JP2001135136A - Metal paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal paste capable of being optimized and further enhance reduction of the layer by incorporating the paste with fatty acid or its salt as additives to supplement the limit or defect of pasting characteristics of metal powder. SOLUTION: The metal paste contains, dominantly, an organic vehicle formed by dissolving an organic binder such as ethylcellulose in an organic solvent such as terpineol and powder of such base metal as nickel, which is incorporated with one type or more of fatty acid or its salt, specifically, fatty acid such as oleic acid, palmitic acid, myristic acid, stearic acid and lauric acid or its salt, as additives.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a metal paste mainly composed of an organic vehicle and a metal fine powder and used as a paste for an internal electrode in a multilayer ceramic capacitor.

[0002]

2. Description of the Related Art In recent years, electronic components have become lighter, thinner and smaller, and multilayer ceramic capacitors (hereinafter, referred to as multilayer chip components) have been developed.
(MLCC)), there is an increasing demand for miniaturization and high capacity. Above all, the base metalization of the internal electrode in the MLCC, particularly the nickelization from palladium and silver-palladium, is proceeding at remarkable momentum, and the demand is increasing year by year. Therefore, ML
As means for reducing the size and increasing the capacity of the CC, there is an urgent need to increase the number of layers and the number of layers by reducing the thickness of the internal electrodes and dielectrics in the capacitor body described below.

That is, this type of MLCC has a capacitor body in which a plurality of dielectric layers and internal electrodes are alternately stacked, and a capacitor body provided outside the capacitor body, one of which is connected to an odd-numbered internal electrode group and the other is connected to the other. Is known in which a main part is composed of a pair of external electrodes connected to an even-numbered internal electrode group.

The MLCC is conventionally manufactured as follows.

First, powdered barium titanate (B
aTiO ₃ ), a dielectric sheet such as a perovskite oxide containing lead and a dielectric sheet containing an organic binder made of polyvinyl butyral resin or an acrylic resin such as butyl methacrylate or methyl methacrylate (generally,
A paste for internal electrodes is formed on the surface of the surface (referred to as a dielectric green sheet) by a screen printing method and dried.

Next, a predetermined number of dielectric sheets on which the above-mentioned internal electrode paste is formed are laminated and thermocompressed, and then the thermocompressed body is cut into a desired size. Subsequently, the thermocompression bonding is performed at about 1300 ° C. for the purpose of burnout (complete combustion) of the organic binder and the following organic vehicle in the internal electrode paste and sintering of the internal electrode and the dielectric in the internal electrode paste. Fire the body.

Next, a plurality of dielectric layers and internal electrodes thus obtained are alternately laminated and polished at both ends of a fired laminated body (capacitor body), and odd-numbered internal electrodes are formed at one end. After exposing the end face of the group and the end face of the even-numbered internal electrode group on the other end side, a pair of external electrodes for connecting the MLCC and an external device are attached to the polished end faces, and the above-described lamination is performed. A ceramic capacitor (MLCC) was completed.

Here, as a paste for an internal electrode formed on the surface of the dielectric sheet, conventionally, an organic vehicle in which an organic binder such as ethyl cellulose is dissolved in an organic solvent such as terpineol, nickel, copper or the like is used. A composition comprising a base metal powder as a main component and a diluting solvent or the like for adjusting viscosity as necessary is applied.

[0009]

By the way, the above MLC
In order to increase the number of layers in response to the miniaturization and high capacity of C, when the paste for internal electrodes is screen-printed in the above-mentioned MLCC manufacturing process, the internal electrodes must be made as thin as possible. In order to achieve this, it is necessary to use an internal electrode paste that has a small applied weight of metal powder per unit area and does not cause electrode breakage during firing.

The conventional internal electrode paste has a high true density and a high filling property in the paste from the viewpoint of reducing the applied weight of the metal powder, and also prevents the occurrence of electrode breakage during the firing. The method basically selects a metal powder having a high sintering start temperature.

However, the true density cannot exceed the theoretical specific gravity of the metal powder, and it is extremely difficult to achieve a higher filling property than that of a spherical or granular monodispersed powder. In addition, it is not easy to design a metal powder that realizes a high sintering temperature and sufficiently sinters and forms a film at a target temperature.

