JP2007220551A - Conductor paste and electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide conductor paste capable of increasing drying density of an internal electrode film before baking by restraining reactivity of conductor powder even when conductor powder having a large specific surface area is used, and resultantly capable of reducing the thickness of an internal electrode layer of an electronic component such as a laminated ceramic capacitor. <P>SOLUTION: This conductor paste has conductor powder containing Ni as a main constituent. The specific surface area of the conductor powder measured by a BET method is larger than 3 m<SP>2</SP>/g and not greater than 9 m<SP>2</SP>/g; and an SEM diameter being the average particle diameter of the conductor powder obtained by SEM observation and a BET diameter calculated from the specific surface area measured by the BET method when it is assumed that the conductor powder is really spherical satisfy a relationship of 1≤(SEM diameter/BET diameter)≤1.25. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive paste capable of thinning an internal electrode layer after firing, and an electronic component such as a multilayer ceramic capacitor having an internal electrode layer formed using the conductive paste.

  A multilayer ceramic capacitor as an example of a multilayer ceramic electronic component includes an element body having a structure in which a plurality of dielectric layers and internal electrode layers are alternately stacked, and a pair of external terminal electrodes formed at both ends of the element body. Consists of. In this multilayer ceramic capacitor, first, a pre-firing element body is manufactured by alternately stacking a required number of dielectric layers (ceramic green sheets) before firing and internal electrode layers (conductor paste for a predetermined pattern of electrodes) before firing. Next, after firing, a pair of external terminal electrodes are formed at both ends of the element body after firing.

  In the production of the multilayer ceramic capacitor, since the pre-firing dielectric layer and the pre-firing internal electrode layer are fired simultaneously, the conductive material contained in the pre-firing internal electrode layer includes a dielectric material contained in the pre-firing dielectric layer. It is required to have a sintering temperature close to the sintering temperature of the powder, not to react with the dielectric material powder, and not to diffuse into the dielectric layer after firing.

  In order to satisfy these requirements, noble metals such as Pt and Pd have been conventionally used for the conductive material contained in the internal electrode layer before firing. However, since these noble metals are expensive, there is a drawback that the resulting multilayer ceramic capacitor is expensive. Therefore, the sintering temperature of the dielectric powder is lowered to 900 to 1100 ° C. so that an inexpensive base metal such as Ni can be used as the conductive material, thereby providing the dielectric material with resistance to reduction, and in a reducing atmosphere. A material that can be fired has been developed.

  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 reduce the thickness of the internal electrode layer as well as the dielectric layer.

  However, when trying to reduce the thickness of the internal electrode layer using Ni powder, which is a base metal, as the conductive material, the Ni powder has high reactivity. At the time of firing, Ni powders reacted with each other to cause swelling and structural defects of the internal electrode layer due to spheroidization. As a result, it has been difficult to reduce the thickness of the internal electrode layer.

Therefore, the present applicant, the average particle diameter (SEM diameter) determined by SEM observation of Ni powder, and the BET diameter calculated by converting from the specific surface area (BET specific surface area) determined by the BET method, A conductor paste satisfying the relationship of 1 ≦ (SEM diameter / BET diameter) ≦ 1.56 and having a BET specific surface area of Ni powder of 3.0 m ² / g or less is disclosed (Patent Document 1). It has been shown that by setting the SEM diameter, the BET diameter and the BET specific surface area within the above ranges, the reactivity of the Ni powder is suppressed, and as a result, the internal electrode layer can be thinned without causing structural defects. .

However, in the specific example of Patent Document 1, the thickness of the internal electrode layer is relatively thick, about 1.3 μm, and can cope with further thinning of the internal electrode layer (for example, about 0.7 μm). It was not easy. For this reason, it has been difficult to reduce the size and thickness of electronic components.
JP 2002-151347 A

  The present invention has been made in view of such a situation, and even when a conductor powder having a large specific surface area is used, the reactivity of the conductor powder is suppressed and the dry density of the internal electrode film before firing is increased. As a result, an object of the present invention is to provide a conductor paste capable of thinning an internal electrode layer of an electronic component such as a multilayer ceramic capacitor. Another object of the present invention is to provide an electronic component having an internal electrode layer formed from the conductive paste and a dielectric layer.

