JP7143875B2 - Multilayer ceramic capacitor internal electrode paste and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductive paste capable of obtaining a high conductive film density, a method for producing the same, and a conductive film obtained from the conductive paste. In particular, the present invention relates to a conductive paste used for forming internal electrodes of a multilayer ceramic capacitor, a method for producing the same, and a conductive film having a high conductive film density.

A multilayer ceramic capacitor (MLCC) has an integrated structure in which ceramic dielectric layers and internal electrode layers are alternately stacked. Powders of noble metals such as palladium are conventionally used as conductive powders for forming internal electrodes of laminated ceramic capacitors. However, at present, from the viewpoint of cost reduction, nickel powder or nickel-based alloy powder is mainly used instead of noble metal powder.

Multilayer ceramic capacitors are generally manufactured by printing a conductive paste, in which conductive powder is dispersed in a vehicle, on a ceramic green sheet, stacking them in multiple layers, and applying heat and pressure to integrate them. The binder is removed by firing at a temperature of 500° C. or less in an oxidizing atmosphere or an inert atmosphere (binder removal step), followed by firing in a reducing atmosphere so as not to oxidize the internal electrodes. (baking process).

In recent years, along with the miniaturization of electronic equipment, miniaturization of various electronic components is progressing rapidly, and multilayer ceramic capacitors are also being miniaturized and increased in capacity. Specifically, multilayer ceramic capacitors have been made multi-layered and internal electrode layers have been made thinner, and it has become necessary to make the dielectric layers and internal electrode layers that constitute them thinner. come. As the dielectric layers of laminated ceramic capacitors become thinner, the thickness of the internal electrodes of laminated ceramic capacitors after sintering has become as thin as about 1 μm at present, and those with a thickness of 1 μm or less have begun to be provided.

In order to reduce the thickness of the internal electrode layers printed on the ceramic green sheets, it is necessary to reduce the particle size of the nickel powder contained in the conductive paste that forms the internal electrodes. Therefore, nickel powder with an average particle size of 0.5 μm or less, and nickel powder with an average particle size of 0.3 μm or less has been required.

Furthermore, the nickel powder used in the conductive paste for the internal electrodes of laminated ceramic capacitors is required to have a high density (conductive film density) even in a conductive film obtained by printing the conductive paste and drying it. .

The conductive film density has a great influence on the occurrence of cracks in the electrodes during manufacturing of the multilayer ceramic capacitor. After the nickel powder is made into a conductive paste, it is printed on the ceramic green sheet and dried there. At this time, in the case of a nickel powder having poor dispersibility or a nickel powder that cannot maintain its dispersibility and agglomerates in the paste, a large number of voids are present in the conductive film, and as a result, , the conductive film becomes thicker. Therefore, since the printing area is constant, the density of the conductive film becomes low when the film thickness is large.

When a low-density conductive film is used to manufacture a multilayer ceramic capacitor, the amount of shrinkage increases in the subsequent firing process in order to fill the voids between the nickel powders during sintering. As a result, a large amount of shrinkage mismatch with the dielectric layer occurs, which may cause a problem of frequent occurrence of structural defects such as cracks. In addition, due to the presence of many voids in the conductive film, shrinkage during sintering cuts off the internal electrode layers, resulting in a problem that the capacity of the multilayer ceramic capacitor is insufficient. Therefore, particularly in the thin internal electrode layers, the conductive film density is required to be high.

In response to the demand for nickel powder used in laminated ceramic capacitors, for example, Patent Document 1 discloses that the particle size distribution is (d10+d90)/d50 of 3.0 to 6.0 and the specific surface area is 1.0 m ² /g. Nickel powders characterized by ˜1.6 m ² /g have been proposed. Patent Document 1 focuses on increasing the CV value and tap density of the nickel powder in order to improve the sintering behavior of the nickel powder.

In Patent Document 2, the bulk density is 1.7 g/cm ³ to 3.5 g/cm ³ and the particle size is 1.5 times or more the average particle size (d50 value) measured by laser diffraction scattering particle size distribution measurement. A nickel powder has been proposed in which the number of particles is 20% or less of the total number of particles, and the number of particles having a particle diameter of 0.5 times or less of the average particle diameter (d50 value) is 5% or less of the total number of particles. . According to Patent Document 2, it has excellent dispersibility in a vehicle, high filling rate in a conductive paste, excellent particle size distribution, and resistance to dielectric breakdown.

