JP4816202B2 - Conductive paste and method for manufacturing ceramic electronic component - Google Patents

Description

  The present invention relates to a conductive paste and a method for manufacturing a ceramic electronic component, and more particularly to a conductive paste used for forming an external electrode of a ceramic electronic component and a method for manufacturing a ceramic electronic component using the conductive paste.

  External electrodes of ceramic electronic components such as multilayer ceramic capacitors are generally formed by applying a conductive paste to the surface of a ceramic body and performing a firing process.

  As this conductive paste, from the viewpoint of enhancing the bondability between the ceramic layer and the external electrode (in the case of a multilayer ceramic electronic component, the ceramic layer and the internal electrode and the external electrode), the sinterability of the external electrode is conventionally increased. From the viewpoint of promotion, those containing a glass component are widely used.

  For example, Patent Document 1 discloses a conductive paste containing Cu powder, glass frit, and organic binder resin, wherein the glass frit is made of Zn and Cu-containing borosilicate glass, and in a molten state in a nitrogen atmosphere. A conductive paste having a contact angle with respect to Cu of 90% or less has been proposed.

  In this Patent Document 1, since the glass frit is contained in the conductive paste, voids formed on the surface of the external electrode, the inside, or the interface with the ceramic layer by the firing process are filled with the glass frit, and the ceramic paste is thereby formed. The bondability between the layer and the external electrode or between the ceramic layer and the internal electrode and the external electrode can be improved. In addition, since the melting point of the glass frit is relatively low, sintering at a low temperature is possible and the sinterability can be promoted.

JP-A-11-260146

  By the way, in ceramic electronic parts, for the purpose of improving heat resistance and solder wettability, wet plating, for example, electrolytic plating is usually applied to the external electrode, thereby forming a plating film such as Ni or Sn on the surface of the external electrode. ing.

  On the other hand, when forming the external electrode of a ceramic electronic component using the electrically conductive paste containing a glass component like patent document 1, a glass component precipitates on the surface of an external electrode after sintering.

  However, since the glass component is inferior in plating resistance as compared with metal components such as Ag and Cu, the deposited glass component is eroded during the wet plating process, which is a subsequent step after the formation of the external electrode. There is a possibility that the plating solution may infiltrate from the formed portion and deteriorate the characteristics as a ceramic electronic component.

  The present invention has been made in view of such circumstances, and a conductive paste capable of ensuring sufficient plating resistance even if it contains a glass component, and a ceramic electronic component using the conductive paste It aims at providing the manufacturing method of.

In order to achieve the above object, a conductive paste according to the present invention is a conductive paste used for forming an external electrode of a ceramic electronic component, and includes a conductive powder, a glass powder, and an organic vehicle. Is coated with a metal film formed of a metal material having a melting point lower than that of the metal powder on the surface of the core metal powder, and the metal powder includes Ag, Cu, Ni, and these metal elements And the metal film is made of any one metal element of Bi and Sb .

  Furthermore, in the method for manufacturing a ceramic electronic component according to the present invention, the conductive paste is applied to the surface of the ceramic body, and then the ceramic body to which the conductive paste is applied is subjected to a firing treatment. And forming a plating film on the surface of the external electrode by performing a plating process thereafter.

According to the conductive paste of the present invention, the conductive powder contains a conductive powder, a glass powder, and an organic vehicle, and the conductive powder is formed of a metal material having a melting point lower than that of the metal powder on the surface of the core metal powder. The metal powder is made of at least one selected from Ag, Cu, Ni, and an alloy containing these metal elements as a main component, and the metal film is made of Bi. And Sb, the metal film having a low melting point melts faster than the metal powder during firing after applying the conductive paste to the ceramic body, and the surface tension of the metal film Gaps generated on the surface, inside, or interface of the external electrode are filled. As a result, the precipitation of the glass component is reduced, and the external electrode can be prevented from being eroded by the plating solution. Accordingly, even when a ceramic electronic component is formed using a conductive paste containing glass powder, it is possible to prevent the characteristics of the ceramic electronic component from deteriorating without impairing the sinterability.

