JP2009146732A - Conductive paste for ceramic electronic component and ceramic electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive paste for a ceramic electronic component capable of suitably performing extraction of a binder and forming an electrode with fewer pores and cracks, and a ceramic electronic component having an external electrode made of such the conductive paste. <P>SOLUTION: The conductive paste for a ceramic electronic component includes metal powder, glass powder, an organic binder, and an organic solvent. The glass powder is organized with the glass powder with a low softening point wherein the softening point T<SB>S1</SB>is (T+10)°C or below when thermal decomposition terminated temperature of the organic binder is T, and the glass powder with a high softening point wherein the softening point T<SB>S2</SB>exceeds (T+10)°C. Furthermore, the content of the glass powder with a low softening point is 0.1 pts.mass or more, and less than 5 pts.mass against the metal powder of 100 pts.mass. The ceramic electronic component has the external electrode formed by using such the conductive paste. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a conductive paste used as an electrode material of a ceramic electronic component such as a multilayer ceramic capacitor, and a ceramic electronic component using such a conductive paste as an external electrode forming material.

  The multilayer ceramic capacitor has a ceramic body in which a plurality of ceramic layers are laminated, and a plurality of internal electrodes formed between the ceramic layers so that each edge is exposed at one end face of the ceramic layer, And an external electrode provided so as to be electrically connected to the exposed internal electrode. The external electrode is formed, for example, by applying and baking a conductive paste obtained by dispersing conductive metal powder and glass powder in an organic vehicle in which an organic binder is dissolved in a solvent. . In general, wet plating of nickel, tin, solder, or the like is performed on the external electrode for the purpose of improving solder wettability and solder heat resistance.

  In recent years, the use of base metals such as nickel, cobalt, and copper has become the mainstream as the metal material that constitutes the internal electrode, and accordingly, the metal powder that constitutes the external electrode has also come to be used. Of these, copper is widely used because it easily forms good electrical connections with various base metals.

  However, the external electrode using such a base metal has a drawback that pores and cracks are likely to occur compared to the conventional external electrode using a noble metal such as silver or silver / palladium for the following reasons. there were.

  That is, in the external electrode, for example, in a tunnel furnace, a process in which a solvent is removed, a process in which an organic binder is burned, decomposed, and scattered (hereinafter also referred to as “binder removal”), a glass is melted, and a metal powder is baked. It is formed through the process of tying. At this time, the higher the oxygen concentration in the atmosphere in the furnace, the better the binder removal. However, in a metal powder made of a base metal, the surface is oxidized when the oxygen concentration in the atmosphere is high (causes pores and cracks, as will be described later). For example, a low concentration oxygen atmosphere of about several to several tens of ppm. As a result, binder removal is insufficient.

  When glass fluidization and sintering of the base metal powder start with insufficient binder removal, carbonaceous organic residues (hereinafter also referred to as residual carbon) such as carbon and vehicle decomposition products are trapped in the film. End up. This confined residual carbon causes various problems at the subsequent high temperature stage, and deteriorates the characteristics and reliability of the electronic component.

  Therefore, after the binder has been completely removed, such as using a resin with good thermal decomposability as the organic binder or using a glass component that is difficult to soften at low temperatures, the glass is melted and the metal powder is sintered. Various methods have been proposed (for example, see Patent Document 1).

However, in these methods, when the binder removal is almost completed, the oxygen concentration in the atmosphere in the furnace, particularly in the film and in the vicinity of the film, is increased, so that oxidation of the metal powder surface is inevitable. When the surface of the metal powder is oxidized, the start of sintering is suppressed to a certain temperature, and when the temperature exceeds the certain temperature, the sintering starts abruptly. At the same time, rapid volume shrinkage occurs, resulting in pores and cracks. When pores or cracks occur, when plating is applied to the surface, the plating solution easily enters the interface between the external electrode and the ceramic layer and the internal electrode, resulting in poor internal defects such as reduced insulation resistance and delamination. May occur.
JP 2006-4734 A

  The present invention has been made to solve the above-described problems of the prior art, and a conductive paste for a ceramic electronic component capable of forming a sufficiently dense electrode with good removal of the binder and few pores and cracks, And it aims at providing the ceramic electronic component which used such an electrically conductive paste as an external electrode formation material.