However, the nickel powders described in Patent Documents 1 and 2 do not give sufficient consideration to their dispersibility, and when used to form thin internal electrode layers, they do not necessarily have a high conductive film density. Structural defects such as cracks and lack of capacity may occur.

Patent Document 3 proposes a nickel powder having an average particle size of 0.1 μm to 0.4 μm, a water content of 1.2% by mass or less, and an oxygen content of 2.0% by mass or less. there is In Patent Document 3, by reducing the content of water, which is a factor that reduces the density of the conductive film, and the nickel oxide and nickel hydroxide contained in the nickel powder, and further preventing the deterioration of the dispersibility caused by the inclusion of these, It is said that a high conductive film density can be obtained.

Patent Documents 1 to 3 described above focus on nickel powder, but from these contents, it can be easily assumed that the dispersibility of nickel powder is also affected by the constituent components of the conductive paste. be.

In Patent Document 4, in order to obtain an internal electrode layer that is dense and excellent in continuity, nickel powder having a carbon component content mass ratio of 0.06% or less and an average particle size of less than 0.20 μm and an average particle size of A conductive paste containing at least ceramic powder having a diameter of less than 0.10 μm has been proposed. However, Patent Document 4 does not particularly mention the relationship between the constituent components of the conductive paste and the dispersibility of the nickel powder, and the solvent simply has the function of dispersing inorganic components such as nickel powder in the paste. It merely describes that a dispersant can be added as a constituent component of the conductive paste.

JP 2005-248198 A JP-A-2001-266653 JP 2011-174121 A JP 2008-277066 A

Therefore, if the present invention is used to form the internal electrode layers of a thin laminated ceramic capacitor, a dense and highly continuous internal electrode layer can be obtained, resulting in a laminated ceramic capacitor free from structural defects such as cracks and lack of capacity. An object of the present invention is to provide a conductive paste and a method for producing the same.

In view of the above-mentioned problems of the prior art, the inventor of the present invention has extensively researched a conductive paste used for forming a multilayer ceramic capacitor. As a result, the inventors of the present invention have found that the above-described problems can be solved at the same time by setting the physical properties of the dispersant in the conductive paste within a specific range. The present invention has been completed based on this finding.

That is, a multilayer ceramic capacitor internal electrode paste according to the present invention for achieving the above object is a multilayer ceramic capacitor internal electrode paste containing nickel powder, a vehicle, a dispersant, and a dielectric powder as main components, X _{i-ac is the} acid value of the organic compounds X ₁ , X ₂ , . When the mass part of the organic compound to the part is w _i (i = 1 to n), the following formulas (I) and (II) are satisfied, and the content of the dispersant (Σw _i ) is 100 parts by mass of the nickel powder and the dispersant contains an organic compound having reactivity to both acids and bases, and at least one component of the organic compound has an acid value or an amine value of 350 mgKOH/g It is characterized by the following .

A method for producing a laminated ceramic capacitor internal electrode paste is a method for producing a laminated ceramic capacitor internal electrode paste containing nickel powder, a vehicle, and a dispersant, wherein the nickel powder and the dispersant are added to the vehicle, It is characterized by kneading these mixtures.

According to the present invention, by using the obtained conductive paste for the internal electrode layers of a thin laminated ceramic capacitor, dense and highly continuous internal electrode layers can be obtained, and structural defects such as cracks and insufficient capacity can be obtained. It is possible to realize a multilayer ceramic capacitor without

According to the present invention, a high conductive film density can be obtained even in a conductive film containing a conductive powder to which a dispersant is adsorbed.

A specific embodiment (hereinafter referred to as "this embodiment") to which the present invention is applied will be described in detail along the following items. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

1. Conductive paste 1-1. Conductive powder 1-2. Vehicle 1-3. Dispersant 1-4. Other constituents 2 . Method for producing conductive paste 3 . Manufacturing method of multilayer ceramic capacitor

[1. Conductive paste]
The conductive paste according to this embodiment is obtained by dispersing a conductive powder, a dispersant and other components in a vehicle. Hereinafter, the conductive paste will be described separately for each component.

