JP4965232B2 - Conductive paste - Google Patents

Description

  The present invention relates to a conductive paste, and more particularly to a conductive paste for an internal electrode of a laminated component. The present invention also relates to an internal electrode of a multilayer component formed using the conductive paste, and a multilayer component including the internal electrode.

  In recent years, as electronic devices have become smaller and lighter, chip components mounted on the electronic devices have also been miniaturized, and multilayer components such as multilayer ceramic capacitors and multilayer inductors have been used.

  For example, a multilayer inductor is usually manufactured by firing a multilayer body of a magnetic green sheet and a layer made of a conductive paste for internal electrodes, and then forming external electrodes. As the conductive paste for internal electrodes, a conductive paste containing a solvent, a binder resin, and conductive particles is used. In general, silver particles are used as the conductive particles.

  In the above-described firing process of the laminate, the layer made of the internal electrode conductive paste tends to shrink more than the magnetic green sheet. Due to this shrinkage difference, cracks and delamination occur in the magnetic layer and internal electrode after firing, or the internal electrode is recessed more inward than the end of the magnetic layer, resulting in insufficient contact with the external electrode. A malfunction may occur. Therefore, it is necessary to adjust the shrinkage difference due to sintering during firing to improve these problems.

In addition to the method of using palladium particles together as the conductive particles of the internal electrode conductive paste, in recent years, a method of improving the shrinkage difference by blending a metal alkoxide such as titanium alkoxide with the paste has been proposed ( Patent Document 1), it was difficult to prevent the occurrence of cracks during firing at high temperatures. In addition, a method has been proposed in which a compound obtained by hydrolyzing alkoxysilane in the paste is mixed to suppress delamination (Patent Document 2). However, in these methods, the paste easily gels and is preserved. There is a problem that it is not suitable for printing fine patterns.
JP-A-6-240183 Japanese Patent Laid-Open No. 5-54714

  An object of the present invention is to provide a conductive paste used for forming an internal electrode of a multilayer component, particularly a multilayer inductor, having a controlled sinterability and excellent conductivity after firing. There is to do.

  The inventors of the present invention have found that the sinterability can be controlled without adversely affecting the conductivity by blending a specific amount of a partial hydrolysis-condensation product of tetraalkoxysilane with the conductive paste. Completed.

That is, the present invention contains 0.1 to 3 parts by weight of a partial hydrolysis condensate of tetraalkoxysilane in terms of SiO _{2 with} respect to 100 parts by weight of conductive particles, binder resin, solvent and conductive particles. The present invention relates to an internal electrode of a multilayer component formed using the conductive paste, and a multilayer component including the internal electrode.

  In the conductive paste according to the present invention, the sinterability is controlled, and defects such as cracks are suppressed in the fired film to be formed and excellent conductivity is maintained. When the internal electrode of a multilayer component such as an inductor is used, good characteristics can be given to the multilayer component.

  As the conductive particles used in the conductive paste of the present invention, those known in the art can be used, preferably silver particles. The shape of the conductive particles is not particularly limited, and examples thereof include spherical shapes and flake shapes. From the viewpoint of paste applicability, a spherical shape is preferred. The average particle diameter of the conductive particles is, for example, 0.01 to 20 μm, preferably 0.05 to 10 μm, and more preferably 0.1 to 7 μm. The conductive particles can be used alone or in combination of two or more.

  As the solvent used in the conductive paste of the present invention, those known in the art can be used, for example, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, amylbenzene, p-cymene, tetralin and petroleum-based solvents. Aromatic hydrocarbon solvents such as aromatic hydrocarbon mixtures; Terpene alcohols such as terpineol, linalool, geraniol, citronellol; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol Mono-n-butyl ether, propylene glycol mono-tert-butyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl Ether alcohol solvents such as ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether and tripropylene glycol monomethyl ether; ketone solvents such as methyl isobutyl ketone; and ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene Examples thereof include ester solvents such as glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate, and water. Solvents can be used alone or in combination of two or more.

  As the binder resin used in the conductive paste of the present invention, those known in the art can be used. For example, cellulose resins such as ethyl cellulose and nitrocellulose, acrylic resins, alkyd resins, saturated polyester resins, butyral Resins, polyvinyl alcohol, hydroxypropyl cellulose and the like can be mentioned. The binder resin can be used alone or in combination of two or more.

  In the conductive paste of the present invention, the amounts of conductive particles, solvent, and binder can be appropriately selected. Usually, electroconductive particle is 70 to 95 weight% in an electroconductive paste.

The conductive paste of the present invention, with respect to 100 parts by weight of the conductive particles, 0.1 to 3 parts by weight in terms of SiO _2, preferably partially hydrolyzed condensate of tetraalkoxysilane 0.2 to 2 parts by weight It is characterized by including.

As a partial hydrolysis-condensation product of tetraalkoxysilane, the formula (1):
Si (OR ₁ ) ₄ (1)
(Wherein, R ₁ is each independently an alkyl group having 1 to 3 carbon atoms) and a partial hydrolysis-condensation product of tetraalkoxysilane. Examples of R ₁ include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group, and among them, an ethyl group and a methyl group are preferable. It is preferable that four R < ₁ > in Formula (1) is the same.

Specifically, a partial hydrolysis-condensation product of tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane or tetraisopropoxysilane is preferred, and in particular, ease of handling, availability, and SiO ₂ content From the viewpoint of height, tetramethoxysilane or a partial hydrolysis condensate of tetraethoxysilane is preferable.

