JP6809280B2 - Method of manufacturing conductive paste - Google Patents

Description

The present invention relates to a method for producing a conductive paste, and is particularly advantageously used for forming an internal conductor film of a laminated ceramic electronic component, and uses ceramic particles for suppressing sintering of conductive metal particles. The present invention relates to a method for producing a contained conductive paste.

In a multilayer ceramic capacitor as an example of a multilayer ceramic electronic component, it is effective to thin the internal electrode, which is an internal conductor film, in order to increase the capacity and reduce the size. The internal electrode often includes a step of forming a film composed of a conductive metal particle such as nickel particles, an organic solvent and an organic binder on a raw dielectric ceramic sheet, and the above-mentioned conductive paste film. Is formed through a step of firing at the same time as a raw dielectric ceramic sheet.

However, in the above-mentioned firing step, there is usually a difference in shrinkage behavior during sintering between the metal component contained in the conductive paste film and the ceramic component contained in the dielectric ceramic sheet. More specifically, the ceramic component has a sintering temperature of 1000 ° C. or higher, whereas the metal component such as nickel has a sintering temperature lower than 1000 ° C., for example, 600 to 800 ° C.

The difference in shrinkage behavior during sintering between the metal component contained in the conductive paste film and the ceramic component contained in the dielectric ceramic sheet is that when the internal electrode is thinned, a gap is created in the internal electrode. Brings inconvenience. That is, in the sintering process, the metal component starts sintering before the ceramic component, and the metal component grows excessively by the time the ceramic component reaches the temperature at which the sintering starts, and the continuity (coverage) of the internal electrodes. Decreases. The decrease in the continuity of the internal electrodes leads to the decrease in the capacitance of the monolithic ceramic capacitor.

In order to solve the above-mentioned problems, for example, as described in Japanese Patent Application Laid-Open No. 2001-110233 (Patent Document 1), ceramic particles called co-materials are contained in a conductive paste for forming an internal electrode. A method of adding the metal component to suppress the sintering of the metal component has been adopted.

However, in order to achieve the effect of suppressing the sintering of the metal component described above, the ceramic particles as the co-material must be arranged as uniformly as possible around the conductive metal particles. If the ceramic particles as the co-material are not uniformly arranged around the conductive metal particles, the sintering of the conductive metal particles will proceed from the place where the co-material does not exist. Therefore, the effect of suppressing sintering by the ceramic particles cannot be sufficiently obtained, and as a result, the continuity of the internal electrodes is lowered.

In paragraph 0020 of Patent Document 1, regarding the method for producing a conductive paste, first, ceramic particles and conductive metal particles are mixed, and an organic solvent, an organic binder and a surfactant (dispersant) are added to the mixture, respectively. It is described that a conductive paste is produced by batch mixing and dispersing in a state.

Japanese Unexamined Patent Publication No. 2001-11233

In order to thin the internal electrode, the ceramic particles contained in the conductive paste must be atomized, but the finer the ceramic particles, the more remarkable the cohesiveness of the ceramic particles.

Therefore, in the case of a conductive paste produced by applying a batch mixing / dispersion treatment as described in Patent Document 1, when the particle size of the ceramic particles contained therein is atomized to, for example, 100 nm or less, the ceramic particles become It has been confirmed by the present inventor that it is difficult to uniformly arrange the fine ceramic particles around the conductive metal particles in the conductive paste due to the aggregating property. In this way, if the fine ceramic particles cannot be uniformly arranged around the conductive metal particles, the sintering of the conductive metal particles proceeds from the place where the ceramic particles do not exist, and the conductive metal particles are formed by using the conductive paste. It becomes difficult to realize thinning and high continuity of the internal electrodes.

Therefore, an object of the present invention is to be advantageously used for forming an internal conductor film of a laminated ceramic electronic component, and ceramic particles for suppressing sintering having a small particle size are uniformly formed on the surface of conductive metal particles. It is an attempt to provide a method for producing a conductive paste that can be adhered to.

The present invention is directed to a method of making a conductive paste, which comprises conductive metal particles, ceramic particles, an organic solvent and an organic binder.

