JP2007186365A - Method of manufacturing dielectric ceramic composition and multilayer ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a dielectric ceramic composition which achieves a high-temperature load life without changing its composition and offers a sufficient reliability even when the thickness of a dielectric layer in a multilayer ceramic capacitor is reduced. <P>SOLUTION: The dielectric ceramic composition comprises a main component containing barium titanate and subcomponents comprising at least MgO, an SiO<SB>2</SB>sintering aid and an oxide of a rare-earth element. The method of manufacturing the dielectric ceramic composition comprises a step of preparing a pre-calcining powder by adding a raw material for the main component and a portion of raw materials for the subcomponents as pre-added subcomponents, a step of preparing a calcined powder by calcining the pre-calcining powder and a step of obtaining a dielectric ceramic composition powder by adding the rest of the raw materials for the subcomponents as post-added subcomponents to the calcined powder. MgO and the SiO<SB>2</SB>sintering aid are separately added as the pre-added subcomponent or the post-added subcomponent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a dielectric ceramic composition, and in particular, a dielectric ceramic composition used for a multilayer ceramic capacitor having a high temperature load life and high reliability even when the rated voltage is set high. It relates to a manufacturing method.

  A multilayer ceramic capacitor, which is an example of an electronic component, is used in various electronic devices. In recent years, there has been an increasing demand for downsizing and high performance of electronic devices, and multilayer ceramic capacitors are no exception, and miniaturization, price reduction, and increase in capacity are rapidly progressing.

  Accordingly, the dielectric layer per layer in the multilayer ceramic capacitor has been thinned, and a dielectric ceramic composition that can maintain the reliability as a capacitor even when the layer is thinned is demanded. In particular, very high reliability is required for the dielectric ceramic composition in order to reduce the size and increase the capacity of the medium voltage capacitor used at a high rated voltage.

  On the other hand, conventionally, expensive noble metals such as platinum and palladium have been used as the material constituting the internal electrode layer, which has been one of the factors for increasing the cost of multilayer ceramic capacitors. In recent years, a reduction-resistant dielectric ceramic composition that can use an inexpensive base metal such as nickel as the internal electrode layer has been developed. However, the multilayer ceramic capacitor using the reduction-resistant dielectric ceramic composition has a problem that the high-temperature load life of the insulation resistance (IR) is short and the reliability is not sufficient.

  In order to improve the above problem, in Patent Document 1, barium titanate that is a main component of a dielectric material and a glass component that is a sintering aid are preliminarily calcined, and the calcined powder and other additives A multilayer ceramic capacitor composed of a dielectric ceramic composition obtained by firing components is disclosed. In this document, the defect rate after the test is calculated under the condition of 1000 ° C. at 85 ° C.-12.6 V (rated voltage is 6.3 V), and the reliability is evaluated. However, for example, when used under severer conditions such as 50 V / μm at 180 ° C., there is a problem that reliability is lacking.

  In addition, the present applicant, in Patent Document 2, a capacitor satisfying X7R characteristics and having a high-temperature accelerated life, a barium titanate as a main component and subcomponents other than a glass component as a sintering aid. This is realized by pre-baking. In Patent Document 3, rare earth elements are divided into two groups according to the value of the effective ion radius at the time of nine coordination, and these two kinds of rare earth elements are used in combination, so that a layer suitable for medium withstand voltage is used. A ceramic capacitor is disclosed.

However, in order to cope with the reduction in size and thickness, the reliability may be insufficient to further reduce the thickness (about 5 μm).
Japanese Patent Laid-Open No. 2003-63862 JP 2000-31828 A JP 2003-277139 A

  The present invention has been made in view of such a situation, and the object thereof is to obtain sufficient reliability even when the dielectric layer of the multilayer ceramic capacitor is thinned, and the dielectric ceramic composition. It is an object of the present invention to provide a method for producing a dielectric ceramic composition having a good high temperature load life without changing the composition of the product. Another object of the present invention is to provide a multilayer ceramic capacitor using the dielectric ceramic composition obtained by the above production method.

  When the thickness of the dielectric layer is reduced, the electric field strength applied to the dielectric layer increases when a DC voltage is applied. For this reason, the insulation resistance decreases rapidly, and the life of the capacitor tends to deteriorate.

  In order to improve the above problem, a method of adding Mg to the dielectric ceramic composition has been performed, but the effect was not sufficient. The inventor of the present invention pays attention to the fact that Mg easily forms a segregation phase in the state of Mg-Si with Si contained as a sintering aid in the dielectric ceramic composition. The inventors have found that by preventing segregation in the -Si state, it is possible to suppress a decrease in insulation resistance and to improve the high-temperature load life, thereby completing the present invention.