  The partial hydrolysis-condensation product of tetraalkoxysilane is preferably an average of 2-20 mer of tetraalkoxysilane, more preferably 5-10 mer, from the viewpoint of stability and workability. It is a thing.

  The partial hydrolysis-condensation product of tetraalkoxysilane can be used by dissolving or dispersing in a suitable solvent such as alcohols.

  The conductive paste of the present invention can be blended with other components within a range that does not interfere with the effects of the present invention. These components include conductive particles such as palladium, non-conductive particles such as ferrite and ceramic, alkoxides of metals such as silicon, titanium, zirconium and magnesium, these metals and acetylacetone, ethyl acetoacetate, etc. Chelate compounds, and salts of these metals with fatty acids such as 2-ethylhexanoic acid and naphthenic acid.

  The conductive paste of the present invention may further contain conventional additives such as glass frit, a dispersant, a rheology modifier, and a pigment as long as the effects of the present invention are not impaired. Also, a plasticizer such as diethyl phthalate can be added.

  The conductive paste of the present invention can be produced by mixing and uniformly dispersing each component using, for example, a lykai machine, a pot mill, a three-roll mill, a rotary mixer, a twin screw mixer or the like. .

  The conductive paste of the present invention can be applied onto a magnetic green sheet (for example, ferrite green sheet) by an appropriate method such as screen printing, laminated, and then fired to form an internal electrode. The firing temperature is usually from 850 to 950 ° C., and the firing time is from 1 to 8 hours, but can be appropriately changed. Thereafter, an external electrode can be formed to form a multilayer inductor. For other multilayer parts such as multilayer ceramic capacitors, the internal electrodes can be formed by the same method or by other known methods.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. Unless otherwise indicated, parts and% represent parts by weight and% by weight. The present invention is not limited by these examples.

Examples 1-3, Comparative Examples 1-7
With the composition shown in Table 1, each component was uniformly kneaded and dispersed by a three-roll mill to obtain pastes of Examples and Comparative Examples.

  The pastes of Examples 1 to 3, Comparative Examples 1, 2 and 4 were printed on a ferrite green sheet using a mask of stainless steel 325 mesh and emulsion thickness 25 μm, and baked at 900 ° C. for 4 hours to form a fired film. Formed. About the baked film, the cross section was observed using a 20 times microscope, and the presence or absence of the crack was confirmed. ○: No crack. X: There is a crack. Further, the volume resistivity of the fired film was calculated from the film thickness after firing and the width / length of the pattern.

  In Examples 1 to 3 and Comparative Example 1, no crack was observed in the fired film, and the volume resistivity was good. In Comparative Example 2, cracks were observed in the fired film. Moreover, in the comparative example 4 using a titanium alkoxide, although the grade of the crack of the fired film was small, it was inferior in the point of volume resistivity.

  The paste of Example 1 and Comparative Examples 2 to 7 was printed on the ferrite green sheet using the same mask as described above, and baked at 930 ° C. for 4 hours to form a baked film. In the same manner as described above, the presence or absence of cracks in the fired film and the volume resistivity of the fired film were determined.

Even when the firing temperature is 930 ° C., in Example 1, no crack is observed in the fired film, and it can be seen that the shrinkage stress due to sintering is suppressed. At the same time, the fired film of Example 1 also had good volume resistivity. In Comparative Examples 3 and 4 using Comparative Example 2 and titanium alkoxide, cracks were observed in the fired film. Moreover, in Comparative Examples 5 and 6 using palladium particles, cracks were not observed in the fired film, but the volume resistivity was poor. Furthermore, even in Comparative Example 7 in which the amount of SiO _{2 in} the partially hydrolyzed tetraalkoxysilane was outside the range of the present invention, the fired film was inferior in volume resistivity although no crack was observed.

  The pastes of Example 1 and Comparative Examples 1 and 2 were continuously printed on a ferrite green sheet using a mask of stainless steel 325 mesh, emulsion thickness 10 μm, and line width 200 μm, and the 50th printing was dried at 150 ° C. for 10 minutes. . With respect to the dried film, the line width was measured with a 100 × microscope to evaluate the printability.

  In Example 1, the line width was not reduced and was good. In Comparative Example 2, the line width slightly decreased. On the other hand, Comparative Example 1 using a hydrolyzate of tetramethoxysilane and dimethylmethoxysilane instead of a partially hydrolyzed condensate was thinned to about 50%, and printability was poor.

  Since the conductive paste for multilayer inductor internal electrode according to the present invention has controlled sinterability, the fired film to be formed is suppressed from defects such as cracks, and retains excellent conductivity. When the film is used as the internal electrode of the multilayer inductor, good characteristics can be given to the multilayer inductor, and the industrial utility is high.

Claims (8)

Conductive particles, a solvent for the binder resin and 100 parts by weight of the conductive particles, including the partially hydrolyzed condensate of tetraethoxy Shishiran an average 2 to 20 mer 0.1-3 parts by weight in terms of SiO ₂ , Conductive paste. The electrically conductive paste of Claim 1 whose partial hydrolysis-condensation product of tetraethoxysilane is an average 5-10 mer . SiO ₂ content of partially hydrolyzed condensate of tetraethoxysilane, is 40 to 48%, according to claim 1 or 2, wherein the conductive paste.   The conductive paste according to claim 1, wherein the conductive particles are silver particles.   The electrically conductive paste of any one of Claims 1-4 for internal electrodes of a laminated component.   An internal electrode of a laminated part formed using the conductive paste according to claim 5.   A laminated part comprising the internal electrode according to claim 6.   The multilayer component according to claim 7, wherein the multilayer component is a multilayer inductor.