JP2001006436A - Conductive paste and manufacture thereof and laminated ceramic capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a paste which has an excellent dispersion characteristic though it uses conductive powder having an average particle diameter not more than specified and which is less in viscosity change over aging by adding an aniornic polymer dispersant as well as an amine based surface active agent to the conductive thick film paste composed of the conductive powder whose average particle diameter is not more than a specified level and an organic vehicle. SOLUTION: Preferably, alkylene oxide or its polymer and aminic surface active agent such as oxyethilenedodesylamine consisting of alkyl group or hydrogne are contained 0.1-5.0 in 100 wt.% of conductive thick film paste using conductive powder whose average particle diameter is not more than 1 μm. To manufacture the paste, anionic polymer dispersant and conductive powder are mixed to thereby obtain intermediate paste where the dispersant is absorbed by the powder, and then an amine based surface active agent is added thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive thick film paste used for forming electrodes of electronic parts, a method for manufacturing the same, and a multilayer ceramic capacitor using the conductive thick film paste.

[0002]

2. Description of the Related Art Conventionally, a conductive thick film paste has been used as a material for forming electrodes of a multilayer ceramic capacitor. As such a conductive thick film paste,
A material in which a conductive powder made of Ni, Cu, Ag, Pd, or the like is dispersed in an organic vehicle obtained by mixing an organic binder and a solvent is used.

[0003]

However, in the case of a conventional conductive thick film paste, when fine particles having a particle diameter of 1 μm or less are used for the conductive thick film paste, the viscosity increases with time after the paste is produced, and screen printing is performed. There is a problem that the film thickness tends to fluctuate when printing on a green sheet by the method described above. As described above, when an electrode dry film having a non-uniform film thickness is laminated and sintered, there is a problem that delamination and cracks are likely to occur due to non-uniform volume change.

In order to effectively and uniformly disperse such fine conductive powder, there is a method of adding a dispersant as an additive. That is, the surface of a conductive powder such as Ni or Cu exhibits basicity. For example, there is a method of adding an anionic polymer dispersant in consideration of acid-base interaction. However, by adding a dispersant, wetting of the conductive powder with the solvent is promoted, and a uniform mixture can be formed in a shorter time. It is easy to form a three-dimensional cross-link with not only the particles but also a plurality of particles, and when such cross-linking proceeds, a problem such as an increase in viscosity and gelation newly occurs.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and it is an electroconductive thick film paste using an electroconductive powder having an average particle diameter of 1 μm or less, and has excellent dispersibility.
It is another object of the present invention to provide a conductive thick film paste with less change in viscosity with time and a method for producing the same.

[0006]

Means for Solving the Problems To achieve the above object, a conductive thick film paste of the present invention is a conductive thick film paste comprising a conductive powder having an average particle diameter of 1 μm or less and an organic vehicle. , An amine-based surfactant and an anionic polymer dispersant.

The amine surfactant is characterized by comprising an alkylene oxide or a polymer thereof, an alkyl group or hydrogen.

The amine-based surfactant is used in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the conductive thick film paste.
It is characterized by containing by weight.

The conductive powder is made of one or more selected from Ni powder, Cu powder, and alloy powders including these metal powders.

[0010] The method for producing a conductive thick film paste of the present invention is characterized in that an anionic polymer dispersant and a conductive powder are mixed, and the conductive powder is adsorbed with the anionic polymer dispersant. A step of obtaining a paste; and a step of adding the amine-based surfactant to the intermediate paste.

Further, a multilayer ceramic capacitor according to the present invention is characterized in that internal electrodes are formed using the above-mentioned conductive thick film paste.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A feature of the present invention is that an excess of anionic polymer dispersing agent added to enhance the dispersibility of the conductive powder in the conductive thick film paste, that is, an acid site, is used as an additive. It is characterized by neutralizing with.

Examples of such an additive include addition of a basic low-molecular compound or a surfactant. An amine surfactant comprising an alkylene oxide or a polymer thereof and an alkyl group or hydrogen is used. However, the increase in viscosity could be effectively suppressed.

The amount of the amine surfactant is preferably 0.1 to 5.0 parts by weight based on 100 parts by weight of the conductive thick film paste. That is, if the addition amount is less than 0.1 part by weight, the effect of addition is not sufficiently exhibited, and the increase in viscosity cannot be suppressed. In addition, the amount added is 5.0.
If the amount is more than 10 parts by weight, the viscosity of the conductive thick film paste is remarkably reduced, and an appropriate viscosity as a printing paste cannot be obtained.

The conductive powder is Ni powder and C powder.
It is preferable to use one or more selected from u powders and alloy powders containing these metal powders. These metal powders or alloy powders are generally used as a conductive component of a conductive thick film paste.

Further, in the method for producing the conductive thick film paste of the present invention, an anionic polymer dispersant and a conductive powder are mixed, and the anionic polymer dispersant is adsorbed on the conductive powder. It is preferable to include a step of obtaining an intermediate paste and a step of adding the amine-based surfactant to the intermediate paste. In other words, it is necessary to adsorb the anionic polymer dispersant to the conductive powder, but if the amine surfactant is added after the addition of the anionic polymer dispersant, the anionic polymer dispersant becomes amine-based surfactant. Since it is sufficiently adsorbed to the conductive powder without being adsorbed by the agent, the effect of dispersing the conductive powder is sufficiently improved.