That is, the method for producing a dielectric ceramic composition according to the present invention includes:
A main component comprising barium titanate;
A first subcomponent comprising MgO;
A _second subcomponent comprising a SiO ₂ -based glass component;
A third subcomponent comprising at least one selected from V ₂ O ₅ , MoO ₃ and WO ₃ ;
A fourth subcomponent including an oxide of R1 (wherein R1 is at least one selected from Y, Ho, Er, Tm, Yb, and Lu);
A fifth subcomponent containing an oxide of R2 (wherein R2 is at least one selected from Dy, Tb, Gd, Eu);
A method for producing a dielectric ceramic composition having a sixth subcomponent containing at least one of MnO and Cr ₂ O ₃ , comprising:
The ratio of each subcomponent to 100 moles of the main component is
1st subcomponent: 0.1-5 mol,
Second subcomponent: 2 to 10 mol,
Third subcomponent: 0 to 0.5 mol (excluding 0),
Fourth subcomponent: 0.1 to 10 mol (however, the number of moles of the fourth subcomponent is the ratio of R1 alone),
Fifth subcomponent: 0.1 to 10 mol (however, the number of moles of the fifth subcomponent is the ratio of R2 alone),
6th subcomponent: 0-0.5 mol (however, 0 is not included),
And
Adding the raw material of the main component and a part of the raw materials of the subcomponents constituting the dielectric ceramic composition, and obtaining a powder before calcining;
Calcining the pre-calcined powder to obtain a calcined powder;
Adding to the calcined powder the raw materials of the remaining subcomponents constituting the dielectric ceramic composition, and obtaining a dielectric ceramic composition powder;
Firing the dielectric ceramic composition powder,
A part of the subcomponent raw material added in the step of obtaining the pre-calcined powder is a preaddition subcomponent, and the remaining subcomponent raw material added in the step of obtaining the dielectric ceramic composition powder, When it is a post-addition accessory component,
The raw material for the first subcomponent and the raw material for the second subcomponent are added separately as a pre-addition subcomponent or a post-addition subcomponent, respectively.

  Conventionally, when Mg and Si coexist, segregation is likely to occur in the Mg—Si state, so that the effect of Mg added to improve the insulation resistance cannot be sufficiently exhibited.

On the other hand, in the present invention, a step of adding the raw material of the main component and a part of the raw material of the auxiliary component (pre-added auxiliary component) to prepare the powder before calcining, and the powder before calcining In the step of calcining the body, preparing the calcined powder, and adding the remaining subcomponent (post-addition subcomponent) to the calcined powder to obtain the dielectric ceramic composition powder, The first subcomponent containing MgO and the _second subcomponent containing the SiO ₂ glass component are added separately as a pre-addition subcomponent or a post-addition subcomponent. By doing so, it is possible to suppress the segregation of Mg—Si, sufficiently exhibit the effect of improving the insulation resistance of Mg, and realize a good high temperature load life. This effect is particularly important when the dielectric layer is thinned (for example, 5 μm or less).

  Preferably, at least a raw material of the first subcomponent is added as the pre-added subcomponent, and at least a raw material of the second subcomponent is added as the post-added subcomponent. The high temperature load life can be further improved by calcining the main component and the first subcomponent added as the pre-added subcomponent.

  Preferably, the average particle size of the main component material is 0.1 to 0.3 μm. When the dielectric layer of the multilayer ceramic capacitor according to the present invention is thinned by using a fine powder having an average particle size of 0.1 to 0.3 μm as a main component material (for example, 5 μm or less) In this case, sufficient reliability can be maintained.

  Preferably, the calcining temperature in the step of preparing the calcined powder is 500 ° C. or higher and 1200 ° C. or lower, more preferably 600 ° C. or higher and 750 ° C. or lower. The calcination may be performed a plurality of times.

  The electronic component according to the present invention has a dielectric layer composed of a dielectric ceramic composition obtained by any one of the above manufacturing methods. 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.

  The multilayer ceramic capacitor according to the present invention has a capacitor element in which dielectric layers composed of a dielectric ceramic composition obtained by any one of the manufacturing methods described above and internal electrode layers are alternately stacked. The multilayer ceramic capacitor is particularly suitable for a medium voltage multilayer ceramic capacitor having a rated voltage of 100 V or higher.

  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, a multilayer ceramic capacitor 2 according to an embodiment of the present invention includes a capacitor element 4 having a configuration in which dielectric layers 10 and internal electrodes 12 are alternately stacked. One internal electrode layer 12 that is alternately stacked is electrically connected to the inside of the external electrode 6 that is 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 external electrode 8 that is formed outside the second end portion 4 b of the capacitor element 4.

  The shape of the capacitor element 4 is not particularly limited and is appropriately selected depending on the purpose and application, but the shape is usually a rectangular parallelepiped. The dimensions are not limited, and are appropriately selected according to the purpose and application, and are usually vertical (0.4 to 5.6 mm) × horizontal (0.2 to 5.0 mm) × height (0.2 to 1). .9 mm).

