JP2007153720A - Ceramic powder, ceramic electronic component and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide ceramic powder used as a raw material of a dielectric layer of a ceramic electronic component and capable of being sintered at a low temperature and giving the ceramic electronic component having high dielectric constant, low dielectric loss even in firing at the low temperature and long IR life. <P>SOLUTION: The ceramic powder is expressed by a general formula, ABO<SB>3</SB>and comprises a plurality of ceramic particles having perovskite type crystal structure. The plurality of the ceramic particles comprise a plurality of first particles and a plurality of second particles. The first particle is a fine particle defined to have a particle diameter equal to or below the average particle diameter of the whole ceramic powder calculated from a specific surface area determined by the BET method. When the average A/B of the first particle is expressed by (α) and the average A/B of the second particle is expressed by (β) in the molar ratio A/B of A site atom to B site atom in the ABO<SB>3</SB>, the relation between of (α) and (β) satisfies α<β. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ceramic powder as a raw material for a dielectric layer of a ceramic electronic component such as a multilayer ceramic capacitor, a ceramic electronic component manufactured using the ceramic powder, and a method for manufacturing the ceramic electronic component.

  Multilayer ceramic capacitors as ceramic electronic components are widely used as small-sized, large-capacity, high-reliability electronic components, and the number used in one electronic device is large.

  Multilayer ceramic capacitors are usually laminated by a sheet method or a printing method using an internal electrode layer paste and a dielectric layer paste, and the internal electrode layer and the dielectric layer in the multilayer body are simultaneously formed. Manufactured by firing.

  As the conductive material for the internal electrode layer, Pd or Pd alloy is generally used. However, since Pd is expensive, a relatively inexpensive base metal such as Ni or Ni alloy has been used. When a base metal is used as the conductive material for the internal electrode layer, there is a problem in that the internal electrode layer is oxidized when fired in the atmosphere. Therefore, it is necessary to perform simultaneous firing of the dielectric layer and the internal electrode layer in a reducing atmosphere. However, when firing in a reducing atmosphere, the dielectric layer is reduced and the specific resistance is lowered. For this reason, non-reducing dielectric materials have been developed.

  In recent years, along with the downsizing and high performance of electronic devices, further downsizing and high capacity of multilayer ceramic capacitors used in the electronic devices are being promoted. In order to realize such a reduction in size and increase in capacity, it is required to reduce the thickness of the internal electrodes and dielectric layers and increase the number of these layers.

  On the other hand, for example, in Patent Document 1, in order to enable thinning of the dielectric layer, the composition variation is reduced while the particle size of the barium titanate powder used as the raw material of the dielectric layer is atomized. A method has been proposed. According to this document, it is described that by using such a fine and homogeneous barium titanate powder, the reliability of the multilayer ceramic capacitor can be maintained high even when the dielectric layer is thinned. Yes.

  On the other hand, when the dielectric layer is thinned or multilayered, if the internal electrode layer is formed from the internal electrode paste containing a base metal such as Ni as a conductive material, there are the following problems. That is, since the base metal such as Ni constituting the internal electrode layer sinters at a lower temperature than the ceramic powder constituting the dielectric layer, when simultaneously firing the dielectric layer and the internal electrode layer, The internal electrode layer shrinks first. As a result, there is a problem in that delamination occurs between the dielectric layers, and the internal electrode is spheroidized, causing a short circuit.

  However, the above-mentioned Patent Document 1 is not intended to cope with such a problem. Therefore, in order to solve such a problem, for example, the following method needs to be adopted. It was. That is, in order to make the shrinkage behavior of the internal electrode layer and the shrinkage behavior of the dielectric layer uniform, a method of lowering the sintering temperature of the dielectric layer by adding a sintering aid to the dielectric layer. There was a need to adopt. However, when the dielectric layer is sintered at a low temperature by adding a sintering aid in this manner, the relative permittivity is lowered, and as a result, it is difficult to increase the capacity.

JP 2003-2739 A

  The present invention has been made in view of such a situation, and the object is to be used as a raw material for a dielectric layer of a ceramic electronic component such as a multilayer ceramic capacitor, and can be sintered at a low temperature and fired at a low temperature. Is to provide a ceramic powder capable of providing a ceramic electronic component having a high relative dielectric constant, a low dielectric loss, and an excellent IR lifetime. Another object of the present invention is to provide a ceramic electronic component obtained by using such a ceramic powder and having the above characteristics, and a method for producing the same.

