JP2010021382A - Method for manufacturing stacked ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that a percentage defective of insulation resistance is remarkably deteriorated by an enlarged sintered body particle since effect on variations of the particle diameter of the sintered body particle constituting a dielectric layer becomes great if the dielectric layer of the stacked ceramic capacitor is made thin. <P>SOLUTION: A method for forming the dielectric layer 1 includes the steps of mixing a raw material powder of barium titanate with powder as a subcomponent and then carrying out temporary firing thereof. Used is the unmixed raw material powder of the barium titanate with a specific surface area of 3.5 m<SP>2</SP>/g or more in which its specific surface area evaluated after heat treatment at a temperature higher by 150°C than the temporary firing temperature of 900-950°C in the temporary firing has a proportion of 0.5 or more compared to the specific surface area prior to heat treatment. This results in not only reducing dispersion in the sintering reaction in the temporary firing or the sintering but also suppressing particle growth of the sintered body particle as well as reducing the percentage defective of the insulation resistance even if the dielectric layer is made thin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a multilayer ceramic capacitor in which a dielectric layer is formed using barium titanate powder.

  In recent years, with the miniaturization and high functionality of electronic devices, multilayer ceramic capacitors used in these devices are required to have a small size and a large capacity.

  In order to cope with this, multilayer ceramic capacitors are designed to be made thinner and multilayered dielectric layers.

  The multilayer ceramic capacitor includes a ceramic body in which dielectric layers and internal electrode layers are alternately stacked, and external electrodes are disposed so as to be electrically connected to the internal electrodes exposed on both end faces of the ceramic body.

  The multilayer ceramic capacitor is formed by first mixing fine powdered raw material barium titanate powder with a powder obtained by adding a minor component such as a rare earth element, followed by calcination and pulverization to produce a pulverized ceramic powder. Next, a ceramic green sheet containing ceramic pulverized powder is formed, and an internal electrode paste serving as an internal electrode layer is printed on the ceramic green sheet serving as a dielectric layer.

  Further, a plurality of ceramic green sheets on which internal electrode paste is formed are stacked and fired.

  In particular, a multilayer ceramic capacitor having a B-characteristic temperature characteristic of capacitance is markedly thinned, and the dielectric layer is thinned to 1 μm to 3 μm to achieve a small size and a large capacity.

As prior art document information relating to the invention of this application, for example, the one shown in Patent Document 1 is known.
JP 2006-290675 A

  However, in such a conventional multilayer ceramic capacitor, when the dielectric layer is thinned, the influence of the variation in the particle diameter of the sintered particles constituting the dielectric layer increases, so the coarse sintered particles As a result, there is a problem that the insulation resistance defect rate is remarkably deteriorated.

  An object of the present invention is to solve such a conventional problem and to provide a method for manufacturing a multilayer ceramic capacitor capable of reducing the insulation resistance defect rate even when the dielectric layer is thinned.

  In order to achieve the above object, the present inventors have conducted extensive research, and as a result, the ratio of the specific surface area evaluated by heat-treating the raw material powder of barium titanate is set within a predetermined range, whereby the insulation resistance of the dielectric layer is determined. The present inventors have found the knowledge that can significantly reduce the defect rate and have completed the present invention.

The present invention relates to a method of manufacturing a multilayer ceramic capacitor in which dielectric layers mainly composed of barium titanate and internal electrode layers are alternately stacked, and the formation of the dielectric layer is performed by using a raw material powder of barium titanate after mixing the subcomponents powder and is intended to include a calcining step, the raw material powder of the barium titanate prior to the mixing is a specific surface area of 3.5 m ² / g or more, and wherein This is a method for manufacturing a multilayer ceramic capacitor using a specific surface area evaluated by heat treatment at a temperature higher by 150 ° C. than the calcining temperature of the calcining and having a ratio of 0.5 or more with respect to the specific surface area before the heat treatment.

  As described above, in the multilayer ceramic capacitor of the present invention, the specific surface area of the raw powder of barium titanate evaluated by heat treatment at a temperature 150 ° C. higher than the calcining temperature is 0.5 or more with respect to the specific surface area before the heat treatment. Thus, the dispersion of excessive sintering reaction in calcination can be reduced, thereby suppressing the growth of particles in which sintered particles become coarse during sintering, and even if the dielectric layer is made thin The insulation resistance defect rate can be reduced.