Dielectric layer 10
The dielectric layer 10 contains a dielectric ceramic composition obtained by the production method of the present invention.
The dielectric ceramic composition obtained by the production method of the present invention comprises a main component containing barium titanate,
A first subcomponent comprising MgO;
A _second subcomponent comprising a SiO ₂ -based glass component;
A third subcomponent comprising at least one selected from V ₂ O ₅ , MoO ₃ and WO ₃ ;
A fourth subcomponent including an oxide of R1 (wherein R1 is at least one selected from Y, Ho, Er, Tm, Yb, and Lu);
A fifth subcomponent containing an oxide of R2 (wherein R2 is at least one selected from Dy, Tb, Gd, Eu);
And a sixth subcomponent containing at least one of MnO and Cr ₂ O ₃ .

The ratio of each subcomponent to 100 moles of the main component is
1st subcomponent: 0.1-5 mol,
Second subcomponent: 2 to 10 mol,
Third subcomponent: 0 to 0.5 mol (excluding 0),
Fourth subcomponent: 0.1 to 10 mol (however, the number of moles of the fourth subcomponent is the ratio of R1 alone),
Fifth subcomponent: 0.1 to 10 mol (however, the number of moles of the fifth subcomponent is the ratio of R2 alone),
6th subcomponent: 0-0.5 mol (however, 0 is not included),
And preferably
1st subcomponent: 0.2-2.5 mol,
Second subcomponent: 2 to 5 mol,
Third subcomponent: 0.01 to 0.1 mol,
Fourth subcomponent: 0.2 to 5 mol (however, the number of moles of the fourth subcomponent is the ratio of R1 alone),
Fifth subcomponent: 0.2-5 mol (however, the number of moles of the fifth subcomponent is the ratio of R2 alone),
6th subcomponent: 0.01-0.25 mol (however, 0.25 is not included),
It is.

  In this specification, each oxide constituting the main component and each subcomponent is represented by a stoichiometric composition, but the oxidation state of each oxide may be out of the stoichiometric composition. . However, the said ratio of each subcomponent is calculated | required by converting into the oxide of the said stoichiometric composition from the metal amount contained in the oxide which comprises each subcomponent.

The reasons for limiting the contents of the subcomponents are as follows.
As described above, MgO contained in the first subcomponent has the effect of improving the insulation resistance and improves the high temperature load life. The first subcomponent other than MgO preferably includes at least one selected from CaO, BaO and SrO. These oxides have the effect of flattening the capacity-temperature change rate. If the content of the first subcomponent is too small, such effects tend not to be obtained. If the content is too large, the sinterability tends to deteriorate and the relative permittivity tends to decrease.

The second subcomponent functions as a sintering aid. When the content of the second subcomponent is too small, the capacity-temperature characteristic is deteriorated and the IR (insulation resistance) tends to decrease. On the other hand, if the content is too large, the IR lifetime tends to be insufficient, and the dielectric constant tends to decrease rapidly. The second _{subcomponent, (Ba, Ca) x SiO} 2 + x ( however, x = 0.8 to 1.2) is preferably. _{X in} (Ba, Ca) _x SiO _{2 + x} is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. If x is too small, that is, if SiO ₂ is too much, it reacts with barium titanate contained in the main component and deteriorates dielectric properties. On the other hand, if x is too large, the melting point becomes high and the sinterability deteriorates, which is not preferable. In the second subcomponent, the ratio of Ba and Ca is arbitrary, and may contain only one.

  The third subcomponent exhibits the effect of flattening the capacity-temperature characteristic above the Curie temperature and the effect of improving the IR lifetime. If the content of the third subcomponent is too small, such an effect becomes insufficient. On the other hand, when the content is too large, IR tends to be remarkably lowered.

  The fourth subcomponent (R1 oxide) exhibits an effect of flattening the capacity-temperature characteristic. When there is too little content of a 4th subcomponent, such an effect will become inadequate and a capacity | capacitance temperature characteristic will worsen. On the other hand, if the content is too large, the sinterability tends to deteriorate.

  The fifth subcomponent (R2 oxide) exhibits the effect of improving insulation resistance (IR), IR lifetime, and DC bias. However, if the content of the fifth subcomponent is too large, the capacity-temperature characteristic tends to deteriorate.

  The sixth subcomponent exhibits an effect of promoting sintering, an effect of increasing IR, and an effect of improving IR life. However, if the content of the sixth subcomponent is too large, the capacity-temperature characteristic tends to deteriorate.