(1-1. Conductive powder)
As the conductive powder, at least one powder selected from nickel (Ni) powder, copper (Cu) powder, palladium (Pd) powder, and silver (Ag) powder can be used. Also, the conductive powder may be an alloy powder containing these metal species as a main component. Among these, low-cost nickel powder or copper powder is more preferable.

The conductive paste is not limited by the average particle size of the conductive powder, but from the viewpoint of thinning the internal electrode layer, the conductive powder having an average particle size of 1.0 μm or less is used. is preferably 0.5 μm or less, more preferably 0.3 μm or less.

A conductive powder having an average particle size of more than 1.0 μm contains a large proportion of coarse particles, which is not only disadvantageous for thinning the multilayer ceramic capacitor, but also causes the coarse particles in the internal electrode layers to form in the ceramic dielectric layers. By penetrating the , an electrical short may occur, resulting in a capacity shortage. The lower limit of the average particle size is not particularly limited, but if it is less than 0.05 μm, the surface activity of the metal powder becomes too high, proper viscosity characteristics cannot be obtained, and the conductive paste deteriorates during long-term storage. there is a risk of

Therefore, the average particle size of the conductive powder is preferably 0.05 μm to 1.0 μm. Also, the average particle size of the conductive powder can be obtained from scanning electron microscope (SEM) photographs.

(1-2. Vehicle)
The vehicle is not particularly limited, and a uniform mixture of a solvent and a binder can be used. For example, terpineol, butyl carbitol acetate, butyl carbitol, dihydroterpineol, dihydroterpineol acetate, etc. can be used as the solvent. As the binder, celluloses such as ethyl cellulose, polyvinyl butyral, and the like can be used.

The content of the binder in the vehicle is not particularly limited, and should be appropriately selected according to its application and required properties. It is preferably adjusted to 1.5 parts by mass to 6 parts by mass, more preferably 1.5 parts by mass to 6 parts by mass.

The content of the vehicle in the conductive paste is not particularly limited as long as each constituent component is uniformly dispersed. It is more preferably 65 parts by mass, and even more preferably 50 to 60 parts by mass.

(1-3. Dispersant)
As the dispersant, at least an acidic organic compound having reactivity to a base and a basic organic compound having reactivity to an acid are required.

As described above, the conductive powder has a small average particle size of 1 μm or less, and therefore has a high surface reactivity. Therefore, conventionally, a dispersant composed of an acidic organic compound having reactivity with a base has been mainly used in order to improve the dispersibility of the conductive powder.

However, the surface of the conductive powder has both basic reaction points that react with acids and acidic reaction points that react with bases. Therefore, by coexisting an acidic dispersant that is reactive with a base and a basic dispersant that is reactive with an acid, not only the basic reaction points on the surface of the conductive powder but also , the dispersant can also be adsorbed on the acidic reaction sites. This action prevents non-volatile components such as conductive powder and binder from agglomerating in the process of evaporating the solvent after the conductive paste is printed on the ceramic green sheet, thereby increasing the density of the conductive film.

Here, the conductive film density (g/cm ³ ) is calculated from the weight and film thickness of the conductive film using the following formula. The term "conductive film" as used herein refers to a dry film obtained by drying a conductive paste applied on a substrate. Although the details will be described later, the characteristics of the internal electrode layers of the laminated ceramic capacitor can be estimated by measuring the conductive film density of the dry film.

Conductive film density (g/cm ³ )
= conductive film weight of conductive paste (g) / volume of conductive film (cm ³ )

The organic compound used for the dispersant may be an organic compound that is reactive with both acids and bases, or at least two kinds of an organic compound that is reactive with bases and an organic compound that is reactive with acids. Although any mixture of more organic compounds may be used, a mixture is preferable in consideration of the content ratio and the upper limit of the content of the dispersant, etc., which will be described later.

The surface of the conductive powder tends to have more basic reactive sites than acidic reactive sites. Therefore, in order to sufficiently increase the density of the conductive film, the total amount of reactivity of the dispersant to bases should be greater than the total amount of reactivity of the dispersant to acids so that the dispersant is sufficiently adsorbed on the surface of the conductive powder. is preferred.