(Embodiment)
A multilayer ceramic capacitor according to an embodiment of the present invention will be described.

  FIG. 1 is a partial cross-sectional perspective view of a multilayer ceramic capacitor.

  As shown in FIG. 1, the multilayer ceramic capacitor has a rectangular ceramic body 3 in which dielectric layers 1 and internal electrode layers 2 are alternately stacked, and external electrodes 4 are provided.

The dielectric layer 1 is composed of sintered particles of a dielectric ceramic composition mainly composed of barium titanate (BaTiO ₃ ), and the internal electrode layer 2 contains a base metal mainly composed of nickel or the like.

  The external electrodes 4 are electrically connected to the internal electrode layers 2 exposed at both end faces of the ceramic body 3 and are disposed at both ends of the ceramic body 3. The external electrodes 4 are ground electrodes provided on the surface of the ceramic body 3. And a metal layer formed by plating on the surface of the base electrode.

  The thickness of the dielectric layer 1 sandwiched between the internal electrode layers 2 is preferably 3 μm or less, and the capacity can be increased by making the dielectric layer 1 thinner. Moreover, it is preferable that the thickness of the dielectric layer 1 is 0.8 μm or more, and the dielectric layer 1 having a high insulation resistance can be obtained and the insulation resistance defect rate can be reduced.

  The dielectric layer 1 is composed of sintered particles, and the average particle size of the sintered particles is preferably 0.30 μm or less, and the insulation resistance defect rate can be reduced. The average particle size of the sintered particles is preferably larger than 0.15 μm, and a high dielectric constant can be obtained.

  The dielectric layer 1 includes at least one selected from the rare earth elements Dy, Ho, Er, and Y as subcomponents, at least one selected from Mn and V, and at least one selected from Si and Al. , Ba and Mg are preferably contained.

  It is preferable that the subcomponent contained in the dielectric layer 1 has the following content with respect to 100 parts by weight of barium titanate.

The content of at least one kind selected from the rare earth elements Dy, Ho, Er, and Y is determined by selecting the selected element as an oxide of the element (Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Y ₂ O _In terms of ₃ ), they are 0.01 parts by weight to 0.4 parts by weight, respectively, whereby the sintered particles can form a core-shell structure, and the temperature characteristics and the DC bias characteristics of the capacitance can be improved.

The content of at least one kind selected from Mn and V is 0.005 parts by weight to 0.02 parts by weight when the selected element is converted into an oxide of the element (Mn ₂ O ₄ , V ₂ O ₅ ). This improves the reduction resistance of the dielectric layer 1 and increases the reliability.

At least one selected from Si and Al is 0.1 parts by weight to 0.2 parts by weight, respectively, when the selected element is converted into an oxide (SiO ₂ , Al ₂ O ₃ ) of the element. Thus, the sintering reactivity of the sintered particles can be improved.

Ba is 1 part by weight to 3 parts by weight in terms of Ba in terms of carbonate (BaCO ₃ ), whereby the sintering reactivity of the sintered body particles can be stabilized.

Mg is 0.5 to 3 parts by weight in terms of Mg converted to hydroxide (Mg (OH) ₂ ), whereby the temperature characteristics of the capacitance can be stabilized.

  The internal electrode layer 2 preferably has a thickness of 1.0 μm to 2.5 μm. Insulation can reduce the occurrence of structural defects such as cracks while ensuring the effective area of the internal electrode layer 2 and maintaining the capacitance. The resistance failure rate can be reduced.

  Next, a method for manufacturing a multilayer ceramic capacitor will be described.

  First, a raw material powder of barium titanate powder used for forming the dielectric layer 1 is prepared.

Raw material powder of barium titanate powder has a specific surface area prior to evaluation by heat treatment are those having more than 3.5 m ² / g, the dielectric increases smaller and sintered particles from 3.5 m ² / g When the thickness of the body layer 1 is reduced to 3 μm or less, the number of sintered particles in the thickness direction of the dielectric layer 1 is reduced, so that the insulation resistance defect rate is remarkably deteriorated.

Further, the raw material powder of barium titanate preferably has a specific surface area of 5.0 m ² / g or less before being evaluated by heat treatment, and if it exceeds 5.0 m ² / g, the dielectric constant of the dielectric layer 1 is increased. It becomes small and it becomes difficult to ensure the capacitance.

