JP2005340289A - Manufacturing method of laminated ceramic element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a laminated ceramic element by using conductive paste comprising a resin component with which degreasing can sufficiently be performed even if calcination is performed at 400°C or below, and to provide the manufacturing method of the laminated ceramic element which secures efficient electrical conductivity with a ceramic body, and does not lead thermal stress into the ceramic main body. <P>SOLUTION: The resin component which is mainly composed of polyoxyalkylene resin or polyacrylic ester resin, solvent and conductive paste for a ceramic green sheet which becomes an outer electrode containing metal particulate are applied to the surface of a laminated sheet of a ceramic green sheet so as to be calcinated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a multilayer ceramic element.

  The multilayer ceramic element is a capacitor, a piezoelectric element, or the like obtained by firing a multilayer sheet obtained by laminating ceramic green sheets on which internal electrodes are printed.

  An external electrode that is electrically connected to the internal electrode is formed on the surface of the multilayer ceramic element. The external electrode is a process in which a paste consisting mainly of metal fine particles, a resin and a solvent, called a conductive paste, is applied to both ends of a laminated sheet of ceramic green sheets so as to be electrically connected to the internal electrode, and the ceramic green sheet is fired And formed by sintering metal fine particles contained in the conductive paste.

  In the firing process, the resin and solvent contained in the conductive paste are removed by volatilization or decomposition, and the external electrode is composed of a sintered metal component.

  In general, the conductive paste contains glass frit in order to adhere the external electrode to the fired ceramic. The glass frit melts during the firing process and can strengthen the bond with the ceramic.

  However, in order to integrate the glass frit and the ceramic, it is necessary to fire at 600 ° C. or higher. Therefore, thermal stress remains in the obtained multilayer ceramic element, and if this residual stress is large, it is heated by soldering or the like. There has been a problem that cracks occur when it is applied.

  In addition, in order to bring the external electrode into close contact with the ceramic, a polymer electrode or the like has been studied, but there is a problem that conductivity is not good.

  Therefore, as disclosed in Patent Document 1, a method of forming an external electrode using a conductive paste containing metal fine particles, a metal organic compound, a resin and a solvent without using glass frit is used. According to Patent Document 1, the adhesion to the ceramic is high even if it uses metal fine particles such as noble metal ultrafine particles having high reactivity and metal organic compounds such as metal alkoxides regardless of glass frit. It is supposed to be done. Moreover, since it does not contain glass frit, it is said that the firing temperature can be suppressed to 400 ° C. or lower.

However, since the conductive paste disclosed in Patent Document 1 has high adhesion to the ceramic without using glass frit, it can be said that a baking temperature of 600 ° C. or higher for melting the glass frit is not necessary. The resin component contained in 1% to 20% is not sufficiently decomposed and removed at 400 ° C. or lower, so that the degreasing is not sufficiently performed in the firing process of the external electrode, and the conductivity with the internal electrode is lowered. was there.
JP 2002-246258 A

  FIG. 1 is a schematic cross-sectional view showing an example of a conventional multilayer ceramic capacitor. The multilayer ceramic capacitor 4 is characterized in that the external electrode 3 has a two-layer structure of a glass contact electrode 7 and a polymer electrode 6, and the glass contact electrode 7 is disposed between the polymer electrode 6 and the ceramic body 1. .

  The glass contact electrode 7 is formed by applying a metal powder, glass frit, a conductive paste made of a resin and a solvent, and baking it.

  In other words, in order to integrate with the ceramic body 4 with sufficient strength, there is no use other than using a glass frit. Integration of the metal powder and the internal electrode 2 is enhanced by the integration of the glass frit and the ceramic. The glass contact electrode 7 also improves the continuity between the internal electrode 2 and the polymer electrode 6.

  However, the provision of the glass contact electrode 7 requires an original problem, that is, high-temperature firing at 600 ° C. or higher with respect to the glass frit, thermal stress remains in the ceramic body, and stress cracking occurs due to heating during soldering. The danger reignites. That is, the glass contact electrode 7 introduced in order to eliminate the defects of the polymer electrode 6 faces a situation where the first defect is restored.

  The introduction of the polymer electrode 6 is a necessary means for preventing stress cracking. In order to eliminate the defect of poor conduction due to the introduction of the polymer electrode 6, there is currently a demand for a technique that can search for means other than adding glass frit and replace the glass contact electrode 7.