Furthermore, it is preferable that the dispersant has a total amount of reactivity to a base that is equal to or greater than the basic reaction points on the surface of the conductive powder. This cannot be explained only by the basic reaction points on the surface of the conductive powder, and the reason is unknown, but it is known that the basic reaction points on the surface of the conductive powder also contribute to promoting the decomposition of the binder. Therefore, in order to suppress the aggregation of the conductive powder including the binder, it is considered that the amount of the dispersant at least equivalent to the basic reaction points on the surface of the conductive powder is required.

The reactivity of an organic compound to a base and an acid can be quantified by expressing it as an acid value and an amine value, respectively. Here, the acid value (mgKOH/g) is obtained by potentiometric titration in accordance with JIS K0070. The amine value (mgKOH/g) is obtained by potentiometric titration using a 0.1N aqueous solution of hydrochloric acid, and then converted to the equivalent of potassium hydroxide. Of course, the acid value and amine value may be obtained by known methods other than the potentiometric titration method.

Also, the acidic solution for determining the amine value is not limited to the hydrochloric acid aqueous solution, and a known one may be appropriately selected in consideration of the solubility with the object to be measured. Thus, for example, an acidic organic compound that is reactive towards bases has a specific acid number.

Using the acid value and the amine value, assuming that _n kinds of organic compounds (n is a natural number of 1 or more) are used as dispersants, the respective organic compounds X ₁ , X ₂ , . When X _i-ac is the valence, X _i-am is the amine value, and w _i (i=1 to n) is the part by mass with respect to 100 parts by mass of the conductive powder, for example, the total amount of reactivity to the base is the conductive It is expressed as Σ(X _i−ac ·w _i ) with respect to the mass of the powder. Therefore, as the dispersant, one that satisfies the following formulas (I) and (II) is used.

In formula (I), the total amount of reactivity to base (Σ(X _i-ac ·w _i )) is relative to the total amount of reactivity to acid (Σ(X _i-am ·w _i )) is insufficient, sufficient dispersibility cannot be obtained, and the density of the conductive film may decrease.

If the total amount of acid reactivity (Σ(X _i−am ·w _i )) is less than 15 mgKOH·parts by mass/g, the absolute amount of the organic compound having acid reactivity is insufficient, resulting in a decrease in the conductive film density. Sometimes. It should be noted that the greater the total amount of reactivity (Σ(X _i−am ·w _i )) with respect to acid, the better the dispersibility.

In the formula (II), if the total amount of base-reactivity is less than 40 mgKOH·parts by mass/g, the absolute amount of the base-reactive organic compound may be insufficient and the density of the conductive film may decrease. On the other hand, the upper limit of the total amount of reactivity to a base is naturally determined by the type of organic compound used in the dispersant and the upper limit of the content of the dispersant, which will be described later, and is not particularly defined here.

In the conductive powder, the smaller the average particle size, the larger the specific surface area (m ² /g). A higher value is preferred.

For conductive powders with an average particle size of 0.5 μm or less (0.05 μm to 0.5 μm), the total amount of reactivity to bases is 50 mg KOH·parts by mass/g, as shown in formula (III) below. It is more preferable to set it as above.

In addition, for conductive powder having an average particle size of 0.3 μm or less (0.05 μm to 0.3 μm), the total amount of reactivity to a base is 60 mg KOH parts by mass, as shown in the following formula (IV). / g or more is more preferable.

The organic compound used as the dispersant is preferably an organic compound in which at least one component used as the dispersant has an acid value and an amine value of 20 mgKOH/g to 350 mgKOH/g. Of course, the acid value or amine value of these organic compounds may be within the above ranges, or both the acid value and amine value may be within the above ranges.

At least one component means that when a plurality of organic compounds are used as a dispersant, at least one component is an organic compound within this range, and an organic compound outside this range can also be used as a dispersant. means.

When only an organic compound having an acid value and an amine value of less than 20 mgKOH/g is used as a dispersant, as can be seen from the relationships shown in formulas (I) to (IV), it is necessary to increase parts by mass of the dispersant with respect to the conductive powder. There are cases where the effects of the present invention cannot be obtained due to the relationship with other constituent components.

