JP2007084418A - Electronic component, dielectric porcelain composition and its producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric porcelain composition which can be fired in a reducing atmosphere, has a high specific dielectric constant, has good DC bias characteristics (the dependency of the dielectric constant on the DC voltage application), is reduced in the electrostriction quantity during the electric voltage application and exhibits capacity-temperature characteristics satisfying X6S characteristics (-55 to 105°C, ΔC/C= within ±22%) in the EIA standards. <P>SOLUTION: The dielectric ceramic composition is characterized in that it has a main component containing BaTiO<SB>3</SB>, SrTiO<SB>3</SB>and CaTiO<SB>3</SB>, and at least a part of the BaTiO<SB>3</SB>, SrTiO<SB>3</SB>and CaTiO<SB>3</SB>being present in the composition does not form a solid solution each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dielectric ceramic composition having resistance to reduction, a method for producing the same, and an electronic component such as a multilayer ceramic capacitor using the dielectric ceramic composition.

  Multilayer ceramic capacitors are widely used as small-sized, large-capacity, high-reliability electronic components, and the number used in electrical and electronic devices is large. In recent years, with the miniaturization and high performance of devices, the demand for further miniaturization, larger capacity, lower cost, and higher reliability of multilayer ceramic capacitors has become increasingly severe.

  At present, ferroelectric ceramic materials are generally used for small-sized and high-capacity ceramic capacitors. Such a ferroelectric ceramic material is accompanied by an electrostriction phenomenon in which mechanical distortion occurs when an electric field is applied. Therefore, when a voltage is applied to a ceramic capacitor using a ferroelectric ceramic material, the electrostriction phenomenon occurs. Vibration due to.

  In particular, such an electrostriction phenomenon can cause vibration of not only the capacitor itself but also the board and surrounding components when a ceramic capacitor is mounted on a circuit board. May emit a vibration sound having an audible frequency (20 to 20000 Hz). This vibration sound may be in a range that is uncomfortable for humans, and countermeasures have been required.

  On the other hand, for example, in Patent Document 1, in order to suppress the transmission of the vibration of the ceramic capacitor due to the electrostriction phenomenon to the substrate, the ceramic capacitor is provided with an electrode connection portion for connecting the external terminal electrode and the substrate, It has been proposed to provide a certain separation distance between the lower surface of the capacitor element body and the substrate.

  However, as described in this document, if a method of providing a certain separation distance by the electrode connecting portion is adopted, the manufacturing cost of the ceramic capacitor increases, and the height direction of the capacitor increases, resulting in a small size. Further improvement has been desired in view of the difficulty in making it easier.

  Patent Document 2 contains at least calcium titanate, strontium titanate, and barium titanate, and the compositional molar ratio of at least barium titanate is 0.3 or less with respect to these three compositional molar ratios. A dielectric ceramic composition comprising at least one of orthorhombic crystal structure is disclosed. The dielectric ceramic composition described in this document is particularly intended to reduce third harmonic distortion (THD). However, the dielectric ceramic composition of this document is not sufficient for improving the above-described electrostriction phenomenon, and has a structure in which the main components calcium titanate, strontium titanate and barium titanate are dissolved in each other. Since it is employed, the capacity-temperature characteristic is not sufficient, and for example, the X6S characteristic of the EIA standard (−55 to 105 ° C., ΔC / C = within ± 22%) cannot be satisfied.

JP 2004-335963 A JP 2000-264729 A

  The present invention has been made in view of such a situation, and an object thereof is to enable firing in a reducing atmosphere, a high relative dielectric constant, and a DC bias characteristic (dependence of dielectric constant on DC voltage application). Dielectric porcelain composition that has good electromagnetism when voltage is applied, and that satisfies capacitance-temperature characteristics of X6S characteristics (-55 to 105 ° C., ΔC / C = within ± 22%) of EIA standards And a method for manufacturing the same.

In order to achieve the above object, the dielectric ceramic composition according to the present invention comprises:
A dielectric ceramic composition having a main component comprising BaTiO ₃ , SrTiO ₃ and CaTiO ₃ ,
At least a part of the BaTiO ₃ , SrTiO ₃ and CaTiO ₃ is not solid-solved with each other.

Preferably, the BaTiO ₃ , SrTiO ₃ and CaTiO ₃ constituting the main component are not substantially dissolved in each other and are contained in the form of BaTiO ₃ , SrTiO ₃ and CaTiO ₃ .

Preferably, the dielectric ceramic composition includes BaTiO ₃ crystal particles, SrTiO ₃ crystal particles, and CaTiO ₃ crystal particles, and the BaTiO ₃ crystal particles, SrTiO ₃ crystal particles, and CaTiO ₃ crystal particles are substantially each other. It is contained in a state where it is not in solid solution.
More preferably, the dielectric ceramic composition has a composite structure including the BaTiO ₃ crystal particles, SrTiO ₃ crystal particles, and CaTiO ₃ crystal particles.

Preferably, in the X-ray diffraction using Cu—Kα ray as an X-ray source, the dielectric ceramic composition has a (110) plane of the BaTiO _{3 and} the SrTiO _{3 in} a range of 2θ = 30 to 35 °, respectively. ₃ separable diffraction peaks based on the (110) plane and the (121) plane of the CaTiO ₃ are observed.

  Preferably, the dielectric ceramic composition further includes an oxide of Mn as a subcomponent, and the content of the oxide of Mn is 0.3 to 0.3 mol in terms of MnO with respect to 100 mol of the main component. 1 mole.

