JP2008053488A - Conductive paste, electronic component, laminated ceramic capacitor, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the provision of good electrode coverage, breakdown voltage, and DC equivalent resistance with the suppression of reduction of an electrostatic capacity, by effectively preventing the spherical formation of the particles, the interrupted electrode or the like, without producing any differences in the effect of increasing the sintering start temperature of conductive particles and with remarkable effect to the suppression of growth of the conductive particles even when especially profiles of internal electrode layers get thinner and the particle size distribution of the conductive particles varies. <P>SOLUTION: A conductive paste contains an alloy of Ni and noble metal as a main component, first conductive particles having an average particle size of 200 to 400 nm, and second conductive particles having an average particle size of 40 to 80 nm. An amount of the noble metal contained in all the conductive components in the paste exceeds 0.3 mol% and is not larger than 13 mol%. An amount of the noble metal contained in the first conductive particles is between 0.3 and 1.5 mol%, and an amount of the noble metal contained in the second conductive particles is between 3.3 and 10 mol%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a conductive paste, an electronic component, a multilayer ceramic capacitor, and a manufacturing method thereof. More specifically, even when the thickness of an internal electrode layer is reduced, the growth of conductive particles in the firing stage is performed. Suppresses and effectively prevents particle spheroidization and internal electrode breakage, and effectively suppresses the decrease in capacitance while maintaining other characteristics (electrode coverage, breakdown voltage, DC equivalent resistance, etc.) The present invention relates to a conductive paste used in a manufacturing process of an electronic component such as a multilayer ceramic capacitor.

  A multilayer ceramic capacitor as an example of an electronic component has an element body having a multilayer structure in which a plurality of dielectric layers and internal electrode layers are alternately arranged. A pair of external terminal electrodes is formed at both ends of the element body. This multilayer ceramic capacitor is manufactured by first laminating a plurality of ceramic green sheets and pre-fired internal electrode layers alternately in a necessary number to produce a pre-fired element body, and then firing this, followed by both ends of the fired element body. And a pair of external terminal electrodes. As the internal electrode layer before firing, an internal electrode paste film or a metal thin film having a predetermined pattern is used.

  Thus, when manufacturing the multilayer ceramic capacitor, the ceramic green sheet and the internal electrode layer before firing are fired simultaneously. For this reason, the conductive material contained in the internal electrode layer before firing has a sintering temperature close to the sintering temperature of the dielectric material powder contained in the ceramic green sheet, does not react with the dielectric powder, It is required not to diffuse into the dielectric layer.

  Conventionally, in order to satisfy these requirements, noble metals such as Pt and Pd have been used for the conductive material contained in the internal electrode layer before firing. However, the noble metal itself is expensive, and as a result, there is a disadvantage that the finally obtained multilayer ceramic capacitor is expensive. Therefore, conventionally, the sintering temperature of the dielectric powder is lowered to 900 to 1100 ° C., and an Ag—Pd alloy is used as the conductive material included in the internal electrode layer before firing, or an inexpensive base metal such as Ni is used. Things are widely known.

  By the way, in recent years, with the miniaturization of various electronic devices, miniaturization and large capacity of the multilayer ceramic capacitor mounted inside the electronic device are progressing. In order to reduce the size and increase the capacity of the multilayer ceramic capacitor, it is required to stack not only a dielectric layer but also a thin internal electrode layer with few defects.

  However, when Ni is used as the conductive material contained in the internal electrode layer before firing, this Ni has a lower melting point than the dielectric powder contained in the ceramic green sheet. For this reason, when these were baked simultaneously, the big difference had arisen between both sintering temperature. If there is a large difference in sintering temperature, sintering at a high temperature will cause cracking and peeling of the internal electrode layer, while sintering at a low temperature may cause firing failure of the dielectric powder.

  Further, when the thickness of the internal electrode layer before firing is reduced, Ni particles contained in the conductive material are spheroidized by grain growth during firing in a reducing atmosphere, and adjacent Ni particles that were connected before firing The space | interval between them opens and a void | hole is produced in arbitrary places, As a result, it becomes difficult to form an internal electrode layer continuously after baking. When the internal electrode layer after firing is not continuous (disconnected), there is a problem that the capacitance of the multilayer ceramic capacitor is reduced.

  Therefore, in order to solve these problems, the present applicant, as shown in Patent Document 1 below, includes conductive particles in which the periphery of Ni particles is covered with a platinum layer, and Ni and a noble metal by sputtering. An alloy thin film is prepared, and the thin film is pulverized to obtain an alloy powder, which is disclosed as conductive particles for forming an internal electrode layer. By using the conductive particles configured in this way, even when the thickness of the internal electrode layer is reduced, the grain growth of Ni particles in the firing stage is suppressed, and spheroidization and electrode breakage are effective. It was found that the decrease in capacitance can be effectively suppressed.

  However, in the case of particles in which Ni particles are coated with platinum, the following problems occur. That is, the particle | grains which coat | covered Ni particle | grains with platinum have the problem that the composition ratio of Ni and platinum will differ with the diameter of Ni particle | grains, when the thickness of a coating layer is considered constant. That is, when the particle diameter of the Ni particles is large, the Ni content is relatively large with respect to platinum. Conversely, when the particle diameter of the Ni particles is small, the Ni content is relatively small with respect to platinum. The content of is reduced.

  If there is no variation in the particle size distribution of the core particles, the composition of each particle should be uniform, but actually, the particle size distribution of the Ni particles varies. For this reason, in the internal electrode layer, where a large amount of Ni particles having a large particle diameter are gathered, the content of platinum is relatively reduced, suppressing grain growth of Ni particles, preventing spheroidization, Small effects such as breaks. Conversely, where a large number of Ni particles having a small particle diameter are gathered, the platinum content is relatively large, and effects such as suppression of grain growth of Ni particles are great. As a result, although the electrostatic capacitance value is satisfied, a portion where the spheroidization is suppressed and a portion where the spheroidization is not suppressed are generated, and the variation in the thickness of the internal electrode is increased. Accordingly, the variation in the thickness of the dielectric layer also increases, and the breakdown voltage (VB) value does not increase.

  Further, in the case of an alloy powder of Ni and a noble metal, there is a problem that the filling property of each particle is low in the internal electrode layer before firing. As a result, the capacitance value is satisfactory, but in the internal electrode layer after firing, the electrode is interrupted, the electrode coverage is reduced, and further, the breakdown voltage value and the DC equivalent resistance are deteriorated. .

Furthermore, in order to produce the above-described two kinds of conductive particles, in the case of alloy particles, there is a problem that the number of steps such as sputtering increases and the production process becomes long. In the case of coated particles, when platinum is precipitated around the Ni particles, platinum segregated particles of several μm or more are generated, and the Ni particles may not be coated with platinum. There was a problem of being bad. Therefore, the above-mentioned two kinds of conductive particles have a demerit that they cannot be produced at low cost.
International Publication No. 2004/070748 Pamphlet

  The present invention has been made in view of such a situation, and the object thereof is to suppress the growth of conductive particles throughout the internal electrode layer even when the thickness of the internal electrode layer is particularly reduced. There is no difference in the effect of conducting, effectively preventing spheroidization of conductive particles, electrode breakage, etc., while effectively suppressing the decrease in capacitance, other characteristics (electrode coverage, breakdown voltage, DC equivalent) It is to provide a conductive paste capable of improving resistance and the like. Another object of the present invention is to provide an electronic component such as a multilayer ceramic capacitor having an internal electrode layer formed using the conductive paste and a dielectric layer, and a method for manufacturing the same.