  In order to realize further thinning of the internal electrode layer, the present inventors require the specific surface area of the conductor powder and the SEM diameter, which is the average particle diameter of the conductor powder obtained by SEM observation, and the BET method. The present invention has found that it is necessary to reduce the actual particle diameter of the conductor powder while controlling the BET diameter of the conductor powder calculated from the specific surface area and suppressing the reactivity of the conductor powder. It came to complete.

That is, the conductor paste according to the present invention is
A conductive paste having a conductive powder mainly composed of Ni,
The specific surface area value of the conductor powder measured by the BET method is larger than 3 m ² / g and not larger than 9 m ² / g,
The average particle diameter of the conductor powder obtained by observation with a scanning electron microscope (SEM) is the SEM diameter,
When assuming that the conductor powder is a true sphere, the BET diameter calculated from the specific surface area value measured by the BET method,
1 ≦ (SEM diameter / BET diameter) ≦ 1.25
It is characterized by having the relationship.

  In the present invention, the SEM diameter is determined as follows. The conductor powder is observed by SEM, and the projected area of one particle of the conductor powder is obtained. An average projected area is calculated from the projected areas obtained for a predetermined number of particles, and the diameter (equivalent circle diameter) of a sphere having the same projected area as this average projected area is taken as the SEM diameter. Therefore, the SEM diameter is synonymous with the actual average particle diameter of the conductor powder.

The BET diameter is a theoretical average particle diameter calculated from the specific surface area (BET specific surface area) of the conductor powder measured by the BET method when the conductor powder is assumed to be a true sphere. The BET specific surface area is a surface area per unit weight of the conductor powder (unit is m ² / g), and the surface area is aR ² (a is a constant, R is the diameter of a true sphere), and its weight (volume × volume). Since the density) is bR ³ (b is a constant, R is the diameter of a true sphere), the BET specific surface area is expressed as aR ² / bR ³ = c / R (c is a constant). The diameter R of the true sphere at this time is the BET diameter. Therefore, the BET diameter and the BET specific surface area are in an inversely proportional relationship.

  Next, focusing on the relationship between the SEM diameter and the BET diameter, the SEM diameter and the BET diameter coincide with each other because the actual particles of the conductor powder are spherical and have a smooth surface (no irregularities). ) State. It can be said that the particles in this case are ideal spherical particles. However, the actual particles of the conductor powder are usually not spherical and the surface is often rough (uneven). When ideal spherical particles and the above-mentioned non-spherical particles or particles having a rough surface have the same SEM diameter, the BET specific surface area of these particles is larger than the BET specific surface area of ideal spherical particles. Since the BET specific surface area and the BET diameter are in an inversely proportional relationship as described above, the BET diameter of these nonspherical particles having a rough surface is smaller than the ideal BET diameter of the spherical particles. That is, the BET diameter becomes smaller than the SEM diameter as the particle shape deviates from a true sphere or the particle surface becomes rougher, and the SEM diameter / BET diameter, which is the ratio of the SEM diameter to the BET diameter, is greater than 1. Also grows. In general, when the BET specific surface area of the particles increases (the BET diameter decreases), the reactivity of the particles tends to increase. On the other hand, in this invention, the reactivity of conductor powder is suppressed by making said SEM diameter / BET diameter into a specific range.

  Preferably, the SEM diameter is 0.08 to 0.25 μm.

  An electronic component according to the present invention includes an internal electrode layer formed using any one of the above-described conductor pastes, and a dielectric layer. The thickness of the internal electrode layer is preferably 0.7 μm or less, more preferably 0.65 μm or less. Although it does not specifically limit as an electronic component, A multilayer ceramic capacitor, a piezoelectric element, a chip inductor, a chip varistor, a chip thermistor, a chip resistor, and other surface mount (SMD) chip type electronic components are illustrated.

According to the present invention, the BET specific surface area of the conductor powder is controlled to be greater than 3 m ² / g and 9 m ² / g or less, and the SEM diameter / BET diameter is within the range of 1 to 1.25. Thus, the actual particle diameter (SEM diameter) of the conductor powder can be reduced while suppressing the reactivity of the conductor powder. As a result, it is possible to increase the dry density of the internal electrode film before firing and realize a thin internal electrode layer.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention.

Multilayer ceramic capacitor 2
As shown in FIG. 1, the multilayer ceramic capacitor 2 according to this embodiment includes a capacitor element 4, a first terminal electrode 6, and a second terminal electrode 8. The capacitor element 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 of the internal electrode layers 12 stacked alternately is electrically connected to the inside of the first terminal electrode 6 formed outside the first end 4 a of the capacitor element 4. The other internal electrode layer 12 that is alternately stacked is electrically connected to the inside of the second terminal electrode 8 that is formed outside the second end 4 b of the capacitor element 4.