Preferably, the dielectric ceramic composition further includes an oxide of Si as a subcomponent, and the content of the oxide of Si is 0.1 in terms of SiO _{2 with} respect to 100 mol of the main component. -0.5 mol.

Preferably, the dielectric ceramic composition further includes at least one selected from oxides of V, Ta, Nb, W, Mo and Cr as subcomponents,
The oxide content of V, Ta, Nb, W, Mo and Cr is 0.02 mol in terms of each element of V, Ta, Nb, W, Mo and Cr with respect to 100 mol of the main component. As mentioned above, it is less than 0.40 mol.

Preferably, regarding the composition molar ratio of the BaTiO ₃ , the SrTiO ₃ and the CaTiO ₃ ,
In the case shown these by a composition formula of _{{(Ba x Sr y Ca z} ) O} m TiO 2, the symbols x in the above formulas, y, z and m,
0.19 ≦ x ≦ 0.23,
0.26 ≦ y ≦ 0.31,
0.46 ≦ z ≦ 0.54,
x + y + z = 1,
0.980 ≦ m ≦ 1.01
Range.

The method for producing a dielectric ceramic composition according to the present invention includes:
A method for producing any one of the above dielectric ceramic compositions,
As the raw material of the main component, using BaTiO ₃ powder, SrTiO ₃ powder and CaTiO ₃ powder,
The BaTiO ₃ powder, SrTiO ₃ powder and CaTiO ₃ powder are used without reacting with each other in advance.

  The electronic component according to the present invention has a dielectric layer made of any one of the above dielectric ceramic compositions. 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 dielectric ceramic composition of the present invention has main components including BaTiO ₃ , SrTiO ₃ and CaTiO ₃ , and at least some of these are contained in a state where they are not in solid solution with each other, preferably these Are contained in a state where they are not substantially dissolved in each other, that is, in the form of BaTiO ₃ , SrTiO ₃ and CaTiO ₃ . Therefore, the dielectric constant is high, the DC bias characteristic is good, the capacitance temperature characteristic can be improved while reducing the amount of electrostriction when a voltage is applied, and in particular, the X6S characteristic of the EIA standard can be satisfied.

  Therefore, by using the dielectric ceramic composition of the present invention as a dielectric layer of an electronic component such as a multilayer ceramic capacitor, an application that requires low vibration, for example, where a film capacitor has been conventionally used (for example, a filter) And application to converters). In particular, the multilayer ceramic capacitor of the present invention is superior in temperature stability (particularly, temperature stability on the high temperature side) as compared with a film capacitor, and therefore the multilayer ceramic capacitor is applied to an application in which the film capacitor was used. As a result, reliability can be improved.

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.
FIG. 2 is a diagram showing an X-ray diffraction pattern of a dielectric layer according to an embodiment of the present invention,
3A is a reflected electron image of the dielectric layer according to the example of the present invention, FIG. 3B is a reflected electron image of the dielectric layer according to the comparative example,
4 (A) to 4 (C) are photographs showing element mapping results of Ba element, Sr element and Ca element of the dielectric layer according to the example of the present invention.

Multilayer ceramic capacitor 1
As shown in FIG. 1, a multilayer ceramic capacitor 1 according to an embodiment of the present invention includes a capacitor element body 10 having a configuration in which dielectric layers 2 and internal electrode layers 3 are alternately stacked. At both ends of the capacitor element body 10, a pair of external electrodes 4 are formed which are electrically connected to the internal electrode layers 3 arranged alternately in the element body 10. The shape of the capacitor element body 10 is not particularly limited, but is usually a rectangular parallelepiped shape. Moreover, there is no restriction | limiting in particular also in the dimension, What is necessary is just to set it as a suitable dimension according to a use.

  The internal electrode layers 3 are laminated so that the end faces are alternately exposed on the surfaces of the two opposite ends of the capacitor element body 10. The pair of external electrodes 4 are formed at both ends of the capacitor element body 10 and are connected to the exposed end surfaces of the alternately arranged internal electrode layers 3 to constitute a capacitor circuit.

Dielectric layer 2
The dielectric layer 2 contains a dielectric ceramic composition.
The dielectric ceramic composition contained in the dielectric layer 2 of this embodiment has a main component including BaTiO ₃ , SrTiO ₃ and CaTiO ₃ .

In the present embodiment, the BaTiO ₃ , SrTiO ₃ and CaTiO ₃ constituting the main component are in a state in which at least a part thereof is not solid-solved with each other. It is more preferable that they are in a state where they are not substantially dissolved in each other. That is, it is preferably contained in the form of BaTiO ₃ , SrTiO ₃ and CaTiO _3. More specifically, in the dielectric ceramic composition contained in the dielectric layer 2, each of the composite oxides It is preferably contained as BaTiO ₃ crystal particles, SrTiO ₃ crystal particles, and CaTiO ₃ crystal particles as separate crystal particles. In particular, these BaTiO ₃ crystal particles, SrTiO ₃ crystal particles, and CaTiO ₃ crystal particles preferably form a composite structure.

However, BaTiO ₃ , SrTiO ₃ and CaTiO ₃ may be substantially contained as BaTiO ₃ crystal particles, SrTiO ₃ crystal particles and CaTiO ₃ crystal particles. For example, BaTiO ₃ crystal particles and SrTiO ₃ crystal particles In the vicinity of the interface, a part of the solid solution phase may be formed.

By making BaTiO ₃ , SrTiO ₃ and CaTiO ₃ into a state in which they are not substantially dissolved in each other, it is possible to improve the capacity-temperature characteristics while maintaining a high dielectric constant. X6S characteristics (−55 to 105 ° C., ΔC / C = within ± 22%) can be satisfied. The reason for this is considered to be, for example, that the Curie temperature peak derived from BaTiO ₃ remains by making it non-solid solution.