In order to achieve the above object, the conductive paste according to the present invention comprises:
First conductive particles mainly composed of an alloy of nickel and a noble metal and having an average particle diameter of 200 nm or more and 400 nm or less;
A conductive paste containing an alloy of nickel and a noble metal as a main component and second conductive particles having an average particle diameter of 40 nm or more and 80 nm or less,
The content of the noble metal with respect to all the conductive components in the conductive paste is more than 0.3 mol% and not more than 13 mol%,
The content ratio of the noble metal in the first conductive particles is 0.3 mol% or more and 1.5 mol% or less,
The content ratio of the noble metal in the second conductive particles is 3.3 mol% or more and 10 mol% or less.

  The conductive paste according to the present invention contains conductive particles mainly composed of an alloy of Ni and a noble metal. The noble metal has a higher melting point than Ni and is excellent in wettability and adhesion to the dielectric layer. Therefore, since the conductive particles mainly composed of an alloy of Ni and a noble metal have a sintering temperature higher than that of the Ni particles, the sintering start temperature can be increased and the spheroidization of the conductive particles can be suppressed.

  Further, as the conductive particles mainly composed of an alloy of Ni and a noble metal, the first conductive particles having an average particle diameter of 200 to 400 nm, preferably 200 to 350 nm, and the average particle diameter of 40 to 80 nm, preferably Uses second conductive particles that are 45-75 nm. An electrode formed using the conductive paste by including the first conductive particles having a relatively large particle diameter and the second conductive particles having a relatively small particle diameter in the conductive paste. In the paste film, the second conductive particles having a small particle size are filled between the particles of the first conductive particles having a large particle size. As a result, the filling property of each particle in the electrode paste film is improved, so that the density of the electrode paste film is increased and the discontinuity of the internal electrode layer tends to be reduced even after firing.

  Further, the content of the noble metal with respect to all the conductive components in the conductive paste is more than 0.3 mol% and 13 mol% or less, preferably more than 0.3 mol and 5.0 mol% or less. If the content of the noble metal is too small, the effects of the present invention tend not to be obtained. On the other hand, if the content of the noble metal is too large, tan δ and DC equivalent resistance tend to deteriorate.

  Further, the content ratio (noble metal concentration) of the noble metal in the first conductive particles is 0.3 to 1.5 mol%, preferably 0.5 to 1.3 mol%, and the noble metal content in the second conductive particles is The content ratio (noble metal concentration) is 3.3 to 10 mol%, preferably 4 to 8 mol%. In this case, the second conductive particles having a small particle size are filled between the particles of the first conductive particles having a large particle size, and the second conductive particles are more than the first conductive particles. Due to the high precious metal concentration, the sintering temperature is high. Therefore, at the time of firing, the second conductive particles have a function of delaying the sintering of the first conductive particles. That is, the sintering start temperature of the first conductive particles can be increased without increasing the noble metal concentration in the first conductive particles, and the spheroidization of the first conductive particles can be effectively suppressed.

  Therefore, in the conductive paste of the present invention, even if the internal electrode layer is thinned, and even if there is a variation in the particle size distribution of the first conductive particles, the conductive particles are fired at the firing stage. There is no difference in the effect of increasing the starting temperature. As a result, it is possible to suppress the grain growth of the conductive particles and effectively prevent spheroidization, electrode breakage, etc., so that other characteristics (electrode coverage, breakdown voltage, DC equivalent resistance, etc.) can be improved.

  On the other hand, in the case of the noble metal-coated Ni particles described in Patent Document 1 (International Publication No. 2004/070748 pamphlet) described above, when the particle size variation of the core Ni particles increases, the composition ratio in each particle In contrast, depending on the location of the electrode layer, a portion having a large effect and a portion having a small effect on prevention of spheroidization and breakage are generated. As a result, data satisfying the capacitance can be obtained, but sufficient electrode coverage cannot be obtained, and electrical characteristics such as breakdown voltage and DC equivalent resistance cannot be improved.

  Moreover, compared with the conventional electroconductive paste containing only the alloy particle | grains of Ni and a noble metal described in patent document 1, the electroconductive paste of this invention has the effect shown next. That is, the conductive particles of the conductive paste of the present invention include first conductive particles having a relatively large particle size and a low precious metal concentration, and second conductive particles having a relatively small particle size and a high precious metal concentration. I know. Since the second conductive particles have a higher precious metal concentration than the first conductive particles, the sintering start temperature is high. Further, by utilizing the difference in particle diameter, the second conductive particles can be filled between the particles of the first conductive particles, and the density of the electrode paste film before firing can be increased. Therefore, at the time of firing, the second conductive particles can delay the sintering of the first conductive particles and increase the sintering start temperature of the first conductive particles. As a result, it is possible to improve other characteristics (electrode coverage, breakdown voltage, DC equivalent resistance, etc.) while suppressing a decrease in capacitance.

  In the present invention, if the average particle size of the first conductive particles is too small, the dispersibility with other additives is lowered, the density of the electrode paste film is lowered, and the electrode coverage, breakdown voltage, DC Equivalent resistance tends to deteriorate. In addition, if the average particle diameter of the first conductive particles is too large, the filling property of the first conductive particles is deteriorated, the surface of the paste film becomes rough, and further, it is difficult to make the internal electrode layer thin. Become. As a result, electrode discontinuity after sintering tends to increase. On the other hand, if the average particle diameter of the second conductive particles is too large, the second conductive particles are hardly filled between the particles of the first conductive particles, and the density of the electrode paste film tends not to increase. On the other hand, if the average particle diameter of the second conductive particles is too small, it is difficult to produce the particles, and the viscosity of the conductive paste is increased, which tends to make it difficult to print the electrode.

  Preferably, the noble metal contains at least one element selected from ruthenium (Ru), rhodium (Rh), rhenium (Re), platinum (Pt), iridium (Ir) and osmium (Os) as a main component. More preferably, it is Re.

  Preferably, the content ratio of the first conductive particles and the second conductive particles to the total conductive components in the conductive paste is, by weight ratio, the first conductive particles: second conductive particles = 70. : 30 to 99: 1, preferably 75:25 to 95: 5. If the content ratio of the first conductive particles is too small (the content ratio of the second conductive particles is too large), the noble metal concentration unevenness of the electrode layer after firing becomes large. As a result, the electrode coverage, capacitance, The breakdown voltage and DC equivalent resistance are reduced. When the content ratio of the first conductive particles is too large (the content ratio of the second conductive particles is too small), there is a portion that is not filled with the second conductive particles between the particles of the first conductive particles. There exists a tendency for the effect of invention to become small.

  Preferably, the conductive paste contains co-material particles, a binder, a solvent, and a dispersant in addition to the first conductive particles and the second conductive particles. The co-material particles are dielectric particles having the same composition as the dielectric particles constituting the dielectric layer of the electronic component, and are interposed around the conductive particles to suppress the growth of the conductive particles. By including the common material particles in the conductive paste together with the second conductive particles having a relatively small particle size and a high precious metal concentration, the common material particles and the second conductive particles become the first conductive particles. It is possible to suppress the spheroidization of the first conductive particles more effectively.

An electronic component manufacturing method according to the present invention is a method of manufacturing an electronic component having an internal electrode layer and a dielectric layer,
Using the conductive paste according to any one of the above, a step of forming an electrode paste film that becomes an internal electrode layer after firing,
Laminating the electrode paste film with a green sheet that becomes a dielectric layer after firing;
Firing a laminate of the green sheet and the electrode paste film;
And annealing the laminated body after firing after firing the laminated body.

  An adhesive layer may be interposed between the electrode paste film and the green sheet. If the green sheet and the electrode paste film are made thin, it tends to be difficult to form the electrode paste film on the surface of the green sheet by a normal printing method or the like. It is preferable to be laminated on the surface. In that case, adhesion between the electrode paste film and the green sheet tends to be difficult, and these are preferably adhered by an adhesive layer. Note that the adhesive layer is removed by a binder removal treatment and / or a firing treatment of the laminate.