The method for producing a conductive paste according to the present invention includes a step of preparing conductive metal particles, ceramic particles, an organic solvent, an organic binder and a dispersant, respectively, and a ceramic particles, an organic solvent and a dispersant, and adsorbs the dispersant. A step of preparing the first slurry in which the ceramic particles are dispersed in an organic solvent, a step of mixing the first slurry and the conductive metal particles, and a mixture of the first slurry and the conductive metal particles. A step of adding at least an organic binder to the slurry to form a paste is provided, and the mixing step is characterized in that the conductive metal particles are mixed with the first slurry without a dispersant.

According to the manufacturing method described above, at the stage of producing the first slurry, the dispersant is previously adsorbed on the surface of the ceramic particles to develop the cross-linking cohesive force of the dispersant, and the dispersant is used in the mixing step. Ceramic particles and conductive metal particles can be bonded by utilizing the cross-linking cohesive force.

In the present invention, the conductive metal particles may also be in the state of a slurry, if necessary. That is, the present invention may further include a step of producing a second slurry containing conductive metal particles and an organic solvent. Therefore, in the mixing step, the first slurry and the second slurry are mixed. It should be noted here that the second slurry before mixing does not contain a dispersant.

In the present invention, the dispersant contained in the first slurry is preferably an anionic dispersant. By using an anionic dispersant, the cross-linking cohesive force can be reliably expressed.

Preferably, in the first slurry, the dispersant contains 0.1 mg / m ² or more and 4.0 mg / m ² or less with respect to the specific surface area of the ceramic particles. The amount of the dispersant of 0.1 mg / m ² or more is an amount sufficient to develop the cross-linking cohesive force. On the other hand, the amount of the dispersant of 4.0 mg / m ² or less is the amount of the dispersant of less than the saturated adsorption amount adsorbed on the ceramic particles. Therefore, it is possible to prevent a situation in which the free dispersant is first adsorbed on the conductive metal particles and the conductive metal particles and the ceramic particles are not bonded due to the cross-linking cohesive force via the dispersant.

The conductive metal particles are preferably nickel particles generally used as a conductive component of the inner conductor film of the laminated ceramic electronic component.

Also, the ceramic particles are widely used as the ceramic constituting the ceramic body in the multilayer ceramic electronic _{component, BaTiO 3, SrTiO 3, CaZrO} 3, MgO, TiO 2 -BaCO 3, SiO 2, Al 2 O 3, It is preferable that the particles are mainly composed of at least one selected from Cr ₂ O ₃ , Mn O ₂ and Y ₂ O ₃ .

The average particle size of the ceramic particles is preferably smaller than the average particle size of the conductive metal particles. According to this configuration, it becomes easy to obtain a state in which fine ceramic particles are uniformly arranged around the conductive metal particles.

According to the present invention, the cross-linking cohesive force of the dispersant allows the ceramic particles to be uniformly dispersed around the conductive metal particles, thereby obtaining a conductive paste capable of exerting an effective sintering suppressing effect. be able to. Therefore, by using this conductive paste, a laminated ceramic electronic component having high continuity and a thin internal conductor film can be manufactured with a high non-defective rate. In addition, it is possible to respond with high reliability to miniaturization and high performance of multilayer ceramic electronic components, for example, miniaturization and large capacity of multilayer ceramic capacitors.

It is sectional drawing which shows typically the laminated ceramic capacitor 1 as an example of the laminated ceramic electronic component constructed by using the conductive paste manufactured by the manufacturing method which concerns on this invention.

FIG. 1 shows a multilayer ceramic capacitor 1 as an example of a multilayer ceramic electronic component. The dimensional relationship of each element included in the multilayer ceramic capacitor 1 shown in FIG. 1 has been appropriately changed for the purpose of clarifying or simplifying the drawings.

The multilayer ceramic capacitor 1 is a component main body, and includes a ceramic element 2 made of a dielectric ceramic. Inside the ceramic body 2, internal electrodes 3 and 4 as internal conductor films are arranged in a state of forming a plurality of layers. The internal electrodes 3 and 4 have a first internal electrode 3 whose edge is exposed on the first end surface 5 of the ceramic element 2 and a second internal electrode 3 whose edge is exposed on the second end surface 6 of the ceramic element 2. It is classified into the internal electrode 4. The plurality of first internal electrodes 3 and the second internal electrodes 4 are respectively arranged so as to face each other via the ceramic layer 7 in their main portions and to be alternately arranged in the stacking direction. The internal electrodes 3 and 4 are formed using a conductive paste produced by a production method described in detail later.