As a result of intensive investigations to achieve the above object, the present inventors have found that the ceramic powder (powder represented by the general formula ABO ₃ ) as a raw material for the dielectric layer has a particle size distribution and an A / B In particular, the A / B of fine particles (first particles) having a relatively small particle size and the A / B of coarse particles (second particles) having a relatively large particle size are specified. As a result of the control, the inventors have found that the above object can be achieved, and have completed the present invention.

That is, the ceramic powder according to the present invention is
A ceramic powder composed of a plurality of ceramic particles represented by the general formula ABO ₃ and having a perovskite crystal structure,
The plurality of ceramic particles are composed of a plurality of first particles and a plurality of second particles,
The first particles are fine particles defined by a particle size of not more than the average particle size of the entire ceramic powder, calculated from the specific surface area determined by the BET method,
Regarding A / B, which is the molar ratio of A-site atoms and B-site atoms in ABO ₃ , the average value of A / B of the first particles is α, and the average value of A / B of the second particles Where β is β, the relationship between α and β is α <β.

In the present invention, the “ceramic particle” means a single particle (that is, a particle as the smallest unit that can be physically separated), while the “ceramic powder” means a plurality of ceramic particles. Means an aggregate. Similarly, the “first particles” and the “second particles” each mean one particle.
In the present invention, the above-mentioned “average particle diameter of the entire ceramic powder calculated from the specific surface area determined by the BET method” refers to the specific surface area of the ceramic powder determined by the BET method as S [m ² / g], When the density of the ceramic powder is ρ [g / cm ³ ], it is defined by 6 / (S · ρ). The density of the ceramic powder can be determined by a pycnometer method or the like.

  Moreover, the average value α of A / B of the first particles and the average value β of A / B of the second particles can be measured by the following method, for example. That is, the ceramic powder is separated into a powder mainly composed of the first particles and a powder mainly composed of the second particles, and each of the separated powders is subjected to a fluorescent X-ray analysis method, an ICP method, or the like. And can be obtained by measuring A / B respectively. A method for separating the ceramic powder into a powder mainly composed of the first particles and a powder mainly composed of the second particles is not particularly limited. For example, the ceramic powder is a solvent such as ethanol. And a method of centrifuging and centrifuging.

Preferably, the A site atom in the ABO _{3 is} at least one selected from Ba, Sr and Ca, and the B site atom is at least one selected from Ti and Zr.
More preferably, the ABO ₃ is BaTiO ₃ .

The ceramic electronic component according to the present invention has an internal electrode layer and a dielectric layer,
The dielectric ceramic composition raw material that constitutes the dielectric layer is manufactured using any one of the above ceramic powders.

A method for producing a ceramic electronic component according to the present invention includes:
A method of manufacturing a ceramic electronic component having an internal electrode layer and a dielectric layer,
Forming a green sheet to be the dielectric layer after firing;
Forming an electrode paste layer to be the internal electrode layer after firing on the surface of the green sheet;
A step of forming a green chip by laminating a green sheet on which the electrode paste layer is formed;
Firing the green chip,
Any one of the above ceramic powders is used as a dielectric ceramic composition material constituting the green sheet.

  The ceramic electronic component according to the present invention is not particularly limited, and examples thereof include surface mount (SMD) chip type electronic components such as a multilayer ceramic capacitor, a piezoelectric multilayer component, a chip varistor, and a chip thermistor.

  The ceramic powder of the present invention has a predetermined relationship between A / B of fine particles (first particles) having a relatively small particle size and A / B of coarse particles (second particles) having a relatively large particle size. It is controlled to become. Specifically, the average value of A / B of fine particles having a relatively small particle size (first particle) is α, and the average value of A / B of coarse particles having a relatively large particle size (second particle). When β is set, control is performed so that α <β. Therefore, by using the ceramic powder of the present invention as a raw material for a dielectric layer of a ceramic electronic component such as a multilayer ceramic capacitor, sintering at a low temperature is possible without increasing the amount of sintering aid. .

  Since sintering at a low temperature is possible, it is possible to effectively prevent the spheroidization phenomenon of the internal electrode when a base metal such as Ni is used as the conductive material constituting the internal electrode layer. Therefore, even when the dielectric layer is made thin or multilayered, a highly reliable ceramic electronic component having a high relative dielectric constant, low dielectric loss, and excellent IR life can be obtained.

