JP5919847B2 - Multilayer ceramic capacitor - Google Patents

Description

The present invention relates to a multilayer ceramic capacitor.

In recent years, there has been a high demand for downsizing and high performance of electronic components due to higher density of electronic circuits, and for this reason, for example, monolithic ceramic capacitors are becoming smaller and larger capacity, but further improvement of characteristics is required. It has been.

In response to such a requirement, for example, in a dielectric ceramic that constitutes a dielectric layer, a phase different from the main component is present to improve the characteristics.

For example, Patent Document 1 discloses a dielectric ceramic mainly composed of a perovskite type compound represented by ABO ₃ , and when ABO ₃ is, for example, BaTiO ₃ , the crystal particles are BaTiO ₃ composed of the main component. Mg-Ni-Ti-O based crystalline oxide particles comprising crystalline particles and comprising a crystalline oxide containing at least Mg, Ni and Ti as a secondary phase, and a crystalline oxide containing at least Ba and Si And Ba—Si—O-based crystalline oxide particles made of It is described that according to this dielectric ceramic, a dielectric ceramic having excellent resistance to thermal shock can be obtained.

Patent Document 2 proposes a dielectric ceramic having a core-shell structure and a Curie temperature of 80 to 90 ° C.

Further, in Patent Document 3, the residual stress in the multilayer dielectric element body constituting the multilayer ceramic capacitor or the residual stress in the outer surface of the multilayer dielectric element body is set to a predetermined value or more to increase the dielectric. It is described that a highly reliable multilayer ceramic capacitor having a high rate and a large acquired capacitance can be obtained.

JP 2010-024086 A JP 2008-239407 A WO2005 / 050679 publication

In response to the demand for a smaller and larger capacity multilayer ceramic capacitor, Patent Document 1 has a problem that the specific dielectric constant of the example is lower than that of the comparative example, and the increase in capacity cannot be accommodated. Furthermore, in the dielectric ceramic described in Patent Document 2, the relative dielectric constant is about 4000 at the maximum, and further improvement of the relative dielectric constant is demanded.
Further, in the multilayer ceramic capacitor described in Patent Document 3, the residual stress is reduced when the number of internal electrodes is small, and a residual stress capable of obtaining a predetermined effect cannot be obtained in a small shape product having a small number of multilayers. Therefore, the dielectric constant cannot be improved without depending on the number of stacked layers.

  The present invention has been made in view of such a situation, and improves the dielectric characteristics (relative permittivity and high temperature load reliability) regardless of the content of components contained in the dielectric ceramic constituting the dielectric layer and the number of laminated layers. An object of the present invention is to provide a multilayer ceramic capacitor that can be used.

  In order to achieve the above object, the inventors of the present invention have intensively studied, and as a result, are multilayer ceramic capacitors in which dielectric layers and internal electrode layers mainly composed of Ni are alternately laminated, The multilayer ceramic capacitor is characterized in that it includes a metal phase mainly composed of Ni and an oxide phase mainly composed of Mg in contact with the metal phase. The inventors have found that the dielectric constant is improved without deteriorating, and have completed the present invention.

Preferably, the dielectric layer is mainly composed of BaTiO ₃ .

  Preferably, the ratio of the length in the thickness direction of the dielectric layer of the metal phase mainly composed of Ni contained in the dielectric layer to the thickness direction of the dielectric layer is 0.06 or more and 0. .40 or less.

  By controlling in the above range, a multilayer ceramic capacitor having a further improved dielectric constant can be obtained.

  Preferably, the ratio (metal phase / oxide phase) of the area of the metal phase mainly composed of Ni contained in the dielectric layer and the oxide phase mainly composed of Mg in contact with the metal phase is 0. .2 or more and 2.0 or less.

  By controlling the segregation phase area within the above range, a multilayer ceramic capacitor having a further improved relative dielectric constant can be obtained.

  The present invention can improve dielectric characteristics (relative permittivity and high temperature load reliability) regardless of the content of components contained in the dielectric ceramic constituting the dielectric layer. There is an effect that a multilayer ceramic capacitor can be provided.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of the dielectric layer 2 shown in FIG.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

<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 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. Although there is no restriction | limiting in particular in the shape of the element main body 10, Usually, it is set as 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.