A first external electrode 8 is formed on the first end surface 5 of the ceramic body 2 so as to be electrically connected to each end edge of the first internal electrode 3. A second external electrode 9 is formed on the second end surface 6 of the ceramic body 2 so as to be electrically connected to each end edge of the second internal electrode 4.

The first and second external electrodes 8 and 9 have their respective edge portions located on the main surfaces 10 and 11 adjacent to the end faces 5 and 6 of the ceramic element 2 and on the side surfaces (not shown).

The external electrodes 8 and 9 are electrically connected to the internal electrodes 3 and 4, respectively, and a metal paste containing a metal component and a glass component is applied onto the end faces 5 and 6 of the ceramic body 2. Then, a baking electrode layer 12 formed by baking is provided as a base layer. A first plating layer 13 containing, for example, nickel as a main component is formed on the baking electrode layer 12, and a second plating layer 14 containing, for example, tin or gold as a main component is further formed on the first plating layer 13.

The method for producing the conductive paste used for forming the internal electrodes 3 and 4 in the multilayer ceramic capacitor 1 as described above will be described below.

In order to produce the conductive paste, first, conductive metal particles, ceramic particles, an organic solvent, an organic binder and a dispersant are prepared.

As the conductive metal particles, for example, particles made of any metal of nickel, silver, copper and palladium, or an alloy containing at least one of them or stainless steel (for example, SUS317) are used, and nickel is preferable. Particles are used. The average particle size of the conductive metal particles is preferably as small as 600 nm or less, for example, about 200 nm.

As the ceramic particles, for example, at least one selected from BaTiO ₃ , SrTIO ₃ , CaZrO ₃ , MgO, TiO _2- BaCO ₃ , SiO ₂ , Al ₂ O ₃ , Cr ₂ O ₃ , MnO ₂ and Y ₂ O ₃ Particles containing the above as the main component are used. The average particle size of the ceramic particles is preferably smaller than the average particle size of the conductive metal particles described above. The average particle size of the ceramic particles is, for example, about 30 nm.

As the organic solvent, for example, a water-insoluble low-polarity solvent such as acetone or ethanol is preferably used.

As the organic binder, for example, an ethyl cellulose resin is used.

As the dispersant, for example, an anionic dispersant such as a carboxylic acid type, a sulfonic acid type, a sulfate ester type, and a phosphoric acid ester type is preferably used.

Next, a first slurry containing ceramic particles, an organic solvent and a dispersant is prepared. More specifically, a predetermined amount of ceramic particles are put into a mixed solution in which an organic solvent and a dispersant are mixed, and the ceramic particles are dispersed by a ball mill or the like. As a result of this dispersion treatment, a first slurry in which the ceramic particles adsorbing the dispersant are dispersed in the organic solvent is obtained. At the stage of producing this first slurry, the dispersant adsorbed on the surface of the ceramic particles is in a state capable of exhibiting a cross-linking cohesive force.

Next, a mixing step of mixing the first slurry and the conductive metal particles is carried out. More specifically, the conductive metal particles are charged into the first slurry, or the first slurry is charged into the conductive metal particles and mixed and stirred. Next, the first slurry mixed with the conductive metal particles is kneaded with a three-roll mill or the like to uniformly disperse the conductive metal particles.

As described above, at the stage of producing the first slurry, the dispersant adsorbed on the surface of the ceramic particles is in a state where the cross-linking cohesive force can be exhibited. The force can be used to bond the ceramic particles to the conductive metal particles. In this way, the ceramic particles can be uniformly dispersed around the conductive metal particles by the cross-linking cohesive force of the dispersant.

The conductive metal particles used in the mixing step may also be in the state of a slurry, if necessary. That is, the step of preparing the second slurry containing the conductive metal particles, the organic solvent and the organic binder may be carried out. Therefore, in the mixing step, the first slurry and the second slurry are mixed.