  The thickness of the dielectric layer 10 is usually 40 μm or less, particularly 10 μm or less per layer, but in the present embodiment, it is preferably 7 μm or less, more preferably 5 μm or less. The lower limit of the thickness is usually about 0.5 μm. The number of laminated dielectric layers 10 is usually about 2 to 1000.

Internal electrode layer 12
The conductive material contained in the internal electrode layer 12 is not particularly limited, but a base metal can be used because the constituent material of the dielectric layer 10 has reduction resistance. As the base metal used as the conductive material, Ni or Ni alloy is preferable. The Ni alloy is preferably an alloy of Ni and one or more elements 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, may be contained about 0.1 wt% or less. The thickness of the internal electrode layer 12 may be appropriately determined according to the application and the like.

External electrodes 6, 8
The conductive material contained in the external electrodes 6 and 8 is not particularly limited, but in the present invention, inexpensive Ni, Cu, and alloys thereof can be used. The thicknesses of the external electrodes 6 and 8 may be appropriately determined according to the application and the like, but are usually preferably about 10 to 50 μm.

The multilayer ceramic capacitor 2 using the dielectric ceramic composition obtained by the production method of the production method the present invention of a multilayer ceramic capacitor 2, as in the conventional multilayer ceramic capacitor, by a normal printing method or sheet method using a paste The green chip is manufactured and fired, and then the external electrode is printed or transferred and fired. Hereinafter, the manufacturing method will be specifically described.

First, a dielectric ceramic composition powder contained in the dielectric layer paste is prepared.
In the present invention, the dielectric ceramic composition powder is obtained through the following first to third steps.
In the first step, the raw material powder of the main component and a part of the raw material powder of the subcomponent that constitutes the dielectric ceramic composition are added and mixed, dried, and calcined. Obtain a pre-powder.

  In the second step, the pre-calcined powder is calcined to obtain a calcined powder. In the third step, the calcined powder and the remaining subcomponent raw material powder constituting the dielectric ceramic composition are added, mixed, and dried to obtain the dielectric ceramic composition. Obtain a powder.

The raw material for barium titanate, which is the main component, can be obtained by a so-called liquid phase method as well as a so-called solid phase method. In the case of using BaCO ₃ and TiO ₂ as starting materials, the solid phase method (calcining method) is a method for obtaining a raw material by weighing, mixing, calcining, and pulverizing a predetermined amount thereof. Examples of the liquid phase method include an oxalate method, a hydrothermal synthesis method, an alkoxide method, and a sol-gel method.

  As a raw material for the accessory component, the above-mentioned oxides, a mixture thereof, or a composite oxide can be used. In addition, various compounds that become the above-described oxide or composite oxide by firing, such as carbonates and oxalates. , Nitrates, hydroxides, organometallic compounds, and the like may be selected as appropriate and used as a mixture. What is necessary is just to determine content of each subcomponent raw material in dielectric ceramic composition powder so that it may become a composition of the above-mentioned dielectric ceramic composition after baking.

In the present embodiment, in the first step, a part of the raw material powder of the subcomponent added to obtain the pre-calcined powder is a pre-added subcomponent, and in the third step, When the raw material powder of the remaining subcomponent added to the calcined powder is the post-addition subcomponent, the first subcomponent raw material containing MgO and the second subcomponent containing the SiO ₂ glass component Are separately added as a pre-addition subcomponent or a post-addition subcomponent.

  For example, the raw material of the 1st subcomponent was added as a pre-addition subcomponent, calcined, and the raw material of the 2nd subcomponent was added to the calcined powder obtained after that as a post-addition subcomponent, and obtained. The method of baking dielectric ceramic composition powder is mentioned. Alternatively, the raw material of the second subcomponent was added as a pre-added subcomponent, calcined, and then the first subcomponent raw material was added as a post-added subcomponent to the calcined powder obtained thereafter. A method of firing the dielectric ceramic composition powder may be employed.

  That is, either the first subcomponent or the second subcomponent is added as a pre-added subcomponent, calcined together with the main component raw material, and then the remaining calcined as the post-added subcomponent is obtained. Add to the finished powder and fire. By carrying out like this, the segregation of Mg-Si can be suppressed and the insulation resistance improvement effect which Mg has can be exhibited.

Preferably, the first subcomponent raw material containing MgO is added as the pre-addition subcomponent, calcined, and then the second subcomponent raw material containing the SiO ₂ -based glass component is obtained as the post-addition subcomponent. It is added to the calcined powder obtained and fired. Other subcomponents may be added as pre-addition subcomponents or may be added as post-addition subcomponents. By adding the first subcomponent as the pre-added subcomponent and calcining together with the main component, the above effect is further increased. More preferably, only the first subcomponent is added and calcined as the pre-added subcomponent, and then the second subcomponent and other subcomponents are obtained as the post-added subcomponent, and the obtained calcined powder Add to body and fire.