It is preferable that the conductive thick film paste of the present invention is used as an internal electrode of a multilayer ceramic capacitor. 2. Description of the Related Art In recent years, multilayer ceramic capacitors have become lighter, thinner and smaller, and there is a demand for a finer conductive powder in a conductive thick film paste used for forming internal electrodes. In response to such demands, the conductive thick film paste of the present invention is a conductive thick film paste using a conductive powder having an average particle diameter of 1 μm or less, yet has excellent dispersibility and little change in viscosity over time. It has the advantage.

[0018]

First, 80 parts by weight of terpineol as a solvent and 20 parts by weight of an ethylcellulose resin as an organic binder are prepared. After the organic binder is added to the solvent, the mixture is uniformly mixed with a stirrer to obtain an organic vehicle.

Next, 45 parts by weight of an organic vehicle, 5 parts by weight of a polyacrylic acid-polyacrylate based anionic polymer dispersant, and Ni powder 5 having an average particle diameter of 0.5 μm were prepared.
The first intermediate paste was obtained by adding 0 parts by weight and uniformly dispersing with a three-roll mill.

Next, as shown in Table 1, different addition amounts of amine surfactants composed of oxyethylene dodecylamine were prepared, added to the first intermediate paste transferred to the mortar, mixed, and the samples 1 to 7 was obtained.

Therefore, the initial viscosities of the conductive thick film pastes of Samples 1 to 7 were measured, and after standing in air at 25 ° C. for 30 days, the viscosities were measured again to determine the change in viscosity.

The viscosity of the conductive thick film paste was measured as follows.
Using an E-type viscometer manufactured by Tokimec Co., Ltd., 25
The measurement was performed at 2.5 ° C. and 2.5 ° C. Sample 1 used for evaluation
The allowable range of the initial viscosity of the conductive thick film paste of Nos. 7 to 7 was 18 ± 3 Pa · s. The viscosity change rate was determined by the following equation. Viscosity change rate (%) = (Viscosity after 30 days−Initial viscosity) / Initial viscosity × 100 In the overall evaluation, ○ was given to samples within the range of the present invention, and × was given to samples outside the range.

[0023]

[Table 1]

As is clear from Table 1, the conductive thick film pastes of Samples 2 to 6 have an initial viscosity of 15.1 to 20.0 Pa · s and an allowable range of the initial viscosity of 18 ± 3 Pa · s. s. On the other hand, Sample 1 to which oxyethylene dodecylamine was not added and Sample 7 to which 5.50 parts by weight were added were 2
It was out of the allowable range at 2.2 Pa · s and 12.3 Pa · s.

After 30 days, the rate of change in viscosity was as follows: 0.10 parts by weight of oxyethylene dodecylamine, 1.50 parts by weight,
Samples 3 to 6 to which 3.50 parts by weight and 5.00 parts by weight were added were 0.6% to 1.0%, which were very small and excellent. On the other hand, 0.05% of oxyethylene dodecylamine was added.
The weight of Sample 2 was 139.0%, which was significantly inferior.
Samples 1 and 7, which had initial viscosities outside the allowable range, were similarly inferior at 155.9% and -34.1%, respectively.

[0026]

As described above, according to the present invention, in a conductive thick film paste comprising a conductive powder having an average particle diameter of 1 μm or less and an organic vehicle, an amine-based surfactant,
By adding an anionic polymer dispersant, the conductive thick film paste using a conductive powder having an average particle size of 1 μm or less has excellent dispersibility and has little change in viscosity with time. The effect is obtained.

The above-mentioned effects are more reliably exhibited when the amine-based surfactant comprises an alkylene oxide or a polymer thereof, and an alkyl group or hydrogen.

The amine-based surfactant is used in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the conductive thick film paste.
By containing the parts by weight, the above-mentioned effects are more reliably exhibited.

Further, the conductive powder is composed of one or more selected from Ni powder, Cu powder, and alloy powder including these metal powders, so that the conductive powder suitable for forming an electrode of an electronic component is formed. The effect that a thick film paste is obtained is obtained.

When the conductive thick film paste of the present invention is used for an internal electrode of a multilayer ceramic capacitor, the effect of the conductive thick film paste containing fine conductive powder is sufficiently exhibited.

A step of mixing an anionic polymer dispersant and a conductive powder to obtain an intermediate paste in which the conductive powder adsorbs the anionic polymer dispersant; Adding a surfactant, the average particle diameter is 1 μm
Although it is a conductive thick film paste using the following conductive powder, it is possible to produce a conductive thick film paste having excellent dispersibility and little change in viscosity over time.

Claims (6)

[Claims] 1. A conductive thick film paste comprising a conductive powder having an average particle size of 1 μm or less and an organic vehicle, wherein an amine-based surfactant and an anionic polymer dispersant are added. Conductive thick film paste. 2. The conductive thick film paste according to claim 1, wherein the amine surfactant comprises an alkylene oxide or a polymer thereof, and an alkyl group or hydrogen. 3. The conductive material according to claim 1, wherein the amine-based surfactant is contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the conductive thick film paste. Thick film paste. 4. The conductive powder comprises Ni powder and C powder.
2. A powder comprising one or two or more selected from u powder and an alloy powder containing these metal powders.
4. The conductive thick film paste according to any one of items 1 to 3. 5. A step of mixing an anionic polymer dispersant and a conductive powder to obtain an intermediate paste in which the anionic polymer dispersant is adsorbed to the conductive powder; Adding a surfactant. A method for producing a conductive thick film paste, comprising: 6. A multilayer ceramic capacitor, wherein an internal electrode is formed by using the conductive thick film paste according to claim 1.