It should be noted that in the mixing step, the conductive metal particles are mixed with the first slurry without the dispersant. It should be noted that even when the second slurry containing the conductive metal particles described above is used, the second slurry before mixing does not contain a dispersant.

As described above, before mixing, the dispersant is added only to the slurry containing the ceramic particles because the cross-linking cohesive force of the dispersants is difficult to develop between the dispersants. That is, when the dispersant enters both the ceramic particle side and the conductive metal particle side, the dispersant adhering to the ceramic particles and the dispersant adhering to the conductive metal particles exist in the mixing step, and the dispersant is cross-linked between the two. Cohesive force is less likely to develop. Therefore, it is important to include the dispersant only in the slurry containing the ceramic particles.

It is permissible to add a dispersant after the mixing step.

Next, a step of adding a predetermined amount of an organic binder to the mixture of the first slurry and the conductive metal particles obtained by the mixing step, and further adding an organic solvent as necessary to make a paste is carried out. The desired conductive paste is obtained.

The conductive paste is advantageously used, for example, to form the internal electrodes 3 and 4 in the multilayer ceramic capacitor 1 shown in FIG. Briefly explaining the method for manufacturing the multilayer ceramic capacitor 1, a raw dielectric ceramic sheet to be the ceramic layer 7 is prepared. A conductive paste is printed in place on the raw ceramic sheet, thereby forming a conductive paste film to be the internal electrodes 3 and 4. A plurality of raw ceramic sheets including a raw ceramic sheet on which a conductive paste film is formed are laminated and pressure-bonded, whereby a raw laminated body is produced. By firing this raw laminate, a ceramic element 2 on which the internal electrodes 3 and 4 are formed is obtained. The multilayer ceramic capacitor 1 is completed by forming the external electrodes 8 and 9 on the ceramic body 2.

The conductive paste according to the present invention is advantageously used not only for forming an internal electrode in the above-mentioned multilayer ceramic capacitor but also for forming an internal conductor film in a laminated ceramic electronic component other than the multilayer ceramic capacitor. Can be done.

Next, an experimental example carried out to confirm the effect of the present invention will be described.

In the experimental example, "heat shrinkage rate" and "electrode continuity" were evaluated by the following methods.

<Heat shrinkage evaluation method>
The heat shrinkage of the obtained dry powder of the conductive paste was measured. More specifically, an arbitrary amount of powder was collected from the obtained dry powder, and columnar pellets having a diameter of about 4 mm and a height of about 2 mm were prepared at a pressure of 58.8 Pa. For the pellets, thermomechanical analyzer (manufactured by Rigaku Corporation, TMA8310) using, in a N ₂ gas atmosphere, the temperature was raised at a heating rate of 10 ° C. / min to measure the heat shrinkage. This heat shrinkage index is an index of a phenomenon in which the conductive metal particles and ceramic particles contained in the conductive paste are sintered and shrink, and the larger the heat shrinkage, the more the sintering is progressing. As the heat shrinkage rate, the shrinkage rate when the temperature was raised up to 600 ° C. and the shrinkage rate when the temperature was raised up to 800 ° C. were determined.

<Electrode continuity evaluation method>
The electrode continuity when the electrode was formed using the conductive paste was evaluated. More specifically, a conductive paste was printed on a raw dielectric ceramic sheet having a thickness of 3 μm so as to have a coating thickness of 1 μm to form a conductive paste film. The printed matter, the temperature was raised at a heating rate of 10 ° C. / min conditions, for 2 hours at 1100 ° C., and calcined in a N ₂ atmosphere, with sintering the green ceramic sheet, sintering the conductive paste films The conductor film was obtained. Then, transmitted light was irradiated from the back surface of the sheet, and the surface of the conductor film was observed in 10 fields under the condition of 100 times magnification using a metallurgical microscope. The average of the areas covered by the conductor film in all of these observation images was calculated as the "coverage" and used as an index of electrode continuity.

[Experimental Example 1]
Experimental Example 1 was carried out in particular to evaluate the effect of the dispersant added to the conductive metal particles side before mixing the ceramic particles and the conductive metal particles.

In Experimental Example 1, the conductive metal particles shown in Table 1 and the ceramic particles shown in Table 2 were used to prepare a conductive paste according to Samples 1 to 3.