The calcining conditions in the above-described steps are not particularly limited, but are preferably performed under the following conditions.
Temperature increase rate: 50 to 500 ° C / hour, more preferably 100 to 300 ° C / hour,
Holding temperature: 500-1200 ° C, more preferably 600-750 ° C,
Temperature holding time: 0.5 to 12 hours, more preferably 2 to 8 hours,
Atmosphere: in air or nitrogen.

  Next, the obtained dielectric ceramic composition powder is made into a paint to prepare a dielectric layer paste.

  The dielectric layer paste may be an organic paint obtained by kneading a dielectric ceramic composition powder and an organic vehicle, or may be a water-based paint.

  In the present embodiment, the average particle size of the dielectric ceramic composition powder is about 0.1 to 0.3 μm before being formed into a paint.

  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 may be appropriately selected from usual various binders such as ethyl cellulose and polyvinyl butyral. Further, the organic solvent to be used is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, toluene, and the like, depending on a method to be used such as a printing method or a sheet method.

  Further, when the dielectric layer paste is used as a water-based paint, a water-based vehicle in which a water-soluble binder or a dispersant is dissolved in water and a dielectric material may be kneaded. The water-soluble binder used for the water-based vehicle is not particularly limited, and for example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, or the like may be used.

  The internal electrode layer paste is obtained by kneading the above-mentioned organic vehicle with various conductive metals and alloys as described above, or various oxides, organometallic compounds, resinates, etc. that become the above-mentioned conductive materials after firing. Prepare.

  The external electrode paste may be prepared in the same manner as the internal electrode layer paste described above.

  There is no restriction | limiting in particular in content of the organic vehicle in each above-mentioned paste, For example, what is necessary is just about 1-5 weight% of binders, for example, about 10-50 weight% of binders. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like as necessary. The total content of these is preferably 10% by weight or less.

  When the printing method is used, the dielectric layer paste and the internal electrode layer paste are laminated and printed on a substrate such as PET, cut into a predetermined shape, and then peeled from the substrate to obtain a green chip.

  When the sheet method is used, a dielectric layer paste is used to form a green sheet, the internal electrode layer paste is printed thereon, and these are stacked to form a green chip.

Before firing, the green chip is subjected to binder removal processing. The binder removal treatment may be appropriately determined according to the type of the conductive material in the internal electrode layer paste. However, when a base metal such as Ni or Ni alloy is used as the conductive material, the oxygen partial pressure in the binder removal atmosphere is 10 It is preferable to be ⁻⁴⁵ to 10 ⁵ Pa. When the oxygen partial pressure is less than the above range, the binder removal effect is lowered. If the oxygen partial pressure exceeds the above range, the internal electrode layer tends to oxidize.

As other binder removal conditions, the temperature rising rate is preferably 5 to 300 ° C./hour, more preferably 10 to 100 ° C./hour, and the holding temperature is preferably 180 to 400 ° C., more preferably. 200 to 350 ° C., and the temperature holding time is preferably 0.5 to 24 hours, more preferably 2 to 20 hours. The firing atmosphere is preferably air or a reducing atmosphere, and as an atmosphere gas in the reducing atmosphere, for example, a mixed gas of N ₂ and H ₂ is preferably used after being humidified.

The atmosphere at the time of green chip firing may be appropriately determined according to the type of conductive material in the internal electrode layer paste, but when a base metal such as Ni or Ni alloy is used as the conductive material, the oxygen content in the firing atmosphere The pressure is preferably 10 ⁻⁸ to 10 ⁻⁴ Pa. When the oxygen partial pressure is less than the above range, the conductive material of the internal electrode layer may be abnormally sintered and may be interrupted. Further, when the oxygen partial pressure exceeds the above range, the internal electrode layer tends to be oxidized.

  Moreover, the holding temperature at the time of baking becomes like this. Preferably it is 1100-1400 degreeC, More preferably, it is 1200-1350 degreeC. If the holding temperature is lower than the above range, the densification becomes insufficient. If the holding temperature is higher than the above range, the electrode temperature is interrupted due to abnormal sintering of the internal electrode layer, the capacity temperature characteristic deteriorates due to diffusion of the constituent material of the internal electrode layer, and the dielectric Reduction of the body porcelain composition is likely to occur.

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. Further, 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 by humidification.

  When firing in a reducing atmosphere, it is preferable to anneal the capacitor element body. Annealing is a process for re-oxidizing the dielectric layer, and this can significantly increase the IR lifetime, thereby improving the reliability.

The oxygen partial pressure in the annealing atmosphere is preferably 10 ⁻³ Pa or more, particularly preferably 10 ^{−2 to} 10 Pa. When the oxygen partial pressure is less than the above range, it is difficult to reoxidize the dielectric layer, and when it exceeds the above range, the internal electrode layer tends to be oxidized.