<Dielectric layer 2>
The dielectric layer 2 is composed of a dielectric ceramic composition. The dielectric ceramic composition has an ABO ₃ perovskite crystal structure represented by a composition formula (Ba _1-x Ca _x ) _m (Ti _1-y Zr _y ) O ₃ as a main component. Hereinafter, the main component is referred to as “ABO ₃ (A is at least one selected from the group consisting of Ba, Ca and Sr, and B is at least one selected from the group consisting of Ti, Zr and Hf). " Further, as subcomponents, an oxide of Mg, an oxide of R element, and an oxide containing Si are contained. The amount of oxygen (O) may be slightly deviated from the stoichiometric composition of the above formula.

  In the above formula, x is preferably 0 ≦ x ≦ 0.06. x represents the number of Ca atoms, and the phase transition point of the crystal can be arbitrarily shifted by changing the symbol x, that is, the Ca / Ba ratio. Therefore, the capacity temperature coefficient and the relative dielectric constant can be arbitrarily controlled. However, in this embodiment, it is good also as an aspect which does not contain x = 0, ie, Ca.

  In the above formula, y is preferably 0 ≦ y ≦ 0.08. y represents the number of Zr atoms, and the Curie point of the dielectric ceramic composition can be controlled by the amount of Zr. When there is too much Zr, there exists a tendency for Curie temperature to become low with respect to a use temperature range. However, in this embodiment, it is good also as an aspect which does not contain y = 0, ie, Zr.

  In the above formula, m is preferably 0.995 ≦ m ≦ 1.020, more preferably 1.000 ≦ m ≦ 1.006. By making m 0.995 or more, it is possible to reliably prevent the formation of a semiconductor with respect to firing in a reducing atmosphere, and by making m to 1.020 or less, it is dense even without increasing the firing temperature. A sintered body can be obtained.

The content of the Mg oxide may be determined according to desired characteristics, but is preferably 0.1 to 2.5 mol in terms of MgO with respect to 100 mol of ABO ₃ . By containing the oxide, there is an advantage that desired capacity-temperature characteristics and IR lifetime can be obtained.

The content of the R element oxide may be determined according to desired characteristics, but is preferably 0.2 to 2.5 mol in terms of R ₂ O _{3 with} respect to 100 mol of ABO ₃ . The inclusion of the oxide has the advantage of improving high temperature load reliability. The R element is at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; And at least one selected from the group consisting of Gd, Tb, Dy and Ho.

The content of the oxide containing Si may be determined according to desired characteristics, but is preferably 0.2 to 3.0 mol in terms of SiO _{2 with} respect to 100 mol of ABO ₃ . Inclusion of the oxide mainly improves the sinterability of the dielectric ceramic composition. The oxide containing Si may be a composite oxide of Si and another metal element (for example, an alkali metal or an alkaline earth metal). In this embodiment, Si, Ba, and Ca are used. (Ba, Ca) SiO ₃ is preferable.

  In the present embodiment, the above dielectric ceramic composition may further contain other subcomponents according to desired characteristics.

For example, the dielectric ceramic composition according to the present embodiment may contain an oxide of Mn and / or Cr. The content of the _oxide, based on ABO 3 100 moles, each in terms of oxide is preferably 0.02 to 0.30 mol.

The dielectric ceramic composition according to the present embodiment may contain an oxide of at least one element selected from V, Ta, Nb, Mo, and W. The content of the _oxide, based on ABO 3 100 moles, each in terms of oxide is preferably 0.02 to 0.30 mol.

  The thickness of the dielectric layer 2 is not particularly limited, and may be determined as appropriate according to desired characteristics and applications. The number of laminated dielectric layers 2 is not particularly limited, but is preferably 20 or more, and more preferably 50 or more.

<Dielectric particles and grain boundaries>
As shown in FIG. 2, the dielectric layer 2 includes dielectric particles 20, grain boundaries 22 formed between a plurality of adjacent dielectric particles 20, and segregation regions 27. In the present embodiment, the dielectric particle 20 may be a particle in which a subcomponent element such as an R element, Mg, or Si is dissolved (diffused) with respect to the main component particle (ABO ₃ particle).

  The crystal particle diameter of the dielectric particles 20 is measured as follows, for example. The element body 10 is cut in the stacking direction of the dielectric layer 2 and the internal electrode layer 3, the average area of the dielectric particles is measured in the cross section, and the diameter is calculated as the equivalent circle diameter, which is 1.27 times. Then, the crystal particle diameter is measured for 200 or more dielectric particles, and the value at which the accumulation is 50% from the cumulative frequency distribution of the obtained crystal particle diameters may be used as the average crystal particle diameter (unit: μm). The crystal particle diameter may be determined according to the thickness of the dielectric layer 2 and the like.

