TWI466968B - Conductive paste for internal electrode of multilayered ceramic capacitor - Google Patents

Description

Conductive paste for internal electrodes of laminated ceramic capacitors

The present invention relates to a conductive paste for internal electrodes of a multilayer ceramic capacitor, and more particularly to a sheet corrosion caused by a conductive paste even if the green sheet of the laminated ceramic capacitor is as thin as 2 to 5 μm. A conductive paste for a laminated ceramic internal electrode which is excellent in drying property and which can effectively suppress the disadvantage caused thereby.

In the electronic devices represented by mobile phones and digital devices, in recent years, the size and size of electronic components used have been reduced, and the multilayer ceramic capacitors (MLCC) for wafer components have been miniaturized and increased in capacity.

Inside the multilayer ceramic capacitor, a laminate in which a dielectric body and an internal electrode overlap each other is provided, and external electrodes are attached to the both ends of the laminated ceramic capacitor at opposite ends of the laminated body.

As the dielectric system, a perovskite-type oxide such as barium titanate, barium titanate or magnesium titanate is used. In order to form the above-mentioned laminated body, it is necessary to disperse the powdered dielectric body in an organic medium composed of a resin such as polyvinyl butyral or acrylic acid and a solvent to form a slurry, which is used in a PET by a doctor blade. The film is formed into a sheet shape, and after drying (generally referred to as a dielectric sheet), a metal paste for internal electrodes is transferred onto the surface of the dielectric sheet by a screen printing method using a predetermined pattern to dry and overlap. The number of sheets of the internal electrode and the green sheet are determined, and after compression and pressing, the hot press is cut to a target size. The electric furnace is usually placed in a belt furnace. In order to remove the organic binder, the organic medium is usually heated at 250 to 330 ° C in an air atmosphere, a nitrogen atmosphere or a mixed gas of air and nitrogen.

Conventionally, in the internal electrodes of the multilayer ceramic capacitor, a noble metal material such as palladium or a silver-palladium alloy has been used. However, in order to reduce the cost, a base metal such as nickel or copper is used. In the laminated ceramic capacitor using the internal electrodes of these metals, in order to prevent nickel, copper, etc. from being oxidized after removing the organic binder, it is necessary to fire in an neutral or reducing atmosphere and then at 850 to 1350 ° C to form internal electrodes. Integrated with the dielectric body.

A layered system in which internal electrodes such as nickel and copper are formed is honed by barrel honing, and the internal electrodes are exposed, and then the external electrode paste is applied to the honed end surface and fired for mounting on the surface. The product is formed after electroplating.

The internal electrode paste is composed of a base metal powder as a conductive component, a dielectric ceramic powder as a baking regulator, a resin as an organic binder, a solvent in which it is dissolved, a dispersant, and an additive, and is passed through a three-roll mill. Kneading was carried out and it was produced by mixing and dispersing. In other words, the internal electrode paste dissolves the resin forming the organic binder in an organic solvent to obtain an organic medium in which the metal powder is dispersed, and the organic solvent is used to adjust the viscosity.

As the organic solvent in the organic medium, terpineol is usually preferably used. Further, as the organic binder, a cellulose resin such as ethyl cellulose or nitrocellulose, or an acrylic resin such as butyl methacrylate or methyl methacrylate is used.

Therefore, in order to form the internal electrode, as described above, the internal electrode for MLCC is screen-printed on the dielectric green sheet with the conductive paste. However, in the manufacturing process of the MLCC, when the dielectric green sheet is fired, There is a problem that poor insulation, interlayer peeling between the dielectric layer and the internal electrode layer, and the like, resulting in severe product characteristics.

With the increase in the capacity of the multilayer ceramic capacitor, the dielectric green sheet is being thinned. In the past, a sheet thickness of 10 to 20 μm has been used in a thinner thickness of 2 to 5 μm in recent years.

That is, in the internal electrode paste, ethyl cellulose which is an organic binder as described above mainly uses terpineol as an organic solvent, but terpineol remains in the coating process during the printing and drying step. In the film, there is a role in which polyvinyl butyral, which is an organic binder, is dissolved in a dielectric green sheet. The dissolution of such an internal electrode paste on the organic binder in the dielectric green sheet is referred to as "plate corrosion."

Due to the corrosion of the sheet, the polyvinyl butyral in the dielectric green sheet is dissolved, and the dielectric green sheet is expanded and dissolved. When the sheet is highly corroded, pores are formed in the nickel paste printed portion at the time of lamination of the sheet, and the interlayer peeling occurs between the dielectric layer and the internal electrode layer during sintering. The thinner the dielectric green sheet is, the more significant the effect of sheet corrosion is.

Due to the influence of the sheet corrosion, the withstand voltage and insulation of the MLCC are lowered, the target electrostatic capacity cannot be obtained, and the load life characteristics are deteriorated. At present, in order to avoid corrosion of the sheet, the solvent component of the conductive paste has been studied.