  In this embodiment, the internal electrode layer 12 is an internal electrode film before firing that will form the internal electrode layer 12 after firing on a green sheet that will form the dielectric layer 10 after firing, as will be described later. It is manufactured by forming it in a predetermined pattern.

  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. In the present embodiment, the thickness of each dielectric layer 10 is preferably 10 μm or less, more preferably 5 μm or less.

  The material of the terminal electrodes 6 and 8 is not particularly limited, but usually copper, copper alloy, nickel, nickel alloy or the like can be used, and silver or silver-palladium alloy 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 (0.4 to 5.6 mm, preferably 0.4 to 3.2 mm) × horizontal (0.2 to 5.0 mm, preferably 0.2 to 1.6 mm) × thickness (0.1 to 1.9 mm, preferably 0.1 to 1.6 mm).

  Next, an example of a method for manufacturing the multilayer ceramic capacitor 2 according to the present embodiment will be described.

  First, in order to manufacture a ceramic green sheet that will form the dielectric layer 10 shown in FIG. 1 after firing, a dielectric layer paste is prepared.

  The dielectric layer paste is usually composed of an organic solvent-based paste or an aqueous paste obtained by kneading a dielectric material and an organic vehicle.

  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 1 μm or less, preferably 0.5 μm or less. 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 ordinary organic solvents such as alcohol, acetone, methyl ethyl ketone (MEK), toluene, xylene, ethyl acetate, butyl stearate, terpineol, butyl carbitol, isobornyl acetate, etc. Is exemplified.

  Then, using this dielectric layer paste, a green sheet having a thickness of preferably 15 μm or less, more preferably 7.5 μm or less is formed on the carrier sheet as the first support sheet by a doctor blade method or the like. . By forming the green sheet with such a thickness, the thickness of the dielectric layer 10 after firing can be reduced to preferably 10 μm or less, more preferably 5 μm or less.

  The internal electrode film before firing is preferably formed on the surface of the green sheet by a thick film forming method such as a printing method using a conductive paste. The thickness of the internal electrode film before firing is preferably 2.5 μm or less. By forming the internal electrode film before firing with such a thickness, the thickness of the internal electrode layer after firing can be set to a desired thickness. When the internal electrode film before firing is formed on the surface of the green sheet by the screen printing method or the gravure printing method which is one type of the thick film method, it is performed as follows.

  First, a conductor paste is prepared. In this embodiment, the conductor paste is prepared by kneading a conductor powder, a common material, and an organic vehicle.

  The conductor powder contains Ni as a main component, and is preferably composed of Ni, a Ni alloy, or a mixture thereof.

  Ni or an Ni alloy is preferably an alloy of Ni and at least one element selected from Mn, Cr, Co, and Al, and the Ni content in the alloy is preferably 95% by weight or more. In addition, in Ni or Ni alloy, various trace components, such as P, Fe, and Mg, may be contained about 0.1 wt% or less.

  In this embodiment, Ni powder is particularly preferable as the conductor powder. In addition, the shape of the conductor powder is preferably a spherical conductor powder in the present embodiment. The conductor powder is preferably contained in an amount of 35 to 70 parts by weight with respect to the entire conductor paste.

  The Ni powder is produced by a gas phase method or a liquid phase method. In the case of a vapor phase method, it is produced by reducing nickel chloride with hydrogen by a CVD method. In the case of the liquid phase method, there are a method in which nickel hydroxide is reduced to precipitate Ni, a method in which a reducing agent is added to a nickel salt solution and Ni is precipitated. The BET specific surface area (specific surface area measured by the BET method) can be controlled by subjecting the Ni powder produced by these methods to further water treatment or heat treatment in the atmosphere. Specifically, when the water treatment is performed for a long time, the BET specific surface area tends to increase, and when the heat treatment is performed for a long time, the BET specific surface area tends to increase.

In the present embodiment, the BET specific surface area of the Ni powder is greater than 3 m ² / g and 9 m ² / g or less, preferably greater than 3 m ² / g and 7 m ² / g or less. If the BET specific surface area is too small, the BET diameter increases, and accordingly, the SEM diameter, which is the actual particle diameter, sometimes increases. On the other hand, if the BET specific surface area is too large, the reactivity of the Ni powder tends to be high, and the Ni powder tends to agglomerate when the conductive paste is produced, and the Ni powder tends to be spheroidized when fired.