  In addition, the specific surface area of the raw material powder of barium titanate evaluated by heat-treating the raw material powder at a temperature 150 ° C. higher than the calcining temperature of the calcining is compared with the specific surface area of the raw material powder before the heat-treating evaluation. The ratio is 0.5 or more. If the ratio of the specific surface area evaluated by heat treatment at a temperature 150 ° C. higher than the calcining temperature is less than 0.5 with respect to the specific surface area before the heat treatment, there is a large variation in the sintering reaction in the calcining and firing. When the grain growth becomes excessive and the dielectric layer 1 is thinned, the insulation resistance defect rate rapidly increases.

  Furthermore, the raw material powder of barium titanate has a specific surface area evaluated by heat-treating the raw material powder at a temperature 150 ° C. higher than the calcining temperature, and the ratio of the specific surface area before the heat treatment is 0.8 or less. Preferably, if it exceeds 0.8, the sintered strength of the ceramic body is lowered and the insulation resistance defect rate is deteriorated.

  Here, the calcination temperature indicates a maximum temperature in a temperature profile of calcination described later.

In addition, the heat treatment for evaluating the specific surface area of the barium titanate raw material powder is performed in the air, and the temperature profile of the heat treatment is increased at the same temperature increase rate as that of calcination and then reaches a predetermined heat treatment temperature. Hold, and further lower the temperature from the heat treatment temperature at the same rate as the calcination,
The holding time at the predetermined heat treatment temperature is the same as the holding time at the calcination temperature in the calcination step.

  The specific surface area was measured by the BET method by nitrogen adsorption, and the measurement method was to prepare 1.0 g of powder to be measured using a BET specific surface area measuring device (Mounttech, Macsorb, HM-1208) at 300 ° C. Then, after performing heat treatment for removing adsorbed substances by holding for 30 minutes, nitrogen gas was introduced and measurement was performed.

  The raw material powder of barium titanate preferably has a lattice constant ratio c / a of the crystal lattice axis of 1.0085 to 1.0105, and the lattice constant ratio c / a of 1 When the ratio is smaller than .0085, the dielectric constant becomes small and the capacitance cannot be secured, and when the lattice constant ratio c / a is larger than 1.0105, the particle diameter of the raw material powder becomes large and the insulation resistance defect rate is remarkably deteriorated. To do.

  Further, the raw material powder of barium titanate preferably has a Ba / Ti ratio of 0.995 to 1.010, which is the molar ratio of Ba and Ti. When the Ba / Ti ratio is smaller than 0.995, the capacitance tangent is increased. When the ratio becomes higher and the Ba / Ti ratio is larger than 1.010, the dielectric constant decreases, and the capacitance cannot be secured.

  Next, the raw material powder of barium titanate and the subcomponent powder are mixed and dried to produce a ceramic mixed powder.

The subcomponent powder is composed of at least one oxide selected from rare earth oxides Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ and Y ₂ O ₃ , Mn ₂ O ₄ and V ₂ O _5. and at least one oxide selected from at least one oxide selected from SiO _2, Al ₂ O _3, a BaCO ₃ and Mg (OH) ₂ Doo, the specific surface area of each powder 5. preferably has a 0m ² /g~120.0m ² / g.

  For the mixing, a wet medium stirring mill is used to mix the raw material powder of barium titanate and the powder of the accessory component together with the zirconia balls and pure water of the medium. The zirconia balls having a diameter of 0.01 mm to 2.0 mm are preferably used, and can be mixed efficiently.

Mixing is performed to uniformly disperse the subcomponents and to crush a part of the aggregate of secondary particles of the raw material powder of barium titanate, and the specific surface area of the ceramic mixed powder after drying is 4.5 m. ² / g to 7.0 m ² / g are adjusted and mixed.

  Further, a ball mill may be added to and mixed with zirconia balls and pure water.

  Subsequently, the ceramic mixed powder is calcined.

  The calcining is performed in the air, and the temperature profile of the calcining is raised at a heating rate of 1 ° C./min to 15 ° C./min at 500 ° C. or higher, and after reaching the maximum calcining temperature, the calcining temperature For 2 hours, and then the temperature is lowered at a temperature lowering rate of 1 ° C./min to 15 ° C./min at 500 ° C. or higher.