  Further, according to the method for manufacturing a ceramic electronic component of the present invention, the conductive paste is applied to the surface of the ceramic body, and then the ceramic body to which the conductive paste is applied is subjected to a firing process to perform the ceramic element. Since an external electrode is formed on the surface of the body and then a plating treatment is performed to form a plating film on the surface of the external electrode, it is possible to prevent the plating solution from entering the external electrode even if the plating treatment is performed. Therefore, various ceramic electronic parts having good characteristics can be produced with high efficiency without impairing the sinterability.

  Next, an embodiment of the present invention will be described in detail.

  The conductive paste as one embodiment of the present invention contains a conductive powder, a glass powder, and an organic vehicle.

  As shown in FIG. 1, the conductive powder is covered with a metal film 2 formed of a metal material having a melting point lower than that of the metal powder 1 on the surface of the metal powder 1 serving as a nucleus.

  That is, in the conductive paste for external electrode formation of ceramic electronic components, from the viewpoint of improving the bonding property between the ceramic layer and the external electrode (the ceramic layer and the internal electrode and the external electrode in a multilayer ceramic capacitor) and promoting the sintering of the external electrode In the past, the conductive paste contains a glass component. However, as described in the section [Problems to be solved by the invention], the glass component is inferior in plating resistance, and thus deposited on the surface of the external electrode. The glass component is eroded by a wet plating process, which is a subsequent process, and as a result, the plating solution may infiltrate from the eroded portion, which may cause deterioration of characteristics as a ceramic electronic component.

  Therefore, in the present embodiment, the metal powder 1 is covered with a metal film 2 formed of a metal material that is superior in plating resistance to glass powder and has a melting point lower than that of the metal powder 1.

  That is, when the metal powder 1 is coated with the metal film 2 having a lower melting point than the metal powder 1, the metal film 2 having a lower melting point melts faster than the metal powder 1 during the firing process, and the surface tension of the metal film 2 Gaps generated on the surface, inside, or interface of the external electrode are filled. And as a result, it can suppress that glass powder precipitates on the surface of an external electrode, and can prevent that an external electrode infiltrates with a plating solution.

  This realizes a conductive paste having good bonding properties between the ceramic layer and the external electrode (in the case of a multilayer ceramic electronic component, the ceramic layer and the internal electrode and the external electrode) and having excellent plating resistance. .

  The material type of the metal powder 1 and the metal film 2 is not particularly limited as long as the melting point of the metal film 2 is lower than the melting point of the metal powder 1. Further, since Ag having a melting point of 961 ° C., Cu having a melting point of 1083 ° C., Ni having a melting point of 1453 ° C., or an alloy containing these as the main components is used, Bi having a melting point of 271 ° C. However, Sb having a temperature of 630 ° C. can be preferably used.

  In addition, as a particle size of the metal powder 1, it is desirable that it is as fine as possible from the viewpoint of obtaining high density, and the metal powder 1 of 0.1 to 1.0 μm can be used preferably. Moreover, the film thickness of the metal film 2 is preferably 0.015 to 0.05 μm. This is because if the film thickness is less than 0.015 μm, the denseness of the external electrode is lowered and the desired effect may not be obtained. If the film thickness exceeds 0.05 μm, the cost increases. It is because there is a possibility of inviting.

As the glass powder contained in the conductive paste is not limited in particular, it is possible to use borosilicate glass powder containing, for example, B ₂ O ₃ and Bi ₂ O _3.