The present invention has been made in view of such a problem, and an object thereof is to compensate for the limitations or defects of the paste properties of the metal powder.
An object of the present invention is to provide a metal paste that can be further thinned by optimizing the metal paste by mixing an appropriate amount of a fatty acid or a salt thereof as an additive in the paste.

[0013]

That is, the invention according to claim 1 is based on the premise that a metal paste containing an organic vehicle in which an organic binder is dissolved in an organic solvent and one or more fine powders of a base metal is used. The invention according to claim 2 is characterized in that at least one fatty acid or a salt thereof is blended, and the metal paste according to the invention according to claim 1 is premised, and the fatty acid or a salt thereof is blended with respect to the entire paste. Characterized in that the proportion is 3% by weight or less,
The invention according to claim 3 is based on the metal paste according to claim 1 or 2, wherein the fatty acid or a salt thereof is selected from oleic acid, palmitic acid, myristic acid, stearic acid, and lauric acid. Or a salt thereof.

[0014]

Embodiments of the present invention will be described below.

That is, the metal paste according to the present invention comprises:
An organic vehicle in which an organic binder such as ethyl cellulose is dissolved in an organic solvent such as terpineol, and a base metal powder such as nickel and copper as a main component. One or more fatty acids or salts thereof are added as additives. It is a feature.

As the above-mentioned fatty acids or salts thereof, lower and higher fatty acids or salts thereof can be applied.
Moreover, it does not matter whether it is saturated or unsaturated. The type of the salt is also arbitrary. Specifically, unsaturated fatty acids such as oleic acid and fatty acids such as elaidic acid or salts thereof,
Fatty acids such as octanoic acid, nonanoic acid, decanoic acid, palmitic acid, myristic acid, stearic acid, and lauric acid, which are saturated fatty acids, and salts thereof.

The other components of the metal paste are the same as in the prior art, and copper, nickel,
Cobalt, molybdenum, tungsten and the like are exemplified.
Examples of the organic solvent in the organic vehicle include terpineol, dihydroterpineol, decanol, octanol, trimethylbenzene, methyl ethyl ketone, and the like.In addition, examples of the organic binder in the organic vehicle include ethyl cellulose, cellulose resins such as nitrocellulose, Acrylic resins such as butyl methacrylate and methyl methacrylate are exemplified. Examples of the above-mentioned diluting solvent include aromatic hydrocarbons, aliphatic hydrocarbons, higher alcohols and the like.

The viscosity of this type of metal paste is generally adjusted so that the viscosity at 100 revolutions in a B-type rotational viscometer is 50 Pa · s (Pascal second) or less.

In the metal paste according to the present invention, the dry film density (g / cm ³ ) increases as the proportion of the fatty acid or salt thereof in the paste increases, and the amount of the applied paste is reduced to that of the conventional paste. Even if the number is set to a smaller value, a conductive film such as an electrode can be formed without interruption.

Therefore, the conductive film can be further thinned. For example, when the conductive film is applied to the above-mentioned paste for an internal electrode in the MLCC, it is possible to cope with the miniaturization and high capacity of the MLCC. Become.

The inventors of the present invention have inferred the following reason why such an effect can be obtained by blending the above fatty acid or its salt in the paste. That is, since the surface of the base metal powder is coated with the fatty acid or the salt thereof by mixing the fatty acid or the salt thereof, the wettability of the base metal powder with respect to the organic vehicle is increased. It is inferred that this is due to the improvement in the filling properties of the base metal powder and the like.

Here, the mixing ratio of the above fatty acid or salt thereof to the whole paste is 4% by weight or less.
Preferably, it is set to 3% by weight or less (claim 2). When the compounding ratio of the fatty acid or its salt exceeds 4% by weight, the drying speed of the metal paste according to the present invention tends to be slow, and for this reason, for example, this metal paste is used for the internal electrode of the MLCC. This is because when applied to a paste, delamination may occur. Note that delamination refers to the above-described delamination phenomenon that occurs between the dielectric layer and the internal electrode. Therefore,
The proportion of the fatty acid or salt thereof relative to the whole paste is set to 4% by weight or less, preferably 3% by weight or less.