  Preferably, the density of the electrode paste film after drying is 90% or more of the theoretical density of the electrode paste film after drying. When an electrode paste film is formed using any of the conductive pastes described above, the electrode paste film is dried. Drying is performed to remove volatile components such as a solvent contained in the electrode paste film. The drying temperature is not particularly limited, but is preferably 70 to 120 ° C., and the drying time is preferably 1 to 30 minutes.

The dried electrode paste film includes conductive particles, co-materials, binders, dispersants, and the like, which are non-volatile components, as constituent components. From the actual density of the electrode paste film after drying and the theoretical electrode paste film density (theoretical density of the electrode paste film) calculated from the density and composition ratio of the components, the relative paste film density shown below is Calculated.
Relative paste film density [%] = (actual density of electrode paste film after drying / theoretical density of electrode paste film) × 100
The relative paste film density represents the filling property of the constituent components in the electrode paste film, and is preferably 90% or more. If the relative paste film density is too low, the dispersibility of each component in the paste film is poor, and the electrode coverage after firing tends to deteriorate.

Preferably, the laminate is fired at a temperature of 1000 to 1300 ° C. in an atmosphere having an oxygen partial pressure of 10 ⁻¹⁰ to 10 ⁻² Pa.

Preferably, after firing the laminate, annealing is performed at a temperature of 1200 ° C. or lower in an atmosphere having an oxygen partial pressure of 10 ^{−2 to} 100 Pa. After the firing, annealing is performed under specific conditions, whereby the dielectric layer is re-oxidized, preventing the dielectric layer from becoming a semiconductor, and high insulation resistance can be obtained.

  Preferably, the thickness of the internal electrode layer of the electronic component manufactured by any one of the methods described above is 0.1 to 0.7 μm, and more preferably 0.1 to 0.5 μm. By using the conductive paste of the present invention, the internal electrode layer can be thinned.

  Preferably, a ratio of an area where the internal electrode layer after firing and annealing actually covers the dielectric layer to an ideal design area where the internal electrode layer after firing and annealing covers the dielectric layer is shown. The electrode coverage is 80% or more. When the electrode coverage is reduced, the discontinuity in the internal electrode layer after firing increases, and as a result, the capacitance tends to decrease.

  In the present invention, the dielectric layer is preferably composed of a dielectric material that can be fired in a reducing atmosphere. Since the internal electrode layer is made of an alloy of Ni and a noble metal, the dielectric layer is preferably made of a dielectric material that can be fired in a reducing atmosphere so as not to be oxidized during simultaneous firing.

  In addition, the material and manufacturing method of the green sheet that can be used in the present invention are not particularly limited, and the ceramic green sheet formed by the doctor blade method, the porous obtained by biaxially stretching the extruded film A ceramic green sheet or the like may be used.

  In the present invention, the electronic component is not particularly limited, and examples thereof include multilayer ceramic capacitors, piezoelectric elements, chip inductors, chip varistors, chip thermistors, chip resistors, and other surface mount (SMD) chip type electronic components. .

Hereinafter, the present invention will be described based on embodiments shown in the drawings. put it here,
FIG. 1 is a schematic cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention.
FIG. 2 is a schematic view of a conductive paste according to an embodiment of the present invention,
3 (A) to 3 (C) and FIGS. 4 (A) to 4 (C) are main part sectional views showing a method of transferring the electrode paste film,
FIG. 5 is a schematic view of an apparatus for producing conductive particles of the present invention by a CVD method,
6A is a schematic diagram of an electrode paste film formed using the conductive paste shown in FIG. 2, and FIG. 6B is an electrode formed using a conductive paste containing noble metal-coated Ni particles according to a conventional example. FIG. 6C is a schematic diagram of a paste film, and FIG. 6C is a schematic diagram of an electrode paste film formed using a conductive paste containing alloy particles of Ni and noble metal according to a conventional example.

  First, an overall configuration of a multilayer ceramic capacitor will be described as an embodiment of an electronic component according to the present invention.

  As shown in FIG. 1, the multilayer ceramic capacitor 2 according to the present embodiment includes a capacitor body 4, a first terminal electrode 6, and a second terminal electrode 8. The capacitor body 4 includes dielectric layers 10 and internal electrode layers 12, and the internal electrode layers 12 are alternately stacked between the dielectric layers 10. One internal electrode layer 12 that is alternately stacked is electrically connected to the inside of the first terminal electrode 6 that is formed outside the first end 4 a of the capacitor body 4. Further, the other internal electrode layers 12 stacked alternately are electrically connected to the inside of the second terminal electrode 8 formed outside the second end portion 4 b of the capacitor body 4.

  The material of the dielectric layer 10 is not particularly limited, and is made of a dielectric material such as calcium titanate, strontium titanate and / or barium titanate. The dielectric layer 10 is preferably made of a dielectric material that can be fired in a reducing atmosphere.

  The thickness of each dielectric layer 10 is not particularly limited, but is generally several μm to several hundred μm. In particular, in this embodiment, the thickness is preferably 5 μm or less, more preferably 3 μm or less.

  In this embodiment, each internal electrode layer 12 shown in FIG. 1 is composed of an alloy layer of nickel and a noble metal. Although a detailed manufacturing method of the internal electrode layer 12 will be described later, it is formed using the conductive paste 12a shown in FIG. 2, and the electrode paste film 12b is transferred to the green sheet 10a as shown in FIGS. Formed. The thickness of the internal electrode layer 12 is thicker than that of the electrode paste film 12b by the amount of horizontal contraction caused by firing. In FIG. 2, illustration of components other than the conductive particles and the common material is omitted.

  Although the material of the terminal electrodes 6 and 8 is not particularly limited, copper, a copper alloy, nickel, a nickel alloy, or the like is usually used, but silver, an alloy of silver and palladium, or the like can also be used. The thickness of the terminal electrodes 6 and 8 is not particularly limited, but is usually about 10 to 50 μm.

  The shape and size of the multilayer ceramic capacitor 2 may be appropriately determined according to the purpose and application. When the multilayer ceramic capacitor 2 has a rectangular parallelepiped shape, it is usually vertical (0.6 to 5.6 mm, preferably 0.6 to 3.2 mm) × horizontal (0.3 to 5.0 mm, preferably 0.3 to 1.6 mm) × thickness (0.1 to 1.9 mm, preferably 0.3 to 1.6 mm).

Next, an example of a method for manufacturing the multilayer ceramic capacitor 2 will be described.
First, a dielectric paste is prepared in order to manufacture a ceramic green sheet that will form the dielectric layer 10 shown in FIG. 1 after firing. The dielectric paste is usually composed of an organic solvent-based paste obtained by kneading a dielectric material and an organic vehicle, or an aqueous paste.

  As the dielectric material, various compounds to be complex oxides and oxides, for example, carbonates, nitrates, hydroxides, organometallic compounds, and the like are appropriately selected and used by mixing. The dielectric material is usually used as a powder having an average particle size of about 0.1 to 3.0 μm. In order to form a very thin green sheet, it is desirable to use a powder finer than the thickness of the green sheet.

  An organic vehicle is obtained by dissolving a binder in an organic solvent. The binder used for the organic vehicle is not particularly limited, and examples thereof include various usual binders such as ethyl cellulose, polyvinyl butyral, and acrylic resin.

  Also, the organic solvent used in the organic vehicle is not particularly limited, and usual organic solvents such as terpineol, alcohol, acetone, methyl ethyl ketone (MEK), toluene, xylene, ethyl acetate, butyl stearate, butyl carbitol, isobornyl acetate, etc. Is exemplified. Further, the dielectric paste may contain additives selected from various dispersants, plasticizers, dielectrics, glass frit, insulators and the like as required.

  Next, using the dielectric paste, by a doctor blade method or the like, as shown in FIG. 4A, on the carrier sheet 30 as the second support sheet, preferably 0.5 to 30 μm, more preferably The green sheet 10a is formed with a thickness of about 0.5 to 10 μm. The green sheet 10 a is dried after being formed on the carrier sheet 30. The drying temperature of the green sheet 10a is preferably 50 to 100 ° C., and the drying time is preferably 1 to 5 minutes.