  The calcining temperature is preferably 900 ° C. to 950 ° C., and the sintering reactivity of the raw material powder of barium titanate in the calcining after mixing can be accurately discriminated before performing the mixing step. This has a remarkable effect that can reduce the variation of the sintering reaction, thereby suppressing the grain growth that causes the sintered body particles to become coarse during the sintering, thereby reducing the insulation resistance defect rate.

  Subsequently, the calcined powder is pulverized using a wet medium stirring mill, and then dried to produce a ceramic pulverized powder.

The pulverization is performed by putting the powder after calcination, zirconia balls and pure water into a container, and the medium zirconia balls preferably have a diameter of 0.01 mm to 2.0 mm. performing grinding specific surface area is adjusted to 4.5m ² /g~6.5m ² / g.

  Next, the ceramic pulverized powder is mixed with a binder, a plasticizer, and a solvent to prepare a ceramic slurry in which the ceramic pulverized powder is dispersed. The ceramic slurry is applied onto a substrate using a method such as a doctor blade and dried. A ceramic green sheet to be the dielectric layer 1 is formed, and an internal electrode paste to be the internal electrode layer 2 is printed on the ceramic green sheet by a gravure printing method, a screen printing method, or the like.

  The internal electrode paste is a mixture of a base metal powder such as Ni or Ni alloy, a binder, a plasticizer, and a solvent, and the average particle diameter of the metal powder is preferably 0.1 μm to 0.3 μm. You may add the ceramic powder which has barium titanate as a main component so that it may not exceed 30 weight part with respect to 100 weight part of internal electrode pastes.

  Subsequently, a protective sheet made of a ceramic green sheet serving as a protective layer, then a ceramic green sheet printed with an internal electrode paste, and a plurality of protective sheets are sequentially stacked, laminated and pressure-bonded, and the internal electrode paste becomes a ceramic green sheet. The laminated body which is alternately laminated on both sides of the substrate is formed.

  Furthermore, after the laminate is cut and separated into individual pieces, the ceramic body 3 is formed by heating to a firing temperature in a reducing atmosphere and firing.

  The firing temperature is preferably 1180 ° C. to 1300 ° C. when the content of subcomponents is small, the dielectric constant is high, and the temperature characteristics of the capacitance and the DC bias characteristics can be improved.

  Next, external electrodes 4 are formed on both ends of the ceramic body 3.

  For the external electrode 4, a conductive paste is applied to the ceramic body 3 and fired to form a base electrode, and then a metal layer is formed on the base electrode by wet plating to produce a multilayer ceramic capacitor.

As described above, in the method of manufacturing a multilayer ceramic capacitor according to the embodiment of the present invention, the raw material powder of barium titanate before being mixed with the subcomponent powder has a specific surface area of 3.5 m ² before heat treatment and evaluation. The specific surface area evaluated by heat treatment at 150 ° C. higher than the calcining temperature has a ratio of 0.5 or more with respect to the specific surface area before the heat treatment. Thus, it is possible to reduce the variation in the excessive sintering reaction in the calcination, and to suppress the particle growth of the sintered body particles in the sintering, and to reduce the insulation resistance defect rate even if the dielectric layer 1 is made thin.

  Specific examples will be described below.

  First, raw material powders of barium titanate of sample numbers 1 to 11 shown in (Table 1) were prepared.

  Table 1 shows the specific surface area, the lattice constant ratio c / a, and the average particle diameter of the barium titanate raw material powder of each sample number before the heat treatment of the barium titanate raw material powder.

  Furthermore, the specific surface area of the raw material powder of barium titanate of each sample number evaluated at each heat treatment temperature (900 ° C., 950 ° C., 1050 ° C., 1100 ° C., 1150 ° C.) with respect to the specific surface area before the heat treatment. The ratio is shown.

  Moreover, the Ba / Ti ratio of the raw powder of barium titanate of each sample number was 0.996.

  The heat treatment is performed in the air, and the temperature profile of the heat treatment is that after raising the temperature to the heat treatment temperature shown in (Table 1) and holding for 2 hours at the heat treatment temperature. It was the same as the rate and the cooling rate, and was performed at a constant temperature gradient of 5 ° C./min at a temperature of 500 ° C. or higher.

  Next, the subcomponent powder added to the raw material powder of barium titanate was weighed so as to have the following composition ratio.