Whether or not BaTiO ₃ , SrTiO ₃ and CaTiO ₃ constituting the main component are dissolved in each other can be confirmed by, for example, X-ray diffraction of the dielectric layer 2. Specifically, the dielectric layer 2 is subjected to X-ray diffraction using Cu-Kα ray as an X-ray source, and BaTiO ₃ , SrTiO ₃ and CaTiO ₃ are respectively obtained in the range of 2θ = 30 to 35 °. This can be confirmed by whether or not the resulting separable three diffraction peaks are observed. The diffraction peaks observed in the range of 2θ = 30 to 35 ° are the diffraction peak of the (110) plane of BaTiO ₃ , the diffraction peak of the (110) plane of SrTiO ₃ , and the (121) plane of CaTiO ₃ , respectively. It is a diffraction peak.

Also, if there is no particular limitation on the molar ratio of composition BaTiO _3, SrTiO ₃ and CaTiO ₃ that constitute the main component, for example, showing them by a composition formula _{{(Ba x Sr y Ca z} ) O} m TiO 2 And the symbols x, y, z and m in the above formula are preferably 0.19 ≦ x ≦ 0.23,
0.26 ≦ y ≦ 0.31,
0.46 ≦ z ≦ 0.54,
0.980 ≦ m ≦ 1.01,
And more preferably
0.195 ≦ x ≦ 0.225,
0.265 ≦ y ≦ 0.305,
0.465 ≦ z ≦ 0.535,
0.985 ≦ m ≦ 1.075,
It is. In the above formula, x + y + z = 1.
By making the symbols x, y, z, and m within the above ranges, it is possible to enhance the effect of improving DC bias characteristics and the effect of reducing the amount of electrostriction during voltage application. In the above composition formula, the amount of oxygen (O) may be slightly deviated from the stoichiometric composition of the above formula.

In the above formula, x represents the content ratio of BaTiO ₃ . As the content of BaTiO _{3 in} the main component increases, the ferroelectricity tends to increase. If x is too small, the relative permittivity tends to be low. In particular, if the relative dielectric constant is too low, it is necessary to increase the number of laminated dielectric layers 2 in order to obtain a desired capacitance. Therefore, there arises a problem that it becomes difficult to reduce the size. On the other hand, if x is too large, although the relative permittivity is improved, the amount of electrostriction when a voltage is applied increases, and the DC bias characteristics tend to deteriorate.

In the above formula, y represents the content ratio of SrTiO ₃ . When the content of SrTiO _{3 in} the main component increases, the paraelectric property tends to increase. If y is too small, the dielectric constant tends to be low. On the other hand, if y is too large, the DC bias characteristics tend to deteriorate.

In the above formula, z indicates the content of CaTiO _3. CaTiO ₃ is mainly effect and of improving the sintering stability has the effect of improving the insulation resistance value. If z is too small, the DC bias characteristics tend to deteriorate. On the other hand, if z is too large, the dielectric constant tends to decrease.

When the content of BaTiO _{3 in} the main component increases, the ferroelectricity becomes stronger. On the other hand, when the content of SrTiO ₃ and CaTiO ₃ in the main component increases, the paraelectric property tends to increase, and the symbol x By setting, y, and z within the above ranges, a balance between the ferroelectric phase and the paraelectric phase can be achieved.

  In the above formula, m represents the ratio of the A site of the perovskite structure to the B site (ratio of Ba, Sr and Ca and Ti). By setting m to 0.980 or more, the grain growth of dielectric particles during firing can be suppressed, and the dielectric particles constituting the dielectric layer after firing can be miniaturized. Further, by setting m to 1.01 or less, a dense sintered body can be obtained without increasing the firing temperature. If m is too small, it is difficult to make the dielectric particles fine, and the DC bias characteristics tend to deteriorate. On the other hand, if m is too large, the sintering temperature becomes too high and sintering tends to be difficult.

The dielectric ceramic composition preferably further contains subcomponents in addition to the above-described main components.
In the present embodiment, as subcomponents, an oxide of Mn, an oxide of Si, and at least one selected from oxides of elements of V, Ta, Nb, W, Mo, and Cr are further included. It is preferable that

  The oxide of Mn has the effect of promoting sintering and the effect of improving the high temperature load life. The content of the Mn oxide is preferably 0.3 to 1 mol and more preferably 0.3 to 0.8 mol in terms of MnO with respect to 100 mol of the main component. If the content of the Mn oxide is too small, the sinterability deteriorates and the high temperature load life tends to be inferior. On the other hand, if the content is too large, the IR defect rate may deteriorate.

The Si oxide mainly acts as a sintering aid, but has an effect of improving the defective rate of the initial insulation resistance when the layer is thinned. The content of the Si oxide is preferably 0.1 to 0.5 mol and more preferably 0.15 to 0.45 mol in terms of SiO _{2 with} respect to 100 mol of the main component. If the content of Si oxide is too small, the firing temperature may increase. On the other hand, when the amount is too large, the IR defect rate tends to deteriorate.

In the present embodiment, Si oxide may be included in the form of a complex oxide. Examples of such composite oxides include composite oxides of SiO ₂ and oxides of elements constituting other main components and subcomponents contained in the dielectric ceramic composition. For example, CaSiO ₃ , SrSiO ₃ , (Ca, Sr) SiO ₃ , MnSiO ₃ , BaSiO _{3 and the} like. When these composite oxides are used, they may be appropriately adjusted so that the composition after firing falls within a desired range.