For example, a conductive paste containing dihydroterpineol acetate (hydrogenated terpinel acetate) as a solvent has been proposed (see Patent Document 1). Further, a conductive paste containing a decane skeleton carboxylic acid adduct such as isodecyl propionate, isodecyl butyrate or isodecyl isobutyrate as a solvent has been proposed (see Patent Document 2).

However, although these solvents are considered to be effective for sheet corrosion avoidance, they have a problem that the evaporation rate is slow and the drying property after paste printing is inferior to that of the commonly used terpineol.

Further, in order to maintain flexibility, an additive such as a plasticizer is mixed in the dielectric green sheet, but since the green sheet is thinned in recent years, in order to maintain the flexibility after drying the green sheet, it is desirable to use a plasticizer in the sheet. There is no such requirement that evaporation disappears during drying, and it is necessary to further reduce the drying temperature of the paste and shorten the drying time. This is because if the dry state is less in the drying step after printing the nickel paste in the green sheet, disadvantages such as sheet sticking or breakage may occur in the subsequent steps.

In order to increase the drying speed of the paste, the applicant has proposed the use of dipropylene glycol methyl ether as a solvent (see Patent Document 3). However, although the solvent dries quickly, the sheet corrosion avoidance is less.

In this case, it is required to develop a conductive paste for internal electrodes which is excellent in drying property after printing, in order to increase the efficiency of the printing and drying step in recent years.

Patent Document 1: Japanese Patent No. 2976268

Patent Document 2: Japanese Laid-Open Patent Publication No. 2006-202502

Patent Document 3: Japanese Laid-Open Patent Publication No. Hei 11-306860

An object of the present invention is to provide a conductive paste for internal electrodes for screen printing on a dielectric green sheet containing polyvinyl butyral as a resin component in view of the problems of the prior art, especially even in green sheets. When the thickness is as small as 2 to 5 μm, it is possible to eliminate the sheet corrosion caused by the conductive paste and to improve the drying property, and it is possible to effectively suppress the conductive paste for the internal electrode of the multilayer ceramic capacitor due to the disadvantage caused by the conductive paste.

The inventors of the present invention have carefully studied the problems of the above-mentioned prior art, and used them as an organic solvent for dissolving ethyl cellulose resin in a conductive paste printed on a dielectric green sheet containing a polyvinyl butyral resin as an organic binder. The solvent is at least one of ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate. The conductive paste is screen printed on the dielectric green sheet, but the organic solvent does not dissolve the polyethylene shrinkage. The aldehyde resin does not cause sheet corrosion and has good drying property, so that workability can be improved. Further, it has been found that by using the above organic solvent, it is different from dihydroterpene alcohol acetate, isodecyl propionate, butyric acid. At least one of the oxime ester and the isodecyl isobutyrate can improve the evaporation rate of the latter solvent such as dihydroterpineol acetate and improve the problem with respect to drying property, and thus the present invention has been completed.

According to a first aspect of the present invention, there is provided a conductive paste for an internal electrode of a multilayer ceramic capacitor for printing on a dielectric green sheet containing a polyvinyl butyral resin, the conductive paste comprising a conductive powder (A) The organic resin (B) and the organic solvent (C) are characterized in that the organic solvent (C) is composed of at least one solvent selected from the group consisting of ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate.

Further, according to a second aspect of the present invention, there is provided a conductive paste for an internal electrode of a multilayer ceramic capacitor for printing on a dielectric green sheet containing a polyvinyl butyral resin, the conductive paste comprising a conductive powder (A) An organic resin (B) and an organic solvent (C), characterized in that the organic solvent (C) is at least one solvent selected from the group consisting of ethylene glycol monobutyl ether acetate or dipropylene glycol methyl ether acetate, and is selected from the group consisting of A mixed solvent of at least one of dihydroterpene alcohol acetate, isodecyl propionate, isodecyl butyrate or isodecyl isobutyrate.

According to a third aspect of the present invention, in the first or second aspect of the invention, the conductive powder (A) is selected from the group consisting of nickel, copper, gold, and silver. a metal powder of platinum, palladium or an alloy thereof.

According to a fourth aspect of the present invention, in the invention of any one of the first to third aspects, the conductive powder is provided in the total amount of the paste. The content of (A) is 30 to 70% by weight.

According to a fifth aspect of the invention, the conductive paste for the internal electrode of the multilayer ceramic capacitor according to any one of the first to fourth aspects, wherein the conductive powder (A) has a particle diameter of 0.05 to 0.05. 1.0 μm.

According to a sixth aspect of the present invention, in the invention of any one of the first to fifth aspects, the organic resin (B) contains ethyl cellulose.

Further, according to a seventh aspect of the present invention, there is provided a conductive paste for an internal electrode of a multilayer ceramic capacitor, characterized in that in the invention according to any one of the first to sixth aspects, the organic resin is The content of B) is from 1 to 5% by weight.