As the conductive metal particles, those having the "component", "average particle size" and "specific surface area" shown in Table 1 were used for each of Sample 1 and Samples 2 and 3. The average particle size of the conductive metal particles and ceramic particles is the median diameter (D50), and the specific surface area is determined by the BET method. As shown in "Amount of Dispersant for Metal" in Table 1, in Sample 1 as an example, no dispersant was added to the conductive metal particle side. On the other hand, in Samples 2 and 3 as comparative examples, a dispersant was added to the conductive metal particle side. In Samples 2 and 3, the amount of the dispersant was 2 mg / m ^{2 with} respect to the specific surface area of the conductive metal particles and 0.7 parts by mass with respect to 100 parts by mass of the conductive metal particles. No solvent was added to the conductive metal particles according to Samples 1 to 3.

As the ceramic particles, those having the "component", "average particle size" and "specific surface area" shown in Table 2 were used for each of Samples 1 to 3.

In each of Samples 1 to 3, the carboxylic acid-based dispersant shown in "Dispersant type" in Table 2 was mixed with acetone as a solvent, ceramic particles were added to this mixed solution, and the mixture was dispersed by a ball mill. 1 slurry was obtained. Here, the amount of the dispersant is 3.0 mg / m ^{2 with} respect to the specific surface area of the ceramic particles and 15.0 with respect to 100 parts by mass of the ceramic particles, as shown in “Amount of dispersant with respect to ceramic” in Table 2. It was taken as a mass part.

Next, the first slurry containing the ceramic particles and the conductive metal particles were mixed and stirred, and kneaded with a three-roll mill to uniformly disperse the conductive metal particles. In this mixing step, the mixing procedure followed the “mixing procedure” in Table 1. In the "mixing procedure" of Table 1, "A⇒B" means that the conductive metal particles (A) are added to the ceramic particles (B), and "B⇒A" is displayed. Means that the ceramic particles (B) are added to the conductive metal particles (A). Further, in the mixing step, as shown in "Volume part of B with respect to 100 parts by volume of A" in Table 2, the ceramic particles were mixed so as to be 8 parts by volume with respect to 100 parts by volume of the conductive metal particles. ..

Then, ethyl cellulose resin as an organic binder and acetone as an organic solvent were added to the above-mentioned mixture of the first slurry and the conductive metal particles, and the mixture was stirred to form a paste to obtain a conductive paste.

With respect to the conductive pastes according to Samples 1 to 3 obtained as described above, "heat shrinkage rate" and "electrode continuity / coverage rate" were evaluated according to the above-mentioned method, as shown in Table 3.

As can be seen from Table 3, before mixing the conductive metal particles and the ceramic particles, the dispersant was not added to the conductive metal particles side, and the dispersant was added only to the ceramic particles side. For example, the "heat shrinkage rate at 600 ° C." is 0.5% of 1% or less, and the "heat shrinkage rate at 800 ° C." is 2.0% of 3% or less, and the ceramic particles have a high sintering inhibitory effect. It was confirmed that it was working. Further, according to Sample 1, the "electrode continuity / coverage" was 91%, and it was confirmed that the electrode continuity was high. It is presumed that this is because the metal and ceramics are bonded by the cross-linking cohesive force via the dispersant, and the sintering suppressing effect is enhanced.

On the other hand, according to Samples 2 and 3 as comparative examples in which dispersants were added to both the conductive metal particle side and the ceramic particle side before mixing the conductive metal particles and the ceramic particles, "600. The "heat shrinkage rate at ° C." was 0.5%, which was 1% or less, but the "heat shrinkage rate at 800 ° C." was 3.5% and 3.7%, which exceeded 3%, and was included in the "mixing procedure". Regardless, it was confirmed that the effect of suppressing sintering by the ceramic particles was low. Further, according to the samples 2 and 3, the "electrode continuity / coverage" was 75% and 74%, and it was confirmed that the electrode continuity was relatively low.

[Experimental Example 2]
Experimental Example 2 was carried out in particular to evaluate the presence or absence of a solvent on the ceramic particle side before mixing and the effect of changing the mixing procedure.