The composition ratio is 0.01 parts by weight of Dy ₂ O ₃ , Ho ₂ O ₃ and Er ₂ O ₃ , Mn ₂ O ₄ and V ₂ O, respectively, with respect to 100 parts by weight of the raw material powder of barium titanate of each sample number. ₅ was 0.01 parts by weight, SiO ₂ and Al ₂ O ₃ were each 0.1 parts by weight, BaCO ₃ was 1 part by weight, and Mg (OH) ₂ was 0.5 parts by weight.

Next, the raw material powder of barium titanate and the subcomponent powder were mixed together with zirconia balls having a diameter of 0.1 mm and pure water using a wet medium stirring mill, and then dehydrated and dried to produce a ceramic mixed powder. At this time, mixing was performed such that the specific surface area of the ceramic mixed powder using the raw material powder of barium titanate of each sample number in Table 1 was 5.5 m ² / g.

  Subsequently, the barium titanate ceramic mixed powder of each sample number was extracted, and calcining having a temperature profile of calcining condition 1 and calcining condition 2 was performed in air.

Calcination condition 1 is that the temperature profile is 500 ° C. or higher, the temperature is raised at a temperature rise temperature of 5 ° C./min and reaches the calcination temperature 900 ° C., then held at 900 ° C. for 2 hours. The temperature was lowered at a rate of ° C / min.

  The calcination condition 2 is a temperature profile having the same temperature increase rate and temperature decrease rate as the calcination condition 1 except that the calcination temperature is different from the calcination condition 1, and the calcination temperature is maintained at 950 ° C. for 2 hours. is there.

Next, the calcined powder was put into a container together with zirconia balls having a diameter of 0.5 mm and pure water, pulverized using a wet medium stirring mill, and then dried to produce a ceramic pulverized powder. In this case the specific surface area of calcined Conditions 1 and calcination conditions 2 ceramic pulverized powder using barium titanate of each sample number was pulverized so as to respectively 5.2 m ² / g.

  Furthermore, ceramic pulverized powder, polyvinyl butyral resin binder, phthalate plasticizer, and butanol solvent are mixed to prepare a ceramic slurry, and the ceramic slurry is applied onto a PET film using a doctor blade method. A ceramic green sheet was formed by drying.

  Next, an internal electrode paste containing Ni powder having an average particle diameter of 0.2 μm and barium titanate powder as a co-material was formed on the ceramic green sheet using gravure printing.

  Further, 160 layers of ceramic green sheets on which the internal electrode paste was printed were laminated and pressure-bonded to form a laminate.

  Subsequently, after the laminated body is cut and separated into individual pieces, the temperature is raised to 1200 ° C. in a reducing atmosphere of hydrogen gas and carbon dioxide gas so that Ni serving as an internal electrode is not excessively oxidized, and sintered and sintered. Got.

  Next, the sintered body was chamfered so that the internal electrodes were completely exposed on both end faces of the sintered body to obtain a ceramic body having an outer diameter of 1.0 mm × 0.5 mm × 0.5 mm.

  Further, a conductive paste containing a powder mainly composed of Cu and glass frit was applied to both end faces of the ceramic body, and then baked in a nitrogen atmosphere at 800 ° C. to form a base electrode.

  A metal layer of Ni plating and Sn plating was sequentially formed on the base electrode to form an external electrode on the surface of the ceramic body, and a multilayer ceramic capacitor sample having a dielectric layer thickness of 1.8 μm was obtained.

  Next, (Table 2) and (Table 3) show the insulation resistance defect rate and capacitance for 100 samples of each multilayer ceramic capacitor.

  Sample numbers 1a to 11a in (Table 2) are monolithic ceramic capacitors obtained by calcining under calcining conditions 1 at a calcining temperature of 900 ° C. using the barium titanate powders of sample numbers 1 to 11 in (Table 1). Sample numbers 1b to 11b in (Table 3) were calcined under the calcining condition 2 at a calcining temperature of 950 ° C. using the barium titanate powders of sample numbers 1 to 11 in (Table 1), respectively. It is a multilayer ceramic capacitor.