  As the organic vehicle, for example, an organic binder such as ethyl cellulose resin dispersed in an organic solvent such as terpineol, for example, at a weight ratio of about 1: 3 can be used. Further, the total amount of the conductive powder and the glass powder, that is, the content of the solid content in the conductive paste is preferably 64 to 94% by weight in consideration of printability. Further, the content of the organic vehicle is preferably about 6 to 36% by weight. As the organic solvent, xylene, dioctyl phthalate or the like may be used in addition to terpineol.

  Next, the manufacturing method of the said electrically conductive paste is demonstrated.

  First, conductive powder in which the metal powder 1 is coated with the metal film 2 is produced.

  That is, a metal powder 1 such as Ag, Cu, or Ni is prepared, and the metal powder 1 is washed with pure water and dispersed in a metal salt aqueous solution containing metal ions such as Bi and Sb in a wet powder state. The reason why the metal powder 1 is dispersed in the metal salt aqueous solution without being dried is to prevent the metal powder 1 from aggregating in the metal salt aqueous solution.

  Next, the reducing agent aqueous solution containing the reducing agent is added to and mixed with the metal salt aqueous solution. Then, a redox reaction occurs between the metal salt and the reducing agent, and the reducing agent emits electrons, while the metal ions accept the electrons and are deposited on the surface of the metal powder 1. For example, when the metal ion is Bi ion, a divalent water-soluble compound such as stannous chloride can be preferably used as the reducing agent. That is, when stannous chloride is added to the Bi salt aqueous solution, a redox reaction occurs between the Bi salt (for example, bismuth chloride) and stannous chloride, and Bi is deposited on the surface of the metal powder 1.

  Then, after that, a drying treatment is performed, and further, a heat treatment is performed as necessary, followed by a pulverization treatment, whereby a conductive powder in which the metal powder 1 is coated with the metal film 2 can be obtained.

  Next, the conductive powder and glass powder thus obtained are dispersed in an organic vehicle using a kneader such as a three-roll mill or a Hoovermarler, thereby producing a conductive paste.

  Next, a multilayer ceramic capacitor as a ceramic electronic component manufactured using the conductive paste will be described in detail.

  FIG. 2 is a cross-sectional view schematically showing an embodiment of the multilayer ceramic capacitor.

  In the multilayer ceramic capacitor, internal electrodes 4 (4a to 4f) are embedded in the ceramic body 3, external electrodes 5a and 5b are formed at both ends of the ceramic body 3, and the external electrodes 5a, 5b, First plating films 6a and 6b and second plating films 7a and 7b are formed on the surface of 5b.

  Specifically, the internal electrodes 4a to 4f are arranged in parallel in the stacking direction, the internal electrodes 4a, 4c, and 4e are electrically connected to the external electrode 5a, and the internal electrodes 4b, 4d, and 4f are external electrodes 5b. And are electrically connected. And the electrostatic capacitance is acquired between the opposing surfaces of the internal conductors 4a, 4c, and 4e and the internal conductors 4b, 4d, and 4f.

  The multilayer ceramic capacitor is manufactured as follows.

  First, a ceramic green sheet mainly composed of a dielectric material such as barium titanate is prepared, and then a conductive paste for forming an internal electrode mainly composed of Ni, Ag, Pd or the like is used. Screen printing is performed thereon to form a conductive pattern having a predetermined shape.

  After that, a plurality of ceramic green sheets on which conductive patterns are formed are laminated in a predetermined direction, sandwiched between ceramic green sheets on which conductive patterns are not formed, crimped, and cut into predetermined dimensions to produce a ceramic laminate. To do. Thereafter, a binder removal process is performed at a temperature of about 500 ° C., and then a firing process is performed in an atmosphere at a temperature of 1000 to 1500 ° C. for a predetermined time, thereby producing the ceramic body 3 in which the internal electrode 4 is embedded.

  Next, the above-described conductive paste for forming an external electrode is applied to both end faces of the ceramic body 3 and then dried, and then fired at a temperature of 600 to 700 ° C. for a predetermined time in an air atmosphere or a low oxygen concentration atmosphere. Apply. As a result, the metal powder in the conductive paste is sintered to form the external electrodes 5a and 5b.