The oxides of each element of V, Ta, Nb, W, Mo, and Cr have an effect of improving the high temperature load life. The content of these oxides is preferably 0.02 mol or more and less than 0.40 mol in terms of each oxide of V, Ta, Nb, W, Mo and Cr with respect to 100 mol of the main component. More preferably, it is 0.05-0.35 mol, More preferably, it is 0.1-0.3 mol. If the content of these oxides is too small, the above effect is difficult to obtain. On the other hand, if too much, IR tends to decrease.
In addition, the said content is content of each element conversion, for example, in the oxide of V, when content in V element conversion is 0.10 mol, it is V ₂ O ₅ which is the oxide The content in terms of conversion is 0.05 mol.

  In addition, in this embodiment, you may contain subcomponents other than the above as needed. Such subcomponents are not particularly limited. For example, Ba, Ca, Sr, Li, Nb, W, Ta, Mo, Mg, Al, Zr, Sc, Y, La, Ce, Pr, Nd, Pm , Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and an oxide of each element of Lu.

  Moreover, the thickness of the dielectric layer 2 is not particularly limited, but is preferably 1 to 7 μm, and more preferably 3 to 6 μm. If the dielectric layer 2 is too thin, the short-circuit defect rate may deteriorate. On the other hand, if it is too thick, it is difficult to reduce the size of the capacitor.

Internal electrode layer 3
The conductive material contained in the internal electrode layer 3 is not particularly limited, but a relatively inexpensive base metal can be used because the constituent material of the dielectric layer 2 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 internal electrode layer 3 may be formed using a commercially available electrode paste. What is necessary is just to determine the thickness of the internal electrode layer 3 suitably according to a use etc.

External electrode 4
The conductive material contained in the external electrode 4 is not particularly limited, but in the present invention, inexpensive Ni, Cu, and alloys thereof can be used. What is necessary is just to determine the thickness of the external electrode 4 suitably according to a use etc.

Manufacturing Method of Multilayer Ceramic Capacitor 1 The multilayer ceramic capacitor 1 of the present embodiment is the same as a conventional multilayer ceramic capacitor. After producing a green chip by a normal printing method or a sheet method using a paste and firing it, It is manufactured by printing or transferring an external electrode and baking. Hereinafter, the manufacturing method will be specifically described.

  First, a dielectric material (dielectric ceramic composition powder) contained in the dielectric layer paste is prepared, and this 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 material and an organic vehicle, or may be a water-based paint.

  As the dielectric material, the above-mentioned main component and subcomponent oxides, mixtures thereof, and composite oxides can be used. In addition, various compounds that become the above oxides or composite oxides by firing, such as carbonic acid, can be used. A salt, an oxalate salt, a nitrate salt, a hydroxide, an organometallic compound, or the like can be selected as appropriate and used in combination. What is necessary is just to determine content of each compound in a dielectric raw material so that it may become a composition of the above-mentioned dielectric ceramic composition after baking. In the state before forming a paint, the particle size of the dielectric material is usually about 0.1 to 1 μm in average particle size.

In the present embodiment, it is preferable to use BaTiO ₃ powder, SrTiO ₃ powder and CaTiO ₃ powder as the raw material of the main component, and in particular, these BaTiO ₃ powder, SrTiO ₃ powder and CaTiO ₃ powder are mutually preliminarily used. It is preferable to use without reacting. BaTiO ₃ , SrTiO _3, and SrTiO ₃ that constitute the main component in the sintered dielectric ceramic composition by using these powders as raw materials of the main component and using them without reacting with each other in advance. the CaTiO _3, each other, can be configured to not substantially dissolved. That is, in the sintered dielectric ceramic composition, these composite oxides can be present in the form of BaTiO ₃ crystal particles, SrTiO ₃ crystal particles, and CaTiO ₃ crystal particles. It can be a composite structure.

In addition to the powders described above, the raw material for the main component is TiO in order to adjust the ratio between the A site and B site of the perovskite structure (ratio of Ba, Sr and Ca and Ti). ₂ may be further added.

  In addition, as raw materials other than the main components (for example, raw materials for subcomponents), each oxide or a compound that becomes each oxide by firing may be used as it is, or calcined and roasted in advance. It may be used as

  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, etc. 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.

  The internal electrode layer paste and the external electrode paste may be commercially available electrode pastes, or may be pastes of commercially available electrode materials.

  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 printed and laminated 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. As binder removal conditions, the temperature rising rate is preferably 5 to 300 ° C./hour, the holding temperature is preferably 180 to 400 ° C., and the temperature holding time is preferably 0.5 to 24 hours. The firing atmosphere is air or a reducing atmosphere.

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 ⁻¹⁰ to 10 ⁻³ 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 1000-1400 degreeC, More preferably, it is 1100-1360 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 is interrupted due to abnormal sintering of the internal electrode layer, the capacity temperature characteristic is deteriorated 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 rate of temperature rise 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 to 3 hours. The time and cooling rate are preferably 50 to 500 ° C./hour, more preferably 200 to 300 ° C./hour. 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 can be 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 ^{−1 to} 10 Pa. When the oxygen partial pressure is less than the above range, it is difficult to re-oxidize the dielectric layer, and when it exceeds the above range, oxidation of the internal electrode layer tends to proceed.