  In the present embodiment, the SEM diameter / BET diameter, which is the ratio of the SEM diameter, which is the average particle diameter obtained by SEM observation, and the BET diameter calculated from the BET specific surface area, obtained by the BET method, is 1 or more. Ni powder of 1.25 or less, preferably 1 or more and 1.15 or less is used as the conductor powder.

The BET diameter is a theoretical average particle diameter calculated from the specific surface area (BET specific surface area) of the Ni powder measured by the BET method when the Ni powder is assumed to be a true sphere. The BET specific surface area is a surface area value per unit weight (unit is m ² / g) and, as described above, is inversely proportional to the diameter of the sphere, that is, the BET diameter. Therefore, when the BET specific surface area is increased, the BET diameter is decreased.

  The SEM diameter is determined as follows. First, the Ni powder is observed with a scanning electron microscope (SEM) for 20 fields (one field is 3 × 4 μm), and the projected area of one observed Ni powder is obtained by image processing. This is performed for all the observed Ni powders, the average projected area is calculated, and the diameter (equivalent circle diameter) of a sphere having the same projected area as the average projected area is taken as the SEM diameter. The SEM diameter is synonymous with the actual particle diameter of the Ni powder. The SEM diameter is preferably 0.08 to 0.25 μm.

  When the SEM diameter matches the BET diameter, that is, when the SEM diameter / BET diameter is 1, as described above, the Ni powder particles are ideally spherical with a spherical shape and a smooth surface. Become particles. In addition, when the particle shape deviates from a true sphere or the particle surface is rough, the SEM diameter / BET diameter is larger than 1. However, in this embodiment, since the spherical Ni powder is used, the particle Has a small influence on the SEM diameter / BET diameter, and the SEM diameter / BET diameter can be used as an index for the surface state of the particles.

  If the SEM diameter / BET diameter is too large, the surface of the particles is too rough, so it is difficult to disperse Ni powder at the time of conductor paste preparation, the agglomerated part remains, and the reactivity of Ni powder is high at the time of firing, Ni tends to spheroidize easily.

  A common material may be included in the conductor paste. The common material is preferably a dielectric material having the same composition as the dielectric material contained in the green sheet. The common material has an effect of suppressing sintering of the conductor powder in the firing process. As the inorganic oxide powder used as the co-material, one having an average particle diameter of preferably 0.002 to 0.2 μm, more preferably 0.005 to 0.1 μm is used. Further, the content in the paste is preferably 5 to 40 parts by weight, more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the conductor powder.

  The organic vehicle contained in the conductor paste may be the same as the organic vehicle contained in the above dielectric layer paste. Further, it may further contain a plasticizer or a pressure-sensitive adhesive for the purpose of improving the adhesiveness with the green sheet, and a dispersant for the purpose of improving the dispersibility of the conductive particles and the co-material and improving the stability of the paint. May further be included.

  The conductor paste can be prepared by mixing each of the above components with a ball mill, a three-roll mill, or the like to form a slurry.

  Then, using this conductor paste, an electrode paste film having a predetermined pattern is formed on a green sheet by a printing method, and then dried to obtain an internal electrode film before firing. 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 15 minutes.

  Next, by stacking a plurality of sheets made of green sheets and pre-fired internal electrode films, a laminate before firing in which a plurality of green sheets and pre-fired internal electrode films are stacked is obtained. A green sheet for an outer layer having a thickness of about 30 μm is laminated on the upper and lower surfaces of the obtained laminate, and then pressed to obtain a laminate after pressing. The pressed laminate is cut into a predetermined size to obtain a green chip, and then the binder removal process is performed on the green chip.

As specific binder removal conditions, temperature rising rate: 5 to 300 ° C./hour, holding temperature: 200 to 700 ° C., holding time: 0.5 to 20 hours, atmosphere: air or humidified N ₂ It is preferable to use a mixed gas of H ₂ and H ₂ .

  Next, the green chip subjected to the binder removal treatment is subjected to firing and heat treatment.

Firing was performed at a heating rate of 50 to 500 ° C / hour, a holding temperature of 1050 to 1350 ° C, a holding time of 0.5 to 8 hours, a cooling rate of 50 to 500 ° C / hour, and an atmospheric gas: humidified. It is preferable to use conditions such as a mixed gas of N ₂ and H ₂ .