  Next, separately from the carrier sheet 30, as shown in FIG. 3A, a carrier sheet 20 as a first support sheet is prepared, and a release layer 22 is formed thereon. Next, an electrode paste film 12b that will form the internal electrode layer 12 after firing is formed in a predetermined pattern on the surface of the release layer 22.

  The electrode paste film 12b is formed of the conductive paste 12a shown in FIG. The thickness t1 (see FIG. 3) of the formed electrode paste film 12b is preferably about 0.1 to 1 μm, more preferably about 0.1 to 0.5 μm. The thickness t2 of the release layer 22 is 50% or less with respect to the thickness of the green sheet 10a.

  The electrode paste film 12b is formed by a printing method, for example. Examples of the printing method include screen printing. An electrode paste film 12b is formed on the surface of the release layer 22 by a screen printing method which is a kind of printing method.

  The electrode paste film 12b can be formed by printing the conductive paste 12a shown in FIG. 2 by a printing method. The conductive paste 12 a has first conductive particles 42 and second conductive particles 44.

  In the present embodiment, the first conductive particles and the second conductive particles are manufactured by a CVD (chemical vapor deposition) method. The CVD method is a manufacturing method using a chemical reaction in the gas phase, and in the production of conductive particles by the CVD method, it is possible to precisely control the average particle diameter, the particle size distribution is sharp, And so on. The manufacturing method will be described below.

  FIG. 5 shows an apparatus 60 for producing conductive particles by the CVD method. This manufacturing apparatus uses a quartz tube as a reaction vessel 62, and the reaction vessel 62 includes a raw material vaporization unit, a reaction unit, and a cooling unit. The raw material vaporization section and the reaction section can be independently controlled by the electric furnace 64.

As a method for producing a metal or alloy by the CVD method, a method of using a metal halide, a metal alkoxide, or the like as a raw material, vaporizing them, and reducing with, for example, H ₂ gas is common. In this embodiment, Ni chloride and a noble metal chloride are used as raw materials for the first conductive particles and the second conductive particles.

A crucible 70 charged with Ni chloride and a crucible 70 charged with a noble metal chloride are installed in the raw material vaporization section of the reaction vessel and heated by an electric furnace to vaporize the Ni chloride and the noble metal chloride. The vaporized Ni chloride and the noble metal chloride are in the form of fine particles, and these fine particles are transported to the reaction section of the reaction vessel together with the carrier gas (for example, Ar gas or N ₂ gas) introduced from the carrier gas introduction nozzle 66. The In the reaction section, Ni chloride and noble metal chloride are reduced by the reducing gas (for example, H ₂ gas) introduced from the reducing gas introduction nozzle 68, and at the same time, alloy particles of Ni and noble metal are generated. The produced alloy particles of Ni and noble metal are transported to the cooling unit together with the carrier gas and cooled. The cooled alloy particles of Ni and noble metal are discharged from the reaction vessel and collected by a collector.

  The average particle diameter of the conductive particles produced by the above method and the noble metal concentration in the conductive particles can be controlled by the flow rate of the carrier gas, the reaction temperature, the ratio of the raw materials to be reacted, and the like. Therefore, even particles having different average particle diameters and noble metal concentrations can be manufactured relatively easily by changing the above conditions.

  In this embodiment, the average particle diameter of the 1st electroconductive particle 42 is 200-400 nm, Preferably, it is 200-350 nm. Moreover, the average particle diameter of the 2nd electroconductive particle 44 is 40-80 nm, Preferably, it is 45-75 nm. Preferably, the average particle diameter of the first conductive particles 42 is 2.5 to 10 times, more preferably 2.7 to 7.7 times the average particle diameter of the second conductive particles 44. is there.

  If the average particle diameter of the first conductive particles 42 is too small, the dispersibility with other additives is lowered, the density of the electrode paste film is lowered, and the electrode coverage, breakdown voltage, and DC equivalent resistance are deteriorated. There is a tendency. Further, if the average particle diameter of the first conductive particles 42 is too large, the filling property of the first conductive particles is deteriorated, the surface of the paste film becomes rough, and further, it is difficult to make the internal electrode layer thin. become. As a result, electrode discontinuity after sintering tends to increase. If the average particle diameter of the second conductive particles 44 is too large, the second conductive particles 44 are not easily filled between the particles of the first conductive particles 42, and the density of the electrode paste film tends not to increase. . On the other hand, if the average particle diameter of the second conductive particles 44 is too small, it is difficult to produce the particles, the conductive paste is thickened, and the electrode tends to be difficult to print.

  In the present embodiment, the content of the noble metal with respect to all the conductive components in the conductive paste is more than 0.3 mol% and 13 mol% or less, preferably more than 0.3 mol and 5.0 mol% or less. is there. If the content of the noble metal is too small, the effects of the present invention tend not to be obtained. On the other hand, if the content of the noble metal is too large, tan δ and DC equivalent resistance tend to deteriorate.

  In the present embodiment, the content ratio of the noble metal in the first conductive particles is 0.3 to 1.5 mol%, preferably 0.5 to 1.3 mol%. When the content ratio of the noble metal in the first conductive particles is too small, the effect of suppressing the spheroidization of the first conductive particles tends to decrease.

  The content ratio of the noble metal in the second conductive particles is 3.3 to 10 mol%, preferably 4 to 8 mol%. When the content ratio of the noble metal in the second conductive particles is too small, the effect of suppressing the spheroidization of the first conductive particles tends to decrease.

  The noble metal in the first conductive particle 42 and the second conductive particle 44 is at least selected from ruthenium (Ru), rhodium (Rh), rhenium (Re), platinum (Pt), iridium (Ir) and osmium (Os). A metal containing one kind of element as a main component is preferable. More preferably, it is Re.

  The content ratio of the first conductive particles 42 and the second conductive particles 44 to the total conductive particles in the conductive paste is, by weight ratio, first conductive particles: second conductive particles = 70: 30 to 99. : 1, preferably in the range of 75:25 to 95: 5. If the content ratio of the first conductive particles 42 is too small (the content ratio of the second conductive particles 44 is too large), the precious metal concentration unevenness of the electrode layer after firing becomes large. The capacity, breakdown voltage, and DC equivalent resistance are reduced. On the other hand, if the content ratio of the first conductive particles 42 is too large (the content ratio of the second conductive particles 44 is too small), the second conductive particles 44 are not filled between the particles of the first conductive particles 42. There is a portion, and the effect of the present invention is reduced.

  The ratio of the alloy of Ni and noble metal contained as the main component in the first conductive particles 42 and the second conductive particles 44 is such that the first conductive particles 42 or the second conductive particles 44 as a whole is 100% by weight. Preferably it is 99-100 weight%, More preferably, it is 99.5-100 weight%. When the ratio of the main component is too small, the effect of suppressing the spheroidization of the conductive particles during firing tends to be reduced. Examples of metal components (impurities) that may be contained in the first conductive particles 42 and / or the second conductive particles 44 in addition to the main component include Cu, Co, Fe, Ta, Nb, W, Zr, and Au. , Pd, etc. Moreover, various trace components, such as S, C, and P, may be contained at about 0.1 mol% or less.

  The conductive paste 12a is made into a paste by kneading the first conductive particles 42 and the second conductive particles 44 together with the organic vehicle. As the organic vehicle, the same one as in the above dielectric paste can be used. In the present embodiment, the conductive paste 12a also includes the common material 46 shown in FIG. Although the average particle diameter of the particle | grains of the common material 46 is not specifically limited, Specifically, 10-50 nm is preferable.

  The common material 46 is a dielectric particle having a composition similar to that of the dielectric particles contained in the dielectric paste, and is present around the conductive particles, and together with the second conductive particles 44, the first conductive particles 42. Grain growth and spheroidization can be more effectively suppressed.