  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 high temperature load life is likely to be shortened. On the other hand, when 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, and the high temperature is increased. The load 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. . 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 main body obtained as described above is subjected to end face polishing, for example, by barrel polishing or sand blasting, and the external electrode paste is applied and fired to form the external electrode 4. Then, if necessary, a coating layer is formed on the surface of the external electrode 4 by plating or the like.
The multilayer ceramic capacitor of this embodiment manufactured in this way is mounted on a printed circuit board or the like by soldering or the like and used for various electronic devices.

  According to the present embodiment, the dielectric layer 2 of the multilayer ceramic capacitor is composed of the above-described dielectric ceramic composition. Therefore, the multilayer ceramic capacitor of this embodiment has a high relative dielectric constant, good DC bias characteristics (dependence of dielectric constant on DC voltage application), reduced electrostriction during voltage application, and The capacity-temperature characteristic can be improved.

  In particular, the multilayer ceramic capacitor of the present embodiment satisfies the EIA standard X6S characteristics (−55 to 105 ° C., ΔC / C = within ± 22%) while maintaining the capacitance-temperature characteristics, Regarding the relative dielectric constant, the following characteristics can be obtained.

That is, the multilayer ceramic capacitor of this embodiment has the following characteristics with respect to the amount of electrostriction when the voltage is applied.
When the number of dielectric layers 2 sandwiched between the pair of internal electrode layers 3 is N layers, the ceramic capacitor is fixed to the substrate, and the ceramic capacitor fixed to the substrate is AC: 0.2 Vrms / μm. The amount of electrostriction defined by the vibration width of the surface of the element body 10 when a voltage is applied under the conditions of DC: 4 V / μm and frequency: 1 kHz is preferably less than 0.125 N [nm], more preferably 0. .1 N [nm] or less. That is, for example, when the number of dielectric layers 2 sandwiched between the pair of internal electrode layers 3 is 100, the amount of electrostriction is preferably less than 12.5 nm, more preferably 10 nm or less. be able to. As the substrate, a normal substrate on which the multilayer ceramic capacitor 1 is mounted, for example, a glass epoxy substrate printed with a predetermined electrode pattern may be used.

  The values of AC and DC under the above voltage application conditions are applied voltages per 1 μm thickness of the dielectric layer. That is, for example, when the thickness of the dielectric layer is 5 μm, the applied voltage is AC: 1.0 Vrms (= 0.2 Vrms / μm × 5 μm) and DC: 20 V (= 4 V / μm × 5 μm). Further, the amount of electrostriction tends to change as the thickness of the dielectric layer 2 changes. Therefore, in this embodiment, when the thickness of the dielectric layer 2 is preferably 1 to 7 [mu] m, more preferably 3 to 6 [mu] m, and particularly 5 [mu] m, the predetermined range is preferable.

  In addition, the multilayer ceramic capacitor of the present embodiment can satisfy the X6S characteristic, and the relative dielectric constant can be preferably 500 or more, more preferably 550 or more, while the electrostriction amount is in the predetermined range. Therefore, a desired capacitance can be obtained without increasing the number of stacked dielectric layers 2, and the capacitor can be downsized while suppressing an increase in manufacturing cost.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this invention.

  For example, in the above-described embodiment, the multilayer ceramic capacitor is exemplified as the electronic component according to the present invention. However, the electronic component according to the present invention is not limited to the multilayer ceramic capacitor, and has a dielectric layer having the above configuration. Anything is fine.

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

Example 1
First, BaTiO ₃ powder, SrTiO ₃ powder, and CaTiO ₃ powder are used as the main component raw materials, and MnCO ₃ , V ₂ O ₅ , and SiO ₂ are used as the auxiliary component raw materials. As raw materials for adjusting the ratio (the ratio of Ba, Sr and Ca and Ti), TiO ₂ was prepared. In addition, MnCO ₃ which is a raw material of the subcomponent is a compound that becomes MnO after firing. In addition, similar characteristics were obtained for BaTiO ₃ powder, SrTiO ₃ powder, and CaTiO ₃ powder even when using raw materials prepared by hydrothermal synthesis powder, oxalate method, or the like.

Subsequently, each raw material prepared above was wet pulverized with a ball mill for 15 hours and dried to obtain a dielectric material. In addition, the mixing ratio of each raw material was adjusted so that it might become the following compositions in the composition after baking. That is, for the main component, in the case shown by a composition formula _{{(Ba x Sr y Ca z} ) O} m TiO 2, the symbols x in the formula, y, z and m,
x = 0.23,
y = 0.27,
z = 0.5,
m = 1.005,
In addition, regarding the content of subcomponents, with respect to 100 moles of the main component,
MnO: 0.5 mol,
V ₂ O ₅ : 0.1 mol,
SiO ₂ : 0.22 mol,
Each was adjusted to be. However, MnO and SiO ₂ are contents in terms of oxides, and V ₂ O ₅ is a content in terms of V elements.

  Next, 100 parts by weight of the obtained dielectric material, 10 parts by weight of polyvinyl butyral resin, 5 parts by weight of dibutyl phthalate (DOP) as a plasticizer, and 100 parts by weight of alcohol as a solvent are mixed with a ball mill to obtain a paste. To obtain a dielectric layer paste.

  In this example, a capacitor electrode paste (a paste mainly containing Ni particles as conductive particles) was used as the internal electrode layer paste.

  Using these pastes, the multilayer ceramic chip capacitor 1 shown in FIG. 1 was manufactured as follows.

  First, a green sheet was formed on a PET film by the doctor blade method using the obtained dielectric layer paste. Next, an electrode pattern was printed on the green sheet by screen printing using the internal electrode layer paste to produce a green sheet on which the electrode pattern was printed. The thickness of the green sheet on which the electrode pattern was printed was 6.5 μm after drying. Next, separately from the above green sheet, a green sheet with no electrode pattern printed on the PET film was manufactured by a doctor blade method using the dielectric layer paste.