  Moreover, the specific surface area before the heat treatment of the barium titanate raw material powder shown in (Table 2) and (Table 3) has the corresponding characteristics of the raw material powder of barium titanate of sample numbers 1 to 11 shown in (Table 1). The ratio of the specific surface area to the specific surface area before the heat treatment of the barium titanate raw material powder evaluated by heat treatment at 1050 ° C. and 1100 ° C. is the same as in sample numbers 1 to 11 shown in (Table 1). The corresponding characteristics of the raw material powder of barium titanate were transcribed, and the heat treatment temperatures 1050 ° C. and 1100 ° C. of the raw material powders shown in (Table 2) and (Table 3) were calcining condition 1 and calcining condition, respectively. The temperature is 150 ° C. higher than the calcination temperature of No. 2.

Further, the insulation resistance defect rate was determined to be defective when the insulation resistance value was less than 1.0 × 10 ⁷ Ω, and the insulation resistance defect rate exceeding 10% was outside the scope of the embodiment of the present invention.

  Capacitance is an average value obtained by applying a voltage of 1 Vrms at a temperature of 20 ° C. and measuring at 1 kHz. The target value of the electrostatic capacity is 1.00 μF, and ± 10% of the target value is ± 10%. Those having an electrostatic capacity exceeding were outside the scope of the embodiment of the present invention.

  As shown in Table 2, when the calcining temperature is 900 ° C., for sample numbers 6a and 7a, the ratio of specific surface areas evaluated by heat-treating barium titanate raw material powder at 1050 ° C. is the heat treatment temperature. They are 0.49 and 0.49, respectively, with respect to the previous specific surface area, which is smaller than 0.5, and the insulation resistance defect rate is higher than 10%.

  On the other hand, in the sample numbers 1a to 5a and 8a to 10a, the ratio of the specific surface area evaluated by heat-treating the raw powder of barium titanate at 1050 ° C. is 0.5 or more with respect to the specific surface area before the heat treatment. It can be seen that the insulation resistance defect rate is remarkably improved.

  Next, when the calcining temperature of (Table 3) is 950 ° C., for sample numbers 5b to 7b and 9b, the ratio of the specific surface area evaluated by heat-treating the raw material powder of barium titanate at 1100 ° C. is The specific surface areas were 0.44, 0.42, 0.44, and 0.46, respectively, which were smaller than 0.5 and the insulation resistance defect rate was worse than 10%.

  Sample No. 11a in (Table 2) and Sample No. 11b in (Table 3) show that the ratio of specific surface areas evaluated by heat-treating the barium titanate raw material powder at 1050 ° C. and 1100 ° C., respectively, Although it is 0.50 or more with respect to the specific surface area of 0.70 and 0.67, respectively, the insulation resistance defect rate is remarkably deteriorated.

Sample Nos. 11a and 11b have a specific surface area before heat treatment of the raw powder of barium titanate of 3.2 m ² / g. If the specific surface area before heat treatment is less than 3.5 m ² / g, barium titanate This is because the raw material powder has a large particle size and a sintered body particle size becomes coarse.

  Next, the relationship between the ratio of the specific surface area evaluated by heat treatment at a temperature exceeding 150 ° C. from the calcining temperature to the specific surface area before the heat treatment and the insulation resistance defect rate will be described.

  In the case of calcination condition 1, for example, a temperature higher by 200 ° C. than the calcination temperature is 1100 ° C. When looking at sample numbers 5a and 7a in (Table 2), the raw material powder of barium titanate used in this sample number is 1100 The specific surface area ratio evaluated by heat treatment at 0 ° C. is the same as 0.44 and 0.44 from (Table 1) with respect to the specific surface area before this heat treatment, but from Table 2 sample number 5a, The insulation resistance defect rate of 7a is 9% and 24%, respectively.

  In the case of calcination condition 2, the temperature 200 ° C. higher than the calcination temperature is 1150 ° C. When looking at sample numbers 3b and 6b in (Table 3), the raw material powder of barium titanate used in this sample number is The specific surface area ratios evaluated by heat treatment at 1150 ° C. are 0.39 and 0.39 from (Table 1) with respect to the specific surface area before heat treatment, respectively. 3% and 38%.

  Thus, in the case of calcination condition 1 and calcination condition 2, the raw material powder of barium titanate is determined by the ratio of the specific surface area evaluated by heat treatment at a temperature 200 ° C. higher than the calcination temperature to the specific surface area before the heat treatment. It can be seen that it is difficult to reduce the insulation resistance defect rate.