  After the electrode paste film 12b shown in FIG. 3A is formed using the conductive paste 12a, next, the adhesive layer 28 is formed on the surface of the carrier sheet 26 separately from the carrier sheets 20 and 30 described above. An adhesive layer transfer sheet is prepared. The carrier sheet 26 is composed of a sheet similar to the carrier sheets 20 and 30.

  In this embodiment, a transfer method is employed in order to form an adhesive layer on the surface of the electrode paste film 12b shown in FIG. That is, as shown in FIG. 3 (B), the adhesive layer 28 of the carrier sheet 26 is pressed against the surface of the electrode paste film 12b, heated and pressurized, and then the carrier sheet 26 is peeled off. As shown, the adhesive layer 28 is transferred to the surface of the electrode paste film 12b.

  The heating temperature at that time is preferably 40 to 100 ° C., and the pressure is preferably 0.2 to 15 MPa. The pressurization may be a pressurization or a calender roll, but is preferably performed by a pair of rolls.

  Thereafter, the electrode paste film 12b is bonded to the surface of the green sheet 10a formed on the surface of the carrier sheet 30 shown in FIG. For that purpose, as shown in FIG. 4B, the electrode paste film 12b of the carrier sheet 20 is pressed against the surface of the green sheet 10a together with the carrier sheet 20 through the adhesive layer 28, and is heated and pressurized, so that FIG. As shown in C), the electrode paste film 12b is transferred to the surface of the green sheet 10a. However, since the carrier sheet 30 on the green sheet side is peeled off, the green sheet 10a is transferred to the electrode paste film 12b through the adhesive layer 28 when viewed from the green sheet 10a side.

  The heating and pressurization at the time of transfer may be pressurization / heating with a press or pressurization / heating with a calender roll, but is preferably performed with a pair of rolls. The heating temperature and pressure are the same as when the adhesive layer 28 is transferred.

  3A to 4C, an electrode paste film 12b having a predetermined pattern is formed on the single green sheet 10a. Using this, a laminated body in which a large number of electrode paste films 12b and green sheets 10a are alternately laminated is obtained. Thereafter, the final pressure is applied to the laminate, and then the carrier sheet 20 is peeled off. The pressure at the time of final pressurization is preferably 10 to 200 MPa. The heating temperature is preferably 40 to 100 ° C. The obtained laminated body is cut into a predetermined size to form a green chip. Then, the green chip is subjected to binder removal processing and firing.

When Ni as a base metal is contained in the conductive particles for forming the internal electrode layer as in the present invention, the atmosphere in the debinding process is preferably an Air or N ₂ atmosphere. As other binder removal conditions, the temperature rising rate is preferably 5 to 300 ° C./hour, more preferably 10 to 50 ° C./hour, and the holding temperature is preferably 200 to 400 ° C., more preferably. The temperature holding time is preferably 250 to 350 ° C., and preferably 0.5 to 20 hours, more preferably 1 to 10 hours.

In the present invention, the green chip is fired in an atmosphere having an oxygen partial pressure of 10 ⁻¹⁰ to 10 ⁻² Pa. The oxygen partial pressure is preferably 10 ⁻¹⁰ to 10 ⁻⁵ Pa. If the oxygen partial pressure during firing is too low, the conductive material of the internal electrode layer may abnormally sinter and break, and conversely if the oxygen partial pressure is too high, the internal electrode layer tends to oxidize. .

  In the present invention, the green chip is fired at a temperature of 1000 to 1300 ° C, preferably 1150 to 1250 ° C. If the firing temperature is too low, the dielectric layer after sintering will be insufficiently densified and the capacitance will tend to be insufficient. If it is too high, the dielectric layer will be overfired, and a DC electric field is applied. There is a tendency that the change with time of the capacity increases.

As other firing conditions, the heating rate is preferably 50 to 500 ° C./hour, more preferably 200 to 300 ° C./hour, and the temperature holding time is preferably 0.5 to 8 hours, more preferably 1 The cooling rate is preferably 50 to 500 ° C / hour, more preferably 200 to 300 ° C / hour for -3 hours. The firing atmosphere is preferably a reducing atmosphere, and as the atmosphere gas, for example, a mixed gas of N ₂ and H ₂ is preferably used in a wet (humidified) state.

  In the present invention, it is preferable to anneal the sintered capacitor chip body. Annealing is a process for re-oxidizing the dielectric layer, whereby the accelerated lifetime of the insulation resistance (IR) can be remarkably increased, and the reliability is improved.

In the present invention, it is preferable to anneal the capacitor chip body after firing under an oxygen partial pressure higher than the reducing atmosphere during firing. Specifically, the oxygen partial pressure is preferably 10 ^{−2 to} 100 Pa, more preferably It is performed in an atmosphere of 10 ^{−2 to} 10 Pa. If the oxygen partial pressure at the time of annealing is too low, it is difficult to re-oxidize the dielectric layer 10, and if it is too high, nickel in the internal electrode layer tends to be oxidized and insulated.

  In the present invention, the holding temperature or maximum temperature during annealing is preferably 1200 ° C. or lower, more preferably 900 to 1150 ° C., and still more preferably 1000 to 1100 ° C. In the present invention, the holding time of these temperatures is preferably 0.5 to 4 hours. If the holding temperature or maximum temperature during annealing is less than the above range, the dielectric material is insufficiently oxidized and the insulation resistance life tends to be shortened. In addition to a decrease, it tends to react with the dielectric substrate and shorten its lifetime. Note that annealing may be composed of only a temperature raising process and a temperature lowering process. That is, the temperature holding time may be zero. In this case, the holding temperature is synonymous with the maximum temperature.

As other annealing conditions, the cooling rate is preferably 50 to 500 ° C./hour, more preferably 100 to 300 ° C./hour. Further, as the annealing atmosphere gas, for example, humidified N ₂ gas or the like is preferably used. In order to humidify the N ₂ gas, for example, a wetter or the like may be used. In this case, the water temperature is preferably about 0 to 75 ° C. The binder removal treatment, firing and annealing may be performed continuously or independently.

The sintered body (element body 4) thus obtained is subjected to end face polishing by, for example, barrel polishing, sand blasting, etc., and terminal electrode paste is baked to form terminal electrodes 6 and 8. The firing conditions for the terminal electrode paste are preferably, for example, about 10 minutes to 1 hour at 600 to 800 ° C. in a humidified mixed gas of N ₂ and H ₂ . Then, if necessary, a pad layer is formed on the terminal electrodes 6 and 8 by plating or the like. In addition, what is necessary is just to prepare the paste for terminal electrodes like the above-mentioned electrode paste.

  The multilayer ceramic capacitor of the present invention thus manufactured is mounted on a printed circuit board by soldering or the like and used for various electronic devices.

  In the present embodiment, it is possible to provide a multilayer ceramic capacitor 2 capable of improving other characteristics (electrode coverage, breakdown voltage, DC equivalent resistance, etc.) while effectively suppressing a decrease in capacitance. it can. The reason can be explained as follows, for example.

  As shown in FIG. 6A, in this embodiment, the first conductive particles 42 having a large particle diameter and a low precious metal concentration and the second conductive particles 44 having a small particle size and a high precious metal concentration are electrically conductive. Included in the paste. Utilizing the difference in particle diameter between the first conductive particles 42 and the second conductive particles 44, the second conductive particles can be filled between the particles of the first conductive particles. Further, since the second conductive particles 44 have a higher precious metal concentration than the first conductive particles 42, the sintering start temperature is high. As a result, at the time of firing, the second conductive particles 44 have a function of delaying the sintering of the first conductive particles, can increase the sintering start temperature, and the first conductive particles 42 are spheroidized. Can be suppressed.