In order to achieve the above object, the conductive paste for a ceramic electronic component of the present invention is a conductive paste containing a metal powder, a glass powder, an organic binder and an organic solvent, and the glass powder is a heat of the organic binder. When the decomposition end temperature is T, the softening point Ts ₁ is composed of a low softening point glass powder having a softening point Ts ₁ of (T + 10) ° C. or less, and a high softening point glass powder having a softening point Ts ₂ exceeding (T + 10) ° C. The content of the low softening point glass powder is 0.1 parts by mass or more and less than 5 parts by mass with respect to 100 parts by mass of the metal powder.

  Moreover, the ceramic electronic component of the present invention comprises an external electrode formed by applying and baking the conductive paste according to any one of claims 1 to 5 on the surface of a ceramic body. It is.

  According to the present invention, a conductive paste for a ceramic electronic component that is capable of forming a sufficiently dense electrode with a good debinding and having few pores and cracks, and an external electrode made of such a conductive paste It is possible to obtain a high-quality, highly reliable ceramic electronic component having

  Hereinafter, the present invention will be described in detail.

  The conductive paste for ceramic electronic parts of the present invention contains metal powder, glass powder, an organic binder and a solvent.

  Examples of the metal powder used in the present invention include a single metal composed of a base metal element such as copper, nickel and cobalt, or a powder composed of an alloy containing at least one selected from the base metal elements. Such metal powders consisting of a single metal or an alloy may be used alone or in combination of two or more.

  The shape of these metal powders is not particularly limited, and may be any shape such as a spherical shape or a flake shape. From the viewpoint of forming an external electrode with few pores and cracks, at least 50% by mass thereof. The above is preferably a spherical metal powder having an average particle size of 0.1 μm or more and less than 3 μm. That is, by containing 50% by mass or more of a spherical metal powder having an average particle size of 0.1 μm or more and less than 3 μm, when forming an external electrode, the voids in the coating film after drying are reduced. In addition, the metal powder itself is easily necked, and as a result, the occurrence of pores and cracks is suppressed. The spherical metal powder having an average particle size of 0.1 μm or more and less than 3 μm is more preferably 75% by mass or more of the whole metal powder, and almost all of the metal powder has an average particle size of 0.1 μm or more and less than 3 μm. It is even more preferable to use a spherical metal powder. In this case, the spherical metal powder preferably has an average particle size of 0.3 μm or more and less than 2.5 μm, and more preferably 0.5 μm or more and less than 2 μm. Here, the average particle diameter of the metal powder is a 50% particle diameter (D50 value) in the number cumulative distribution measured by microtrack with an echene solvent.

  The content of the metal powder in the conductive paste for ceramic electronic components is preferably 65% by mass or more and less than 85% by mass of the entire conductive paste for ceramic electronic components, and is 70% by mass or more and less than 80% by mass. More preferably. If it is less than 65% by mass, pores (voids) increase and the conductivity decreases. On the other hand, if it exceeds 85% by mass, the surface appearance becomes poor.

  The glass powder used in the present invention is basically added to facilitate the sintering of the metal powder, but in the present invention, the low softening point glass powder and the high softening point glass powder are used in combination. .

The low softening point glass powder is a glass that softens when the binder removal is completed or shortly after the binder removal is finished, specifically, when the thermal decomposition end temperature of the organic binder is T The softening point Ts ₁ is (T + 100) ° C. or lower, preferably (T + 50) ° C. or lower, more preferably (T + 20) ° C. or lower. The softening point Ts ₁ of the low softening point glass powder is preferably 400 ° C. or higher and lower than 500 ° C., more preferably 425 ° C. or higher and lower than 475 ° C.