The mixing ratio of the base metal powder to the whole paste is preferably set in the range of 30% by weight to 60% by weight. If the content is less than 30% by weight, the electrode thickness after firing becomes small and the resistance value increases, or the conductivity is lost. For example, when the electrode is applied to an internal electrode paste of MLCC, a desired capacitance is obtained. This is because it may not be possible. On the other hand, if it exceeds 60% by weight, the electrode thickness after firing becomes large, which may cause the above-described delamination.

Next, the blending ratio of the organic vehicle with respect to the whole paste is preferably set in the range of 20% by weight to 40% by weight. If the amount is less than 20% by weight, the strength of the dried film is low. For example, when the film is applied to the internal electrode paste of MLCC, the surface of the internal electrode after printing tends to be damaged. Since the thickness of the electrode later becomes small and the resistance value increases or the conductivity is lost, for example, when applied to the internal electrode paste of MLCC, the desired capacitance may not be obtained. is there. In addition, the amount of gas generated during binder removal increases, which may cause the above-described delamination.

The application of the metal paste according to the present invention is arbitrary, and is not limited to the above-mentioned paste for the internal electrode of the MLCC.

[0026]

Embodiments of the present invention will be specifically described below.

[Preparation of Paste] An organic vehicle applied to the metal paste for an internal electrode was prepared as follows. That is, it was prepared by heating terpineol to a temperature of 80 ° C. in an oil bath and gradually adding a resin for an organic binder while stirring with a stirring blade.

At the end of the preparation, a part of the dissolved material was taken out, and it was confirmed that the resin for an organic binder was completely dissolved on the preparation and that there was no undissolved residue.

Further, a mixed solution of toluene and ethanol (a solution having a weight ratio of 1: 1) is used as the organic binder resin.
The viscosity when this resin is dissolved at 5% by weight is 0.15.
Ethyl cellulose having characteristics in the range of Pa · s (Pascal second) to 0.25 Pa · s (Pascal second) is applied. The composition of the prepared organic vehicle is as follows:
Terpineol was 85% by weight, and the remainder was the above-mentioned ethyl cellulose resin.

Next, 35 g of the above organic vehicle, 50 g of nickel powder having an average particle size of about 0.5 μm (SNP-122, manufactured by Sumitomo Metal Mining Co., Ltd.), and a diluting solvent (mineral spirits, manufactured by Nippon Oil Co., Ltd.) After 15 g of A) was weighed and thoroughly kneaded with a three-roll mill, the mixing ratio with respect to the entire paste is shown in Table 1 below (that is, 0.5%, 1.0%, 2.0%, 3.0%). %, 4.0%;
However, in weight percent, fatty acids and their salts (ie, oleic, palmitic, myristic, stearic,
Lauric acid and calcium oleate) were added, and kneaded similarly with three rolls to produce a plurality of types of nickel paste. Further, as a comparative example, the above fatty acid was not added (that is, the mixing ratio was 0.1%).
0%) nickel paste was also manufactured.

When the viscosity of each of the produced nickel pastes was measured using a Brookfield B-type viscometer, the viscosity at 100 rotations was 50 Pa or less (Pa · s). confirmed.

Then, a conductive film is formed by using the obtained nickel pastes, and the dry film density (g / cm ³ ) of each conductive film and the electrode forming ability (whether or not the formed conductive film is interrupted or not). ) Was measured by the following method.

(Measurement of Dry Film Density) Each of the obtained nickel pastes was put on a pet film (polyethylene terephthalate film) to a thickness of 100 μm, 50 mm × 100 mm.
After printing in an area of mm, it is dried in air at 120 ° C. for 60 minutes. Next, the dried film was cut into 30 mm × 30 mm, and the thickness and the weight were measured with a micrometer to calculate the density of the dried film. The number of samples in one type of nickel paste is five, and the dry film density is an arithmetic average value.

Table 1 shows the dry film density (g / cm ³ ) formed by using each nickel paste.