  Therefore, in the conductive paste of the present invention, even if the internal electrode layer is thinned, and even if the particle size distribution of the first conductive particles 42 varies, the conductive particles in the firing stage are not affected. There is no difference in the effect of increasing the sintering start temperature. As a result, it suppresses grain growth of conductive particles, effectively prevents spheroidization, electrode breakage, etc., and effectively suppresses the decrease in capacitance, while other characteristics (electrode coverage, breakdown voltage, direct current) Equivalent resistance, etc.) can be improved.

  Further, in the present embodiment, by including the common material 46 in the conductive paste, the common material 46 exists around the conductive particles, and the first conductive particles 42 grow along with the second conductive particles 44. And spheroidization can be more effectively suppressed.

  On the other hand, as shown in FIG. 6 (B), the precious metal-coated Ni particles 48 described in Patent Document 1 (International Publication No. 2004/070748 pamphlet) described above have large particle size variation of the Ni particles as the core. The composition ratio is different, and a location where the noble metal is rich and a location where the noble metal is poor are generated depending on the location of the paste film 12c. For this reason, in the paste film 12c, a portion that is effective for preventing the spheroidization interruption and a portion that is less effective are generated. Further, the production of the noble metal-coated Ni particles 48 has the disadvantage that the production process is long and cannot be produced inexpensively.

  As shown in FIG. 6C, in the case of the conventional conductive paste including only the alloy particles 50 of Ni and noble metal described in Patent Document 1, the filling property of each particle in the electrode paste film 12d. Is bad. Therefore, in the internal electrode layer after firing, the electrodes are interrupted, the electrode coverage is deteriorated, and the characteristics such as breakdown voltage and DC equivalent resistance are also deteriorated. Further, since the alloy particles 50 of Ni and noble metal are made into conductive particles by pulverizing a thin film alloy formed by sputtering, there is a demerit that the manufacturing process is long and cannot be manufactured at low cost. 6A to 6C, illustration of components other than the conductive particles and the common material is omitted.

  In this embodiment, since the 1st electroconductive particle 42 and the 2nd electroconductive particle 44 are manufactured by CVD method, manufacture of an electroconductive particle is easy. Therefore, a conductive paste having a performance equal to or higher than that of the conventional paste containing the noble metal-coated Ni particles 48 or the alloy particles 50 of Ni and noble metal, and has a short manufacturing process and can be manufactured at low cost. Can be provided.

The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.
For example, the present invention is not limited to a multilayer ceramic capacitor and can be applied to other electronic components.

Hereinafter, the present invention will be described based on further detailed examples, but the present invention is not limited to these examples.
Example 1
Production of conductive paste

First, the 1st electroconductive particle and the 2nd electroconductive particle were manufactured by CVD method. Ni chloride and Re chloride were used as raw materials for the first conductive particles. A crucible charged with 200 g of Ni chloride and a crucible charged with 5 g of Re chloride were placed in the raw material vaporization section to vaporize Ni chloride and Re chloride. The vaporized Ni chloride and Re chloride fine particles were transported to the reaction part by N ₂ as a carrier gas. The flow rate of the carrier gas was 3 L / min. The reaction part was heated to 1100 ° C., and a reduction reaction of Ni chloride and Re chloride occurred by H ₂ gas as a reducing gas supplied to the reaction part at 5 L / min, and Ni—Re alloy particles were generated. . The produced Ni—Re alloy particles were cooled together with the carrier gas in the cooling section, then discharged from the reaction vessel, and collected by a collection device.

The second conductive particles were the same as described above except that the amounts of Ni chloride and Re chloride introduced into the crucible were 170 g and 35 g, respectively, and the flow rate of the N ₂ gas as the carrier gas was 5 L / min. Manufactured.

  The obtained first conductive particles were uniform Ni—Re alloy particles having an average particle diameter of 300 nm and a Re content ratio (Re concentration) of 1 mol% in the particles. On the other hand, the obtained second conductive particles were uniform Ni—Re alloy particles having an average particle diameter of 60 nm and a Re content ratio (Re concentration) in the particles of 6.5 mol%. Further, regarding the particle diameters of the first conductive particles and the second conductive particles, the standard deviations of the respective particle size distributions were calculated, and the respective CV values (= standard deviation / logarithmized average particle diameter) were calculated. It became 0.3. Therefore, the first conductive particles and the second conductive particles have the same particle size distribution. The first conductive particles and the second conductive particles produced as described above were mixed at a weight ratio of 85:15 to obtain conductive particles.

To 100 parts by weight of the conductive particles, 20 parts by weight of BaTiO ₃ powder (BT-005 / Sakai Chemical Industry Co., Ltd.) having an average particle diameter of 50 nm as co-material particles is added, and further an organic vehicle (ethyl cellulose as a binder resin) is added. A resin paste containing 4.5 parts by weight of resin dissolved in 228 parts by weight of terpineol) was added and kneaded with three rolls to form a slurry, which was used as a conductive paste for forming internal electrodes.
Evaluation of electrode paste film

Next, the conductor paste prepared above was applied on a PET film with an applicator of Gap 100 μm, and then dried under a condition of 100 ° C. for 30 minutes in a blower dryer. An electrode paste film was obtained. In this example, the electrode paste film was formed so that the film thickness after drying was 5 to 10 μm. Then, the density of the electrode paste film after drying was calculated from the volume of the obtained electrode paste film (= electrode film formation area × electrode film thickness) and weight, and the relative paste film density was calculated. The relative paste film density is preferably 90% or more. The results are shown in Table 1.
Preparation of dielectric layer paste

BaTiO ₃ powder (BT-02 / Sakai Chemical Industry Co., Ltd.), MgCO ₃ , MnCO ₃ , (Ba _0.6 Ca _0.4 ) SiO ₃ and rare earths (Gd ₂ O ₃ , Tb ₄ O ₇ , Dy ₂ A powder selected from O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ , Y ₂ O ₃ ) with a ball mill for 16 hours. A dielectric material was obtained by drying. The average particle diameter of these raw material powders was 0.1 to 1 μm. (Ba _0.6 Ca _0.4 ) SiO ₃ was prepared by wet-mixing BaCO ₃ , CaCO ₃ and SiO ₂ with a ball mill, followed by drying and firing in the air using a ball mill.

  In order to make the obtained dielectric material into a paste, an organic vehicle was added to the dielectric material and mixed with a ball mill to obtain a dielectric green sheet paste. The organic vehicle is based on 100 parts by mass of the dielectric material, polyvinyl butyral: 6 parts by mass as a binder, bis (2-ethylhexyl) phthalate (DOP): 3 parts by mass, ethyl acetate: 55 parts by mass, toluene: The blending ratio is 10 parts by mass and 0.5 parts by mass of paraffin as a release agent.

  Next, a paste obtained by diluting the dielectric green sheet paste with ethanol / toluene (55/10) twice by weight was used as a release layer paste.

Next, an adhesive layer paste was prepared by diluting the same dielectric green sheet paste described above with toluene in a weight ratio of 4 with the exception that the dielectric particles and the release agent were not added.
Green sheet formation

First, a green sheet having a thickness of 1.0 μm was formed on a PET film (second support sheet) using the above dielectric green sheet paste, using a wire bar coater.
Formation of electrode paste film

  The release layer paste was applied and dried on another PET film (first support sheet) with a wire bar coater to form a release layer having a thickness of 0.3 μm.

Using the above conductive paste, an electrode paste film 12b having a predetermined pattern was formed on the surface of the release layer by screen printing as shown in FIG. The thickness of the film 12b after drying was 0.5 μm. In addition, when screen printing was impossible using the prepared conductive paste, the subsequent steps were not performed.
Formation of adhesive layer

The above adhesive layer paste is coated and dried with a wire bar coater on another PET film (third support sheet) whose surface has been subjected to a release treatment with a silicone resin, and an adhesive layer having a thickness of 0.2 μm. 28 was formed.
Formation of final laminate (element body before firing)

  First, the adhesive layer 28 was transferred to the surface of the electrode paste film 12b by the method shown in FIG. At the time of transfer, a pair of rolls was used, the pressure was 0.1 MPa, and the temperature was 80 ° C.