The high softening point glass powder is a glass that softens when the metal powder is sintered. Specifically, the softening point Ts ₂ is higher than (T + 100) ° C., preferably higher than (T + 150) ° C. Preferably, it is higher than (T + 200) ° C. The softening point Ts ₂ of the high softening point glass powder is preferably 500 ° C. or higher and lower than 700 ° C., more preferably 550 ° C. or higher and lower than 650 ° C.

  When such a low softening point glass powder and a high softening point glass powder are used in combination, the low softening point glass powder is first melted and the metal powder is necked before the oxidation of the metal powder surface proceeds, Since the high softening point glass powder is softened and the sintering of the metal powder proceeds, the glass powder shrinks without causing pores or cracks. As a result, an external electrode free from pores and cracks is formed.

  In order to suppress the occurrence of pores and cracks without reducing the efficiency of binder removal and necking the metal powder, the low softening point glass powder is 0.1 parts by mass or more with respect to 100 parts by mass of the metal powder, It mix | blends in the range below 5 mass parts. Preferably they are 0.5 mass part or more and less than 3 mass parts, More preferably, they are 1 mass part or more and less than 2 mass parts. Moreover, it is preferable to mix | blend the high softening point glass powder in the range used as 5 to less than 15 mass% of the whole electrically conductive paste for ceramic electronic components. More preferably, it is the range which becomes 6 mass% or more and less than 12 mass%.

  In addition, the low softening point glass powder has an average particle diameter measured by LA-920 manufactured by HORIBA, Ltd. of 0.1 μm or more and less than 5 μm, which makes it possible to sinter the metal powder in a small amount. The melted glass powder is preferable because it is less likely to become an inhibitor of binder removal. The average particle size is more preferably 0.5 μm or more and less than 3 μm.

Examples of the low softening point glass powder and the high softening point glass powder include borate glass, silicate glass, borosilicate glass, and a mixture thereof. In particular, it is preferable to use Bi ₂ O ₃ —B ₂ O ₃ —ZnO glass powder and / or PbO—SiO ₂ —B ₂ O ₃ glass powder as the low softening point glass powder. Ceramic electronic parts with high height can be obtained.

  The organic binder used in the present invention is preferably one that thermally decomposes even when the oxygen concentration in the furnace atmosphere is low. For example, a (co) polymer of (meth) acrylate ester, (meth) acrylate ester and ( An acrylic resin such as a copolymer with (meth) acrylic acid is used. Specific examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, iso- Butyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, glycidyl methacrylate, methyl glycidyl methacrylate, 2-hydroxy (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate , Diethylaminoethyl (meth) acrylate, dimethylamino (meth) acrylate, dimethylaminoethyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate Rate, 1,6-hexanediol (meth) acrylate. Among these, iso-butyl methacrylate is preferable because it has good thermal decomposability, little residual carbon, and does not deteriorate electrical characteristics.

  An organic binder may be used individually by 1 type, and 2 or more types may be mixed and used for it. Further, the content in the conductive paste for ceramic electronic components is 2 mass of the entire conductive paste for ceramic electronic components from the viewpoint of facilitating pasting and reducing the voids in the coating film after drying. % Or more and less than 15% by mass, preferably 4% by mass or more and less than 8% by mass.

  The solvent used in the present invention can be used without any limitation as long as it can dissolve the organic binder, but when the conductive paste is applied, the coating film dries too quickly. Those without are preferred. Specifically, for example, dioxane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, butyl cellosolve acetate, butyl carbitol, butyl carbitol acetate, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diacetone alcohol, benzyl alcohol, Terpineol, dihydroterpineol and the like are used. Further, aliphatic hydrocarbons, phthalic acid esters such as butyl lactate, dibutyl phthalate and dioctyl phthalate, and adipic acid esters such as dibutyl adipate and dioctyl adipate can also be used. These solvents may be used alone or in combination of two or more. Among them, terpineol and dihydroterpineol are preferable as the solvent because a conductive paste having an appropriate viscosity can be obtained.

