KR101040391B1 - Method for producing inorganic powder paste - Google Patents

Abstract

In preparing an inorganic powder paste comprising an inorganic powder component in an solvent and an organic compound having an action of improving the dispersibility of the inorganic powder component by adsorbing the inorganic powder component, when the inorganic powder component is atomized, It becomes impossible to adhere an organic compound to the surface enough, and the dispersibility of an inorganic powder paste falls.

A first mixture 1 comprising at least an inorganic powder component and a second mixture 2 comprising at least a solvent and an organic compound but not including an inorganic powder component are obtained and then before mixing them The process (3) which applies a shearing force to the to-be-mixed object 2 of this is performed, and the 1st to-be-mixed body 1 and the 2nd to-be-mixed body 2 are mixed after that.

Inorganic powder component, organic powder component, first mixture, second mixture

Description

Manufacturing method of inorganic powder paste {METHOD FOR PRODUCING INORGANIC POWDER PASTE}

TECHNICAL FIELD This invention relates to the manufacturing method of an inorganic powder paste. Specifically, It is related with the manufacturing method of the inorganic powder paste which can be advantageously applied as a manufacturing method of the electrically conductive paste for forming the internal conductor in laminated ceramic electronic components.

In order to obtain the inorganic powder paste in which the fine inorganic powder is dispersed in the solvent, it is important to uniformly disperse the inorganic powder in the paste. As a method for uniformly dispersing the inorganic powder in the paste, for example, there is a method of adsorbing an organic compound as a dispersant for improving the dispersion stability of the inorganic powder to the inorganic powder. In this method, the point is how to attach the organic compound in an optimal state to the inorganic powder.

Inorganic powder pastes generally have a high viscosity, which makes it difficult to uniformly disperse the inorganic powder. Therefore, a method of adding a low boiling point dilution solvent at the time of dispersion to uniformly disperse the inorganic powder and then volatilizing and removing the dilution solvent is described, for example, in JP 2001-67951 A (Patent Document 1). . As described in Patent Document 1, the organic compound can be sufficiently adsorbed on the surface of the inorganic powder by lowering the viscosity using a diluent solvent during dispersion.

However, due to the further atomization of the inorganic powders, the above-mentioned methods alone do not allow sufficient organic compounds to adhere to the surface of the inorganic powders. Therefore, the inventors have found that, in order to solve these problems, the shearing force is imparted to the organic compound, so that the organic compound as a polymer can be decomposed to create a state in which the inorganic powder can be efficiently attached. Specifically, the shearing force is imparted by a wet high pressure treatment apparatus, a shear mixer, or the like, which is applied by spraying pressure to the paste.

However, it has been found that there is a new problem that a desired dispersion effect cannot be obtained even if the shearing force is applied as described above in the state of containing the inorganic powder. This is because when the inorganic powder is present, a very large shear force is required in order to obtain a decomposition state equivalent to that in which the inorganic powder is not included, because it is practically difficult to obtain such a large shear force with existing equipment.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2001-67951

Therefore, this invention is going to provide the manufacturing method of the inorganic powder paste which can solve the above-mentioned problem.

This invention is a method for manufacturing the inorganic powder paste which contains the organic compound which has an effect which improves the dispersibility of the said inorganic powder component by adsorb | sucking to an inorganic powder component and the said inorganic powder component in a solvent, The technical description mentioned above In order to solve the problem, a step of obtaining a first to-be-mixed substance containing at least an inorganic powder component, a step of obtaining a second to-be-mixed mixture containing at least a solvent and an organic compound but not containing an inorganic powder component, and a second And a step of applying a shearing force to the mixture to be mixed, followed by mixing the first mixture and the second mixture.

The present invention is characterized in that the step of applying the shearing force as described above is carried out in the absence of an inorganic powder component. In this case, the first to-be-compounded mixture containing the inorganic powder component and an organic compound are included. The second to-be-mixed mixture may be prepared separately and mixed at the end, or may be mixed first, or the organic compound may be separated from the mixture and subjected to shearing force and then mixed again.