  Next, the electrode paste film 12b was adhered (transferred) to the surface of the green sheet 10a through the adhesive layer 28 by the method shown in FIG. At the time of transfer, a pair of rolls was used, the pressure was 0.1 MPa, and the temperature was 80 ° C.

Next, the electrode paste film 12b and the green sheet 10a were laminated one after another, and finally, a final laminated body in which 21 layers of the electrode paste film 12b were laminated was obtained. The lamination conditions were a pressure of 50 MPa and a temperature of 120 ° C.
Production of sintered body

  Next, the final laminate was cut into a predetermined size and subjected to binder removal processing, firing, and annealing (heat treatment) to produce a chip-shaped sintered body.

Binder removal
Temperature increase rate: 5-300 ° C / hour Holding temperature: 200-400 ° C,
Retention time: 0.5-20 hours,
Atmospheric gas: humidified N ₂ gas,
I went there.

Firing is
Temperature increase rate: 5 to 500 ° C / hour Holding temperature: 1200 ° C
Holding time: 0.5 to 8 hours Cooling rate: 50 to 500 ° C./hour Atmosphere gas: Mixed gas of humidified N ₂ and H ₂
Oxygen partial pressure: 10 ⁻⁷ Pa,
I went there.

Annealing (reoxidation)
Temperature rising rate: 200 to 300 ° C / hour,
Holding temperature: 1050 ° C,
Retention time: 2 hours
Cooling rate: 300 ° C / hour,
Atmospheric gas: humidified N ₂ gas,
Oxygen partial pressure: 10 ⁻¹ Pa,
I went there. The atmosphere gas was humidified using a wetter at a water temperature of 0 to 75 ° C.

Next, after polishing the end face of the chip-shaped sintered body with sand blasting, the external electrode paste is transferred to the end face and baked at 800 ° C. for 10 minutes in a humidified N ₂ + H ₂ atmosphere. A multilayer ceramic capacitor sample having the structure shown in FIG. 1 was obtained.

  The size of each sample thus obtained is 3.2 mm × 1.6 mm × 0.6 mm, the number of dielectric layers sandwiched between internal electrode layers is 21, and the thickness is 1 μm. The thickness of the internal electrode layer 12 was 0.5 μm. The thickness (film thickness) of each layer was measured by observing with SEM.

  Moreover, about each sample, the electrode coverage was measured as characteristic evaluation.

  The electrode coverage was measured by cutting a sample of a multilayer ceramic capacitor so that the electrode surface was exposed, observing the electrode surface with an SEM, and performing image processing. The electrode coverage was 80% or more.

  Furthermore, the characteristics of each sample were evaluated for electrical characteristics (capacitance C, dielectric loss tan δ, breakdown voltage VB, and DC equivalent resistance ESR). Electrical characteristics (capacitance C, dielectric loss tan δ, breakdown voltage VB, and DC equivalent resistance ESR) were evaluated as follows.

  Capacitance C (unit: μF) was measured with a digital LCR meter (YHP 4274A) at a reference temperature of 25 ° C. and a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms. . The capacitance C is preferably 1.18 μF or more, more preferably 1.20 μF or more.

  The dielectric loss tan δ was measured at 25 ° C. with a digital LCR meter (4274A manufactured by YHP) under the conditions of a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms. The dielectric loss tan δ is preferably less than 0.1.

  The breakdown voltage VB (unit: V) was defined as the breakdown voltage when the boosting speed was 100 V / sec and the detection current was 10 mA. The breakdown voltage is preferably 145 V or higher, more preferably 150 V or higher.

  The DC equivalent resistance ESR (unit: mΩ) was measured by measuring a frequency-ESR characteristic with an impedance analyzer (4194A manufactured by HP) under a measurement voltage of 1 Vrms and reading a value at which the impedance is minimized. . The DC equivalent resistance is preferably 9.5 mΩ or less, more preferably 9 mΩ or less.

In addition, these characteristic values were calculated | required from the average value of the value measured using the sample number n = 10 piece. These results are shown in Table 1. In Table 1, “◯” in the column of the evaluation criteria indicates that a screen printing was possible and a sample of a multilayer ceramic capacitor was obtained, and the results showing good results in all the above characteristics were obtained. Show. “X” indicates that a screen could not be printed and a multilayer ceramic capacitor could not be produced, or that one of the above characteristics did not give good results.
Examples 2-9

Conductive particles are produced in the same manner as in Example 1 except that the flow rate of the carrier gas N ₂ is changed and the average particle diameters of the first conductive particles and the second conductive particles are set to the values shown in Table 1. did. Using the obtained conductive particles, a conductive paste was prepared, a capacitor sample was prepared, and the characteristics were evaluated. The results are shown in Table 1.
Comparative Examples 1-12

Conductive particles are produced in the same manner as in Example 1 except that the flow rate of the carrier gas N ₂ is changed and the average particle diameters of the first conductive particles and the second conductive particles are set to the values shown in Table 1. did. Using the obtained conductive particles, a conductive paste was prepared, a capacitor sample was further prepared, and the characteristics were evaluated. In addition, when screen printing of the conductive paste was impossible, the subsequent steps were not performed. The results are shown in Table 1.

  From Table 1, all of Examples 1 to 9 can be screen-printed, and all characteristics (relative paste film density, electrode thickness, capacitance, tan δ, electrode coverage, breakdown voltage, and DC equivalent resistance). ) Was good.

On the other hand, when the average particle diameter of the first conductive particles is smaller than the range of the present invention (Comparative Example 1), the dispersibility of the conductive paste is lowered, and the relative paste film density, the electrode coverage, and the breakdown Voltage and DC equivalent resistance deteriorated. On the other hand, when the average particle diameter of the first conductive particles is larger than the range of the present invention (Comparative Example 2), the surface roughness of the paste film is deteriorated, and the internal electrodes are discontinuous. Capacity and breakdown voltage decreased.
When the average particle diameter of the second conductive particles was smaller than the range of the present invention (Comparative Examples 3, 5, and 7), the conductive paste thickened and screen printing became impossible. On the other hand, when the average particle diameter of the second conductive particles is larger than the range of the present invention (Comparative Examples 4, 6, and 8), the relative paste film density deteriorates, and the internal electrodes are also discontinuous, Capacitance, breakdown voltage and DC equivalent resistance decreased.
When the average particle diameters of the first conductive particles and the second conductive particles were the same (Comparative Example 9), the relative paste film density was low, and as a result, the capacitance and the electrode coverage were reduced.
Furthermore, when the second conductive particles are not added (Comparative Examples 10 and 11), that is, when only the first conductive particles are included in the conductive paste, the relative paste film density and the electrode coverage are low. As a result, breakdown voltage and DC equivalent resistance deteriorated. Moreover, it can confirm that it is the same result as the comparative example 11 also when not adding 1st electroconductive particle (comparative example 12), ie, when only 2nd electroconductive particle is included in an electroconductive paste.
Examples 10-35, Comparative Examples 13-61

Other than changing the content of Re (Re concentration) in the conductive particles to the values shown in Tables 2 to 4 by changing the amount of Ni chloride and Re chloride introduced into the crucible installed in the raw material vaporization section of the CVD apparatus Produced the first conductive particles and the second conductive particles in the same manner as in Example 1. Using the obtained first conductive particles and second conductive particles, a conductive paste was prepared, and a capacitor sample was prepared and evaluated. In addition, when screen printing of the conductive paste was impossible, the subsequent steps were not performed. The results are shown in Tables 2-4.
Among Tables 2-4, Table 2 is a table | surface which shows the characteristic evaluation result at the time of setting the mixing ratio of 1st electroconductive particle and 2nd electroconductive particle to 70:30 by weight ratio. Table 3 is a table showing the characteristic evaluation results when the mixing ratio of the first conductive particles and the second conductive particles is 85:15 by weight. Table 4 is a table showing the characteristic evaluation results when the mixing ratio of the first conductive particles and the second conductive particles is 99: 1 by weight.