  Next, electrolytic plating is performed to form first plating films 6a and 6b made of Ni, Cu or the like on the surfaces of the external electrodes 5a and 5b. Further, solder or Sn is formed on the surfaces of the first plating films 6a and 6b. The second plating films 7a and 7b made of etc. are formed, whereby a multilayer ceramic capacitor is manufactured.

  As described above, in the present multilayer ceramic capacitor, the external electrodes 5a and 5b are formed on both end faces of the ceramic body 3 by using the conductive paste described above, and therefore the external electrodes 5a and 5b are formed densely. Since it is also excellent in plating resistance, it is possible to prevent the plating solution from entering the external electrodes 5a and 5b even if wet plating treatment such as electrolytic plating is subsequently performed, and as a ceramic electronic component It is possible to avoid deterioration of characteristics.

  In addition, although this invention is not limited to the said embodiment, In the said embodiment, although electroconductive powder is formed by the electroless-plating method, it is not limited to this. In the above embodiment, the case where the conductive paste of the present invention is applied to a multilayer ceramic capacitor has been described. Needless to say, the present invention can also be applied to other ceramic electronic components.

  Next, examples of the present invention will be specifically described.

  First, Ag (melting point: 961 ° C.), Cu (melting point: 1083 ° C.), and Ni (melting point: 1453 ° C.) having an average particle diameter of 1 μm are prepared as the metal powder that becomes the core of the conductive powder, and then the electroless plating method. A Bi film (melting point: 271 ° C.) having an average film thickness of 0.015 to 0.05 μm or an Sb film (melting point: 630 ° C.) having a film thickness of 0.015 μm is formed on the surface of these metal powders using a metal film. A conductive powder coated with metal powder was obtained.

  The metal film thickness was adjusted by controlling the plating time.

  Next, an organic vehicle was produced by uniformly dispersing the ethyl cellulose resin in terpineol so that the ratio of ethyl cellulose resin to terpineol was 2.67: 1 by weight.

  Next, the conductive powder, the B-Bi-Si glass as the glass powder, and the organic vehicle were kneaded with a Hoovermarler so as to be the composition components of Examples 1 to 6 in Table 1, thereby conducting the conductive paste. Was made.

  Further, as a comparative example, Ag, Cu, Ni, and Bi having an average particle diameter of 1 μm are prepared as conductive powders, and these conductive powders and glass powders are used as the composition components of Comparative Examples 1 to 4 in Table 1. B-Bi-Si based glass and the above organic vehicle were kneaded with a Hoovermarler to produce a conductive paste.

  Table 1 has shown the component composition of each electrically conductive paste of Examples 1-6 and Comparative Examples 1-4.

次に、Ｎｉを主成分とする内部電極が埋設され、かつチタン酸バリウムを主成分とした外形寸法が長さ１．６ｍｍ、幅０．８ｍｍ、厚み０．８ｍｍのセラミック素体を用意した。

Next, a ceramic body was prepared in which an internal electrode mainly composed of Ni was embedded and the outer dimensions mainly composed of barium titanate were 1.6 mm in length, 0.8 mm in width, and 0.8 mm in thickness.

  Next, the conductive paste is applied to both end faces of the ceramic body, dried at a temperature of 150 ° C. for 10 minutes, and then at a maximum temperature of 600 ° C. and 700 ° C. for 10 minutes in a nitrogen atmosphere with an oxygen concentration of 100 ppm or less. It hold | maintained and the baking process was performed by this and the external electrode was formed and the samples of Examples 1-6 and Comparative Examples 1-4 were produced.

  Next, after cross-polishing the external electrode of each sample, the surface layer surface of the external electrode, the intermediate portion, and the interface with the ceramic body were observed with a scanning electron microscope (SEM) for image analysis. Then, the area obtained by dividing the area of the metal part by the area of the measured region and adding 100 to that value was calculated as the density.