  The grain boundary 22 is mainly composed of an oxide of an element contained in the dielectric ceramic composition, but an oxide of an element mixed as an impurity in the process or an oxide of an element constituting the internal electrode layer, etc. May be included. Further, the grain boundary 22 is usually mainly composed of an amorphous material, but may be composed of a crystalline material.

<Segregation area>
As shown in FIG. 2, the dielectric layer 2 further includes a segregation region 27 having a composition different from that of the dielectric particles 20 and the internal electrode layer 3.

  The components constituting the segregation region 27 shown in FIG. 2 include a metal phase mainly composed of Ni (hereinafter referred to as segregated Ni metal phase) 28 and an oxide phase mainly composed of Mg in contact with the metal phase (hereinafter referred to as “separated Ni metal phase”). (Segregated Mg oxide phase) 29 is preferably included.

  In this case, it is preferable that Ni is 90 mol% or more in the segregated Ni metal phase. The segregated Ni metal phase may be an alloy phase containing a metal component other than Ni (Cu, Cr, Pt, Re, etc.).

  Further, in the segregated Mg oxide phase in contact with the metal phase, it is preferable that Mg is 50 mol% or more in a content ratio excluding oxygen, and Cr, Mn, Ti, Zr, Ba, Ca, Ni, Cu , V, and R elements may be included.

  A reaction layer such as a NiO layer may be formed at the interface between the segregated Ni metal phase 28 and the segregated Mg oxide phase 29 in contact with the metal phase.

  In addition, as shown in FIG. 1, the length of the segregated Ni metal phase 28 in the thickness direction of the dielectric layer 2 and the dielectric strength of the cross section of the element body 10 cut in the stacking direction of the dielectric layer 2 and the internal electrode layer 3 as shown in FIG. The thickness ratio with the body layer 2 is preferably 0.06 or more and 0.40 or less, more preferably 0.10 to 0.30. The relative dielectric constant can be increased by controlling the ratio of the length of the segregated Ni metal phase 28 in the thickness direction of the dielectric layer to the thickness of the dielectric layer 2 within the above range.

  Further, as shown in FIG. 1, the ratio of the segregated Ni metal phase 28 to the segregated Mg oxide phase 29 area (with respect to the cross section cut in the stacking direction of the dielectric layer 2 and the internal electrode layer 3 as shown in FIG. (Ni metal phase / Mg oxide phase) is preferably 0.2 or more and 2.0 or less. More preferably, it is 0.5-1.5. By controlling the ratio of the size of the segregated Ni metal phase 28 and the segregated Mg oxide phase 29 within the above range, high temperature load reliability can be improved.

  The method for observing the segregation region 27 in the cross section is not particularly limited as long as the segregation region 27 is observed in the entire cross section of the element body 10. For example, the observation may be performed by dividing into a plurality of fields of view. However, in consideration of measurement accuracy and variation, it is preferable to observe the images by dividing into a plurality of fields of view, particularly five or more fields of view.

  In the present embodiment, the length of the segregated Ni metal phase 28 in the thickness direction of the dielectric layer is an average value when the entire cross section of the element body 10 is measured for 10 visual fields at a magnification of 20000 times. The length in the thickness direction of the dielectric layer of the segregated Ni metal phase 28 obtained by measuring at least 10 fields of view at such a magnification is the dielectric of the segregated Ni metal phase 28 obtained by observing the entire cross section of the element body 10. It has been confirmed that it substantially matches the length in the thickness direction of the layer.

  Similarly, the thickness of the dielectric layer 2 is set to an average value obtained by selecting 10 views of the entire cross section of the element body 10 at a magnification of 20000 times and measuring 300 locations per view.

  Further, the magnification is not particularly limited and may be set as appropriate. However, a magnification that includes at least a pair of internal electrodes in one visual field is preferable. By setting such a magnification, the length of the dielectric layer 2 in the thickness direction can also be measured. The length of the segregated Ni metal phase 28 in the thickness direction of the dielectric layer and the length of the dielectric layer 2 in the thickness direction. The ratio can be calculated.

  A method for calculating the area ratio between the segregated Ni metal phase 28 and the segregated Mg oxide phase 29 is not particularly limited, but in the above field of view, a region having a contrast different from that of the dielectric layer 2 and the internal electrode layer 3 is segregated. A region having the same contrast as the internal electrode layer 3 in the dielectric layer 2 as the Mg oxide phase 29 is set as the segregated Ni metal phase 28, and the area ratio may be calculated visually or by software for image processing.