According to an eighth aspect of the present invention, there is provided a conductive paste for an internal electrode of a multilayer ceramic capacitor, characterized in that in the second invention, the organic solvent (C) is a glycol monobutyl ether acetate of the first solvent. a mixed solvent of at least one solvent selected from the group consisting of dihydroterpene alcohol acetate or isodecyl propionate of the second solvent, and a mixing ratio of ethylene glycol monobutyl ether acetate as the first solvent in a weight ratio It is calculated to be 20% or more and less than 100%.

According to a ninth aspect of the present invention, there is provided a conductive paste for an internal electrode of a multilayer ceramic capacitor, characterized in that in the second invention, the organic solvent (C) is a first solvent of ethylene glycol monobutyl ether acetate. And a mixed solvent of at least one solvent selected from the group consisting of isodecyl butyrate or isodecyl isobutyrate of the second solvent, and the mixing ratio of the ethylene glycol monobutyl ether acetate of the first solvent is 30 by weight. More than %, less than 100%.

According to a tenth aspect of the present invention, there is provided a conductive paste for an internal electrode of a multilayer ceramic capacitor, characterized in that in the second invention, the organic solvent (C) is a dipropylene glycol methyl ether acetate as a first solvent and The mixed solvent of the dihydroterpene alcohol acetate of the second solvent and the mixing ratio of the dipropylene glycol methyl ether acetate of the first solvent are 60% or more and less than 100% by weight.

According to an eleventh aspect of the present invention, there is provided a conductive paste for an internal electrode of a multilayer ceramic capacitor, characterized in that in the second invention, the organic solvent (C) is dipropylene glycol methyl ether acetate as a first solvent and The mixed solvent of isodecyl propionate as the second solvent has a mixing ratio of dipropylene glycol methyl ether acetate of the first solvent of 70% or more and less than 100% by weight.

According to a twelfth aspect of the present invention, there is provided a conductive paste for an internal electrode of a multilayer ceramic capacitor, characterized in that in the second invention, the organic solvent (C) is a dipropylene glycol methyl ether acetate of the first solvent and a mixed solvent of at least one solvent selected from the group consisting of isodecyl butyrate or isodecyl isobutyrate; the mixing ratio of dipropylene glycol methyl ether acetate of the first solvent is 80% or more by weight, less than 100%.

According to a thirteenth aspect of the present invention, there is provided a conductive paste for an internal electrode of a multilayer ceramic capacitor, characterized in that the first or second invention further comprises an inorganic additive (D) containing and forming a dielectric sheet. The same ingredients of the material.

Since the conductive paste for internal electrodes of the multilayer ceramic capacitor of the present invention has the above structure, when screen printing is performed on a dielectric green sheet containing polyvinyl butyral as a resin component, in particular, even if the thickness of the green sheet is thin, When it is 2 to 5 μm, the sheet corrosion due to the conductive paste can be eliminated and the drying property is good, and the occurrence of disadvantages due to it can be effectively suppressed.

Thereby, there is an effect that the laminated ceramic capacitor can be produced efficiently and at low cost without lowering the characteristics of the laminated ceramic capacitor.

In the following, the conductive paste for internal electrodes of the multilayer ceramic capacitor of the present invention (hereinafter also referred to as conductive paste) will be described in detail.

The conductive paste of the present invention is characterized in that it is a laminated ceramic comprising a conductive powder (A), an organic resin (B) and an organic solvent (C) which can be printed on a dielectric green sheet containing a polyvinyl butyral resin. In the conductive paste for a capacitor internal electrode, the organic solvent (C) is composed of at least one selected from the group consisting of ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate.

Further, the conductive paste of the present invention is characterized in that it is printed on a dielectric green sheet containing a polyvinyl butyral resin, and comprises a conductive powder (A), an organic resin (B), and an organic solvent (C). In the conductive paste for internal electrodes of a multilayer ceramic capacitor, the organic solvent (C) is at least one selected from the group consisting of ethylene glycol monobutyl ether acetate or dipropylene glycol methyl ether acetate, and is selected from the group consisting of dihydroterpineol. A mixed solvent composed of at least one of acetate, isodecyl propionate, isodecyl butyrate or isodecyl isobutyrate.

1. Conductive powder (A)

In the present invention, the conductive powder used in the conductive paste is not particularly limited, and may be any electrode of a laminate member such as a laminated ceramic capacitor. For example, nickel, copper, gold, silver, platinum, or palladium may be used. Or a metal powder or an alloy thereof. In particular, in order to increase the capacity, it is preferable to use nickel or copper which is advantageous in price among the internal electrodes of the high buildup multilayer ceramic capacitor having a large number of layers of electrodes.

