is soldered to electrode 1- or a solder coating is applied, the silver electrode and the solder in the solder layer may interact with each other. This causes the solder layer cracking phenomenon, which causes the solder layer to diffuse and migrate, resulting in disadvantages such as being susceptible to adverse effects such as a decrease in the acquired capacity and a decrease in solder heat resistance. In the external electrodes of leadless components such as chip-shaped multilayer ceramic capacitors and chip-shaped resistors, 10 to 30% of silver powder is added as a means to improve the solder layer phenomenon and solder heat resistance. A method has been adopted in which a conductive paste containing Pd powder is used to construct the silver-Pd burnt electrode as an electrode. In general, since the Pd content is greatly affected, the higher the additive effect of the Pdv system, the greater the amount of Pd used, making the electrode formation cost extremely expensive. Moreover,
Even with l/X using the above method, prevention of solder layer phenomenon and solder heat resistance are insufficient), and the intermediate layer of the electrode is coated with a metal layer such as N1, etc. Therefore, it was necessary to take a method such as forming the solder layer by a method, thereby preventing the solder layer phenomenon and improving the solder heat resistance. In order to improve the soldering heat resistance, it was necessary to add a large amount of expensive Pd or to perform a peeling process, which inevitably led to high product costs.

Purpose of the Invention Therefore, the present invention eliminates the above-mentioned conventional drawbacks, forms an electrode that is highly effective in preventing the solder layer phenomenon, has excellent solder heat resistance, and has high electrode strength, at a very low cost. The purpose is to provide paste.

In order to achieve the configuration of the present invention, the conductive paste according to the present invention is characterized in that it contains metal particles and conductive particles whose surfaces are coated with silver on the surface of core particles. .

That is, as shown in FIG. 1, the conductive paste according to the present invention includes conductive particles whose surfaces are coated with silver 2 and metal particles, which are dispersed in an organic vehicle together with crow lift. It is something that In this case, the silver-coated conductive particles are added in an amount of 0.5 to 30% by weight based on the total amount of the metal particles. If the amount added is less than 0.5%, there is no addition effect;
Moreover, if it exceeds 30% by weight, it becomes difficult to solder and cannot be used as an electrode paste, and if it exceeds 50% by weight, the function as an electrode is impaired.

The core particles 1 are those having the same composition as the dielectric ceramic that becomes the magnetic capacitor, for example, BaTiO3, Ti02, A, which are commonly used in magnetic capacitors.
In order to obtain a semiconductor ceramic capacitor made of a metal infusion such as l2O3, 1% Zr, or 5i02, it is generally made of a valence-controlled semiconductor ceramic that is a semimetal oxide. In addition, Ni, Cr
, Go, A1. It can also be composed of base metals or semimetals such as Fe, Pb, Sn, alloys thereof, carbon, conductive ceramics, and the like. In this case, it is desirable that the core particles 1 be classified to have a particle size of 1 m or less, ideally about 0.5 to 0.8 m.

Then, conductive particles are obtained by coating the surfaces of the particles 1 classified into a predetermined particle size as described above with the silver 2. Appropriate methods for coating the particles 1 with silver 2 include a metal bullet electrolysis method, a solution reduction method, and a vapor phase deposition method.

Further, the metal particles used together with the silver-coated conductive particles are generally made of silver. However, it is also possible to use other metal materials, such as noble metals such as Pt, Au, and Pd, or alloys thereof.

-I = The conductive paste according to the present invention having the above-mentioned composition can be produced by the screen printing method, the dip method, the roll coke method or the dip method, as well as the conventional conductive paste. The electrodes are formed by applying it to a ceramic substrate or the like by coating or other means and then firing it. FIG. 2 is a sectional view showing a model of the electrode structure of the magnetic capacitor thus formed.

As shown in the figure, the electrode structure when using the conductive paste according to the present invention is obtained by baking a conductive layer 4 made of silver coating the core 1 and metal particles used together with the silver on the surface of the dielectric ceramic 3. is formed, and a solder layer 5 is provided on the second side of this conductive layer 4.