  A method for segregating the segregated Ni metal phase 28 and the segregated Mg oxide phase 29 in contact with the metal phase inside the dielectric layer 2 is not particularly limited, but after producing composite particles of metal Ni and Mg oxide It may be added to the dielectric ceramic composition. Alternatively, Ni and Mg composite oxide particles may be prepared and then added to the dielectric ceramic composition, and by adjusting the firing conditions, Ni oxide may be reduced to deposit adjacent particles of metal Ni and Mg oxide. . Further, after adding the MgO oxide, it may be reacted with Ni in the internal electrode layer 2 and then Ni may be precipitated by reduction.

  Usually, the dielectric layer 2 after firing has dielectric particles 20 (main component particles) and grain boundaries 22 formed between them. The grain boundary 22 contains an element that could not be dissolved in the main component particles during firing or an element that is difficult to dissolve. Further, in the segregation region 27, an element that cannot be dissolved in the main component particles during firing or an element that does not easily dissolve is precipitated. When the segregated Ni metal phase 28 is deposited inside the dielectric layer 27 in the segregation region 27, the same effect as increasing the number of layers can be produced and the dielectric constant of the dielectric can be improved. The conductive phase is present inside a certain dielectric layer, and the high temperature load reliability deteriorates. However, in the present embodiment, the segregated Ni metal phase 28 and the segregated Mg oxide phase 29 in contact with the metal phase are segregated, thereby suppressing deterioration in high temperature load reliability due to the conductivity of the segregated Ni metal phase 28. it can.

<Internal electrode layer 3>
The conductive material contained in the internal electrode layer 3 is not particularly limited, but Ni or Ni alloy is preferable in the present embodiment. 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. 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.

<Method for Manufacturing Multilayer Ceramic Capacitor 1>
In the multilayer ceramic capacitor 1 of this embodiment, a green chip is produced by a normal printing method or a sheet method using a paste, and fired, and then printed or transferred an external electrode, similarly to a conventional multilayer ceramic capacitor. It is manufactured by baking. Hereinafter, the manufacturing method will be specifically described.

  First, a dielectric material for forming a dielectric layer is prepared, and this is made into a paint to prepare a dielectric layer paste.

As dielectric materials, first, an ABO ₃ material, an Mg oxide material, an R oxide material, and an oxide material containing Si are prepared. As these raw materials, oxides of the above-described components, mixtures thereof, and composite oxides can be used. In addition, various compounds that become the above-described oxides or composite oxides by firing, such as carbonates and oxalic acid. They can be appropriately selected from salts, nitrates, hydroxides, organometallic compounds, and the like, and can also be used as a mixture.

In addition to the so-called solid phase method, the raw material of ABO ₃ can be produced by various methods such as those produced by various liquid phase methods (for example, oxalate method, hydrothermal synthesis method, alkoxide method, sol-gel method, etc.). What was manufactured can be used.

  Further, when the dielectric layer contains components other than the main component and subcomponents, as described above, oxides of these components, mixtures thereof, and composite oxides are used as the raw materials of the components. Can be used. In addition, various compounds that become oxides or composite oxides by firing can be used.

  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 dielectric ceramic composition mentioned above 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.

  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.

  An organic vehicle is obtained by dissolving a binder in an organic solvent. A binder is not specifically limited, What is necessary is just to select suitably from normal various binders, such as an ethyl cellulose and polyvinyl butyral. The organic solvent is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene depending on the printing method, the sheet method, and the like.

  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 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-described organic vehicle with the above-described conductive material made of Ni or Ni alloy, or various oxides, organometallic compounds, resinates, etc. that become Ni or Ni alloy after firing. What is necessary is just to prepare. The internal electrode layer paste may contain a common material. The common material is not particularly limited, but preferably has the same composition as the main component.

  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 and firing processing. The binder removal process and the firing process may be appropriately determined according to the type of the conductive material in the internal electrode layer paste. 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 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.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

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

<Experimental example 1>
In Experimental Example 1, a multilayer ceramic capacitor sample as shown in Table 1 was prepared, and the influence of the type of segregation phase was examined.