And each green sheet manufactured above was laminated | stacked in the following order, and the green chip | tip was manufactured by pressing the obtained laminated body.
First, green sheets on which no electrode patterns were printed were laminated until the total thickness reached 300 μm. On top of that, five green sheets printed with electrode patterns were laminated. Further thereon, a green sheet on which no electrode pattern was printed was laminated until the total thickness reached 300 μm to obtain a laminate. The obtained laminate was heated and pressurized under the conditions of a temperature of 80 ° C. and a pressure of 1 t / cm ² to obtain a green chip.

Next, the obtained green chip was cut into a predetermined size and subjected to binder removal processing, firing and annealing under the following conditions to obtain a multilayer ceramic fired body.
The binder removal treatment conditions were temperature rising rate: 30 ° C./hour, holding temperature: 250 ° C., temperature holding time: 8 hours, and atmosphere: in the air.
Firing conditions are: temperature rising rate: 200 ° C./hour, holding temperature: 1180-1280 ° C., temperature holding time: 2 hours, cooling rate: 200 ° C./hour, atmospheric gas: mixed gas of humidified N ₂ and H ₂ (H ₂ : 3%).
The annealing conditions were temperature rising rate: 200 ° C./hour, holding temperature: 1000 ° C., temperature holding time: 2 hours, cooling rate: 200 ° C./hour, and atmospheric gas: humidified N ₂ gas.
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 Sample 1 of the multilayer ceramic capacitor shown in FIG. The size of the obtained capacitor sample is 2.5 mm × 2.5 mm × 3.2 mm, the thickness of the dielectric layer is 5 μm, the thickness of the internal electrode layer is 1.5 μm, and the dielectric layer sandwiched between the internal electrode layers is The number was 4.

  For each of the obtained capacitor samples, X-ray diffraction measurement, capacitance-temperature characteristics (X6S characteristics), relative dielectric constant, electrostriction amount due to voltage application, and DC bias characteristics were measured by the following methods.

X-ray diffraction measurement The dielectric layer after firing is pulverized, and X-ray generation conditions are 50 kV-300 mA and scan width is 0 between 2θ = 30 to 35 ° with a powder X-ray (Cu-Kα ray) diffractometer .01 °, scan speed 0.1 ° / min, X-ray detection conditions: parallel slit 10 mm, divergence slit 0.3 mm, light receiving slit open, 2θ = 30 to 35 ° It was confirmed whether or not there were three separated diffraction peaks in the range. When three separated diffraction peaks are present in the range of 2θ = 30 to 35 °, BaTiO ₃ , SrTiO ₃ , and CaTiO ₃ are substantially dissolved in each other in the dielectric layer. It will exist in a state that is not. The results are shown in Table 1. Moreover, the X-ray-diffraction pattern of the sample number 1 which is an Example of this invention is shown collectively in FIG. From FIG. 2, in Sample No. 1, the existence of three separated diffraction peaks attributed to BaTiO ₃ , SrTiO ₃ and CaTiO ₃ can be confirmed in the range of 2θ = 30 to 35 °.

Capacity-temperature characteristics (X6S characteristics)
For the capacitor sample, the capacitance at each temperature of −55 ° C., 25 ° C. and 105 ° C. was measured, and the change rate ΔC of the capacitance at −55 ° C. and 105 ° C. with respect to the capacitance at 25 ° C. (unit: %) Was calculated. In this example, a sample in which the rate of change in electrostatic capacitance satisfies the X6S characteristic of the EIA standard (−55 to 105 ° C., ΔC = within ± 22%) is considered good. The results are shown in Table 1. In Table 1, samples that satisfy the X6S characteristics are indicated by “◯”, and samples that do not satisfy the X6S characteristics are indicated by “X”.

Dielectric constant ε
First, at a reference temperature of 25 ° C., a capacitor with a frequency of 1 kHz and an input signal level (measurement voltage) of 1.0 Vrms is input with a digital LCR meter (YHP 4284A), and the capacitance C is measured. did. Then, the relative dielectric constant ε (no unit) was calculated based on the thickness of the dielectric layer, the effective electrode area, and the capacitance C obtained as a result of the measurement. It is preferable that the relative dielectric constant is high. In this example, 500 or more was considered good. The results are shown in Table 1.

Electrostriction due to voltage application First, the capacitor sample was fixed by soldering to a glass epoxy substrate on which electrodes of a predetermined pattern were printed. Next, a voltage is applied to the capacitor sample fixed on the substrate under the conditions of AC: 0.2 Vrms / μm, DC: 4 V / μm, and frequency: 1 kHz, and the vibration width of the capacitor sample surface during voltage application is measured. This was the amount of electrostriction. A laser Doppler vibrometer was used to measure the vibration width of the capacitor sample surface. In this example, the average value of values measured using 10 capacitor samples was used as the amount of electrostriction. The amount of electrostriction is preferably low, and in this example, less than 0.5 nm (less than 0.125 N [nm], N = 4) was considered good. The results are shown in Table 1.

The DC bias characteristic was measured by calculating the change in relative permittivity (unit:%) when a DC voltage of 4 V / μm was applied to a DC bias characteristic capacitor sample at a constant temperature (25 ° C.). In this example, the DC bias characteristic was an average value of values measured using 10 capacitor samples. The DC bias characteristic is preferably as close to 0 as possible. In this example, −14% or more, particularly −10% or more was considered good. The results are shown in Table 1.