In the latter embodiment, the method further includes a step of preparing a mixture containing at least an inorganic powder component, a solvent, and an organic compound, and a step of separating at least an organic compound from the mixture. The inorganic powder component contained in the first mixture is left after removing the organic compound from the mixture by performing a step of separating the organic compound from the mixture, and the organic compound contained in the second mixture is organic from the mixture. It is taken out from a mixture by performing the process of separating a compound.

It is preferable that the inorganic powder component contained in a 1st to-be-mixed object is a state disperse | distributed in a solvent.

It is preferable that an inorganic powder component contains the electroconductive metal powder whose average particle diameter is 10-300 nm.

It is preferable that the weight average molecular weights of an organic compound are 100-500000, and the amount of acid groups is 100-2000 micromol / g.

The step of applying a shear force to the second to-be-mixed object includes a step of spraying the second to-be-mixed object from a predetermined injection port while applying pressure to the second to-be-mixed object, and applied to the second to-be-mixed object. The pressure is preferably selected from 50 to 300 MPa.

According to this invention, a shear force is applied to a second mixture to be in a state excluding at least an inorganic powder among the components contained in the inorganic powder paste to be obtained, and then the organic compound is made to be easily adsorbed to the inorganic powder. Since the second to-be-mixed body is mixed with the 1st to-be-mixed body containing an inorganic powder component, it is easy to provide a shearing force with respect to an organic compound, and to make it easy to adsorb | suck to an inorganic powder. Therefore, even if a fine inorganic powder is used, excellent dispersibility can be exhibited and the inorganic powder paste which has favorable dispersibility can be obtained.

Therefore, the significance of the improvement of the dispersibility of this invention becomes remarkable when the said inorganic powder component contains the electroconductive metal powder whose average particle diameter is 10-300 nm. That is, even if it contains the fine electroconductive metal powder whose average particle diameter is 10-300 nm, according to this invention, the electrically conductive paste with favorable dispersibility is obtained. Therefore, when the electrically conductive paste manufactured by this invention is used in order to form the internal conductor in laminated ceramic electronic components, the surface smoothness of the coating film of an electrically conductive paste can improve, and it can prevent that a short defect arises easily.

The manufacturing method of the inorganic powder paste which concerns on this invention further includes the process of preparing the mixture containing an inorganic powder component, a solvent, and an organic compound, and the process of isolate | separating at least an organic compound from this mixture, The above-mentioned 1st In the case where the inorganic powder component contained in the mixture to be removed is left after removing the organic compound from the mixture, and the organic compound contained in the above-described second mixture is extracted from the mixture, the preparation method according to the present invention is used as a mixture. Using the applied inorganic powder paste, the process of exerting a shear force on the second mixture and the subsequent mixing of the first mixture and the second mixture can be repeated, resulting in more dispersibility. This excellent inorganic powder paste can be obtained.

When the inorganic powder component contained in the first mixture is dispersed in the solvent, the handling properties of the first mixture including the inorganic powder component can be improved.

If the weight average molecular weight of an organic compound is 100-500000, and an acidic radical amount is 100-2000 micromol / g, it can be made more suitable for adsorb | sucking an organic compound to inorganic powder and improving dispersibility.

In applying the shear force to the second to-be-mixed body, the second to-be-mixed body is sprayed from a predetermined injection hole while applying pressure to the second to-be-mixed body, and at this time, the pressure applied to the second to-be-mixed body is By selecting from 50 to 300 MPa, the shear force can be reliably applied to the second mixture.

BRIEF DESCRIPTION OF THE DRAWINGS The process drawing which shows the manufacturing method of the inorganic powder paste which concerns on the 1st Embodiment of this invention. The inorganic powder paste to be obtained contains an inorganic powder component in an solvent and an organic compound having the effect of improving the dispersibility of the inorganic powder component by adsorbing the inorganic powder component.