When an organic compound having an acid value and an amine value exceeding 350 mgKOH/g is used as a dispersant, the organic compound has a relatively small molecular weight and a low ratio of functional groups other than those contributing to adsorption with the conductive powder. Therefore, even if a sufficient amount is contained, the effect of dispersing the conductive powder may not be exhibited.

The content (Σw _i ) of the dispersant is preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, in total with respect to 100 parts by mass of the conductive powder. If the content of the dispersant exceeds 2.0 parts by mass, the effect of the conductive paste may not be obtained due to the relationship with other constituent components. The lower limit is not specified here because it is naturally determined by the type of organic compound used in the dispersant and the relationship between the formulas (I) and (II).

The type of organic compound used in the dispersant is not limited to the following, but examples of acidic organic compounds having reactivity to bases include aliphatic carboxylic acids, polyoxyethylene alkyl ether carboxylic acids, n- Acylsarcosine, n-acylglutamic acid, alkyl phosphate, polyoxyethylene alkyl ether phosphate and derivatives and polymers thereof are preferred. Alkylamines, polyoxyethylenealkyletheramines, alkylaminoamides, and derivatives and polymers thereof are preferred as the basic organic compounds reactive to acids. As the organic compound reactive with both acids and bases, amino acids, derivatives and polymers thereof, and salts of acidic organic compounds and basic organic compounds are preferred.

(1-4. Other constituents)
In the conductive paste, dielectric powder, a viscosity modifier, a flame retardant, an anti-settling agent, etc. may be added in addition to the dispersant described above, depending on the application.

The dielectric powder is also called a common material, and is sometimes included in the conductive paste for the purpose of matching the sintering behavior of the internal electrode layers with the sintering behavior of the ceramic green sheets during firing. When the dielectric powder is contained, its composition, particle size and content are appropriately selected according to the average particle size of the target ceramic green sheet and conductive powder.

The viscosity modifier is a component added to adjust the viscosity of the conductive paste when it is not possible to print well on an object such as a ceramic green sheet with only the conductive powder, vehicle and dispersant described above.

From the viewpoint of imparting suitable drying properties and solubility to the conductive paste, such a viscosity modifier must contain a petroleum-based hydrocarbon as a main component. In particular, the viscosity modifier preferably has a boiling point in the range of 150°C to 260°C, more preferably in the range of 160°C to 200°C.

If the boiling point of the viscosity modifier is less than 150° C., the drying time is very short and the viscosity of the conductive paste increases rapidly during printing, making it difficult to form desired internal electrode layers. On the other hand, if the boiling point exceeds 260° C., the drying properties are significantly deteriorated, and a long time is required for drying after printing, making it difficult to dry the conductive paste in a normal drying process.

Viscosity modifiers that satisfy the above conditions include, for example, those mainly composed of methylethylbenzene, trimethylbenzene, tridecane, nonane, cyclohexane, and the like. Specifically, A solvent manufactured by Idemitsu Kosan Co., Ltd. (trade name, boiling point: 150 ° C. to 200 ° C.), dry solvent soft manufactured by JX Nippon Oil & Energy Co., Ltd. (trade name, boiling point: 160 ° C. to 195 ° C.) , S solvent (trade name, boiling point: 200° C. to 260° C.).

The viscosity modifier does not show any effect even if it is added in a small amount to the conductive paste, and the content thereof is preferably 10 parts by mass to 50 parts by mass, more preferably 10 parts by mass with respect to 100 parts by mass of the conductive powder. parts to 40 parts by mass. If the content of the viscosity modifier is less than 10 parts by mass, the above effects cannot be sufficiently obtained. On the other hand, if the content of the viscosity modifier exceeds 50 parts by mass, the viscosity is significantly reduced, the conductive paste bleeds during printing, and it becomes difficult to control the thickness of the internal electrode layers within the desired range.

Additives such as flame retardants and anti-settling agents (hereinafter simply referred to as "additives") are added for desired purposes, and those having a decomposition temperature in the range of 150°C to 350°C are preferred. If the decomposition temperature is less than 150° C., it may easily decompose during mixing or kneading, and the effect of adding the additive may not be obtained. On the other hand, if the decomposition temperature exceeds 350°C, structural defects such as cracks and delamination may occur due to gases generated by thermal decomposition of these other additives during the binder removal process or firing process during the manufacture of the multilayer ceramic capacitor. may occur.