  Furthermore, since the firing can be performed at a low temperature, the energy cost required for the firing can be reduced, and damage to the firing furnace can be suppressed. Therefore, the manufacturing cost can be reduced.

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 As shown in FIG. 1, a multilayer ceramic capacitor 1 according to an embodiment of the present invention includes a capacitor body 10 having a configuration in which dielectric layers 2 and internal electrode layers 3 are alternately stacked. A pair of external electrodes 4, 4 are formed at both ends of the capacitor body 10 and are electrically connected to the internal electrode layers 3 arranged alternately in the body 10. The internal electrode layers 3 are laminated so that the side end faces are alternately exposed on the surfaces of the two opposite ends of the capacitor body 10. The pair of external electrodes 4, 4 are formed at both ends of the capacitor body 10 and are connected to the exposed end surfaces of the alternately arranged internal electrode layers 3 to constitute a capacitor circuit.

  The outer shape and dimensions of the capacitor body 10 are not particularly limited and can be appropriately set depending on the application. Usually, the outer shape is substantially a rectangular parallelepiped shape, and the dimensions are usually vertical (0.4 to 5.6 mm) × It can be about horizontal (0.2 to 5.0 mm) × height (0.2 to 2.5 mm).

  The conductive material contained in the internal electrode layer 3 is not particularly limited, but a base metal can be used when a material having reduction resistance is used as the constituent material of the dielectric layer 2. As the base metal used as the conductive material, Ni, Cu, Ni alloy or Cu alloy is preferable. When the main component of the internal electrode layer 3 is Ni, a method of firing at a low oxygen partial pressure (reducing atmosphere) is employed so that the dielectric is not reduced.

  The thickness of the internal electrode layer 3 may be appropriately determined according to the application and the like, but is usually 0.5 to 5 μm, particularly preferably 1 to 2.5 μm.

The dielectric layer 2 has a dielectric ceramic composition composed of a plurality of ceramic crystal particles.
The ceramic crystal particles constituting the dielectric ceramic composition are crystal particles containing a dielectric oxide represented by the general formula ABO ₃ as a main component and having a perovskite crystal structure.

The A site atom and B site atom constituting ABO ₃ as the main component are not particularly limited, but the A site atom is preferably at least one selected from Ba, Sr and Ca, more preferably Ba. The B site atom is preferably at least one selected from Ti and Zr, more preferably Ti. That is, in this embodiment, BaTiO _{3 in} which the A site atom is Ba and the B site atom is Ti is particularly preferable.

The dielectric layer preferably contains subcomponents in addition to the main component. In the present embodiment, as subcomponents, at least Mg oxide and R oxide (where R is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, And at least one selected from Ho, Er, Tm, Yb and Lu). The content of the Mg oxide is preferably 0.1 to 3 mol in terms of MgO with respect to 100 mol of ABO _{3 as} the main component. The content of the R oxide is more than 0 mol and not more than 5 mol in terms of R ₂ O _{3 with} respect to 100 mol of ABO _{3 as} the main component.

  In this embodiment, in addition to these Mg oxide and R oxide, at least one selected from Ba oxide and Ca oxide, Si oxide, Mn oxide, and V oxidation It is preferable to further contain at least one selected from a material and an oxide of Mo.

The total content of Ba oxide and Ca oxide is preferably 2 to 12 mol in terms of (BaO + CaO) with respect to 100 mol of ABO _{3 as} the main component.

The content of Si oxide in the case of containing Si oxide is 2 to 12 mol in terms of SiO _{2 with} respect to 100 mol of ABO _{3 as} the main component. Further, in the case of containing an oxide of Mn, an oxide of V and / or an oxide of Mo, the content of each oxide is 100% of ABO _{3 as} the main component, respectively, in terms of MnO, 0.5 mol or less, 0.3 mol or less in terms of V ₂ O ₅ , and 0.3 mol or less in terms of MoO ₃ .

  Various conditions such as the number of layers and thickness of the dielectric layer 2 may be appropriately determined according to the purpose and application. In the present embodiment, the thickness of the dielectric layer 2 is preferably 0.1 to 6.0 μm, More preferably, the layer is thinned to 0.2 to 3.0 μm. In this embodiment, since the ceramic powder of the present invention, which will be described later, is used as the ceramic powder that is the raw material of the dielectric layer 2, it is possible to sinter at a low temperature. Even in the case of a change, reliability can be kept high.