In order to manufacture such an inorganic powder paste, a step of obtaining a first mixture 1 containing at least an inorganic powder component, and a second mixture including at least a solvent and an organic compound but not containing an inorganic powder component ( The process of obtaining 2) is performed.

Next, a shearing action applying step (3) of exerting a shearing force on the second to-be-mixed object (2) is performed, followed by a mixing step of mixing the first mixture (1) and the second mixture (2). (4) is performed, whereby the inorganic powder paste 5 is obtained. In order to obtain the inorganic powder paste 5, resin may be further added as needed.

Although the 1st to-be-mixed body 1 contains a solvent normally in addition to an inorganic powder component, Preferably it is a state in which an inorganic powder component is disperse | distributed in a solvent. In addition, the second to-be-mixed object 2 is made on condition that an organic compound will necessarily be contained in it. In addition, the 1st to-be-mixed body 1 may contain the organic compound contained in this 2nd to-be-mixed body 2.

The case where the inorganic powder paste 5 is an electrically conductive paste is demonstrated below.

When the conductive paste is to be produced as the inorganic powder paste 5, the first mixture 1 contains the conductive metal powder as the inorganic powder component. In the case where the conductive paste is used to form the internal conductor in the multilayer ceramic electronic component, the metal component constituting the conductive metal powder may be one that can withstand the firing temperature and atmosphere of the ceramic to be co-fired, for example, Ni, Pd. , Ag, Au, Pt or Cu, or mixtures or alloys thereof may be used.

It is preferable that the content rate of the conductive metal powder as a solid component in an electrically conductive paste is 20 to 70 weight%. By adjusting the content rate of a solid component in this range, the target printed coating film thickness can be obtained stably. In addition, when the particle diameter of the conductive metal powder is in the range of 10 to 300 nm as the average particle diameter, the coagulation effect is usually remarkable, and according to the present invention, since the dispersibility is improved, the average particle diameter is 10 to 300 nm. It can be said that the effect of the dispersibility improvement which concerns on this invention becomes remarkable. On the other hand, from the standpoint of whether or not the effect according to the present invention can be exhibited, the lower limit does not exist in the average particle diameter. When the average particle diameter is less than 10 nm, the conductive paste is too thick. It is not preferable because the handling property is lowered.

In the first mixture 1, an oxide solid component may be added as part of the inorganic powder component for the purpose of delaying the sintering of the conductive metal powder in addition to the conductive metal powder. As the oxide solid component, for example, respective oxides such as Ba, Ti, Zr, Dy, Mg, Si, Y, or a mixture of these oxides can be used. Although the content rate of the oxide solid component in an electrically conductive paste can adjust suitably according to the sinterability of an electroconductive metal powder in the range of 1-40 weight%, It is preferable to set it as the addition amount especially 5-20 weight% with respect to an electroconductive metal powder. .

As a solvent contained in the 2nd to-be-mixed object 2, it is preferable to contain the main solvent which remains in the obtained electrically conductive paste, and the diluent solvent used only in the process of manufacturing an electrically conductive paste which does not remain in an electrically conductive paste. In order to promote the adsorption of organic compounds, the solubility parameter of the main solvent is preferably 8.0 to 10.5, and the solubility parameter of the diluting solvent is preferably 7.4 to 13.8. Specifically, solvents such as esters, terpenes, ketones, ethers and alcohols can be used as the main solvent, and solvents such as ketones, alcohols and hydrocarbons can be used as the diluting solvent. It is preferable that the content rate of the main solvent in the obtained electrically conductive paste shall be 10 to 70 weight%.

Examples of the organic compound included in the second mixture 2 include a dispersant, a resin, an additive, and the like. The organic compound, especially the dispersant, is preferably an anionic dispersant having a weight average molecular weight of 100 to 50000 and an acidic acid group of 100 to 2000 mol / g. For example, a carboxylic acid compound, a sulfonic acid compound, a phosphoric acid compound and the like are used. The addition amount of the dispersant is preferably selected from 0.1 to 10% by weight based on the powder component (including the conductive metal powder and the oxide solid component).