The total content of the additive is preferably 1.0 parts by mass or less, more preferably 0.5 parts by mass or less, with respect to 100 parts by mass of the conductive powder. If the content of the additive exceeds 1.0 part by mass, the effects of the present invention may not be obtained due to the relationship with other constituent components.

[2. Method for producing conductive paste]
The conductive paste according to this embodiment can be produced by the same method as in the prior art as long as the constituent components described above can be uniformly dispersed. For example, it can be produced by uniformly kneading the constituent components described above with a three-roll mill or the like until a desired particle size is obtained.

[3. Manufacturing method of multilayer ceramic capacitor]
The conductive paste according to this embodiment can be applied to a multilayer ceramic capacitor using a general manufacturing method. For example, a conductive paste is printed on a ceramic green sheet, which is laminated in multiple layers and then thermocompressed and integrated, and then fired at a temperature of 500 ° C. or less in an oxidizing atmosphere or an inert atmosphere. By doing so, the binder is removed (binder removal step). Next, the obtained multilayer structure is fired in a reducing atmosphere so that the internal electrodes are not oxidized (firing step), thereby obtaining a multilayer ceramic capacitor to which the conductive paste according to the present embodiment is applied.

In laminated ceramic capacitors, the density (conductive film density) of a conductive film obtained by printing a conductive paste on a ceramic green sheet and drying it is also required to be high. The reason for this is that the conductive film density has a great influence on the occurrence of cracks in the electrodes during manufacturing of the multilayer ceramic capacitor.

Therefore, in the conductive paste according to the present embodiment, the conductive film density of the conductive film formed on the ceramic green sheet can be 4.5 g/cm ³ or more. In the internal electrode layer of the multilayer ceramic capacitor, when the conductive film density is as low as less than 4.5 g/cm ³ , in the subsequent firing process, the amount of shrinkage is to fill the voids between the nickel powders during sintering. becomes larger.

As a result, a large amount of shrinkage mismatch with the dielectric layer (ceramic green sheet) may occur, and structural defects such as cracks may occur frequently. In addition, due to the presence of numerous voids in the internal electrode layers, shrinkage during sintering may cause the internal electrode layers to be cut off, resulting in a shortage of the capacity of the multilayer ceramic capacitor. Therefore, particularly in thin internal electrode layers, the conductive film density is required to be as high as 4.5 g/cm ³ or more.

Here, the conductive film density (g/cm ³ ) can be calculated from the weight and film thickness of the conductive film using the following formula.

Conductive film density (g/cm ³ )
= conductive film weight of conductive paste (g) / volume of conductive film (cm ³ )

Here, the measuring method is not particularly limited as long as the conductive film density can be measured accurately. For example, after applying a conductive paste on a substrate by a conventional method and drying, the obtained conductive film is peeled off from the substrate and cut out, and the weight (g) and film thickness (cm) of the conductive film are measured. . Next, from the measured weight and film thickness, the conductive film density (g/cm ³ ) is calculated using the above formula. The base material is not particularly limited as long as it does not adversely affect the measurement of the conductive film density. For example, a ceramic green sheet, a PET sheet, or the like can be used.

When manufacturing a laminated ceramic capacitor, a predetermined pattern is printed on a ceramic green sheet, dried to remove the solvent, and an internal electrode layer is formed. After that, the binder is removed at a predetermined temperature in an oxidizing atmosphere or an inert atmosphere, and the internal electrode layers are formed by heating and firing at a predetermined temperature in a reducing atmosphere so as not to oxidize.

At this time, if the conductive film density is high, a dense internal electrode layer can be obtained, and the capacitance will be close to the design value. If the cohesiveness of the conductive powder in the conductive paste and the stability of the binder are poor, the density of the conductive film will decrease. Therefore, by measuring the conductive film density of the conductive film obtained by printing and drying the conductive paste, it is possible to estimate the characteristics of the internal electrode layers in the multilayer ceramic capacitor.