  In the past, in order to obtain a multilayer ceramic element having no thermal stress residue and no problem in electrical conductivity, a resin that can be fired and degreased at a low temperature of 400 ° C. or lower has been demanded. A resin component capable of degreasing was not obtained. The subject of this invention is providing the manufacturing method of the laminated ceramic element using the electrically conductive paste containing the resin component which can fully degrease, even if it bakes at 400 degrees C or less. Accordingly, it is possible to provide a method for manufacturing a multilayer ceramic element that ensures efficient electrical conductivity with the ceramic body and does not introduce thermal stress into the ceramic body.

  In the present invention, as shown in FIG. 2, a resin mainly composed of a polyoxyalkylene resin or a polyacrylic resin is applied to the internal electrode 2 exposed on the surface of a laminated sheet obtained by laminating ceramic green sheets on which the internal electrode 2 is printed. This is a method for manufacturing a multilayer ceramic element 4 in which a conductive paste for a ceramic green sheet containing a component, a solvent, and metal fine particles is applied so as to be an external electrode 3 electrically connected to the internal electrode 2 and the multilayer sheet is fired.

  In the method for manufacturing the multilayer ceramic element 4 of the present invention, the resin contained in the conductive paste for ceramic green sheets used for forming the external electrode 3 is a resin mainly composed of a polyoxyalkylene resin or a polyacrylic resin. Since it can be fired at 400 ° C. or lower, the multilayer ceramic element 4 can be produced at a low firing temperature.

Details of the present invention will be described below.
In the present invention, a conductive paste for a ceramic green sheet that becomes the external electrode 3 is applied so as to be electrically connected to the internal electrode 2 exposed on the surface of the laminated sheet in which the ceramic green sheets on which the internal electrodes 2 are printed are laminated.

  The method for applying the conductive paste for the ceramic green sheet to the surface of the multilayer ceramic sheet is not particularly limited. For example, the blade method, the extrusion method, the screen printing method, the dipping method, the spray method, the dispense coating method using a die bonder, etc. Is mentioned.

  In the dipping method, the conductive paste for ceramic green sheets is stored in a container having a constant volume, and the paste surface is adjusted horizontally. Next, the surface on which the internal electrode 2 is exposed is immersed in a predetermined width in the direction perpendicular to the paste surface to form a coating film for the external electrode. This is performed for both end faces.

The viscosity characteristic of the conductive paste for ceramic green sheets is preferably thixotropic, and this viscosity characteristic can be evaluated using, for example, an E-type viscometer manufactured by Tokimec.
Due to this characteristic, the stringiness when applied is suppressed, and a uniform thickness can be formed.
This viscosity characteristic can be appropriately set according to the application conditions by mainly adjusting the ratio of the resin component described later contained in the conductive paste for ceramic green sheets.

  The conductive paste for a ceramic green sheet used in the present invention contains metal fine particles, a resin component, and a solvent as main components.

  The metal fine particles are not particularly limited, and known metals that can be sintered at 400 ° C. or lower are used, and examples thereof include gold fine particles, silver fine particles, and copper fine particles. In addition, since the activity increases when the metal fine particle is changed from a nano size called an ultra fine particle to a sub-micron size, the metal fine particle is preferably an ultra fine particle size metal ultra fine particle. Since the metal ultrafine particles are likely to aggregate, the metal surface is more preferably a surface-treated metal ultrafine particle whose surface is coated with a fatty acid, a fatty acid salt or a fatty acid ester.

  As described above, the ultrafine metal particles include ultrafine particles formed of a single metal and ultrafine particles in which the periphery of the metal core is covered with an organic substance. Examples of the latter ultrafine metal particles include ultrafine particles disclosed in JP-A-10-183207. These ultrafine particles have metal nuclei inside, surrounding them with metal organic compounds as the base material, and organic components are arranged facing outward, so that the aggregation of ultrafine metal particles in organic solvents It is a small and stable dispersion state. As an example, there are silver ultrafine particles coated with fatty acids, particularly silver ultrafine particles coated with linear fatty acids.

  The metal nuclei of the ultrafine metal particles include Cu, Ag, Au, Zn, Cd, Ga, In, Si, Ge, Sn, Pd, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, There are V, Cr, Mn, Y, Zr, Nb, Mo, Ca, Sr, Ba, Sb and the like, and the diameter of the metal core is 1 to 100 nm.