  Furthermore, regarding the relationship between the ratio of the specific surface area evaluated by heat treatment at a temperature lower than 150 ° C. from the calcining temperature to the specific surface area before heat treatment and the insulation resistance failure rate, in the case of calcining condition 1, the heat treatment temperature is 950. The temperature is 50 ° C. higher than the calcining temperature 900 ° C. For example, when looking at sample numbers 4a and 6a in (Table 2), the raw material powder of barium titanate used in this sample number is as shown in (Table 1). In addition, the ratio of specific surface areas at a heat treatment temperature of 950 ° C. is 0.71 and 0.71, respectively, and the insulation resistance defect rates shown in Table 2 are 4% and 25%, respectively.

  In the case of calcination condition 2, the heat treatment temperature of 1050 ° C. is 100 ° C. higher than the calcination temperature of 950 ° C. For example, sample number 9b in (Table 3) is 1050 ° C. heat treatment of this raw material powder of barium titanate. The ratio of the specific surface area of the temperature is 0.55 and the ratio of the specific surface area is 0.50 or more, but the insulation resistance failure rate becomes 18% and the insulation resistance failure rate becomes high.

  Thus, in the case of calcination condition 1 and calcination condition 2, the ratio of the specific surface area evaluated by heat treatment at a temperature lower than the calcination temperature by 100 ° C. or less is 0.5 or more with respect to the specific surface area before this heat treatment. It can be seen that it is difficult to reduce the rate of defective insulation resistance by using the raw material powder of barium titanate having the following.

As described above, the raw material powder of barium titanate before being mixed with the subcomponent powder has a specific surface area of 3.5 m ² / g or more and is heat-treated at a temperature 150 ° C. higher than the calcining temperature in calcining. When the specific surface area evaluated in this way has a ratio of 0.5 or more with respect to the specific surface area before the heat treatment, the defective rate of insulation resistance can be reduced.

  Regarding the capacitance, sample numbers 1a to 9a in (Table 2) and sample numbers 1b to 9b in (Table 3) satisfy the target value of capacitance, but sample numbers in (Table 2). 10a and 10b of (Table 3) are smaller than the target value of capacitance. This is because the dielectric constant decreases when the ratio c / a of the lattice constant of the raw powder of barium titanate is smaller than 1.0085.

  For sample number 11a in (Table 2) and sample number 11b in (Table 3), the ratio c / a of the lattice constant of the raw material powder of barium titanate is 1.0108 as shown in (Table 1). If the ratio is larger than 1.0105, the sample number 11b of the calcining condition 2 with a high calcining temperature has a larger sintered body particle size and a larger dielectric constant (Table 3). It can be seen that there are cases where the target value is not satisfied when the value is exceeded.

  As described above, by setting the lattice constant ratio c / a of the raw material powder of barium titanate to 1.0085 to 1.0105, the insulation resistance defect rate of the multilayer ceramic capacitor is reduced, and the capacitance target It can be seen that the value can be satisfied.

  The method for producing a multilayer ceramic capacitor of the present invention has the effect of reducing the insulation resistance defect rate even when the dielectric layer is thinned and reduced in size and capacity, and the dielectric layer is formed using barium titanate powder. It is useful for multilayer ceramic electronic parts such as ceramic capacitors.

Partial sectional perspective view of multilayer ceramic capacitor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric layer 2 Internal electrode layer 3 Ceramic body 4 External electrode

Claims (3)

A method for manufacturing a multilayer ceramic capacitor in which dielectric layers mainly composed of barium titanate and internal electrode layers are alternately stacked,
The formation of the dielectric layer includes a step of calcining after mixing the raw material powder of barium titanate and the subcomponent powder, and the raw material powder of barium titanate before mixing is The specific surface area is 3.5 m ² / g or more, and the specific surface area evaluated by heat treatment at a temperature 150 ° C. higher than the calcining temperature of the calcining is a ratio of 0.5 or more to the specific surface area before the heat treatment. A method for manufacturing a monolithic ceramic capacitor using the above. The method for producing a multilayer ceramic capacitor according to claim 1, wherein the calcining temperature is 900 ° C. to 950 ° C. 2. The method for manufacturing a multilayer ceramic capacitor according to claim 1, wherein the raw material powder of barium titanate has a lattice constant ratio c / a of 1.0085 to 1.0105.

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