As described above, the conductive paste according to the present embodiment is a conductive paste containing a conductive powder, a vehicle, and a dispersant, and the total amount of reactivity to acid (Σ(X _i-am · w _i )) is 15 or more and less than the total amount of reactivity (Σ(X _i-ac ·w _i )) with respect to bases, and the dispersant content (Σw _i ) is 100 parts by mass of the conductive powder It is obtained by adding a dispersant under the condition of 2.0 parts by mass or less in total.

By using such a conductive paste for the internal electrode layers of thin-film laminated ceramic capacitors, dense and highly continuous internal electrode layers can be obtained, and lamination without structural defects such as cracks and lack of capacity. It becomes possible to realize a ceramic capacitor.

In addition, in the multilayer ceramic capacitor, by applying the conductive paste according to the present embodiment, the conductive paste is dried, and the conductive film obtained by adsorbing the dispersant on the surface of the conductive powder has a conductive film. The film density can be as high as 4.5 g/cm ³ or higher.

By measuring the conductive film density of the conductive film obtained by using the conductive paste, it is possible to estimate the characteristics of the internal electrode layers of the multilayer ceramic capacitor. Thus, internal electrode layers with excellent properties can be obtained.

The present invention will be described in further detail using the following examples and comparative examples. In each of the examples and comparative examples, the present invention is explained by taking as an example the case of using nickel powder among the above-mentioned conductive powders. However, the present invention is not limited to this, and can be similarly applied even when copper powder or the like is used.

[Example 1]
(Preparation of conductive paste)
In Example 1, nickel powder (manufactured by Sumitomo Metal Mining Co., Ltd.) having an average particle size of 0.2 μm was prepared as the conductive powder. In Example 1, 60 parts by mass (ethyl cellulose: 3 parts by mass) of a vehicle obtained by mixing ethyl cellulose and terpineol at a mass ratio of 1:19 with respect to 100 parts by mass of nickel powder was weighed. Furthermore, in Example 1, with respect to 100 parts by mass of nickel powder, 25 parts by mass of BaTiO 3 powder having an average particle size of 0.07 μm as a dielectric powder and 25 parts by mass of BaTiO ₃ powder with an average particle size of 0.07 μm were weighed. did.

Next, in Example 1, these components were mixed simultaneously, and the grain size measured by the FOG gauge (grain gauge) was A conductive paste was produced by kneading until the diameter became 10 μm or less.

(Measurement of conductive film density of conductive paste)
In Example 1, the obtained conductive paste was applied to a PET film having a thickness of 100 μm with a film thickness of 200 μm using an applicator in a size of 10 cm square, and dried in a vacuum at 120° C. for 1 hour. did. This conductive film was peeled off from the PET film, further cut into 1.5 cm squares, the weight (g) and film thickness (cm) of the cut film were measured, and from the weight and film thickness measured using the following formula The density of the conductive film (g/cm ³ ) was calculated, and those of 4.5 g/cm ³ or more were accepted.

Conductive film density (g/cm ³ )
= conductive film weight of conductive paste (g) / volume of conductive film (cm ³ )

In Example 1, Table 2 shows the measurement results of the conductive film density in the conductive paste.

[Examples 2 to 13]
In Examples 2 to 13, conductive pastes were prepared in the same manner as in Example 1 except that the dispersants in Table 1 were weighed in the parts by mass shown in Table 2, respectively, and the conductive film densities thereof were measured. Table 2 shows the measurement results of the conductive film density of the conductive pastes obtained in Examples 2 to 13.

[Comparative Example 1]
In Comparative Example 1, a conductive paste was prepared in the same manner as in Example 1 except that no dispersant was used, and the density of the conductive film was measured. In Comparative Example 1, Table 2 shows the measurement results of the conductive film density of the obtained conductive paste.

[Comparative Examples 2 to 6]
In Comparative Examples 2 to 6, conductive pastes were prepared in the same manner as in Example 1 except that the dispersants in Table 1 were weighed in the parts by mass shown in Table 2, respectively, and the conductive film densities thereof were measured. Table 2 shows the measurement results of the conductive film densities of the conductive pastes obtained in Comparative Examples 2 to 6.

In Examples 1 to 13, the total amount of reactivity to acid (Σ(X _{i -am} ·wi )) is 15 or more and less than the total amount of reactivity to base (Σ(X _{i -ac} ·wi )) and the content (Σw _i ) of the dispersant was 2.0 parts by mass or less in total with respect to 100 parts by mass of the conductive powder.