  Table 2 shows the measurement results.

比較例１は、導電性粉末として粒径１μｍのＡｇ粉のみを使用しているため、緻密度は、焼成温度が６００℃の場合で６５％、焼成温度が７００℃の場合で７０％であった。

Since Comparative Example 1 uses only Ag powder having a particle size of 1 μm as the conductive powder, the density is 65% when the firing temperature is 600 ° C. and 70% when the firing temperature is 700 ° C. It was.

  In contrast, in Examples 1 to 3, Ag powder having a particle size of 1 μm is coated with a Bi film, so that the density becomes 99% at both the firing temperatures of 600 ° C. and 700 ° C., and the denseness is remarkably improved. I understood that.

  Comparative Example 2 is a mixture of Ag powder and Bi powder having a particle size of 1 μm so that the composition component of the conductive powder is the same weight ratio as in Example 1. The Ag powder is a Bi film. Since it is not a coated form, the density is 94% when the firing temperature is 600 ° C. and 97% when the firing temperature is 700 ° C., which is higher than that in Example 1 in which Ag powder is coated with a Bi film. It turned out to be inferior.

  In Example 4, Ag powder was coated with an Sb film instead of the Bi film. In this case, the density was 99% at both the firing temperatures of 600 ° C. and 700 ° C. That is, it was confirmed that the denseness was improved by using a conductive powder coated with a metal film having a melting point lower than that of the metal powder.

  Example 5 and Comparative Example 3 are samples in which the weight composition ratio of the Cu component and the Bi component in the conductive powder is 20: 1. In Comparative Example 3, Cu powder and Bi powder having a particle diameter of 1 μm are simply mixed, so the density is 86% when the firing temperature is 600 ° C. and 96% when the firing temperature is 700 ° C. there were. On the other hand, in Example 5, since the Cu powder was coated with the Bi film, the density was 99% at both the firing temperatures of 600 ° C. and 700 ° C., and it was found that the denseness was improved.

  Example 6 and Comparative Example 4 are samples in which the weight composition ratio of the Ni component and the Bi component in the conductive powder is 5.8: 1. In Comparative Example 4, since Ni powder and Bi powder having a particle diameter of 1 μm are simply mixed, the density is 48% when the firing temperature is 600 ° C. and 55% when the firing temperature is 700 ° C. there were. On the other hand, in Example 6, since Ni powder was coated with a Bi film, the density was 65% when the firing temperature was 600 ° C. and 75% when the firing temperature was 700 ° C. It was found that the denseness was improved as compared with. That is, it was confirmed that the metal powder was coated with a metal film having a melting point lower than that of the metal powder, thereby improving the denseness.

It is sectional drawing which shows typically one Embodiment of the electroconductive powder contained in the electroconductive paste which concerns on this invention. It is sectional drawing which shows one Embodiment of the multilayer ceramic capacitor as a ceramic electronic component manufactured using the electrically conductive paste of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal powder 2 Metal film 3 Ceramic body 5a, 5b External electrode 6a, 6b Plating film 7a, 7b Plating film

Claims (2)

A conductive paste used for forming external electrodes of ceramic electronic components,
Contains conductive powder, glass powder and organic vehicle,
The conductive powder is coated with a metal film formed of a metal material having a melting point lower than that of the metal powder on the surface of the core metal powder ,
The metal powder is composed of at least one selected from Ag, Cu, Ni, and an alloy containing these metal elements as a main component, and the metal film is one of Bi and Sb. A conductive paste comprising any of the above metal elements . The conductive paste according to claim 1 is applied to the surface of the ceramic body, and then the ceramic body to which the conductive paste is applied is fired to form external electrodes on the surface of the ceramic body, and then A method for producing a ceramic electronic component, comprising performing a plating treatment to form a plating film on the surface of the external electrode.

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