The conductive material contained in the external electrode 4 is not particularly limited, and usually Cu, Cu alloy, Ni, Ni alloy, or the like can be used. Of course, Ag, Ag—Pd alloy, or the like can also be used. In the present embodiment, inexpensive Ni, Cu, and alloys thereof can be used.
The thickness of the external electrode may be appropriately determined according to the use, etc., but is usually preferably about 10 to 50 μm.

Manufacturing Method of Multilayer Ceramic Capacitor Next, a manufacturing method of the multilayer ceramic capacitor 1 will be described. In this embodiment, the green chip is manufactured by a normal printing method or a sheet method using a paste, fired, and then printed or transferred and fired by external electrodes. Hereinafter, the manufacturing method will be specifically described.

First, a dielectric ceramic composition raw material contained in the dielectric layer paste is prepared.
The dielectric ceramic composition raw material can be prepared by mixing a dielectric oxide raw material that constitutes the main component and a raw material of each subcomponent that is used as necessary.

In the present embodiment, the ceramic powder of the present invention is used as a dielectric oxide raw material constituting the main component.
The ceramic powder of the present invention is composed of a plurality of ceramic particles represented by the general formula ABO ₃ and having a perovskite crystal structure. In the present embodiment, “ceramic particles” mean one particle (that is, particles as the smallest unit that can be physically separated), while “ceramic powder” means a plurality of ceramic particles. Means a collection of

The plurality of ceramic particles include a plurality of first particles that are fine particles defined by the average particle diameter of the entire ceramic powder, the particle diameter of which is calculated from the specific surface area determined by the BET method, A plurality of second particles that are particles, and regarding the molar ratio A / B between the A site atom and the B site atom in the general formula ABO ₃ , the average value of A / B of the first particle is α, When the average value of A / B of the second particles is β, the relationship between α and β is α <β. That is, when focusing on A / B, which is the molar ratio of A site atoms to B site atoms, as a ceramic powder, a relatively small A / B value is obtained in a region where the particle size is relatively small. On the other hand, in a region having a relatively large particle size, ceramic powder containing particles having a relatively large A / B value is used.

  This embodiment has the greatest feature in that such ceramic powder is used as a dielectric oxide raw material constituting the main component. By using such ceramic powder, sintering aid is used. The dielectric ceramic composition raw material can be sintered at a low temperature without increasing the amount of the agent. Therefore, the firing temperature in the firing step described later can be lowered, and the problem of the spheroidization phenomenon of the internal electrode can be effectively prevented when a base metal such as Ni is used as the conductive material of the internal electrode layer 3. . As a result, it is possible to reduce the dielectric loss and improve the IR life while keeping the relative dielectric constant high. Furthermore, by enabling firing at a low temperature, the energy cost required for firing can be reduced, and damage to the firing furnace can be suppressed. Therefore, the manufacturing cost can be reduced.

In addition, although it does not specifically limit as a method of measuring the average value (alpha) and (beta) of A / B of the said 1st particle | grain and 2nd particle | grain, For example, it can measure by the following method.
That is, first, ceramic powder is placed in a ball mill together with ZrO ₂ balls using ethanol as a solvent, and mixed and pulverized for 16 hours in a wet manner to obtain a ceramic powder dispersion. Then, the obtained ceramic powder dispersion is centrifuged and centrifuged at a rotational speed of 2500 to 3000 rpm. Then, the ceramic powder dispersed in the supernatant and the ceramic powder deposited on the bottom by centrifugation are sampled from the obtained dispersion liquid after centrifugation. Here, the ceramic powder dispersed in the supernatant is mainly composed of a plurality of first particles, and the ceramic powder deposited on the bottom is mainly composed of a plurality of second particles. However, the ceramic powder dispersed in the supernatant liquid may contain the second particles as long as it is in a trace amount. Similarly, the ceramic powder deposited on the bottom portion contains the first particle in the trace amount. Particles may be contained.
In addition, since the wet mixing is performed by the ball mill, the fine particles generated when the ceramic powder is scraped may be included in the first particles and the second particles, although they are slightly. In addition, mixing with a ball mill does not substantially change the particle size of the ceramic powder, but the specific surface area may increase slightly.