  From Table 2, Examples 10-18 in which the Re concentration in the conductive particles is within the range of the present invention were all good as in Examples 1-9.

On the other hand, when the Re concentration in the first conductive particles is outside the range of the present invention (Comparative Examples 13, 17 to 24, 28), the capacitance, the electrode coverage, the breakdown voltage, and the DC equivalent resistance It can be confirmed that any of these characteristics tend to deteriorate.
Further, when the Re concentration in the second conductive particles is smaller than the range of the present invention (Comparative Examples 13 to 17), the capacitance, electrode coverage, breakdown voltage, All the characteristics of the DC equivalent resistance tended to deteriorate, and the decrease in capacitance was particularly noticeable. When the Re concentration in the second conductive particles is larger than the range of the present invention (Comparative Examples 24-28), the internal electrode layer after firing is less likely to be a uniform alloy layer. It can be confirmed that all of the characteristics of the rate, breakdown voltage, and DC equivalent resistance tend to deteriorate, and in particular, the deterioration of the DC equivalent resistance is noticeable.

  From Table 3, it can be confirmed that even when the mixing ratio of the first conductive particles and the second conductive particles is 85:15 by weight, the same tendency as in Table 2 is observed. In the sample of Comparative Example 45, the Re concentration in the first conductive particles and the second conductive particles is 0, that is, the first conductive particles and the second conductive particles are Ni particles. In this case, the expansion of the internal electrode layer due to the spheroidization of the Ni particles was noticeable, and as a result, the electrode coverage was deteriorated. It can also be confirmed that all of the capacitance, breakdown voltage, and DC equivalent resistance are deteriorated.

  From Table 4, even when the mixing ratio of the first conductive particles and the second conductive particles is 99: 1 by weight, it can be confirmed that the tendency is the same as in Table 2.

  If the content ratio of the first conductive particles is too small (the content ratio of the second conductive particles is too large), unevenness of the Re concentration in the internal electrode layer after firing tends to increase, and the first conductivity If the content ratio of the particles is too large (the content ratio of the second conductive particles is too small), the relative paste film density decreases, and as a result, the capacitance, the electrode coverage ratio, etc. tend to deteriorate. It was confirmed by the inventors.

  From Tables 1 to 4, the conductive paste according to the present invention can increase the density of the electrode paste film after drying even when the internal electrode layer is thinned. Furthermore, since the grain growth, spheroidization, and electrode breakage of the conductive particles can be effectively prevented even during firing, other characteristics (electrode coverage, breakdown voltage, DC equivalent resistance, etc.) can be improved.

FIG. 1 is a schematic cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is a schematic view of a conductive paste according to an embodiment of the present invention. FIG. 3A to FIG. 3C are cross-sectional views of relevant parts showing a method for transferring an electrode paste film. 4 (A) to 4 (C) are cross-sectional views showing the main part of the process subsequent to FIGS. 3 (A) to 3 (C). FIG. 5 is a schematic view of an apparatus for producing conductive particles of the present invention by a CVD method. 6A is a schematic diagram of an electrode paste film formed using the conductive paste shown in FIG. 2, and FIG. 6B is an electrode formed using a conductive paste containing noble metal-coated Ni particles according to a conventional example. FIG. 6C is a schematic diagram of a paste film, and FIG. 6C is a schematic diagram of an electrode paste film formed using a conductive paste containing alloy particles of Ni and noble metal according to a conventional example.

Explanation of symbols

2 ... Multilayer ceramic capacitor 4 ... Capacitor body 4a ... First end 4b ... Second end 6,8 ... Terminal electrode 10 ... Dielectric layer 10a ... Green sheet 12 ... Internal electrode layer 12a ... Conductive paste 12b ... Electrode Paste film 12c ... Electrode paste film 12d ... Electrode paste film 20 ... Carrier sheet 22 ... Release layer 26 ... Carrier sheet 28 ... Adhesive layer 30 ... Carrier sheet 42 ... First conductive particle 44 ... Second conductive particle 46 ... Common material 48 ... Precious metal-coated Ni particles 50 ... Alloy particles of Ni and precious metals 60 ... Conductive particle manufacturing apparatus 62 ... Reaction vessel 64 ... Electric furnace 66 ... Carrier gas introduction nozzle 68 ... Reducing gas introduction nozzle 70 ... Crucible

Claims (11)

First conductive particles mainly composed of an alloy of nickel and a noble metal and having an average particle diameter of 200 nm or more and 400 nm or less;
A conductive paste containing an alloy of nickel and a noble metal as a main component and second conductive particles having an average particle diameter of 40 nm or more and 80 nm or less,
The content of the noble metal with respect to all the conductive components in the conductive paste is more than 0.3 mol% and not more than 13 mol%,
The content ratio of the noble metal in the first conductive particles is 0.3 mol% or more and 1.5 mol% or less,
The conductive paste, wherein the content ratio of the noble metal in the second conductive particles is 3.3 mol% or more and 10 mol% or less.   The noble metal according to claim 1, wherein at least one element selected from ruthenium (Ru), rhodium (Rh), rhenium (Re), platinum (Pt), iridium (Ir) and osmium (Os) is a main component. The conductive paste as described.   The content ratio of the first conductive particles and the second conductive particles to the total conductive components in the conductive paste is, by weight ratio, first conductive particles: second conductive particles = 70: 30 to The conductive paste according to claim 1 or 2, which is in a range of 99: 1.   The electrically conductive paste in any one of Claims 1-3 containing a co-material particle | grain, a binder, a solvent, and a dispersing agent other than a said 1st electroconductive particle and a said 2nd electroconductive particle. A method of manufacturing an electronic component having an internal electrode layer and a dielectric layer,
Using the conductive paste according to any one of claims 1 to 4, a step of forming an electrode paste film that becomes an internal electrode layer after firing;
Laminating the electrode paste film with a green sheet that becomes a dielectric layer after firing;
Firing a laminate of the green sheet and the electrode paste film;
And a step of annealing the laminated body after firing after firing the laminated body.   The method for manufacturing an electronic component according to claim 5, wherein the density of the electrode paste film after drying is 90% or more of the theoretical density of the electrode paste film after drying. The manufacturing method of the electronic component of Claim 5 or 6 which bakes the said laminated body at the temperature of 1000-1300 degreeC in the atmosphere which has an oxygen partial pressure of 10 ^{< -10} > ^{-10 <-2} > Pa. The method for manufacturing an electronic component according to any one of claims 5 to 7, wherein after firing the laminate, annealing is performed at a temperature of 1200 ° C or lower in an atmosphere having an oxygen partial pressure of 10 ^{-2 to} 100 Pa. An electronic component manufactured by the method according to claim 5,
An electronic component having a thickness of the internal electrode layer of 0.1 μm or more and 1.0 μm or less.   The electrode coverage ratio indicating the ratio of the area where the internal electrode layer after firing and annealing actually covers the dielectric layer to the ideal design area where the internal electrode layer after firing and annealing covers the dielectric layer Is 80% or more, The electronic component according to claim 9. A method of manufacturing a multilayer ceramic capacitor having an element body in which internal electrode layers and dielectric layers are alternately stacked,
Forming an electrode paste film to be an internal electrode layer after firing using the conductive paste according to claim 1;
A step of alternately stacking the electrode paste film with a green sheet that becomes a dielectric layer after firing;
Firing a laminate of the green sheet and the electrode paste film;
And a step of annealing the multilayer body after firing the multilayer body.

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