  The addition amount of the solvent is preferably 5 parts by mass or more and less than 30 parts by mass with respect to 100 parts by mass of the metal powder from the viewpoint of preventing sagging when applying the conductive paste. More preferably, it is less than 20 parts by mass.

  In addition to the above components, a dispersant may be added to the conductive paste for ceramic electronic components of the present invention for the purpose of improving the dispersibility of the metal powder. In addition, a leveling agent, a thickener, a thixotropic agent, an antifoaming agent, and the like can be added for the purpose of adjusting the coating shape when applied to the ceramic body. Any of these additives is used as long as the effects of the present invention are not impaired.

  The conductive paste for ceramic electronic parts of the present invention is a paste obtained by sufficiently mixing the metal powder, glass powder, organic binder, solvent, and various components blended as necessary. Can be obtained. The viscosity of the conductive paste for ceramic electronic components of the present invention is preferably 20 to 100 Pa · s (E-type viscometer, 3 ° cone, 2.5 rpm, 25 °).

  The conductive paste for ceramic electronic components of the present invention can be used for multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer ceramic inductors, multilayer ceramic thermistors, etc. It can also be used as a sex paste.

  Next, an embodiment of the ceramic electronic component of the present invention using the conductive paste for a ceramic electronic component of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a multilayer ceramic capacitor according to an embodiment of the ceramic electronic component of the present invention.

  As shown in FIG. 1, the multilayer ceramic capacitor 10 of the present embodiment includes a ceramic body 12, an internal electrode 14, an external electrode 16, and a plating film 18.

The ceramic body 12 is formed by laminating a plurality of ceramic green sheets (for example, about 30 to 50 sheets) to be the ceramic layer 12a, which are mainly composed of a dielectric material, for example, BaTiO ₃ and fired at a predetermined temperature. is there. The ceramic body 12 has a substantially rectangular parallelepiped shape.

  The internal electrode 14 is formed between the ceramic layers 12a so that each edge is exposed at one of the opposing end surfaces of the ceramic body 12. These internal electrodes 14 are formed by, for example, applying a conductive paste containing a conductive component such as copper or nickel onto a predetermined ceramic green sheet directly in a desired pattern by screen printing, an ink jet method, or the like, and simultaneously firing it. Is done.

  The thickness of the internal electrode 14 can be controlled by adjusting the coating amount of a conductive paste containing a conductive component by a known technique. Specifically, it can be controlled by a method of applying a plurality of times, a method of increasing or decreasing the solid content concentration, a method of changing the depth of the printing plate, the resist thickness of the screen plate, and the like.

  The external electrode 16 is formed by applying the conductive paste of the present invention to both end surfaces of the ceramic body 12 where the internal electrode 14 is exposed by a known method such as dipping or screen printing, and drying, for example, 700 It is formed by baking at about 900 ° C. for about 30 minutes to 2 hours. That is, the external electrode 16 is composed of a sintered body of the conductive paste of the present invention. These external electrodes 16 are electrically and mechanically joined to the internal electrode 14. The firing of the conductive paste for the external electrode 16 may be performed simultaneously with the firing of the ceramic body 12. That is, the ceramic green sheets coated with the conductive paste for the internal electrode 14 may be laminated, and the conductive paste for the external electrode 16 may be coated on both end faces of the laminated body, and then fired at the same time.

  The plating film 18 is formed by wet plating with, for example, nickel, tin, solder, or the like so as to cover the external electrode 16.

  In the multilayer ceramic capacitor 10 configured as described above, since the external electrode 16 having a high density with little residual carbon and no pores or cracks can be obtained, it is possible to prevent the occurrence of internal defect defects due to the penetration of the plating solution. And can have high reliability.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all.

Examples 1-7, Comparative Examples 1-3
Using the components shown in Table 1, a conductive paste having the composition shown in Table 2 was prepared.
First, an organic binder (component (D)) is dissolved in a solvent (component (E)), then other compounding components (components (A) to (C)) are added to this solution, and dispersed and kneaded with three rolls. Thus, a conductive paste was prepared.