  The holding temperature at the time of annealing is preferably 1100 ° C. or less, particularly 500 to 1100 ° C. When the holding temperature is lower than the above range, the dielectric layer is not sufficiently oxidized, so that the IR is low and the IR life tends to be short. On the other hand, if the holding temperature exceeds the above range, not only the internal electrode layer is oxidized and the capacity is lowered, but the internal electrode layer reacts with the dielectric substrate, the capacity temperature characteristic is deteriorated, the IR is lowered, the IR Life is likely to decrease. 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 temperature holding time is preferably 0 to 20 hours, more preferably 2 to 10 hours, and the cooling rate is preferably 50 to 500 ° C / hour, more preferably 100 to 300 ° C / hour. And Further, as the annealing atmosphere gas, for example, humidified N ₂ gas or the like is preferably used.

In the above-described binder removal processing, firing and annealing, for example, a wetter or the like may be used to wet the N ₂ gas or mixed gas. In this case, the water temperature is preferably about 5 to 75 ° C.

  The binder removal treatment, firing and annealing may be performed continuously or independently.

The capacitor element 4 main body obtained as described above is subjected to end surface polishing by, for example, barrel polishing or sand blasting, and the external electrode paste is printed or transferred and baked to form the external electrodes 6 and 8. The firing conditions of the external 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 coating layer is formed on the surfaces of the external electrodes 6 and 8 by plating or the like.

  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. Particularly, it is suitable for a medium voltage multilayer ceramic capacitor having a rated voltage of 100V or more.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in various aspects. .

  For example, in the above-described embodiment, the multilayer ceramic capacitor is exemplified, but the electronic component according to the present invention is not limited to the multilayer ceramic capacitor, and is constituted by the dielectric ceramic composition obtained by the above manufacturing method. Any material having a certain dielectric layer may be used.

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

Example 1
First, a main component material and a subcomponent material were prepared. As the main component material, BaTiO ₃ having an average particle size of 0.1 to 0.3 μm was used. As subcomponent materials, MgO (first subcomponent), (Ba _0.6 Ca _0.4 ) SiO ₃ (second subcomponent), V ₂ O ₅ (third subcomponent), Y ₂ O ₃ (first 4 subcomponents), Tb ₄ O ₇ (fifth subcomponent), and MnO (sixth subcomponent) were used. As for MgO and MnO, carbonates were used as raw materials, and oxides were used as other subcomponent raw materials. (Ba _0.6 Ca _0.4 ) SiO ₃ (hereinafter also referred to as BCG) was produced by the method shown below.

BCG was produced by wet mixing BaCO ₃ , CaCO ₃ and SiO ₂ with a ball mill for 16 hours, drying, firing in air at 1150 ° C., and further wet pulverizing with a ball mill for 100 hours.

Next, the composition of these raw materials after firing is 2 mol of MgO, 3 mol of BCG, 0.01 mol of V ₂ O ₅ and 1 mol of Y _{2 with} respect to 100 mol of BaTiO _3. Weighed so as to be O ₃ (2 moles in terms of Y), 0.5 moles of Tb ₄ O ₇ (2 moles in terms of Tb), and 0.2 moles of MnO. did. About each subcomponent raw material, the quantity weighed here becomes the final addition amount.

  Next, the raw material of the main component and the raw material of the auxiliary component shown as the pre-added auxiliary component in Table 1 were mixed by a ball mill for 16 hours, and after drying, a pre-calcined powder was obtained. This pre-calcination powder was calcined under the following conditions.

Temporary firing temperature rising rate: 200 ° C / hour holding temperature: 650 ° C
Holding time: 4 hours Atmosphere: in air

  To the obtained calcined powder, the remaining auxiliary component materials shown as post-added auxiliary components in Table 1 were added and mixed by a ball mill. After drying, a dielectric ceramic composition powder was obtained.

  100 parts by weight of the dielectric ceramic composition powder thus obtained, 4.8 parts by weight of acrylic resin, 40 parts by weight of methylene chloride, 20 parts by weight of ethyl acetate, 6 parts by weight of mineral spirits, 4 parts of acetone The parts by weight were mixed with a ball mill and made into a paste to obtain a dielectric layer paste.

  100 parts by weight of Ni particles having an average particle size of 0.1 to 0.3 μm, 40 parts by weight of an organic vehicle (8 parts by weight of ethyl cellulose dissolved in 92 parts by weight of butyl carbitol), and 10 parts by weight of butyl carbitol It knead | mixed with 3 rolls and was made into the paste and obtained the paste for internal electrode layers.

  Using the obtained dielectric layer paste, a green sheet having a thickness of 5.5 μm was formed on a PET film. After the internal electrode paste was printed thereon, the sheet was peeled from the PET film. Next, these green sheets and protective green sheets (not printed with internal electrode layer paste) were laminated and pressure-bonded to obtain a green laminate.