  Then, for each of a powder composed of a plurality of first particles (ceramic powder dispersed in the supernatant liquid) and a powder composed of a plurality of second particles (ceramic powder deposited on the bottom), fluorescent X-ray analysis, ICP A / B is measured by the method. For example, in the fluorescent X-ray analysis method, a powder composed of a plurality of first particles and a powder composed of a plurality of second particles are irradiated with X-rays, and the characteristic X-rays of the constituent elements generated by the X-ray irradiation are obtained. By detecting, the abundance ratio of each composition present in the powder can be measured by weight ratio. Then, the number of moles of each element is calculated from the weight ratio of each composition, and the number of moles of elements entering the A site (for example, Ba, Sr, Ca) is changed to the number of moles of elements entering the B site (for example, Ti, Zr). The value of A / B can be obtained by dividing by a number.

  Α, which is the average value of A / B of the first particles, is not particularly limited as long as α <β is satisfied with respect to β, which is the average value of A / B of the second particles. The value of is preferably in the range of 0.998 ≦ α ≦ 1.010, more preferably in the range of 1.000 ≦ α ≦ 1.007. Further, β, which is the average value of A / B of the second particles, is not particularly limited as long as α <β is satisfied, but the value of β is in the range of 1.002 ≦ β ≦ 1.015, More preferably, the range is 1.004 ≦ β ≦ 1.010.

  Moreover, the value of A / B in the whole ceramic powder is preferably 0.990 to 1.030, more preferably 0.995 to 1.010. If the A / B in the entire ceramic powder is too small, abnormal grain growth tends to occur during firing and the insulation resistance value tends to decrease. On the other hand, if it is too large, the sinterability tends to be reduced, and it becomes difficult to obtain a dense sintered body.

In addition, the average value of the specific surface area of ceramic powder becomes like this. Preferably it is 2.0-20.0 m < ² > / g, More preferably, it is 3.0-15.0 m < ² > / g. If the specific surface area of the ceramic powder is too small, it is difficult to make the dielectric layer 2 thinner. On the other hand, if it is too large, abnormal grains are likely to grow during firing.

  The content of the first particles in the ceramic powder is preferably 10 to 45 parts by weight, more preferably 20 to 40 parts by weight with respect to 100 parts by weight of the entire ceramic powder. If the content of the first particles is too small, sintering at a low temperature tends to be difficult. On the other hand, if the amount is too large, abnormal grain growth during firing tends to occur.

  The method for obtaining such a ceramic powder is not particularly limited. For example, the ceramic powder can be obtained by mixing the following first raw material powder and second raw material powder. That is, as the first raw material powder, a powder having a relatively small A / B and mainly containing a plurality of fine particles constituting the first particles is used. As the second raw material powder, , Using a powder having a relatively large A / B and mainly containing a plurality of coarse particles constituting the above-mentioned second particles, and these first raw material powder and second raw material powder And can be prepared by mixing.

  Or the raw material powder which has a certain particle size distribution is prepared, A / B of the powder which consists of several 1st particle | grains and the powder which consists of several 2nd particle | grains about the prepared raw material powder by centrifugation mentioned above, for example It is also possible to adopt a method of measuring the above and selecting and using those within the above range.

  The method for synthesizing the ceramic powder is not particularly limited, and examples thereof include a solid phase method, an oxalate method, a hydrothermal synthesis method, an alkoxide method, and a sol-gel method.

  The raw material of the subcomponent is appropriately selected from the above-mentioned oxides and composite oxides, or various compounds that become these oxides and composite oxides upon firing, such as carbonates, nitrates, hydroxides, and organometallic compounds. Can be used.

  Next, the dielectric ceramic composition raw material obtained by mixing the dielectric oxide raw material that constitutes the main component and the raw materials of the subcomponents used as necessary is made into a paint, and the dielectric Prepare body layer paste.