However, the oxygen partial pressure in the atmosphere during firing is preferably 10 ⁻² Pa or less. If the above range is exceeded, the internal electrode layer tends to oxidize, and if the oxygen partial pressure is too low, the electrode material of the internal electrode layer tends to abnormally sinter and tend to break.

The heat treatment (annealing) after such firing is preferably performed at a holding temperature or a maximum temperature of 900 ° C. or higher. If the holding temperature or maximum temperature during heat treatment 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. Oxygen partial pressure at the thermal treatment is higher oxygen partial pressure than reducing atmosphere at firing, and preferably ¹⁰ -3 Pa~1Pa. Below the range, it is difficult to re-oxidize the dielectric layer 10, and when the range is exceeded, the internal electrode layer 12 tends to oxidize.

Then, as the other heat treatment conditions, retention time: 0-6 hours, cooling rate: 50 to 500 ° C / time, Atmosphere gas: it is preferable that a wet _{N 2} gas or the like.

  Further, the binder removal treatment, firing and heat treatment 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.

  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 conductor paste of the present invention can be applied not only to a multilayer ceramic capacitor but also to other electronic components.

  In the above-described embodiment, the internal electrode film before firing is directly formed on the green sheet by a printing method, but may be formed by, for example, a transfer method.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
The following dielectric layer paste and conductor paste were prepared.

Dielectric Layer Paste First, in order to form a dielectric material mainly composed of barium titanate, an organic vehicle was added to the dielectric material and mixed with a ball mill to obtain a dielectric layer paste. The organic vehicle is based on 100 parts by weight of the dielectric material, polyvinyl butyral: 6 parts by weight as a binder, bis (2-ethylhexyl) phthalate (DOP): 3 parts by weight, ethanol: 85 parts by weight, toluene: 15 The blending ratio of parts by mass was used.

Conductor paste First, Ni powder having SEM diameter, BET diameter and BET specific surface area shown in Table 1 as conductor powder: 40 parts by weight, dielectric material having an average particle diameter of 0.05 μm as co-material: 10 wt. Part, ethyl cellulose resin as binder : 2 parts by weight, terpineol as solvent : 48 parts by weight were prepared. As the dielectric material, a material having the same composition as the dielectric material contained in the dielectric layer paste was used.

  Next, the raw material prepared above was kneaded with three rolls to make a slurry, and a conductor paste having a viscosity of 10 Pa · s when the rotational speed of the rotational viscometer was 100 rpm was produced.

Evaluation of internal electrode film before firing Next, the conductive paste prepared above is applied onto a PET film with an applicator of Gap 250 μm, and then dried at 100 ° C. for 15 minutes in a blow dryer. Thus, an internal electrode film before firing after coating and drying was obtained. In this example, the internal electrode film before firing was formed so that the film thickness after drying was 30 to 45 μm. And the density after application | coating and drying of each internal electrode film before baking was calculated | required from the volume (= formation area of electrode film x electrode film thickness) of each obtained internal electrode film before baking, and weight. The higher the density, the better. The results are shown in Table 1.

Multilayer Ceramic Capacitor Sample Using the dielectric layer paste and conductor paste obtained above, a multilayer ceramic capacitor sample was manufactured as follows.

That is, first, a green sheet was formed using the dielectric layer paste obtained above. Next, using the conductive paste obtained above, an internal electrode film before firing was formed by a printing method under the condition that the adhesion amount to the green sheet was 0.88 mg / cm ² .

  Next, another green sheet is formed on the internal electrode film before firing, and further another internal electrode film before firing is formed on the green sheet, and these are successively formed to form a laminate. Got the body. In this example, the thickness of the green sheet was 3 μm.

Next, green sheets for outer layers were laminated on the upper and lower surfaces of the obtained laminate, and then the laminate was pressed to obtain a pressed laminate. The press conditions were as follows: press temperature: 120 ° C., press pressure: 1 t / cm ² , press time: 10 minutes.