The particle diameter of the conductive powder is not particularly limited. For the internal electrodes of the multilayer ceramic capacitor having a high buildup and a high capacity, the average particle diameter of these metal powders is preferably 0.05 to 1.0 μm. The average particle diameter is a value obtained by a scanning electron microscope (FE-SEM) photograph. When the average particle diameter exceeds 1.0 μm, it is difficult to achieve thinning of the multilayer ceramic capacitor. Further, when the average particle diameter is less than 0.05 μm, the surface activity of the metal powder is not too high, and an appropriate viscosity characteristic cannot be obtained, which may deteriorate in long-term storage of the conductive paste.

The content of the conductive powder in the conductive paste is preferably from 30 to 70% by weight based on the total amount of the paste. When the content is less than 30% by weight, the formation ability of the electrode film at the time of sintering is low, and it is difficult to obtain a predetermined capacitor capacity. When it exceeds 70% by weight, thinning of the electrode film is difficult. The content of the conductive powder is more preferably 40 to 60% by weight based on the total amount of the paste.

2. Organic resin (B)

In the present invention, examples of the organic resin include cellulose resins such as ethyl cellulose and nitrocellulose, and acrylic resins. In particular, in the ethyl cellulose resin which is preferable as the organic resin, there are various grades. For example, in the ethyl cellulose resin manufactured by Dow Chemical Co., Ltd., including a combination of grades STD type, MED type, HE type, and viscosity grade type 4, 10, 45, 100, 200, 350, etc. according to the ethoxy group content, via By selecting these resin grades, the viscosity of the organic medium can be adjusted.

Further, the ethyl cellulose resins are dissolved in the following solvent of the present invention, and thus an organic medium is obtained. The amount of the resin to be mixed is not particularly limited, and may be 1 to 30% by weight in the organic solvent. By combining with the above resin grade, an organic medium having an appropriate viscosity can be prepared. The amount of the resin to be mixed is preferably from 5 to 20% by weight in the organic medium.

Further, the content of the organic resin relative to the total conductive paste is preferably from 1 to 5% by weight. When the amount is less than 1% by weight, the strength of the dried film is lowered, and when the layer is laminated, the adhesion between the electrode pattern of the paste and the dielectric sheet is deteriorated, and the film is easily peeled off. On the other hand, when it exceeds 5% by weight, the content of the resin is large, and the debonding property is deteriorated to be unsatisfactory.

3. Organic solvent (C)

In the present invention, the organic solvent is an essential component of an organic medium having a function of dissolving an ethyl cellulose resin, but when printing on a dielectric green sheet, it is necessary to avoid sheet corrosion.

Specifically, in the present invention, as the organic solvent, at least one selected from the group consisting of ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate can be used alone (hereinafter, it is also referred to as the first organic Solvent) or, as the case may be, it is necessary to use at least one of the first organic solvent and one selected from the group consisting of dihydroterpene alcohol acetate, isodecyl propionate, isodecyl butyrate or isodecyl isobutyrate (also This is referred to as a second organic solvent), and such a mixed solvent composed of the first organic solvent and the second organic solvent is necessary.

As described above, when the internal electrode paste is connected to the dielectric green sheet, the organic medium (polyvinyl butyral) used in the dielectric green sheet is dissolved by the organic solvent in the internal electrode paste. produce. Therefore, the solvent must have the following properties: almost no solubility for the organic binder of the dielectric green sheet, and solubility to the ethyl cellulose resin of the internal electrode paste, and the dissolved substance thereof has a suitable viscosity which can be used as a paste. Sex.

Further, the organic solvent must have appropriate drying properties when the internal electrode paste is printed on the dielectric green sheet. If only the drying property is considered, it is also possible to consider only a substance having a low boiling point, for example, a solvent having a boiling point of 180 ° C or less, but the solvent is usually a substance having a low ignition point (for example, a temperature of < 70 ° C at 21 ° C, equivalent to a fire protection method). In the case of "hazardous substance class 4, second petroleum class"), in the case of treating a paste containing the solvent, it is necessary to adopt a safety in consideration of the safety of the paste product transportation in consideration of the risk of ignition in the operating environment. Rules, so you need to avoid the solvent with a low ignition point.

At present, with respect to the main solvent, it is attempted to improve the evaporation rate by adding a solvent composed of an aliphatic hydrocarbon or an aromatic hydrocarbon which is partially equivalent to the low-boiling petroleum type of the "hazardous substance class 4 second petroleum type", but The hydrocarbon solvent hardly dissolves the polyvinyl butyral and hardly dissolves the ethyl cellulose. Therefore, according to the added amount, not only the solubility of the ethyl cellulose in the paste composition is lowered, but also the resin is easily precipitated, the viscosity changes with time, and the paste is likely to be separated over time, which is not preferable.

Therefore, the results of measuring the evaporation rate of the organic solvent or the like used in the present invention by TG/DTA are shown in Fig. 1 . In the TG/DTA measurement, about 30 mg of various solvents were added to an alumina grid having a diameter of 5 mmφ, and the temperature was raised from room temperature to 120 ° C at a rate of 40 ° C/min in a TG/DTA apparatus (manufactured by SEIKO Co., Ltd.). In this state, it was maintained at 120 °C. Ambient conditions circulate air at a rate of 200 ml/min. In addition to the first organic solvent, the evaporation rates of various known solvents can be measured for comparison.