In Experimental Example 2, the conductive metal particles shown in Table 4 and the ceramic particles shown in Table 5 were used to prepare a conductive paste according to Samples 11 to 13.

As the conductive metal particles, those having the "component", "average particle size" and "specific surface area" shown in Table 4 were used for each of the samples 11 to 13. Here, no dispersant was added to the conductive metal particles according to Samples 11 to 13. Further, as shown in "Presence or absence of solvent before mixing" in Table 4, acetone as a solvent was added to the conductive metal particles according to Samples 11 and 13 to form a second slurry, and the conductive metal according to Sample 12 was prepared. No solvent was added to the particles.

As the ceramic particles, those having the "component", "average particle size" and "specific surface area" shown in Table 5 were used for each of the samples 11 to 13.

In each of the samples 11 to 13, the carboxylic acid-based dispersant shown in "Dispersant type" in Table 5 was mixed with acetone as a solvent, ceramic particles were added to the mixed solution, and the mixture was dispersed by a ball mill. 1 slurry was obtained. Here, the amount of the dispersant is 3.0 mg / m ^{2 with} respect to the specific surface area of the ceramic particles and 15.0 with respect to 100 parts by mass of the ceramic particles, as shown in “Amount of dispersant with respect to ceramic” in Table 5. It was taken as a mass part.

Next, the first slurry containing the ceramic particles and the conductive metal particles or the second slurry were mixed and stirred, and kneaded with a three-roll mill to uniformly disperse the conductive metal particles. In this mixing step, the mixing procedure followed the “mixing procedure” in Table 4. Further, in the mixing step, as shown in “100 parts by volume of A with respect to 100 parts by volume of A” in Table 5, the ceramic particles were mixed so as to be 8 parts by volume with respect to 100 parts by volume of the conductive metal particles. ..

Then, an ethyl cellulose resin as an organic binder and acetone as an organic solvent are added to the above-mentioned mixture of the first slurry and the conductive metal particles or the second slurry, and the mixture is stirred to form a paste to obtain a conductive paste. It was.

With respect to the conductive pastes related to the samples 11 to 13 obtained as described above, the "heat shrinkage rate" and the "electrode continuity / coverage rate" were evaluated according to the above-mentioned method, as shown in Table 6.

As shown in Table 5, according to Samples 11 to 13 in which the dispersant was added only to the ceramic particle side, as shown in Table 6, the "heat shrinkage rate at 600 ° C." was 0% or less. It was 5%, and the "heat shrinkage rate at 800 ° C." was 2.1% or more and 2.2% or less, which was 3% or less, and it was confirmed that the high sintering suppressing action of the ceramic particles was working. Further, according to the samples 11 to 13, the "electrode continuity / coverage" was 88% or more and 90% or less, and it was confirmed that the electrode continuity was high. This is done before mixing the conductive metal particles and the ceramic particles, regardless of whether the conductive metal particles are filled with a solvent and regardless of the mixing procedure, as shown in Table 4. It is presumed that the cause is that the metal particles and the ceramic particles are bonded by the cross-linking cohesive force via the agent, and the sintering suppressing effect is enhanced.

[Experimental Example 3]
Experimental Example 3 was carried out in particular to evaluate the effect of changing the amount of the dispersant added to the ceramic particles side.

In Experimental Example 3, the conductive metal particles shown in Table 7 and the ceramic particles shown in Table 8 were used to prepare a conductive paste according to Samples 21 to 25.

As the conductive metal particles, those having the "component", "average particle size" and "specific surface area" shown in Table 7 were used for each of the samples 21 to 25. No dispersant was added to the conductive metal particles according to the samples 21 to 25, and no solvent was added.

As the ceramic particles, those having the "component", "average particle size" and "specific surface area" shown in Table 8 were used for each of the samples 21 to 25.

In each of the samples 21 to 25, the carboxylic acid-based dispersant shown in "Dispersant type" in Table 2 was mixed with acetone as a solvent, ceramic particles were added to the mixed solution, and the mixture was dispersed by a ball mill. 1 slurry was obtained. Here, as shown in “Amount of Dispersant for Ceramic” in Table 8, the amount of the dispersant is applied to 100 parts by mass of the ceramic particles in the range of 0 to 4.1 mg / m ² with respect to the specific surface area of the ceramic particles. On the other hand, it was changed in the range of 0 to 20.5 parts by mass.