As shown in Tables 1 and 2, in Examples 1 to 13, the conductive film density was improved by 10% or more compared to Comparative Example 1 containing no dispersant, and was 4.5 g/cm ³ . A very dense film was formed. Further, in Examples 1 to 13, the continuity of the conductive film was also good.

Here, the content of the acidic dispersant (A-1) is the same, and Example 2 containing it together with the basic dispersing agent and Comparative Example 2 containing no basic dispersing agent. By comparison, it was found that the density of the conductive film was remarkably improved by containing both an acidic dispersant and a basic dispersant.

On the other hand, when comparing the conductive film density of Comparative Example 2 containing only an acidic dispersant and Comparative Example 3 containing only a basic dispersant and Comparative Example 1 containing no dispersant, the comparative example 2 and Comparative Example 3 were higher, but the amount of increase was small, and the effect of the dispersant was limited.

In Comparative Example 4, both an acidic dispersant and a basic dispersant are contained, but the total amount of reactivity to base (Σ(X _i-ac ·w _i )) is less than 40 mg KOH·parts by mass/g. Therefore, the effect of improving the conductive film density was low.

In Comparative Example 5, the total amount of reactivity to base (Σ(X _i-ac ·w _i )) was 40 mgKOH·parts by mass/g or more, and the content of the dispersant was the same as in Examples 2 and 3. However, since the total amount of reactivity to base (Σ(X _i−ac ·w _i )) is smaller than the total amount of reactivity to acid (Σ(X _i−am ·w _i )), the conductive film density is It was clearly lower than Example 2 and Example 3.

In Comparative Example 6, since the content of the dispersant exceeded 2.0 parts by mass, the drying speed of the coating film was slow, and it was difficult to peel it off from the PET film and cut it into 1.5 cm squares. gave up the measurement.

Therefore, the conductive pastes obtained in Examples 1 to 13 are dense and highly continuous, and can obtain conductive films having a conductive film density of 4.5 g/cm ³ or more, so that they can be made thin. When used for the internal electrode layers of a laminated ceramic capacitor, dense and highly continuous internal electrode layers can be obtained, making it possible to realize a laminated ceramic capacitor free from structural defects such as cracks and lack of capacity.

As described above, the conductive paste according to the present invention has been described as a conductive paste for internal electrodes of a laminated ceramic capacitor, but the present invention is, of course, not limited to this. For example, it can be widely applied to a wiring layer of a wiring board, an interlayer connection material of a multilayer wiring board, an electrode layer and a wiring layer of a solar cell or an electronic component, and a conductive paste used to form a conductive film of an electronic component. Moreover, it does not prevent the conductive paste of the present invention from containing the components by appropriately changing the constituent components according to the use of the conductive paste.

Claims (4)

A multilayer ceramic capacitor internal electrode paste containing nickel powder, a vehicle, a dispersant and a dielectric powder,
X _{i-ac is the} acid value of the organic compounds X ₁ , X ₂ , . The following formulas (I) and (II) are satisfied when w _i (i=1 to n) is the part by mass of the organic compound with respect to 100 parts by mass of the nickel powder,
The dispersant content (Σw _i ) is 2.0 parts by mass or less in total with respect to 100 parts by mass of the nickel powder,
The dispersant contains the organic compound having reactivity to both acids and bases,
A paste for internal electrodes of a laminated ceramic capacitor , wherein at least one component of the organic compound has an acid value or an amine value of 350 mgKOH/g or less .

2. The paste for internal electrodes of a laminated ceramic capacitor according to claim 1, wherein said nickel powder has an average particle size of 0.05 μm to 1.0 μm. 3. The paste for internal electrodes of a multilayer ceramic capacitor according to claim 1, wherein the nickel powder has an average particle size of 0.05 μm to 0.5 μm and satisfies the following formula (III).

A method for producing a paste for a laminated ceramic capacitor internal electrode according to any one of claims 1 to 3,
A method for producing a paste for internal electrodes of a laminated ceramic capacitor, characterized by adding the nickel powder and the dispersant to the vehicle and kneading the mixture.