The graph of Fig. 1 is as follows: the left scale on the vertical axis indicates temperature, the right scale on the vertical axis indicates the evaporation ratio of the solvent, and the horizontal axis indicates time. Line 1 is a curve indicating temperature rise, and lines 2 to 6 each represent ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, terpineol, dihydroterpene alcohol acetate, and propionic acid The curve of the evaporation ratio of oxime ester. Ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate have a faster evaporation rate than terpineol, dihydrofurfuryl alcohol acetate or isodecyl propionate. Thus, since ethylene glycol monobutyl ether acetate or dipropylene glycol methyl ether acetate has a high evaporation rate, it is excellent in drying property after paste printing.

In addition, ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate are classified into the fourth petroleum category of the fire protection method, so the ignition point is high, the operation is safe, and the risk of transportation is small. . Therefore, these organic solvents can be used singly or in combination with each other.

Further, according to the measurement method of the TG/DTA apparatus, the drying property of the paste cannot be directly evaluated. However, the evaporation rate which cannot be determined only by the boiling point of the solvent can be quantitatively compared. Therefore, it can be used to search for a new solvent, and to evaluate and select a solvent monomer.

When ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate are used in combination, the mixing ratio is not particularly limited, and the mixing ratio may be adjusted in consideration of drying property.

Further, in the present invention, as the organic solvent (C), at least one selected from the group consisting of ethylene glycol monobutyl ether acetate or dipropylene glycol methyl ether acetate may be used as the first organic solvent. A mixed solvent of at least one selected from the group consisting of dihydroterpene alcohol acetate, isodecyl propionate, isodecyl butyrate or isodecyl isobutyrate.

Ethylene glycol monobutyl ether acetate or dipropylene glycol methyl ether acetate has the characteristics as described above, by mixing therein a mixture selected from the group consisting of dihydroterpene alcohol acetate, isodecyl propionate, isodecyl butyrate And at least one of isodecyl isobutyrate, so that an organic solvent which is low in cost and which can satisfy a certain evaporation rate and which can improve the drying property can be obtained.

When the first organic solvent and the second organic solvent are mixed, if there is no particular requirement for the drying condition of the paste, there is no limitation on the mixing ratio. However, as described in the background art, in order to prevent the plasticizer in the green sheet from evaporating and disappearing during drying, and to reduce the drying temperature of the paste and to shorten the drying time, etc., the following mixing ratio is suggested.

(C1) in the case where the first organic solvent is ethylene glycol monobutyl ether acetate

(1) In the case where at least one selected from the group consisting of dihydroterpineol acetate and isodecyl propionate is mixed as the second organic solvent, the first organic solvent is made 20% or more by weight, less than 100 %, so that drying at a lower temperature and in a short time can be obtained.

(2) In the case where at least one selected from the group consisting of isodecyl butyrate or isodecyl isobutyrate is used as the second organic solvent, the first organic solvent is 30% by weight or more and less than 100% by weight. Therefore, drying at a lower temperature and in a short time can be obtained.

(C2) in the case where the first organic solvent is dipropylene glycol methyl ether acetate

(3) In the case where dihydroterpineol acetate is mixed as the second organic solvent, the first organic solvent is made 60% or more by weight or less, and is less than 100%, so that a lower temperature can be obtained. Dryness in a short time.

(4) In the case where isodecyl propionate is mixed as the second organic solvent, the first organic solvent is made 70% or more by weight or less, and less than 100%, so that a lower temperature can be obtained in a short time. Dryness.

(5) In the case where at least one selected from the group consisting of isodecyl butyrate or isodecyl isobutyrate is used as the second organic solvent, the first organic solvent is made 80% by weight or more and less than 100% by weight. Therefore, drying at a lower temperature and in a short time can be obtained.

Briefly, the lower the evaporation rate of the second organic solvent, or the lower the evaporation rate of the first organic solvent mixed therewith, if the mixing ratio of the first organic solvent is not high, the lower temperature and the shorter temperature cannot be obtained. Dryness required in the dry state during the time.

4. Inorganic additives (D)

In the conductive paste for internal electrodes of the multilayer ceramic capacitor, in order to conform the sintering shrinkage of the internal electrode to the sintering shrinkage action of the ceramic sheet during firing, it is necessary to mix the inorganic additive. In general, the inorganic additive is also referred to as an auxiliary material, and other inorganic materials such as commercially available BaTiO ₃ , BaTi _x Zr _1-x O ₃ (x is 0.8), or the like, and the same composition as the ceramic constituting the green sheet may be appropriately mixed. Oxide, etc.