Next, the first slurry containing the ceramic particles and the conductive metal particles were mixed and stirred, and kneaded with a three-roll mill to uniformly disperse the conductive metal particles. In this mixing step, the mixing procedure was “A⇒B”. Further, in the mixing step, as shown in “100 parts by volume of A with respect to 100 parts by volume of A” in Table 8, the ceramic particles were mixed so as to be 8 parts by volume with respect to 100 parts by volume of the conductive metal particles. ..

Then, ethyl cellulose resin as an organic binder and acetone as an organic solvent were added to the above-mentioned mixture of the first slurry and the conductive metal particles, and the mixture was stirred to form a paste to obtain a conductive paste.

With respect to the conductive pastes related to the samples 21 to 25 obtained as described above, the "heat shrinkage rate" and the "electrode continuity / coverage rate" were evaluated according to the method described above, as shown in Table 9.

As shown in Table 9, in the sample 25 as a comparative example in which the dispersant was not added to the conductive metal particles and the ceramic particles before mixing, the heat shrinkage rate at 600 ° C. was 0.5%. However, it was confirmed that the heat shrinkage rate at 800 ° C. was relatively high at 3.6%, and the coating rate showing electrode continuity was also relatively low at 74%, so that sufficient sintering suppression behavior could not be exhibited.

On the other hand, no dispersant was added to the conductive metal particles before mixing, but in Samples 21 to 24 as an example in which the dispersant was added to the ceramic particles, the heat shrinkage rate at 800 ° C. was 3.4%. It was confirmed that the coating ratio, which is relatively low as below and shows electrode continuity, is also relatively high as 77% or more, and shows sufficient sintering suppression behavior.

In particular, in the samples 21 to 23 in which the dispersant was added to the ceramic particles before mixing in the range of 0.1 mg / m ² or more and 4.0 mg / m ² or less, the heat shrinkage rate at 600 ° C. was 0.5%. It was confirmed that the heat shrinkage rate at 800 ° C. was as low as 3.0% or less, and the coating rate indicating electrode continuity was as high as 80% or more, showing good sintering suppression behavior. This is because if the amount of the dispersant is equal to or less than the saturated adsorption amount adsorbed on the ceramic particles as a co-material, the metal particles and the ceramic particles are bonded by the cross-linking cohesive force via the dispersant, and the sintering suppressing effect is enhanced. It is presumed that this is the factor.

On the other hand, for the sample 24 having a dispersant amount of 4.1 mg / m ² , the heat shrinkage rate at 800 ° C. exceeded 3.0%, and the coverage rate indicating electrode continuity was also lower at 77%, resulting in firing. It was confirmed that the effect of suppressing the blotting was lower than that of the samples 21 to 23. This is not a serious problem in practical use, but when the amount of the dispersant exceeds the saturated adsorption amount adsorbed on the ceramic particles as a co-material, the free dispersant is first adsorbed on the metal particles and dispersed. It is presumed that the cause is that the metal particles and the ceramic particles did not bond due to the cross-linking cohesive force mediated by the agent.

[Experimental Example 4]
Experimental Example 4 was carried out in particular to evaluate the effect of changing the dispersant type, changing the composition of the ceramic particles, and changing the composition of the conductive metal particles.

In Experimental Example 4, the conductive metal particles shown in Table 10 and the ceramic particles shown in Table 11 were used to prepare a conductive paste according to Samples 31 to 46.

As the conductive metal particles, those having the "component", "average particle size" and "specific surface area" shown in Table 10 were used for each of the samples 31 to 46. Here, in the samples 43 to 46, the "component" of the conductive metal particles was made different from that of the other samples. No dispersant was added to the conductive metal particles according to Samples 31 to 46, and no solvent was added.

As the ceramic particles, those having the "component", "average particle size" and "specific surface area" shown in Table 11 were used for each of the samples 31 to 46. Here, in the samples 31 to 33, the "dispersant type" was made different from the other samples. Further, in the samples 34 to 42, the "component" of the ceramic particles was made different from that of the other samples. As the ceramic particles according to the sample 37, those containing TiO ₂ and BaCO ₃ in a molar ratio of 1: 1 were used.