Comparative Example 1
A capacitor sample (sample) was obtained in the same manner as in Example 1 (sample number 1), except that BaCO ₃ , SrCO ₃ , CaCO _3, and TiO ₂ were calcined in advance at 1100 ° C. as the main component materials. No. 2) was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2
A capacitor sample (sample number 3) was used in the same manner as in Example 1 (sample number 1), except that BaTiO ₃ , SrTiO ₃ and CaTiO ₃ preliminarily calcined at 1100 ° C. were used as raw materials for the main components. Was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3
A capacitor sample (sample) was obtained in the same manner as in Example 1 (sample number 1) except that BaTiO ₃ and SrTiO ₃ preliminarily calcined at 1100 ° C. and CaTiO ₃ were used as raw materials for the main components. No. 4) was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4
A capacitor sample (sample number 5) was prepared in the same manner as in Example 1 (sample number 1) except that BaCO ₃ , SrCO ₃ , CaCO ₃ and TiO ₂ were used as the main component raw material. Evaluation was performed in the same manner as above. The results are shown in Table 1. In Comparative Example 4, each of the above-described raw materials was used without being calcined in advance.

  In Table 1, the raw materials of the main components used when producing Sample No. 1 (Example 1) and Sample Nos. 2 to 5 (Comparative Examples 1 to 4), the mode of calcining, and the evaluation results of each property Indicates.

From Table 1, sample No. 1 in which BaTiO ₃ powder, SrTiO ₃ powder, and CaTiO ₃ powder were used as the main components without pre-calcining, separated in the range of 2θ = 30 to 35 ° 3 Two diffraction peaks existed, and it was confirmed that BaTiO ₃ , SrTiO ₃ , and CaTiO ₃ were present in a state where they were not substantially dissolved in each other. Sample No. 1 satisfies the X6S characteristic in capacitance-temperature characteristics, has a relative dielectric constant of 500 or more, a DC bias characteristic of -10% or more, and an electrostriction amount when applying a voltage is less than 0.5 nm. It was a good result.

In contrast, in Sample No. 2 using BaCO ₃ , SrCO ₃ , CaCO ₃ and TiO ₂ preliminarily calcined, there are three separated diffraction peaks in the range of 2θ = 30 to 35 °. First, BaTiO ₃ , SrTiO ₃ , and CaTiO ₃ existed in a state of solid solution with each other. Sample No. 2 has a result that the capacity-temperature characteristic does not satisfy the X6S characteristic even though the constituent ratio of each element constituting the main component and the addition ratio of the subcomponent are the same as those of Sample No. 1. became.

Similarly, for sample numbers 3 to 5, there are no three separated diffraction peaks in the range of 2θ = 30 to 35 °, and BaTiO ₃ , SrTiO ₃ , and CaTiO ₃ are in solid solution with each other. As a result, the capacity-temperature characteristic did not satisfy the X6S characteristic (however, in the sample number 4, BaTiO ₃ preliminarily calcined and SrTiO ₃ were dissolved).

  3A and 3B show backscattered electron images of the dielectric layers of Sample No. 1 and Sample No. 2, respectively. Here, FIG. 3A is a reflected electron image of sample number 1, and FIG. 3B is a reflected electron image map of sample number 2.

As shown in FIG. 3A, in sample number 1, white particles (note that the white particles are particles containing a large amount of Ba element are confirmed by the EPMA element map shown in FIG. 4A. In addition, two white lines are Ni electrode portions.) Are scattered in the dielectric layer, and it can be confirmed that BaTiO ₃ is present without substantially dissolving. . On the other hand, as shown in FIG. 3B, in Sample No. 2, unlike Sample No. 1, white particles could not be confirmed in the dielectric layer, and the Ba element was uniformly dispersed in the dielectric layer. .

4A to 4C, the Ba element (FIG. 4A), Sr element (FIG. 4B), and Ca element (FIG. 4C) of the dielectric layer of sample number 1 are shown. The photograph showing the element mapping result by EPMA of) is shown. Note that these photographs were measured for the same part as in FIG. From FIG. 4A, in sample number 1, it can be confirmed that portions containing a large amount of Ba element (black portions in the figure) are scattered in the dielectric layer. 4B and 4C, the Sr element and the Ca element (the black portions in the respective drawings) are also scattered in the dielectric layer like the Ba element. I can confirm. In particular, from FIG. 4A to FIG. 4C, the Ba element, the Sr element, and the Ca element are scattered at different positions. From this result, BaTiO ₃ , SrTiO ₃ , and CaTiO ₃ are , It can be confirmed that they exist without solid solution.

Example 2
A capacitor sample (sample number) was obtained in the same manner as in Example 1 (sample number 1) except that the addition amounts of the main component raw material and subcomponent raw material were changed so that the composition after firing became the composition shown in Table 2. 11-22) were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

Table 2 shows the main component composition of Sample Nos. 1 and 11-22, the amount of each subcomponent added, and the evaluation results of each characteristic. In Table 2, the addition amount of the respective subcomponents is the number of moles with respect to 100 moles of the main component, MnO, each in terms of oxide for SiO _2, with V terms of element for V 2 _{O 5,} respectively amount Indicated. Sample number 1 in Table 2 is the same sample as sample number 1 in Example 1.

  From the results of sample numbers 1 and 11 to 15, it can be confirmed that the same tendency can be obtained even when the main component composition and the subcomponent composition are changed.

  On the other hand, in Sample Nos. 16 to 22 in which the main component composition is outside the preferable range of the present invention, the capacity-temperature characteristic tends to satisfy the X6S characteristic, while other characteristics tend to deteriorate.