In the conductive paste of the present invention, the average particle diameter of the inorganic additive such as BaTiO ₃ is not particularly limited, and particularly preferably 0.01 to 0.1 μm if used in an internal electrode of a high-layer, high-capacity multilayer ceramic capacitor. . The average particle diameter was determined by scanning electron microscopy (FE-SEM). If the resistance value after firing was increased outside the range, the formation of the electrode film was insufficient, and the electrostatic capacity of the prepared multilayer capacitor could not be obtained.

Further, the content of the inorganic additive is not particularly limited, but is preferably from 1 to 30% by weight in the paste. When the content is less than 1% by weight, when the conductive paste and the dielectric sheet are simultaneously fired, a difference in sintering shrinkage occurs, and cracks are likely to occur in the sintered body, and if the content is more than 30% by weight, the conductivity is lowered. , electrostatic capacity cannot be obtained.

(other additives)

In the present invention, in order to improve the dispersibility or viscosity of the conductive powder, various additives may be mixed. For example, a dispersing agent, a surfactant, a chelating agent, an antifoaming agent, a plasticizer, a viscosity adjuster, etc. are mentioned. The printing characteristics of the conductive paste may be adjusted by mixing one or a combination of a plurality of commercially available additives in an organic medium.

5. Manufacture of conductive paste

Hereinafter, the procedure for preparing the conductive paste of the present invention will be described. The conductive paste of the present invention is prepared by first dissolving an organic resin in an organic solvent to prepare an organic medium, and then adding a conductive powder, an inorganic additive, and other additives, and dispersing in an organic medium.

First, an organic solvent such as an ethyl cellulose resin and ethylene glycol monobutyl ether acetate or dipropylene glycol methyl ether acetate is prepared. The ethyl cellulose resin was gradually added to the thermostat bath which heated the solvent to 50 to 60 ° C, and then the resin was stirred until dissolved and heated at the same time.

Then, weigh a predetermined amount of conductive powder, inorganic additive, and prepared organic medium, add it to the mixer, add other additives as appropriate, stir, and then uniformly disperse and mix the conductive powder, inorganic additives, and the organic medium in a three-roll mill. Other additives.

The conductive powder is preferably 30 to 70% by weight based on the total amount of the paste, and the inorganic additive is preferably 1 to 30% by weight based on the total amount of the paste, and the other additives are preferably 1 with respect to the total amount of the paste. ～3% by weight. Further, the resin in the organic medium is preferably from 1 to 5% by weight based on the total amount of the paste. The viscosity of the conductive paste can be appropriately adjusted depending on the printing method or printing conditions. As an example, the paste viscosity in the printing step in the screen printing can be 10 rpm on the rotating shaft according to a Brookfield B-type viscometer. (The shear rate is 4 s ^-1 /25 ° C), and the viscosity is adjusted to be about 10 to 30 Pa ‧ s.

Thereby, the conductive powder and the inorganic additive can be sufficiently dispersed in the organic medium, and the conductive paste of the present invention obtained by suppressing the sheet corrosion at the time of forming the internal electrode of the multilayer ceramic capacitor can be suppressed.

Example

Hereinafter, the examples and comparative examples of the present invention will be described in detail, but the present invention is not limited by the following examples.

(Evaluation of raw tablets)

A barium titanate-based dielectric green sheet having a thickness of about 3 μm of a polyvinyl butyral resin was prepared and used to evaluate the characteristics of the organic solvent. The green sheet was obtained by coating a barium titanate-based dielectric paste with a doctor blade on a PET film of about 10 μm and drying it so as to have a dry film thickness of about 3 μm.

(dryness)

The dried nickel foil conductive paste was adjusted to have a dry film thickness of 2 μm on the green sheet, screen printed, and the green sheet was dried at 60 ° C for 1 minute to form an electrode pattern. The dried film of the conductor paste was observed from the upper portion with a stereoscopic microscope, and the dryness was confirmed from the surface state of the dried body. In addition, the drying condition at 60 ° C for 1 minute is based on the requirement that the plasticizer in the extremely thin green sheet does not evaporate during drying, and the drying temperature is required to be lower, and the drying time is shortened. Required level.

The judgment that the drying was complete was ○, the surface was still partially wet, the drying was insufficient, and the determination was Δ, and the determination that all were not dried was ×.

(plate corrosive)

After confirming the drying property, in order to confirm the sheet corrosivity, the inner surface of the printed sheet was observed with a stereoscopic microscope to confirm the expansion or deformation of the sheet.

The case where there is substantially no change is denoted by ○, the case where there is swelling or deformation is denoted by Δ, and the case where dissolution and rupture is denoted by ×.

(sheet peel test)

After evaluating the corrosiveness of the sheet, the adhesive sheet was peeled off from the PET film using the adhesive tape, and it was confirmed whether or not the printed portion of the conductive paste was peeled off without any problem.

The portion where the printed pattern portion was smoothly peeled off was denoted by ○, and the portion where the printed pattern portion was broken was denoted by ×.

(Examples 1 to 2)

(Manufacture of organic media)

Ethylene glycol monobutyl ether acetate or dipropylene glycol methyl ether acetate shown in Table 1 was used as an organic solvent, and an ethyl cellulose resin was dissolved therein to prepare an organic medium used in the internal electrode paste.