  Examples of the metal organic compound include an organometallic complex, an organometallic compound, and a metal alkoxide. Specific examples include metal salts of fatty acids such as naphthenic acid, octylic acid, stearic acid, benzoic acid, p-toluic acid, and n-decanoic acid; metal alkoxides such as isopropoxide and ethoxide; and metal complex salts of acetylacetone. Examples of the naphthenic acid metal salt include silver naphthenate, bismuth naphthenate, vanadium naphthenate, and the like, and not only precious metals but also various metal naphthenates are used.

  The conductive paste for ceramic green sheets used in the present invention contains a polyoxyalkylene resin or a polyacrylic resin as a main component as a resin component.

  Examples of the polyacrylic resin include poly (meth) acrylic acid ester resin, poly (meth) acrylic acid amide resin, polyamino (meth) acrylate resin, polyepoxy (meth) acrylate resin, and the like.

  A mixed resin obtained by mixing a polyoxyalkylene resin and a poly (meth) acrylic resin may be used as the resin component. Furthermore, a crosslinked resin obtained by crosslinking a polyoxyalkylene resin and a poly (meth) acrylic resin with a crosslinking agent may be contained as a resin component.

  Although it does not specifically limit as polyoxyalkylene resin, For example, polyoxypropylene glycol, polyoxyethylene glycol, polyoxytetramethylene glycol etc. are mentioned. Among them, it is preferable to use as a mixed resin of polyoxypropylene glycol and polyoxyethylene glycol and / or polyoxytetramethylene glycol, and the content of polyoxypropylene in the mixed resin is more than 50% by weight. preferable. By adjusting the mixing ratio of the resin using such a mixed resin, it is possible to adjust the temperature disappearing by firing and degreasing and the time until disappearance.

  The molecular weight of the polyoxyalkylene resin is not particularly limited, but a preferred lower limit is 500 and a preferred upper limit is 5 million.

  The polyoxyalkylene resin may be a copolymer, such as polymethylene glycol (polyacetal), polyethylene glycol, polypropylene glycol, polytrimethylene glycol, polytetramethylene glycol, polybutylene glycol, and the like. Examples include a plurality of different segments. Moreover, what contains components, such as a polyurethane, polyester, polyamide, a polyimide, and a (poly) oxyalkylene component obtained from this, is mentioned. In addition, these include (meth) acrylic polymers having a (poly) alkylene glycol segment in the graft chain, vinyl polymers such as polystyrene, and the like, and a plurality of these polymers may be used in combination.

  The number average molecular weight of the copolymer is not particularly limited, but the preferred lower limit is 5000 and the preferred upper limit is 5 million.

  The resin component contained in the conductive paste for ceramic green sheets used in the present invention may be a curable resin.

  For example, those obtained by crosslinking a polyoxyalkylene resin and a poly (meth) acrylic resin can be mentioned. Specifically, for example, polyoxyalkylene or poly (meth) having a functional group curable with a curing agent. Mention may be made of those obtained from acrylic esters.

  The polyoxyalkylene resin in the present invention is preferably a polyalkylene glycol resin having a hydrolyzable silyl group as a functional group. Examples of commercially available products include MS polymers S-203, S-303, S-903 and the like as trade name MS polymers manufactured by Kaneka Chemical Industry Co., Ltd .; -403, MA-447, etc .; EP103S, EP303S, EP505S, etc. as trade name epions; ESS-2410, ESS-2420, ESS-3630, etc. as trade name excel manufactured by Asahi Glass Co., Ltd. are mentioned.

  Specifically, alkoxysilyl-modified polypropylene glycol (MS polymer S-303, manufactured by Kaneka Chemical Co., Ltd.), poly (isobutyl methacrylate) (molecular weight 300,000), terpineol as a solvent, and dibutyltin dilaurate as a curing agent are used as a resin component. It is preferable to use it.

  The polyoxyalkylene resin may be a cross-linked resin that is cross-linked using a chain extender.