In this case, the conductive paste according to the present invention is a conductive paste whose surface is coated with silver on the surface of the core particles, and contains I atoms, so it is made of noble metals such as Pt, Au, Pd, alloys thereof, or silver, etc. By reducing the amount of expensive metal particles used, it is possible to form an electrode with excellent solder heat resistance while achieving a significant cost reduction. Moreover, the firing material has an electrode structure in which the nuclei 1 are scattered in the conductive layer 4 formed by silver and other metal particles that coat the nuclei 1, so that the conductive layer 4 is formed by the nuclei 1. Mutual diffusion of solder layer 4 and solder layer 5 is prevented. Therefore, the solder eating phenomenon of the electrodes is prevented. Further, since the core particles 1 can be made of a composition similar to that of the dielectric ceramic 3 that becomes the magnetic capacitor, the adhesive strength to the dielectric ceramic 3 can be increased, and the electrode strength can be increased.

Example Using dielectric porcelain as core particles, a powder of silver-coated conductive particles having a final composition of silver:dielectric porcelain=75:25 was produced. With this silver-coated conductive particle powder, silver in conventional silver paste can be reduced by 0.5 to 5.
Each conductive paste was prepared with substitution in the range of 0% by weight. Next, samples of ceramic capacitors were prepared using this conductive paste, and the solder heat resistance and solder aging strength of each ceramic capacitor were measured. The measurement results are shown in FIGS. 3 and 4. The soldering heat resistance shown in FIG. 3 is measured as a capacitance change rate (%) (FIG. 3). In addition, the solder aging strength in Figure 4 is 155° for the sample.
After aging for 2 hours in an atmosphere of
During the measurement, a tensile force in the vertical direction was applied.

As is clear from these test results, when using a conductive paste in which the silver coated conductive particle powder replaces the silver powder in the conventional silver paste, 0.5 to 30% by weight
Within the substitution range of , the soldering heat resistance and half H'' aging strength are significantly improved compared to those using conventional silver paste. If the amount of substitution exceeds 30% by weight, soldering becomes difficult and cannot be used, and if the amount exceeds 50% by weight, the function as an electrode is impaired.

As mentioned above, the main use of the conductive paste of the present invention is as a conductive paste for forming external electrodes of leadless components such as electrodes of ceramic capacitors, chimney-shaped multilayer ceramic capacitors, and chip-shaped resistors. However, it goes without saying that there are various other uses as well.

Effects of the present invention As described above, the conductive paste according to the present invention has
A conductive paste containing conductive particles whose surfaces are coated with silver on the surfaces of core particles and metal particles, wherein the conductive particles have a particle size of 0.5 with respect to the total sum with the metal particles.
The conductive paste is characterized in that it is added in an amount of ~30% by weight, so it has a high effect of preventing solder eating, has excellent solder heat resistance, and can form electrodes with high electrode strength at a very low cost. can be provided.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view modeling the structure of the conductive paste according to the present invention, FIG. 2 is a cross-sectional view modeling the electrode structure of a ceramic capacitor using the conductive paste according to the present invention, and FIG. 4 is a diagram showing the solder aging strength measurement results, and FIG. 5 is a diagram showing the solder aging strength measurement method of FIG. 4. ■...Core particle? ...Silver Figure 6 4 Rei Coating Okego (EttX) 10- Figure 5 "

Claims (5)

[Claims] (1) A conductive paste containing conductive particles whose surfaces are coated with silver on the surfaces of core particles, and metal particles, wherein the conductive particles have a particle size of 0.5 with respect to the total amount of the metal particles. A conductive paste characterized in that the amount of the conductive paste is 30% by weight. (2) The conductive paste according to claim 1, wherein the core particles are made of at least one type of metal oxide or semimetal oxide. (3) The conductive paste according to claim 1, wherein the core particles have electrical conductivity. (4) The core particles are Ni, Cr, Co,
The conductive paste according to claim 3, characterized in that it is made of at least one kind of base metal or semimetal such as AI, Fe, or an alloy thereof. (5) The conductive paste according to claim 3, wherein the core particles are made of at least one of carbon and conductive ceramic.