Each solvent was heated with a heater to a temperature of 60 ° C, stirred with a stirring paddle and slowly added to the ethyl cellulose resin to dissolve, thereby obtaining an organic medium. In order to confirm that the resin was completely dissolved, a part of the dissolved matter was taken out, and it was confirmed that there was no residue of the resin on the sample.

The content of ethyl cellulose was 15 parts by weight based on 100 parts by weight of the total solvent. As the ethyl cellulose, the grades STD-45 and STD-300 manufactured by Dow Chemical Co., Ltd. were used in combination, and the mixing ratio of the two was adjusted to achieve a predetermined viscosity to prepare a test organic medium.

(Manufacture of conductive paste)

Then, using the above organic medium, a nickel paste was prepared as follows.

100 parts by weight of nickel powder having an average particle diameter of 0.2 μm as a conductive powder, 20 parts by weight of a barium titanate powder having a commercially available average particle diameter of 0.1 μm as an inorganic additive, and 73 parts by weight of 73 bar parts as shown in Table 1 were mixed with a mixer. An organic medium of various organic solvents, an appropriate amount of other additives, a honing base material, and a three-roll mill kneading dispersion. In order to adjust the viscosity, the same solvent as used in the organic medium to be used was added, and the viscosity of the paste was diluted and adjusted to have a viscosity of 10 rpm of 10 to 30 Pa·s measured by a Brookfield B-type viscometer to obtain a nickel conductive paste.

Table 1 shows the evaluation results of the drying property, the sheet corrosion, and the sheet peeling test of the conductive paste prepared using various solvents.

(Comparative Examples 1 to 8)

Except for the organic solvent instead of the terpineol, dihydroterpene alcohol acetate, isodecyl propionate, isodecyl butyrate, isodecyl isobutyrate shown in Table 1, and Examples 1, 2 A conductive paste (Comparative Examples 1 to 5) was prepared in the same manner.

Further, a conductive paste (Comparative Examples 6 to 8) was prepared in the same manner as in Examples 1 and 2 except for diethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether.

Table 1 shows the evaluation results of the drying property, the sheet corrosion, and the sheet peeling test of the conductive paste prepared using various solvents.

As shown in Table 1, in Examples 1 and 2, since ethylene glycol monobutyl ether acetate and dipropylene glycol methyl ether acetate were used as the solvent, all of them were in the drying property, the sheet corrosion, and the sheet peeling test. Shows good results.

On the other hand, in Comparative Example 1, terpineol was used as a solvent, and the sheet corrosion was inferior, and voids were formed in the sheet. In Comparative Examples 2 to 5, the sheet corrosion property was good, but the drying property at 60 ° C - 1 minute was inferior, and in Comparative Examples 6 to 7, the sheet corrosion property and the drying property at 60 ° C - 1 minute were inferior, and in the comparative example. Among them, the drying property at 60 ° C for 1 minute was good, but the sheet corrosion was inferior, and it was confirmed that there was a significant difference compared with Examples 1 and 2. Further, in Comparative Examples 2 and 3, it was judged that these solvents were not suitable for use alone in the drying property of 60 ° C - 1 minute.

(Examples 3 to 10) (Comparative Examples 9 to 10)

As the first solvent, ethylene glycol monobutyl ether acetate is used, and as the second solvent, dihydroterpineol acetate, isodecyl propionate, isodecyl butyrate, isodecyl isobutyrate, The mixed solvent was mixed at various ratios, and a conductive paste (Examples 3 to 10) was prepared in the same manner as in Examples 1 and 2.

Further, as the first solvent, ethylene glycol monobutyl ether acetate was used, and as the second solvent, a conductive paste (Comparative Examples 9 to 10) was prepared in the same manner.

Table 2 shows the evaluation results of the drying property, the sheet corrosion, and the sheet peeling test of the conductive paste prepared using various mixed solvents.

From Examples 3 and 4 of Table 2, in the case of using a mixed solvent of ethylene glycol monobutyl ether acetate and dihydroterpene alcohol acetate, the drying property was improved as compared with Comparative Example 2, but the permeation was mixed. 20% by weight of ethylene glycol monobutyl ether acetate can further improve low temperature and short-term drying.

In Examples 5 and 6, when a mixed solvent of ethylene glycol monobutyl ether acetate and isodecyl propionate was used, the drying property was improved as compared with Comparative Example 3, but the mixture was mixed by 20% by weight or more. Ethylene glycol monobutyl ether acetate can further improve low temperature and short-term drying.

From Examples 7 and 8, in the case of using a mixed solvent of ethylene glycol monobutyl ether acetate and isodecyl butyrate, the drying property was improved as compared with Comparative Example 4, but the weight ratio was 30. The ethylene glycol monobutyl ether acetate having a % by weight or more can further improve the low temperature and short-term drying property.