  A resin having a polymerizable unsaturated group such as a (meth) acryloyl group or a styryl group and a polyalkylene glycol segment is also preferable. For example, α, ω-di (meth) acryloyloxypolypropylene glycol, α, ω-di (meth) ) Acryloyloxypolyethylene glycol, α- (meth) acryloyloxypolypropylene glycol, α- (meth) acryloyloxypolyethylene glycol and the like, and commercially available products include, for example, Nippon Oil & Fats Bremer Series; Shin-Nakamura Chemical Company NK Ester M Series; Company NK Ester AMP Series; Company NK Ester BPE Series; Company NK Ester A Series; Company NK Ester APG Series; Toa Gosei Co., Ltd. Aronix M-240; Toa Gosei Co., Ltd. Aronix M − 45; Aronix M-260 manufactured by Toa Gosei Co., Ltd. Aronix M-270 manufactured by Toa Gosei Co., Ltd .; PE series manufactured by Daiichi Kogyo Seiyaku; BPE series manufactured by Daiichi Kogyo; BPP series manufactured by Kyoeisha Chemical Co. 9EG; Company light ester 14EG; Company light acrylate MTG-A; Company light acrylate DPM-A; Company light acrylate P-200A; Company light acrylate 9EG; Company light acrylate BP-EPA and the like.

  Examples of the poly (meth) acrylate resin include poly (meth) acrylate methyl, poly (meth) ethyl acrylate, poly (meth) acrylate propyl, poly (meth) acrylate butyl, and poly (meth) acrylate. ) Hexyl acrylate, octyl poly (meth) acrylate, and the like. The copolymer is not limited to these homopolymers and may be a copolymer with other copolymerizable monomers.

  The ratio of the resin component contained in the ceramic green sheet conductive paste is preferably 40 to 50 parts by weight with respect to 100 parts by weight of the metal fine particles. When the amount is less than 40 parts by weight, the viscosity required for the conductive paste for ceramic green sheets is difficult to obtain and it may be difficult to apply. In addition, the strength of the external electrode 3 after firing may be reduced. On the other hand, if the amount is more than 50 parts by weight, the conductivity of the external electrode is lowered, and heating for a long time is required for sufficient degreasing. Therefore, the ratio of the resin component is appropriately adjusted so as to satisfy both the strength and the conductivity.

  The solvent contained in the conductive paste for ceramic green sheets used in the present invention is not particularly limited as long as it is an organic solvent, since almost all of the solvent volatilizes at 400 ° C. or less. Ultrafine metal particles, metal organic compounds and resins Known organic solvents for preparing pastes that can dissolve the solvent can be used, for example, aliphatic alcohols, alcohol esters, carbitol solvents, cellosolve solvents, ketone solvents, hydrocarbon solvents, and the like. And liquid hydrocarbons such as alcohol, alcohol ester, alcohol ether, acetone, hexane and pentane, and liquid aromatic hydrocarbons such as toluene and xylene.

  Since the organic component is removed by firing, the ceramic green sheet conductive pace eventually becomes the external electrode 3 composed of only the metal component. Accordingly, the weight ratio of the metal component, the resin and the solvent in the conductive paste for ceramic green sheets is determined by the ease of the coating process and the ease of firing, and is not particularly limited. 10 to 90% by weight is appropriate.

  In addition, additives such as a viscosity modifier, a pigment, a dye, an antifoaming agent, and a surfactant can be further blended with the conductive paste for ceramic green sheets, if necessary.

  The conductive paste for the ceramic green sheet is applied to the internal electrode 2 exposed on the surface of the laminated sheet in which the ceramic green sheets printed with the internal electrode 2 are laminated, and the laminated sheet is baked at 400 ° C. or less to obtain the resin component and Components other than the solvent and metal components are volatilized or decomposed and removed, and degreased to form external electrodes, whereby the multilayer ceramic element 4 is manufactured.

  Since the decomposition start temperature of the polyoxyalkylene resin or polyacrylic resin used in the present invention is at least 250 ° C. or higher, the firing temperature is preferably 250 ° C. or higher. In consideration of realistic firing time, the firing temperature is preferably 300 ° C. or higher. The firing time is not particularly limited because it depends on the firing temperature, but it is preferably 1 hour to 10 hours.

  The conductive paste for ceramic green sheets first heats and shrinks because of the solvent volatilization of the resin component and solvent during the firing process, but the conductive paste shrinks during the firing process by using a (thermo) curable resin as the resin component. Therefore, the resin component of the conductive paste for ceramic green sheets is preferably a (thermo) curable resin.

  The external electrode 3 in which the metal fine particles are sintered is formed by firing. Since the formed external electrode 3 is made of sintered metal, it becomes an electrode having a large number of voids. Therefore, it is preferable to coat the electrode surface with a conductive polymer or a reactive curable resin containing metal fine particles in order to increase the electrode strength and improve the conductivity, and select a curing agent for the reactive curable resin as appropriate. If this is done, the curing temperature can be lowered.