That is, from the result of the sample number 16, when the value of x was too small (that is, when the content of BaTiO ₃ was too small), the relative dielectric constant was much lower than 500. On the other hand, from the result of the sample number 17, when the value of x was too large, the electrostriction amount was increased.

Further, from the results of sample numbers 18 and 19, when the value of z is too small (that is, when the content of CaTiO ₃ is too small), the DC bias characteristics deteriorate, while the value of z is large. When it was too much, the dielectric constant decreased. From the result of the sample number 20, when the value of y is too large (that is, when the content of SrTiO ₃ is too large), the DC bias characteristics are deteriorated.

  Further, from the results of the sample numbers 21 and 22, when the value of m is too small, the DC bias characteristics are deteriorated. On the other hand, when the value of m is too large, the sintering temperature is increased. , Could not be sintered.

Example 3
A capacitor sample (sample number) was obtained in the same manner as in Example 1 (sample number 1) except that the addition amounts of the main component raw material and subcomponent raw material were changed so that the composition after firing became the composition shown in Table 3. 23 to 26) were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 3.

In Table 3, the addition amount of the respective subcomponents is the number of moles with respect to 100 moles of the main component, MnO, each in terms of oxide for SiO _2, with V terms of element for V 2 _{O 5,} respectively amount Indicated.

From Table 3, the same results can be obtained even when the amount of V ₂ O ₅ added as an accessory component is 0.2 mol, 0.3 mol, and 0.36 mol in terms of V element. (Sample Nos. 23 to 25). In these sample numbers 23 to 25, the DC bias was slightly lowered, but the high temperature accelerated life could be improved.
On the other hand, when the amount of V ₂ O ₅ added as a subcomponent is excessively increased to 0.4 mol (sample number 26), a sample that can evaluate each characteristic can be obtained because IR is insufficient. could not.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is a diagram showing an X-ray diffraction pattern of a dielectric layer according to an example of the present invention. FIG. 3A is a reflected electron image of the dielectric layer according to the example of the present invention, and FIG. 3B is a reflected electron image of the dielectric layer according to the comparative example. 4A is a photograph showing the element mapping result of Ba element of the dielectric layer according to the embodiment of the present invention, and FIG. 4B is the element mapping result of Sr element of the dielectric layer according to the embodiment of the present invention. FIG. 4C is a photograph showing the element mapping result of Ca element of the dielectric layer according to the example of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 10 ... Capacitor element main body 2 ... Dielectric layer 3 ... Internal electrode layer 4 ... External electrode

Claims (11)

A dielectric ceramic composition having a main component comprising BaTiO ₃ , SrTiO ₃ and CaTiO ₃ ,
A dielectric ceramic composition characterized in that at least a part of the BaTiO ₃ , SrTiO ₃ and CaTiO ₃ are not in solid solution with each other. 2. The BaTiO ₃ , SrTiO ₃ and CaTiO ₃ constituting the main component are not substantially dissolved in each other and are contained in the form of BaTiO ₃ , SrTiO ₃ and CaTiO _3. Dielectric porcelain composition. The dielectric ceramic composition contains BaTiO ₃ crystal particles, SrTiO ₃ crystal particles and CaTiO ₃ crystal particles,
2. The dielectric ceramic composition according to claim 1, wherein the BaTiO ₃ crystal particles, SrTiO ₃ crystal particles, and CaTiO ₃ crystal particles are contained in a state where they are not substantially dissolved in each other. The dielectric ceramic composition according to claim 3, wherein the dielectric ceramic composition has a composite structure including the BaTiO ₃ crystal particles, SrTiO ₃ crystal particles, and CaTiO ₃ crystal particles. In the X-ray diffraction using Cu—Kα ray as the X-ray source, the dielectric ceramic composition has a (110) plane of the BaTiO ₃ and (110) of the SrTiO _{3 in} the range of 2θ = 30 to 35 °, respectively. ) Plane and _three separable diffraction peaks based on the (121) plane of the CaTiO ₃ are observed. The dielectric ceramic composition further includes an oxide of Mn as a subcomponent,
The dielectric ceramic composition according to any one of claims 1 to 5, wherein a content of the oxide of Mn is 0.3 to 1 mol in terms of MnO with respect to 100 mol of the main component. The dielectric ceramic composition further includes an oxide of Si as a subcomponent,
The dielectric ceramic composition according to any one of claims 1 to 6, wherein a content of the Si oxide is 0.1 to 0.5 mol in terms of SiO _{2 with} respect to 100 mol of the main component. . The dielectric ceramic composition further includes at least one selected from oxides of elements of V, Ta, Nb, W, Mo and Cr as subcomponents,
The oxide content of V, Ta, Nb, W, Mo and Cr is 0.02 mol in terms of each element of V, Ta, Nb, W, Mo and Cr with respect to 100 mol of the main component. The dielectric ceramic composition according to claim 1, wherein the dielectric ceramic composition is less than 0.40 mol. A method for producing the dielectric ceramic composition according to claim 1,
As the raw material of the main component, using BaTiO ₃ powder, SrTiO ₃ powder and CaTiO ₃ powder,
The method for producing a dielectric ceramic composition, wherein the BaTiO ₃ powder, SrTiO ₃ powder and CaTiO ₃ powder are used without reacting with each other in advance.   The electronic component which has a dielectric material layer comprised with the dielectric material ceramic composition in any one of Claims 1-8.   A multilayer ceramic capacitor having a capacitor element body in which dielectric layers composed of the dielectric ceramic composition according to claim 1 and internal electrode layers are alternately laminated.