Although ethyl cellulose resin is especially preferable as resin, acrylic resin, urethane resin, phenol resin, etc. may be used in addition. It is preferable that the content rate of resin is chosen to 1-10 weight% with respect to an electrically conductive paste.

Although an additive is added as needed for the viscosity adjustment of an electrically conductive paste, It is preferable to use an amine compound etc., for example. The amount of the additive added is preferably selected to be 0.1 to 10% by weight relative to the powder component.

In the shear action applying step 3 performed on the second to-be-mixed object 2, a wet high pressure treatment apparatus is used, for example, and a second to-be-mixed object ( 2) is injected from a predetermined injection port. At this time, it is preferable that the pressure applied to the second mixture 2 is selected from 50 to 300 MPa. In the shear action applying step (3), a shear mixer may be used in place of the wet high pressure treatment apparatus.

In the mixing process 4, the 2nd to-be-mixed object 2 which completed the above-mentioned shearing | action action application process 3 is made to collide with the 1st to-be-mixed body 1. FIG. In this way, the first to-be-mixed object 1 is collided with the second to-be-mixed object 2 after the shearing action is applied to the surface of the inorganic powder contained in the first to-be-mixed object 1, so that the second to-be-mixed material is mixed. The organic compound which has a dispersing action contained in (2) can be stuck efficiently. In this mixing process (4), it is preferable to adjust so that the temperature of the 2nd to-be-mixed body 2 may be less than the boiling point of a solvent, being 25 degreeC or more.

2 is a flowchart showing a method for producing an inorganic powder paste according to a second embodiment of the present invention. In FIG. 2, the thing which corresponds to the element shown in FIG. 1 is attached | subjected with the same code | symbol, and the overlapping description is abbreviate | omitted.

In 2nd embodiment, the mixing slurry 11 which is a mixture containing an inorganic powder component, a solvent, and an organic compound at least is prepared, The separation process of separating an organic compound with a solvent from this mixed slurry 11 through a filter. (12) is characterized by the above-mentioned. In addition, the inorganic powder component contained in the 1st to-be-mixed body 1 is what remained after removing the organic compound from the mixed slurry 11 by performing the separation process 12, and is contained in the 2nd to-be-mixed body 2 The organic compound is taken out from the mixed slurry 11 by performing the separation step 12. The subsequent steps are the same as those in the first embodiment.

The mixed slurry 11 prepared in 2nd Embodiment may be the inorganic powder paste 5 obtained by 1st Embodiment mentioned above, and also the inorganic powder paste 5 obtained by 2nd Embodiment. ) May be used. In this manner, the shearing action applying step 3 is repeated, whereby the dispersibility of the obtained inorganic powder paste 5 can be further improved.

In other words, when the process of mixing the first to be mixed 1 and the second to be mixed 2 by collision is performed only once, the inorganic powder component may remain in the aggregated state. As described above, the shearing action applying step 3 is repeated, so that the dispersibility can be further increased as the number of times of the repetition increases. On the other hand, since the preferable number of repetitions of the shearing action applying step (3) depends on the composition of the inorganic powder paste (5) to be obtained or the particle diameter of the inorganic powder, the obtained inorganic powder paste (5) is evaluated in advance, and the inorganic powder It is preferable to set the number of repetitions for each kind of the paste 5.

Inorganic powder pastes produced by the manufacturing method according to the present invention are typically conductive pastes, but such conductive pastes are used for forming internal conductors, for example, multilayer ceramic capacitors, multilayer ceramic inductors, multilayer ceramic LC components, A multilayer ceramic electronic component such as a multilayer ceramic substrate can be manufactured.

Next, the experimental example performed to confirm the effect which concerns on this invention is demonstrated.

In this experiment example, the electrically conductive paste which concerns on samples 1-7 was produced with the composition and processing conditions shown to the following Tables 1-7.