  Examples of the curing agent include a chemical reaction type curing agent, an ultraviolet curing type curing agent, and an electron beam curing type curing agent.

  Further, it is more preferable to further apply metal plating to the layer formed by the conductive polymer covering the surface of the external electrode 3. Thereby, the conduction performance of the external electrode 3 can be further improved.

  In the present invention, a resin component mainly composed of a polyoxyalkylene resin or a polyacrylic resin, a solvent and metal fine particles are applied to the internal electrode 2 exposed on the surface of the laminated sheet obtained by laminating the ceramic green sheets on which the internal electrode 2 is printed. The contained conductive paste for ceramic green sheet is applied so as to be the external electrode 3 electrically connected to the internal electrode 2, and the laminated sheet is fired and degreased to form the external electrode 3, thereby producing the laminated ceramic element 4.

  Since the resin contained in the conductive paste used to form the external electrode 3 is a resin mainly composed of a polyoxyalkylene resin or a polyacrylic resin, it can be sufficiently degreased even when baked at 400 ° C. or lower. For this reason, it is possible to manufacture the multilayer ceramic element 4 having excellent electrical conductivity between the internal electrode 2 and the external electrode 3 and having no thermal stress remaining.

(Example)
(Vehicle adjustment with room temperature curable resin 1)
In a 200 mL beaker, 80 g of alkoxysilyl-modified polypropylene glycol (MS Polymer S-303, Kaneka Chemical Co., Ltd.), 20 g of poly (isobutyl methacrylate) (molecular weight 300,000), 2 g of dibutyltin dilaurate, and 100 g of terpineol as a solvent are shielded from light. The mixture was mixed at 80 ° C. until uniform and degassed under reduced pressure to prepare a vehicle.

(Vehicle adjustment with room temperature curable resin 2)
In a 200 mL beaker, 100 g of solid bisphenol A-type epoxy resin (Japan Epoxy Resin, Epicoat 1001) and 100 g of terpineol as a solvent are mixed under light shielding until uniform at 80 ° C., and defoamed under reduced pressure to prepare a vehicle. did.

(Example 1)
A ceramic green sheet comprising 50% by weight of silver stearate-coated silver ultrafine particles (average diameter of silver fine particles 5 nm), 20% by weight of vehicle containing 30% by weight of terpineol, and 20% by weight of vehicle containing room temperature curable resin prepared in room temperature curable resin. A conductive paste was prepared. This conductive paste was applied to the exposed portions of the internal electrodes 2 on both sides of the laminated ceramic green sheets and baked at 400 ° C. for 1 hour. The formed external electrode 3 showed good electrical conductivity with the internal electrode 2. Even when the multilayer ceramic fired body was divided and the cross section thereof was observed with an electron microscope, the resin component was completely degreased only with the metal film in which the silver ultrafine particles were melted.

(Comparative Example 1)
Conductivity for ceramic green sheet in the same manner as in Example 1 except that the vehicle containing 20% by weight of the curable resin prepared in Preparation 2 of room temperature curable resin, 29% by weight of terpineol, and 1 part by weight of dicyandiamide was used. A paste was prepared. This conductive paste was applied to the exposed portions of the internal electrodes 2 on both sides of the laminated ceramic green sheets and baked at 400 ° C. for 1 hour. The formed external electrode 3 did not show electrical conductivity with the internal electrode 2. When the multilayer ceramic fired body was divided and the cross section was observed with an electron microscope, the metal film was not sufficiently degreased and the metal film was porous, and the resin content remained.

  The present invention can be used in a method for manufacturing a multilayer ceramic element such as a ceramic capacitor or a ceramic inductor.

It is a schematic sectional drawing which shows an example of the conventional laminated ceramic element. It is a schematic sectional drawing which shows an example of the laminated ceramic element of this invention.

Explanation of symbols

1 ceramic body 2 internal electrode 3 external electrode 4 laminated ceramic element 6 polymer electrode 7 glass contact electrode

Claims (1)

A ceramic containing a resin component mainly composed of polyoxyalkylene resin or polyacrylic resin, metal fine particles, and a solvent on an internal electrode exposed on the surface of a laminated sheet obtained by laminating ceramic green sheets on which internal electrodes are printed A method for producing a multilayer ceramic element, comprising applying a conductive paste for a green sheet to be an external electrode electrically connected to an internal electrode, and firing the multilayer sheet.

Images