  Next, each conductive paste thus obtained was applied to both ends of a 1005 type ceramic body by dipping, dried at 150 ° C. for 15 minutes, and then heated at 800 ° C. for 50 minutes in a nitrogen atmosphere. The paste was baked to form external electrodes. Thereafter, a nickel plating film was formed on the external electrode by electroless plating, and a tin plating film was further formed on the nickel plating film by electrolytic plating to produce a multilayer ceramic capacitor.

  Various characteristics of the conductive pastes and multilayer ceramic capacitors obtained in the above Examples and Comparative Examples were evaluated by the methods shown below. The results are also shown in Table 1.

[Denseness]
The ceramic body on which the external electrode was formed was cut from one external electrode to the other external electrode, and the area ratio of pores on the cut surface (external electrode) was calculated by image analysis and evaluated according to the following criteria (sample) Number 50 each).
◎: Pore area ratio 0% or more, less than 1% ○: Pore area ratio 1% or more, less than 5% ×: Pore area ratio 5% or more [crack]
The cut surface (external electrode) was observed, and the occurrence of cracks (dents reaching the end of the ceramic body) or dents was examined and evaluated according to the following criteria (50 samples each).
◎: No crack or dent of 3 μm or less ○: No crack, but dent of 3 μm or less ×: Cracked [High temperature test]
The insulation resistance of the multilayer ceramic capacitor was measured, and after heat treatment at 180 ° C. for 10 hours, the insulation resistance was measured again, and the reduction rate was calculated and evaluated according to the following criteria (200 samples each). In addition, evaluation was performed by the average value of all the samples.
◎: Reduction rate 0% or more, less than 3% ○: Reduction rate 3% or more, less than 10% ×: Reduction rate 10% or more

  As is clear from Table 2, all of the examples were free from cracks, had high density, and the results of the high temperature test were also good. On the other hand, in Comparative Example 1 and Comparative Example 3 to which no low softening point glass powder was added, cracks occurred, and the decrease in insulation resistance in the high temperature test was large. Further, in Comparative Example 2 in which the low softening point glass powder was excessively blended, the compactness was reduced, cracks were generated, and the insulation resistance was greatly reduced in the high temperature test.

It is sectional drawing which shows one Embodiment of the ceramic electronic component of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Multilayer ceramic capacitor (ceramic electronic component), 12 ... Ceramic body, 12a ... Ceramic layer, 14 ... Internal electrode, 16 ... External electrode, 18 ... Plating film

Claims (6)

A conductive paste containing metal powder, glass powder, organic binder and organic solvent,
The glass powder has a low softening point glass powder having a softening point Ts ₁ of (T + 100) ° C. or lower and a softening point Ts ₂ higher than (T + 100) ° C., where T is the thermal decomposition end temperature of the organic binder. Made of softening point glass powder, and
Content of the said low softening point glass powder is 0.1 mass part or more and less than 5 mass parts with respect to 100 mass parts of said metal powder, The electrically conductive paste for ceramic electronic components characterized by the above-mentioned. Softening point Ts ₁ of the low-softening point glass powder is 400 ° C. or more and less than 500 ° C., a softening point Ts ₂ high softening point glass powder is 500 ° C. or higher, according to claim 1, wherein less than 700 ° C. Conductive paste for ceramic electronic parts.   The conductive paste for ceramic electronic parts according to claim 1 or 2, wherein the low softening point glass powder has an average particle diameter of 0.1 µm or more and less than 5 µm. 4. The low softening point glass powder includes Bi ₂ O ₃ —B ₂ O ₃ —ZnO-based glass powder and / or PbO—SiO ₂ —B ₂ O ₃ -based glass powder. The conductive paste for ceramic electronic components according to claim 1.   5. The conductive paste for a ceramic electronic component according to claim 1, wherein 50% by mass or more of the metal powder is a spherical metal powder having an average particle diameter of 0.1 μm or more and less than 3 μm. .   A ceramic electronic component comprising an external electrode formed by applying and baking the conductive paste according to any one of claims 1 to 5 on a surface of a ceramic body.

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