(1) Sample 1

(2) Sample 2

(3) Sample 3

(4) Sample 4

(5) Sample 5

(6) Sample 6

(7) Sample 7

In Tables 1-7, "weight% / paste" shown in the column of "addition ratio" represents the weight% in the obtained electrically conductive paste, and "weight% / powder" represents the weight% with respect to the powder component added. have.

In addition, the "soluble parameter" is calculated by the fedos method. The amount of acid groups is measured by neutralization titration. "Weight average molecular weight" is calculated | required by melt | dissolving in tetrahydrofuran (THF) and performing molecular weight distribution evaluation of the obtained solution by high performance liquid chromatography.

The manufacturing procedure of the electrically conductive paste which concerns on each of the samples 1-7 is as follows.

In order to obtain the first to-be-mixed substance, as shown in the column of the "first to-be-mixed substance" of Table 1-Table 7, a main solvent is added to a powder component, and depending on a sample, a diluent solvent, a dispersing agent, resin, and / Or the additive was further added and these were mixed and stirred using the shear mixer.

On the other hand, in order to obtain a second to-be-mixed body, as shown in the column of "2nd to-be-mixed body" of Table 1-Table 7, a dispersing agent is added to a main solvent, and depending on a sample, a diluent solvent, a dispersing agent, resin, and And / or further additives were mixed and stirred using a shear mixer.

Next, in order to apply the shear force to the second mixture to be obtained as described above, using a wet high pressure treatment apparatus, the pressure shown in the column of 'treatment pressure' in 'treatment conditions' in Tables 1 to 7 The mixture of 2 was pressurized and sprayed.

Next, the first to-be-mixed second mixture is controlled by a heater or chiller water so as to be the temperature shown in the column of the 'mixture temperature' in 'treatment conditions' in Tables 1 to 7 after the pressure injection. The electrically conductive paste was obtained by making it collide with the to-be-mixed material of.

About the sample in which the "processing frequency" in the "processing conditions" of Table 1-Table 7 is plural times, the electrically conductive paste obtained as mentioned above was filtered, and the slurry containing an inorganic powder component by this, a solvent, and organic The organic compound solution containing the compound component but not the inorganic powder component is separated, and the organic compound solution is subjected to shearing under the same conditions as described above, and the organic compound solution after the shearing action is included in the inorganic powder component. The treatment to impinge the slurry to be repeated was repeated the number of times indicated in the number of treatments. In addition, the processing frequency was managed by the processing time. For example, in the case where it is desired to process X times, the processing is performed for the processing time calculated by the processing time = (conductive paste amount) / (conductive paste processing speed) x X.

In addition, in the sample 7 shown in Table 7, the 1st to-be-mixed body and the 2nd to-be-mixed body were simply mixed with each other, and mixed and stirred with the shear mixer, and the electrically conductive paste was obtained without performing the process as mentioned above.

Next, the organic vehicle obtained by mixing previously the ethyl cellulose resin which is a resin component and a main solvent so that it may become 20:80 by weight ratio is added to the electrically conductive paste according to each sample, and the electrically conductive paste which content of an ethyl cellulose resin becomes 2 weight% Were combined so as to obtain, followed by mixing and stirring using a shear mixer.

Next, after adjusting the electrically conductive paste after the said mixing stirring to a viscosity of 0.5 Pa * s or less, openings are 10 micrometers, 5 micrometers, and 3 micrometers, and the average of the conductive metal powder 1 at the last stage is 1 A filtration treatment was performed in which agglomerates were removed by pressure filtration at a pressure of less than 1.5 kg / cm 2 using a membrane filter having pores twice as large as the primary particle diameter.

Finally, when the dilution solvent is included in the conductive paste after the filtration treatment, the dilution solvent is removed by heating to a temperature of 40 ° C. under a reduced pressure of 2.0 × 10 ⁻¹ atmosphere, and then the membrane having a thickness of 3 μm with respect to the conductive paste after the filtration treatment. Using a filter, pressure filtration of less than 1.5 kg / cm < 2 >

In order to evaluate the electrically conductive paste concerning each sample obtained in this way, the laminated ceramic capacitor was produced as follows.