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

The binder removal was performed at a holding temperature of 600 ° C., a holding time of 2 hours, an atmospheric gas: a humidified mixed gas of N ₂ and H ₂ , and an oxygen partial pressure of 10 ⁻¹⁹ Pa. Firing was performed at a holding temperature of 1250 ° C., a holding time of 2 hours, an atmosphere gas: a humidified mixed gas of N ₂ and H ₂ , and an oxygen partial pressure of 10 ⁻⁷ Pa. Annealing (reoxidation) was performed at a holding temperature of 1000 ° C., a holding time of 2 hours, an atmospheric gas: a humidified N ₂ gas, and an oxygen partial pressure of 10 ⁻¹ Pa. Note that a wetter was used for humidifying the atmospheric gas during binder removal, firing, and annealing.

Next, after polishing the end face of the chip-shaped sintered body by 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. And a multilayer ceramic capacitor sample having the configuration shown in FIG. 1 was obtained. In this example, each capacitor sample was manufactured using the conductor paste prepared above.

  The size of each sample thus obtained was 2.0 mm × 1.25 mm × 0.65 mm, and the number of dielectric layers sandwiched between internal electrode layers was 220.

  Subsequently, the thickness of the internal electrode layer and the dielectric layer was evaluated for each obtained capacitor sample.

  First, each capacitor sample was cut along a plane perpendicular to the stacking direction, and the cut surface was polished. Then, the polished surface was observed with an SEM, and the thicknesses of the internal electrode layer and the dielectric layer were determined from the SEM photograph. The thickness of the dielectric layer was 2.0 μm. Table 1 shows the result of measuring the thickness of the internal electrode layer. The internal electrode layer had a thickness of 0.7 μm or less.

  From Table 1, in the samples of Examples 1 to 4, the SEM diameters are all 0.13 μm, but the BET diameters are different. The samples of Examples 1 to 4 are samples when the SEM diameter / BET diameter, which is the ratio of the SEM diameter to the BET diameter, is changed between 1 and 1.25, which is the range of the present invention, and firing. The dry density of the front internal electrode film was high, and the thickness of the internal electrode layer was 0.7 μm or less. It was also confirmed that the closer the SEM diameter / BET diameter was to 1, the higher the dry density of the internal electrode film before firing, and the thinner the internal electrode layer.

  On the other hand, in the samples of Comparative Examples 1a and 1, the SEM diameter is 0.13 μm, which is the same as the samples of Examples 1 to 4, but the SEM diameter / BET diameter is larger than the range of the present invention. Furthermore, the sample of Comparative Example 1 also has a BET specific surface area larger than the range of the present invention. As a result, it was confirmed that the thickness of the internal electrode layer could not be 0.7 μm or less because the dry density of the internal electrode film before firing was low and the reactivity of the Ni powder was high.

  Further, in the sample of Comparative Example 2, the SEM diameter / BET diameter is 1.06, which is the same as that of Example 2, but the BET specific surface area is smaller than the range of the present invention. The diameter increases, and the SEM diameter is also large. As a result, although the dry density of the internal electrode film before firing was high, it was confirmed that the thickness of the internal electrode layer could not be 0.7 μm or less. In addition, this sample is corresponded to the sample in the Example of patent document 1 (Unexamined-Japanese-Patent No. 2002-151347).

  From the above results, according to the present invention, since the reactivity of the Ni powder is suppressed, the Ni powder having a small actual particle diameter can be uniformly dispersed in the conductor paste, and the internal electrode before firing The dry density of the membrane can be increased. Further, during firing, the Ni powder can be prevented from being spheroidized, and the thickness of the internal electrode layer after firing can be reduced to 0.7 μm or less.

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

Explanation of symbols

2 ... Multilayer ceramic capacitor 4 ... Capacitor element 4a ... First end 4b ... Second end 6, 8 ... Terminal electrode 10 ... Dielectric layer 12 ... Internal electrode layer

Claims (4)

A conductive paste having a conductive powder mainly composed of Ni,
The specific surface area value of the conductor powder measured by the BET method is larger than 3 m ² / g and not larger than 9 m ² / g,
An SEM diameter which is an average particle diameter of the conductor powder obtained by observation with a scanning electron microscope (SEM);
When assuming that the conductor powder is a true sphere, the BET diameter calculated from the specific surface area value measured by the BET method,
1 ≦ (SEM diameter / BET diameter) ≦ 1.25
A conductor paste characterized by the following relationship.   The conductor paste according to claim 1, wherein the SEM diameter is 0.08 to 0.25 μm.   An electronic component having an internal electrode layer formed using the conductor paste according to claim 1 and a dielectric layer. The electronic component according to claim 3, wherein the internal electrode layer has a thickness of 0.7 μm or less.

Images