  The dielectric layer paste may be an organic paint obtained by kneading a dielectric ceramic composition material and an organic vehicle, or may be a water-based 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. 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, a dispersant, or the like is dissolved in water and a dielectric ceramic composition raw 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. 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 ⁻⁷ 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, in this embodiment, since the above-mentioned predetermined ceramic powder is used as the dielectric ceramic composition material, the firing temperature (holding temperature) can be set to a lower temperature than in the prior art. That is, low temperature sintering becomes possible. The firing temperature varies depending on the subcomponents used, but is preferably 1100 to 1250 ° C, more preferably 1120 to 1230 ° C, and even more preferably 1150 to 1200 ° C. In particular, when the above-described subcomponent is used as a subcomponent in the dielectric ceramic composition and the composition is in the above range, the firing temperature is preferably 1140 to 1250 ° C, more preferably 1150 to 1230 ° C. And

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 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 0.1 Pa or more, particularly 0.1 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. In addition, you may comprise annealing only from a temperature rising process and a temperature falling 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, mixed gas, or the like. 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. When these are performed continuously, after removing the binder, the atmosphere is changed without cooling, and then the temperature is raised to the holding temperature at the time of baking to perform baking, and then cooled to reach the annealing holding temperature. Sometimes it is preferable to perform annealing by changing the atmosphere. On the other hand, when performing these independently, at the time of firing, after raising the temperature under N ₂ gas atmosphere with N ₂ gas or wet to the holding temperature of the binder removal processing, further continuing the heating to change the atmosphere Preferably, after cooling to the holding temperature at the time of annealing, it is preferable to change to the N ₂ gas or humidified N ₂ gas atmosphere again and continue cooling. In annealing, the temperature may be changed to a holding temperature in an N ₂ gas atmosphere, and then the atmosphere may be changed, or the entire annealing process may be a humidified N ₂ gas atmosphere.

The capacitor element body obtained as described above is subjected to end surface polishing, for example, by barrel polishing or sand blasting, and the external electrode paste is printed or transferred and baked to form the external electrode 4. 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 surface of the external electrode 4 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.

  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 as the ceramic electronic component according to the present invention. However, the ceramic electronic component according to the present invention is not limited to the multilayer ceramic capacitor and has the above-described 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 (ceramic powder) as a main component material was prepared. In this embodiment, as BaTiO ₃ powder, BaTiO ₃ powder whole (i.e., the first particle + second particles) A / B in (i.e., Ba / Ti ratio) is 1.004, an average particle size of 0.35 .mu.m, BaTiO ₃ having a specific surface area (SSA) of 3.70 m ² / g, an average value α of A / B of the first particles of 1.002, and an average value β of A / B of the second particles of 1.005 A powder was prepared. That is, BaTiO ₃ powder in which α <β was prepared.

The A / B average value α of the first particles and the A / B average value β of the second particles were measured by the following methods. That is, first, 50 g of BaTiO ₃ powder was placed in a ball mill together with ZrO ₂ balls in 100 cc of ethanol, and mixed and pulverized in a wet manner for 16 hours to prepare a dispersion. Next, the dispersion was centrifuged at a speed of 3000 rpm using a centrifuge. Then, from the obtained dispersion liquid after centrifugation, the powder contained in the supernatant liquid and the powder deposited on the bottom are collected, and the powder contained in the supernatant liquid is a powder comprising a plurality of first particles. On the other hand, the powder deposited on the bottom is made into a powder composed of a plurality of second particles, and a powder composed of a plurality of first particles and a powder composed of a plurality of second particles, respectively, inductively coupled plasma (ICP) light emitting device Was used to measure A / B.

Next, separately from the above, a raw material for subcomponents was prepared. As raw materials for subcomponents, MgO, MnO, V ₂ O ₅ , Y ₂ O ₃ , BaO + CaO, and SiO ₂ were prepared in predetermined amounts.

Subsequently, the dielectric ceramic composition raw material was prepared by wet-mixing the BaTiO ₃ powder prepared above and the raw materials of each subcomponent by a ball mill for 16 hours.

  Next, the dielectric ceramic composition raw material prepared above: 100 parts by weight, acrylic resin: 4.8 parts by weight, ethyl acetate: 100 parts by weight, mineral spirit: 6 parts by weight, and toluene: 4 parts by weight Were mixed with a ball mill to form a paste, and a dielectric layer paste was obtained.

  Subsequently, Ni particles having an average particle size of 0.2 to 0.8 μm: 100 parts by weight, an organic vehicle (ethyl cellulose: 8 parts by weight dissolved in butyl carbitol: 92 parts by weight): 40 parts by weight, butyl carby Toll: 10 parts by weight was kneaded with three rolls to obtain a paste, and an internal electrode layer paste was obtained.

  Next, Cu particles having an average particle size of 0.5 μm: 100 parts by weight, an organic vehicle (ethyl cellulose resin: 8 parts by weight dissolved in butyl carbitol: 92 parts by weight): 35 parts by weight, and butyl carbitol: 7 Part by weight was kneaded into a paste to obtain an external electrode paste.