That is, the conductive paste according to each sample was printed by the screen printing method on the dielectric ceramic green sheet of 2 micrometers in thickness, and the coating film which consists of a conductive paste of 1 micrometer in thickness was formed. Here, the coating film shape was observed with the three-dimensional shape measuring device, and the coating film surface roughness was measured. The results are shown in Table 8.

Next, after drying the electrically conductive paste, the dielectric ceramic green sheet was laminated and pressed to obtain a laminated structure of 450 layers, and then cut to have a planar shape of 3.2 mm x 2.5 mm to obtain a laminate chip. Next, the laminate chip is degreased at a maximum temperature of 280 ° C., and then calcined at a maximum temperature of 1200 ° C. in a hydrogen / nitrogen mixed gas, and after firing, an external electrode is formed by coating and baking to form a multilayer ceramic capacitor on each sample. Got it.

For 100 multilayer ceramic capacitors according to each obtained sample, the capacitance was measured with an LCR meter and the short defective rate was calculated. The results are shown in Table 8. With respect to the short defective rate shown in Table 8, it is judged as a good product when it is less than 10%, and when it is 10% or more.

From Table 8, according to the samples 1-6, it can be confirmed that the print film smoothness is improved, and as a result, the short defective rate of the multilayer ceramic capacitor can be suppressed to less than 10%. This is presumably because the adsorption state of the organic compound to the powder component is optimized and the dispersibility of the powder component in the conductive paste is improved.

On the other hand, in Sample 7, the print film smoothness is inferior to Samples 1 to 6, and the short defective rate is greatly increased. This is presumably because the adsorption state of the organic compound to the powder component is not good and the dispersibility of the conductive paste is lowered.

BRIEF DESCRIPTION OF THE DRAWINGS The process drawing which shows the manufacturing method of the inorganic powder paste which concerns on the 1st Embodiment of this invention.

2 is a flowchart showing a method for producing an inorganic powder paste according to a second embodiment of the present invention.

[Description of the code]

1 first mixture

2 second mixture

3 Shear action application process

4 mixing process

5 inorganic powder paste

11 Mixed Slurry

12 Separation Process

Claims (6)

As a method for manufacturing the inorganic powder paste which contains the organic compound which has an effect which improves the dispersibility of the said inorganic powder component by making it adsorb | suck to an inorganic powder component and the said inorganic powder component in a solvent, Obtaining a first mixture to contain at least the inorganic powder component; Obtaining a second mixture to contain at least the solvent and the organic compound but not the inorganic powder component; A step of applying a shear force to the second mixture, And then mixing the first to-be-mixed material with the second to-be-mixed material. The method of claim 1, Preparing a mixture containing at least the inorganic powder component, the solvent and the organic compound, Separating at least the organic compound from the mixture, The inorganic powder component included in the first mixture is left after removing the organic compound from the mixture by performing a step of separating the organic compound from the mixture, The method for producing an inorganic powder paste, wherein the organic compound contained in the second mixture is taken out from the mixture by performing a step of separating the organic compound from the mixture. The method according to claim 1 or 2, The said inorganic powder component contained in a said 1st to-be-mixed body is a state disperse | distributed in a solvent, The manufacturing method of the inorganic powder paste characterized by the above-mentioned. The method according to claim 1 or 2, The said inorganic powder component contains the conductive metal powder whose average particle diameter is 10-300 nm, The manufacturing method of the inorganic powder paste characterized by the above-mentioned. The method according to claim 1 or 2, The said organic compound has the weight average molecular weights 100-10000, and the acid group group is 100-2000 micromol / g, The manufacturing method of the inorganic powder paste characterized by the above-mentioned. The method according to claim 1 or 2, The step of applying a shear force to the second to-be-mixed object includes the step of injecting the second to-be-mixed object from a predetermined injection hole while applying pressure to the second to-be-mixed object, The pressure to be applied to the second mixture is selected from 50 to 300 MPa.

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