  Next, the green laminate was cut into a predetermined size to obtain a green chip, and the binder removal treatment, firing and annealing were performed under the following conditions to obtain a multilayer ceramic fired body.

Binder removal treatment Temperature rising rate: 25 ° C / hour,
Holding temperature: 260 ° C
Temperature holding time: 8 hours,
Atmosphere: in the air.

Firing Temperature rising rate: 200 ° C / hour,
Holding temperature: 1200-1260 ° C,
Temperature holding time: 2 hours,
Cooling rate: 200 ° C / hour,
Atmosphere: humidified N ₂ + H ₂ gas mixture,
Oxygen partial pressure: ^10-12 atm.

Annealing Temperature rising rate: 200 ° C / hour,
Holding temperature: 1050 ° C,
Temperature holding time: 2 hours,
Cooling rate: 200 ° C / hour,
Atmosphere: humidified N ₂ gas,
Oxygen partial pressure: 10 ⁻⁵ atm.
A wetter with a water temperature of 20 ° C. was used for humidifying the atmospheric gas during firing and annealing.

  Next, after polishing the end face of the obtained multilayer ceramic fired body by sand blasting, In-Ga was applied as an external electrode to obtain a sample of the multilayer ceramic capacitor shown in FIG.

  The size of the obtained capacitor sample was 3.2 mm × 1.6 mm × 0.6 mm, the number of dielectric layers sandwiched between internal electrode layers was 5, and the thickness of the dielectric layers per layer (interlayer thickness) ) Was 4 μm, and the thickness of the internal electrode layer was 1.5 μm.

About the obtained capacitor | condenser sample, the dielectric constant (epsilon) _r , CR product, high temperature load lifetime, and X7R characteristic were evaluated by the method shown below.

Dielectric constant ε _r
With a digital LCR meter (YHP4274A manufactured by Yokogawa Electric Corporation) at a reference temperature of 20 ° C, the capacitor sample was electrostatically charged under the conditions of a frequency of 1 kHz and an input signal level (measurement voltage) of 0.25 Vrms / μm The capacity C was measured. The relative dielectric constant (no unit) was calculated from the obtained capacitance, the dielectric thickness of the multilayer ceramic capacitor, and the overlapping area of the internal electrodes. The relative dielectric constant was 700 or more. The results are shown in Table 1.

CR product First, with respect to the capacitor samples, by using an insulating resistance meter (manufactured by Advantest Corporation R8340A), a DC voltage of 100V at 20 ° C, was measured insulation resistance IR after applying 1 minute capacitor samples. The CR product was measured by determining the product of the capacitance C (unit: μF) measured above and the insulation resistance IR (unit: MΩ). A CR product of 500 or more was considered good. The results are shown in Table 1.

High temperature load life (HALT)
The high temperature load life (HALT) was evaluated by measuring the average life time while maintaining the obtained sample at a DC voltage of 10 V / μm or 50 V / μm at 180 ° C. In this example, the time until the insulation resistance (IR) is 2 × 10 ⁵ Ω or less (unit is time) is defined as the lifetime. Further, this high temperature load life was carried out for 10 capacitor samples. The evaluation criteria were 200 hours or more for 180 ° C and 10 V / μm, and 30 hours or more for 180 ° C and 50 V / μm. The results are shown in Table 1.

  A state in which a DC voltage of 50 V / μm is applied is a state in which the electric field strength (about 40 V / μm) applied when the thickness between the dielectric layers becomes 5 μm is larger.

  In Patent Document 2 (Japanese Patent Application Laid-Open No. 2000-31828), the high temperature load life is measured under a condition where a DC voltage of 10 V / μm is applied at 180 ° C.

X7R characteristics For X7R characteristics, when the reference temperature is 25 ° C for the capacitor sample, the digital LCR meter (4274A manufactured by YHP) is used under the conditions of a frequency of 1 kHz and an input signal level (measurement voltage) of 0.25 Vrms. Then, the capacitance is measured, and whether the capacitance change rate with respect to temperature (ΔC / C) satisfies the EIAJ standard X7R characteristics (within ± 15%) within the temperature range of -55 to 125 ° C. In the case of being satisfied, “◯” was given, and in the case of not being satisfied, “X”. The results are shown in Table 1.

From Table 1, the first subcomponent containing MgO and the second subcomponent containing BCG, which is a SiO ₂ glass component, are added as pre-added subcomponents and calcined (samples 4 and 8) or after When added as an additive subcomponent (samples 5 and 9), it was confirmed that Mg-Si segregation occurred, and that only the same characteristics as those obtained when the calcining step was not provided (sample 10) were obtained.