  Next, a 2.4 μm-thick green sheet was formed on the PET film using the dielectric layer paste, and after printing the internal electrode layer paste thereon, the green sheet was peeled off 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 green chips. The number of sheets having internal electrodes was four.

  Next, the green chip was cut into a predetermined size and subjected to binder removal processing, firing and annealing to obtain a multilayer ceramic fired body.

The binder removal treatment was performed under the conditions of a temperature rising time of 15 ° C./hour, a holding temperature of 280 ° C., a holding time of 8 hours, and an air atmosphere.
Firing is performed under conditions of a temperature rising rate of 200 ° C./hour, a holding temperature of 1250 ° C., a holding time of 2 hours, a cooling rate of 300 ° C./hour, and a humidified N ₂ + H ₂ mixed gas atmosphere (oxygen partial pressure is 10 ⁻⁹ atm). went.
The annealing was performed under the conditions of a holding temperature of 900 ° C., a temperature holding time of 9 hours, a cooling rate of 300 ° C./hour, and a humidified N ₂ gas atmosphere (oxygen partial pressure was 10 ⁻⁵ atm). Note that a wetter with a water temperature of 35 ° C. was used for humidifying the atmospheric gas during firing and annealing.
Next, after polishing the end face of the multilayer ceramic fired body by sand blasting, the external electrode paste is transferred to the end face and fired at 800 ° C. for 10 minutes in a humidified N ₂ + H ₂ atmosphere to form the external electrode. A sample of the multilayer ceramic capacitor having the configuration shown in FIG. 1 was obtained.

  The size of the capacitor sample thus obtained is 1.0 mm × 0.5 mm × 0.5 mm, the number of dielectric layers sandwiched between internal electrode layers is 160, and the thickness thereof is 1.6 μm. The thickness of the internal electrode layer was 1.0 μm.

  With respect to the obtained capacitor sample, the average crystal grain size, relative dielectric constant, dielectric loss, and IR lifetime of the crystal particles constituting the dielectric layer were evaluated.

Average crystal grain size First, a capacitor sample was cut along a plane perpendicular to the stacking direction, and the cut surface was polished. Then, the polished surface was subjected to chemical etching, and then observed with a scanning electron microscope (SEM) to measure the crystal grain size of the ceramic crystal particles in the field of view of 15 × 15 μm. Next, the average crystal grain size was calculated by calculating the average value of the crystal grain size of each ceramic crystal grain. The crystal grain size of each ceramic crystal particle was determined by assuming that the shape of each ceramic crystal particle was a sphere. The results are shown in Table 2.

The relative dielectric constant ε is measured with a digital LCR meter (YHP 4274A) at a reference temperature of 25 ° C. and a frequency of 1 kHz and an input signal level (measurement voltage) of 1.0 Vrms with respect to the capacitor sample. Calculated from the measured capacitance (no unit). In this example, 3800 or more was considered good. The results are shown in Table 2.

Dielectric loss Dielectric loss (tan δ) is measured with a digital LCR meter (YHP 4274A) at a reference temperature of 25 ° C. and a frequency of 1 kHz and an input signal level (measurement voltage) of 1.0 Vrms with respect to a capacitor sample. did. In this example, 45% or less was considered good. The results are shown in Table 2.

IR life IR (insulation) life was measured by holding a capacitor sample in a state where a DC voltage of 80 V / μm was applied at 180 ° C. In this example, the time from the start of application to the time when the resistance drops by an order of magnitude was defined as the lifetime, which was performed on 10 capacitor samples, and the average lifetime was calculated. This IR lifetime is particularly important when the dielectric layer is thinned. In this example, 100 hours or longer was considered good. The results are shown in Table 2.

Examples 2 and 3
As BaTiO ₃ powder as the main component material, as well as use the BaTiO ₃ powder as shown in Table 1, the holding temperature at firing except for using each temperature shown in Table 2, in the same manner as in Example 1, Capacitor samples were prepared and evaluated in the same manner as in Example 1. Examples 2 and ₃ were carried out using BaTiO ₃ powder in which the average value α of A / B of the first particles and the average value β of A / B of the second particles were in a relationship of α <β. It is an example. The results are shown in Table 2.