From Examples 9 and 10, in the case of using a mixed solvent of ethylene glycol monobutyl ether acetate and isodecyl isobutyrate, the drying property was improved as compared with Comparative Example 5, but the weight ratio was mixed. The ethylene glycol monobutyl ether acetate of 30% by weight or more can further improve the low temperature and short-term drying property.

On the contrary, from Comparative Examples 9 and 10, if ethylene glycol monobutyl ether acetate was mixed with terpineol, the drying property was improved as compared with Comparative Example 1, but no improvement in sheet corrosivity was observed.

(Examples 11 to 18) (Comparative Examples 11 to 12)

Using dipropylene glycol methyl ether acetate as the first solvent, using dihydroterpene alcohol acetate, isodecyl propionate, isodecyl butyrate, isodecyl isobutyrate as the second solvent, mixed in various ratios A mixed solvent was prepared, and a conductive paste (Examples 11 to 18) was prepared in the same manner as in Examples 1 and 2.

Further, a conductive paste (Comparative Examples 11 to 12) was prepared in the same manner by using dipropylene glycol methyl ether acetate as the first solvent and terpineol as the second solvent.

Table 3 shows the evaluation results of the drying property, the sheet corrosion, and the sheet peeling test of the conductive paste prepared using various mixed solvents.

From Examples 11 and 12 of Table 3, in the case of using a mixed solvent of dipropylene glycol methyl ether acetate and dihydroterpene alcohol acetate, the drying property was improved as compared with Comparative Example 2, and 60% by weight was mixed. Dipropylene glycol methyl ether acetate of a ratio or more can further improve the low temperature and short-time drying property.

In Examples 13 and 14, when a mixed solvent of dipropylene glycol methyl ether acetate and isodecyl propionate was used, the drying property was improved as compared with Comparative Example 3, and by mixing 70% by weight or more of dipropylene glycol A Ether acetate can further improve low temperature and short-term drying.

In Examples 15 and 16, when a mixed solvent of dipropylene glycol methyl ether acetate and isodecyl butyrate was used, the drying property was improved as compared with Comparative Example 4, and 80% by weight or more of dipropylene glycol was permeated. Ether acetate can further improve low temperature and short-term drying.

From Examples 17 and 18, when a mixed solvent of dipropylene glycol methyl ether acetate and isodecyl isobutyrate was used, the drying property was improved as compared with Comparative Example 5, and 80% by weight or more of dipropylene glycol was mixed. Methyl ether acetate can further improve the low temperature and short-term drying property.

On the contrary, in Comparative Examples 11 and 12, if dipropylene glycol methyl ether acetate was mixed with terpineol, the drying property was improved as compared with Comparative Example 1, but no improvement in sheet corrosivity was observed.

Fig. 1 is a graph showing the results of confirming the evaporation rates of various solvents by TG/DTA.

Claims (7)

A conductive paste for internal electrodes of a multilayer ceramic capacitor, characterized in that it is printed on a dielectric green sheet containing a polyvinyl butyral resin, and contains conductive powder (A), organic resin (B), and first mixing. a conductive paste for internal electrodes of a laminated ceramic capacitor of a solvent (c1) and an organic solvent (C) of a second solvent (c2); wherein the first solvent (c1) is dipropylene glycol methyl ether acetate, and the second solvent (c2) Is composed of at least one solvent selected from the group consisting of dihydroterpineol acetate, isodecyl propionate, isodecyl butyrate, or isodecyl isobutyrate; and the mixing ratio of the first solvent is in the first When the disolvent is dihydroterpene alcohol acetate, it is 60% or more and less than 100% by weight, and when the second solvent is isodecyl propionate, it is 70% or more and less than 100% by weight. When the second solvent is isodecyl butyrate or isodecyl isobutyrate, it is 80% or more and less than 100% by weight. The conductive paste for internal electrodes of a multilayer ceramic capacitor according to the first aspect of the invention, wherein the conductive powder (A) is a metal powder selected from the group consisting of nickel, copper, gold, silver, platinum, palladium or alloys thereof. The conductive paste for internal electrodes of a multilayer ceramic capacitor according to claim 1 or 2, wherein the content of the conductive powder (A) is 30 to 70% by weight based on the total amount of the paste. The conductive paste for internal electrodes of a multilayer ceramic capacitor according to claim 1 or 2, wherein the conductive powder (A) has a particle diameter of 0.05 to 1.0 μm. The conductive paste for internal electrodes of a multilayer ceramic capacitor according to the first aspect of the invention, wherein the organic resin (B) contains ethyl cellulose. The conductive paste for internal electrodes of a multilayer ceramic capacitor according to claim 1 or 5, wherein the content of the organic resin (B) is 1 to 5% by weight based on the total amount of the paste. The conductive paste for internal electrodes of a multilayer ceramic capacitor according to the first aspect of the invention, further comprising an inorganic additive (D) containing the same components as those constituting the dielectric sheet.