On the other hand, a first subcomponent including MgO, if a second subcomponent including BCG is a SiO ₂ -based glass components were respectively added as separately before addition subcomponent or post-addition subcomponent (samples 1-3, In 6 and 7), the high temperature load life could be improved while maintaining the relative dielectric constant and the CR product in good condition. Among these, when the first subcomponent containing MgO is added as a pre-added subcomponent and calcined (Samples 1, ₂ , and 6), the second subcomponent containing BCG, which is a SiO ₂ glass component, is pre-added. It was confirmed that it was better than when added as a subcomponent and calcined (Samples 3 and 7).

  In particular, when the pre-addition subcomponent is only the first subcomponent containing MgO (sample 6), that is, when the main component and only the first subcomponent are calcined, Patent Document 2 (Japanese Patent Application Laid-Open No. 2000-2000). 311828), it was confirmed that the lifetime was three times or more that of the sample D3 (121h) having the best high-temperature load lifetime (electric field strength: 10 V / μm). Furthermore, even when the electric field strength is 50 V / μm, a good high temperature load life is shown.

Example 2
A sample was prepared and evaluated for properties in the same manner as Sample 6 of Example 1 except that the calcining temperature was changed to the temperature shown in Table 2. The results are shown in Table 2.

  From Table 2, it was confirmed that even when the calcining temperature was changed, the high temperature load life could be improved while maintaining the relative dielectric constant and the CR product.

  From the above results, according to the present invention, even when the dielectric layer of the multilayer ceramic capacitor is thinned (4 μm), it satisfies the X7R characteristics, maintains the relative permittivity and the CR product, and maintains the high temperature. It was confirmed that the load life could be improved. Therefore, even when the dielectric layer of the medium voltage capacitor used at a high rated voltage is thinned, sufficient reliability can be ensured.

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 ... External electrode 10 ... Dielectric layer 12 ... Internal electrode layer

Claims (6)

A main component comprising barium titanate;
A first subcomponent comprising MgO;
A _second subcomponent comprising a SiO ₂ -based glass component;
A third subcomponent comprising at least one selected from V ₂ O ₅ , MoO ₃ and WO ₃ ;
A fourth subcomponent including an oxide of R1 (wherein R1 is at least one selected from Y, Ho, Er, Tm, Yb, and Lu);
A fifth subcomponent containing an oxide of R2 (wherein R2 is at least one selected from Dy, Tb, Gd, Eu);
A method for producing a dielectric ceramic composition having a sixth subcomponent containing at least one of MnO and Cr ₂ O ₃ , comprising:
The ratio of each subcomponent to 100 moles of the main component is
1st subcomponent: 0.1-5 mol,
Second subcomponent: 2 to 10 mol,
Third subcomponent: 0 to 0.5 mol (excluding 0),
Fourth subcomponent: 0.1 to 10 mol (however, the number of moles of the fourth subcomponent is the ratio of R1 alone),
Fifth subcomponent: 0.1 to 10 mol (however, the number of moles of the fifth subcomponent is the ratio of R2 alone),
6th subcomponent: 0-0.5 mol (however, 0 is not included),
And
Adding the raw material of the main component and a part of the raw materials of the subcomponents constituting the dielectric ceramic composition, and obtaining a powder before calcining;
Calcining the pre-calcined powder to obtain a calcined powder;
Adding to the calcined powder the raw materials of the remaining subcomponents constituting the dielectric ceramic composition, and obtaining a dielectric ceramic composition powder;
Firing the dielectric ceramic composition powder,
A part of the subcomponent raw material added in the step of obtaining the pre-calcined powder is a preaddition subcomponent, and the remaining subcomponent raw material added in the step of obtaining the dielectric ceramic composition powder, When it is a post-addition accessory component,
The method for producing a dielectric ceramic composition, wherein the raw material for the first subcomponent and the raw material for the second subcomponent are added separately as a pre-addition subcomponent or a post-addition subcomponent, respectively. 2. The dielectric ceramic composition according to claim 1, wherein at least a raw material of the first subcomponent is added as the pre-added subcomponent, and at least a raw material of the second subcomponent is added as the post-added subcomponent. Method. 3. The method for producing a dielectric ceramic composition according to claim 1, wherein an average particle size of the main component material is 0.1 to 0.3 μm. The method for producing a dielectric ceramic composition according to claim 1, wherein a calcining temperature in the step of obtaining the calcined powder is 500 ° C. or more and 1200 ° C. or less. The electronic component which has a dielectric material layer comprised with the dielectric material ceramic composition obtained by the method in any one of Claims 1-4. A multilayer ceramic capacitor having a capacitor element in which dielectric layers composed of the dielectric ceramic composition obtained by the method according to any one of claims 1 to 4 and internal electrode layers are alternately laminated. .

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