Comparative Examples 1 and 2
As BaTiO ₃ powder as the main component material, as well as use the BaTiO ₃ powder as shown in Table 1, the holding temperature at firing except for using each temperature shown in Table 2, in the same manner as in Example 1, Capacitor samples were prepared and evaluated in the same manner as in Example 1. Comparative Example 1 is a comparative example using BaTiO ₃ powder in which the average value α of A / B of the first particles and the average value β of A / B of the second particles are in a relationship of α> β. Yes, Comparative Example 2 is a comparative example using BaTiO ₃ powder in which the average value α of A / B of the first particles and the average value β of A / B of the second particles are in a relationship of α = β. is there. The results are shown in Table 2.

Evaluation 1
From Tables 1 and 2, the following can be confirmed. That is, used as BaTiO ₃ powder (ceramic powder), and the average value alpha of the A / B of the first particles, and the average value beta of A / B of the second particles, but the BaTiO ₃ powder in a relationship of alpha <beta The first to third embodiments of the present invention can be sintered at a low temperature of 1250 ° C., 1245 ° C., and 1255 ° C., respectively. Further, even when firing at such a low temperature, the relative dielectric constant, Excellent dielectric loss and IR lifetime were obtained. In particular, from the results of this example, it can be confirmed that by using the ceramic powder of the present invention, low-temperature sintering can be achieved without lowering the dielectric constant.

On the other hand, Comparative Examples 1 and 2 using BaTiO ₃ powder in which the average value α of A / B of the first particles and the average value β of A / B of the second particles have a relationship of α ≧ β are Although the composition of the body layer was the same as in Examples 1 to 3, the sintering could not be performed unless the firing temperature was increased to 1275 ° C.

Comparative Examples 3 and 4
A capacitor sample was prepared and evaluated in the same manner as in Comparative Examples 1 and 2 except that the firing temperature was 1255 ° C. Specifically, Comparative Example 3 is a comparative example using the same BaTiO ₃ powder as Comparative Example 1, and the firing temperature is changed to 1255 ° C. Further, Comparative Example 4 is a comparative example using the same BaTiO ₃ powder as Comparative Example 2, it is obtained by changing the firing temperature to 1255 ° C.. The results are shown in Table 3. In Table 3, in addition to the results of Comparative Examples 3 and 4, for comparison, the results of Example 3 fired at the same temperature (1255 ° C.) as Comparative Examples 3 and 4 are also described. did.

Evaluation 2
From Table 3, in Comparative Examples 3 and 4 using BaTiO ₃ powder in which the average value α of A / B of the first particles and the average value β of A / B of the second particles are in the relationship of α ≧ β. It can be confirmed that when the firing temperature is lowered to 1255 ° C., the sintering becomes insufficient, resulting in inferior relative dielectric constant, dielectric loss and IR life.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment 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 (5)

A ceramic powder composed of a plurality of ceramic particles represented by the general formula ABO ₃ and having a perovskite crystal structure,
The plurality of ceramic particles are composed of a plurality of first particles and a plurality of second particles,
The first particles are fine particles defined by a particle size of not more than the average particle size of the entire ceramic powder, calculated from the specific surface area determined by the BET method,
Regarding A / B, which is the molar ratio of A-site atoms and B-site atoms in ABO ₃ , the average value of A / B of the first particles is α, and the average value of A / B of the second particles A ceramic powder characterized in that, when β is β, the relationship between α and β is α <β. The A site atom in the ABO _{3 is} at least one selected from Ba, Sr and Ca, and the B site atom is at least one selected from Ti and Zr. Ceramic powder. The ceramic powder according to claim 1, wherein the ABO ₃ is BaTiO ₃ . A ceramic electronic component having an internal electrode layer and a dielectric layer,
The ceramic electronic component manufactured using the ceramic powder in any one of Claims 1-3 as a dielectric ceramic composition raw material which comprises the said dielectric material layer. A method of manufacturing a ceramic electronic component having an internal electrode layer and a dielectric layer,
Forming a green sheet to be the dielectric layer after firing;
Forming an electrode paste layer to be the internal electrode layer after firing on the surface of the green sheet;
A step of forming a green chip by laminating a green sheet on which the electrode paste layer is formed;
Firing the green chip,
The manufacturing method of the ceramic electronic component using the ceramic powder in any one of Claims 1-3 as a dielectric material ceramic composition raw material which comprises the said green sheet.

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