(Measurement of Electrode Forming Ability) Each of the obtained nickel pastes was printed on a 10 μm dielectric sheet so as to have a weight of 0.7 to 1.0 mg / cm ^{2 in} terms of nickel weight. A 3 mm green chip is prepared for each paste. Subsequently, after debinding these green chips in air at 300 ° C., 1300 ° C. and H ₂
Then, firing was carried out in a mixed gas of / N ₂ , and external electrodes were attached to these chips, and the capacitance was measured by an LCR meter. The electrical characteristics are expressed as% of the measured capacitance value with respect to the design capacitance value (ie, measured capacitance value / set capacitance value × 100).
%). The capacitance value is an arithmetic average value of 10 chips obtained using each paste.

Table 1 shows the results of evaluating the electrode forming ability of each nickel paste.

[0037]

[Table 1] "Confirmation" The following can be confirmed from the results in Table 1 above.

First, with respect to the dry film density, a comparative example (that is, a compounding ratio of a fatty acid or a salt thereof is 0.0%)
It is confirmed that the ratio tends to increase as the proportion of the fatty acid or its salt increases. However, it is also confirmed that when the mixing ratio of the fatty acid or its salt exceeds 3% by weight, the increase in the dry film density does not tend to be affected so much.

On the other hand, since the electric capacitance of each chip is equal to or larger than the set capacitance value, the electrode forming ability (whether or not the formed conductive film is interrupted) in each paste is determined by the conditions. It is also confirmed that they are provided. It is also confirmed that the electric capacity of each chip can be set to the target 100% under the condition that the mixing ratio of the fatty acid or its salt is 3% by weight or less. Furthermore, when the mixing ratio of the fatty acid or its salt is 0.0% by weight, the electric capacity of the chip becomes 103% under the manufacturing conditions described in the above “Measurement of electrode forming ability”, and the electric capacity of the chip is targeted. It is also confirmed that it cannot be set to 100%.

(Test of nickel paste application amount)
A nickel paste application amount test was performed using a nickel paste in which the blending ratio of oleic acid was set to 1.0% by weight and a nickel paste according to a comparative example in which no fatty acid or a salt thereof was blended.

That is, the application amount (mg / cm ² ) of each nickel paste was set to 0.70, 0.74, 0.81,
The values were set to 0.86, 0.92, 0.94, and 1.00, respectively, and the% of the above capacitance value (that is, measured capacitance value / set capacitance value × 100%) was evaluated.

The results are shown in Table 2 below.

[0043]

[Table 2] Then, from the results of the comparative example in Table 2 (that is, the mixing ratio of the fatty acid or its salt is 0.0%), when the application weight of the nickel paste is reduced, the obtained capacity is reduced, and the application weight is 0.81 ( mg / cm ² ) or less, it is confirmed that the acquired volume sharply decreases (that is, becomes equal to or less than the set volume value).

On the other hand, from the results of the examples in Table 2 (that is, the nickel paste in which the blending ratio of oleic acid was set to 1.0% by weight), the obtained capacity increased due to the blending of oleic acid. The application weight is 0.74 (m
g / cm ² ), it is confirmed that the acquisition capacity can be set to approximately 100%.

[0045]

According to the metal pastes according to the first to third aspects of the present invention, as the proportion of the fatty acid or its salt in the paste is increased, the dry film density is increased, and the coating amount is reduced. Even if it is set smaller, it is possible to form a conductive film such as an electrode without interruption or the like.

Accordingly, since the conductive film can be further thinned, when applied to, for example, a paste for an internal electrode in an MLCC, it is possible to cope with the miniaturization and high capacity of the MLCC. Has an effect.

Claims (3)

[Claims] 1. A metal paste containing an organic vehicle in which an organic binder is dissolved in an organic solvent and one or more fine base metal powders, wherein one or more fatty acids or salts thereof are compounded as additives. And metal paste. 2. The metal paste according to claim 1, wherein the mixing ratio of the fatty acid or the salt thereof to the whole paste is 3% by weight or less. 3. The metal paste according to claim 1, wherein the fatty acid or a salt thereof is a fatty acid selected from oleic acid, palmitic acid, myristic acid, stearic acid, and lauric acid or a salt thereof. .