In each of the samples 31 to 46, the dispersant shown in "Dispersant type" in Table 11 was mixed with acetone as a solvent, ceramic particles were added to this mixed solution, and the first slurry was dispersed by a ball mill. Obtained. Here, the amount of the dispersant is 3.0 mg / m ^{2 with} respect to the specific surface area of the ceramic particles and 15.0 with respect to 100 parts by mass of the ceramic particles, as shown in “Amount of dispersant with respect to ceramic” in Table 11. It was taken as a mass part.

Next, the first slurry containing the ceramic particles and the conductive metal particles were mixed and stirred, and kneaded with a three-roll mill to uniformly disperse the conductive metal particles. In this mixing step, the mixing procedure was “A⇒B”. Further, in the mixing step, as shown in "100 parts by volume of A with respect to 100 parts by volume of A" in Table 11, the ceramic particles were mixed so as to be 8 parts by volume with respect to 100 parts by volume of the conductive metal particles. ..

Then, ethyl cellulose resin as an organic binder and acetone as an organic solvent were added to the above-mentioned mixture of the first slurry and the conductive metal particles, and the mixture was stirred to form a paste to obtain a conductive paste.

With respect to the conductive pastes related to the samples 31 to 46 obtained as described above, the "heat shrinkage rate" and the "electrode continuity / coverage rate" were evaluated according to the above-mentioned method, as shown in Table 12.

As shown in Table 12, in each of the samples 31 to 46, the heat shrinkage rate at 600 ° C. was 0.5% or more and 0.8% or less, and the heat shrinkage rate at 800 ° C. was 3.0% or less. It was confirmed that the coating ratio, which was low and showed electrode continuity, was as high as 87% or more, and showed good sintering suppression behavior. This is because even if the dispersant type is changed, the composition of the ceramic particles is changed, or the composition of the conductive metal particles is changed, the metal particles and the ceramic particles are separated by the cross-linking cohesive force via the dispersant. It is presumed that the cause is that they are combined and the effect of suppressing sintering is enhanced.

1 Multilayer ceramic capacitor 2 Ceramic element 3, 4 Internal electrodes 7 Ceramic layer

Claims (7)

A method for producing a conductive paste, which comprises conductive metal particles, ceramic particles, an organic solvent and an organic binder.
The process of preparing conductive metal particles, ceramic particles, organic solvent, organic binder and dispersant, respectively.
A step of preparing a first slurry containing the ceramic particles, the organic solvent, and the dispersant, in which the ceramic particles adsorbing the dispersant are dispersed in the organic solvent.
A mixing step of mixing the first slurry and the conductive metal particles,
A step of adding at least the organic binder to the mixture of the first slurry and the conductive metal particles to form a paste.
With
The mixing step is characterized in that the conductive metal particles are mixed with the first slurry without a dispersant.
A method for producing a conductive paste. A step of preparing a second slurry containing the conductive metal particles and the organic solvent but not containing a dispersant is further provided, and the mixing step includes a step of mixing the first slurry and the second slurry. The method for producing a conductive paste according to claim 1. The method for producing a conductive paste according to claim 1 or 2, wherein the dispersant contained in the first slurry is an anionic dispersant. The conductivity according to any one of claims 1 to 3, wherein in the first slurry, the dispersant contains 0.1 mg / m ² or more and 4.0 mg / m ² or less with respect to the specific surface area of the ceramic particles. Method for producing sex paste. The method for producing a conductive paste according to any one of claims 1 to 4, wherein the conductive metal particles are nickel particles. The ceramic _{particles, BaTiO 3, SrTiO 3, CaZrO} 3, MgO, TiO 2 -BaCO 3, SiO 2, Al 2 O 3, Cr 2 O 3, MnO 2 and _Y 2 _{O 3} main at least one selected from The method for producing a conductive paste according to any one of claims 1 to 5, which is a particle as a component. The method for producing a conductive paste according to any one of claims 1 to 6, wherein the average particle size of the ceramic particles is smaller than the average particle size of the conductive metal particles.

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