(Comparative Example 1-1)
First, as the main component raw material, (Ba _0.96 Ca _0.04 ) (Ti _0.94 Zr _0.06 ) O ₃ having an average raw material particle size of 0.35 μm produced by a solid phase reaction method is added to MgO. , Mn ₃ O ₄ , BaCO ₃ , CaCO ₃ , SiO ₂ , Y ₂ O ₃ , V ₂ O ₅ are added and wet-mixed by a ball mill for 16 hours. As a final composition, (Ba _0.96 Ca _0.04 ) (Ti _0.94 Zr _0.06 ) O ₃ , MgO: 0.1 mol%, MnO: 0.2 mol%, Y ₂ O ₃ : 0.4 mol%, (Ba, Ca) SiO ₃ : 1.25 mol% , V ₂ O ₅ : A dielectric material containing 0.05 mol% was obtained.

  Next, the obtained dielectric material: 100 parts by weight, polyvinyl butyral resin: 10 parts by weight, dibutyl phthalate (DBP) as a plasticizer: 5 parts by weight, and alcohol as a solvent: 100 parts by weight with a ball mill The mixture was pasted into a dielectric layer paste.

  Separately from the above, Ni particles: 45 parts by weight, terpineol: 52 parts by weight, and ethylcellulose: 3 parts by weight were kneaded with three rolls to form a slurry, thereby preparing an internal electrode layer paste.

  Then, using the dielectric layer paste prepared above, a green sheet was formed on the PET film so that the thickness after drying was 0.9 μm. Next, the electrode layer was printed in a predetermined pattern using the internal electrode layer paste thereon, and then the sheet was peeled off from the PET film to produce a green sheet having the electrode layer. Next, a plurality of green sheets having electrode layers were laminated and pressure-bonded to form a green laminate, and this green laminate was cut into a predetermined size to produce a green chip.

  Next, the obtained green chip was subjected to binder removal treatment and heat treatment conditions were as follows to produce a multilayer ceramic fired body.

  The binder removal treatment conditions were temperature rising rate: 25 ° C./hour, holding temperature: 250 ° C., temperature holding time: 8 hours, and atmosphere: in the air.

[Firing condition 1-A]
Temperature rising rate: 600 ° C./hour, holding temperature: 1200 ° C., temperature holding time: 2 hours, cooling rate: 600 ° C./hour, atmospheric gas: humidified (N ₂ + H ₂ ) mixed gas (oxygen partial pressure: 10 ^{− 12} MPa), followed by heat treatment, followed by heating rate: 200 ° C./hour, holding temperature: 1000 ° C., temperature holding time: 2 hours, cooling rate: 200 ° C./hour, atmospheric gas: humidified N ₂ gas Heat treatment (oxygen partial pressure: 10 ⁻⁷ MPa) was performed.

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 produce a sample of the multilayer ceramic capacitor shown in FIG. The size of the obtained capacitor sample is 2.0 mm × 1.2 mm × 0.5 mm, the thickness of the dielectric layer is 0.8 μm, the thickness of the internal electrode layer is 0.7 μm, and the dielectric sandwiched between the internal electrode layers The number of layers was ^200, and the counter electrode area per layer was 1.7 mm ² .

(Comparative Example 1-2)
First, composite particles were produced. MgCO ₃ and NiO powders are weighed so as to have a molar ratio of 1: 1, then mixed by a ball mill, heat-treated in air at a temperature of 1000 ° C., and powders of composite oxide particles of Mg—Ni—O Got. The average particle size of the composite oxide particle powder was 0.05 μm.

  Next, Comparative Example 1-1 except that 0.1% by weight of the composite oxide particles was added to the dielectric material paste similar to Comparative Example 1-1: 100% by weight to the dielectric layer paste. Similarly to the above, a sample of the multilayer ceramic capacitor of Comparative Example 1-2 was produced.

(Comparative Example 1-3)
Comparative Example 1 except that 0.05% by weight of Ni metal powder having an average particle size of 0.05 μm was added to the dielectric material paste of Comparative Example 1-1 with respect to 100% by weight of the dielectric material of Comparative Example 1-1. Similarly to -1, a sample of the multilayer ceramic capacitor of Comparative Example 1-3 was produced.

(Example 1-1)
First, composite particles were produced. The powder of MgCO ₃ and Ni metal is weighed so as to have a molar ratio of 1: 1, then mixed by a ball mill, heat-treated at a temperature of 1000 ° C. in a reducing atmosphere, and the composite particles of Ni metal and Mg oxide are mixed. A powder was obtained. The average particle size of the composite particle powder was 0.05 μm.

  Next, the composite particles were the same as in Comparative Example 1-1 except that 0.1% by weight was added to the dielectric layer paste with respect to 100% by weight of the same dielectric material as in Comparative Example 1-1. A sample of the multilayer ceramic capacitor of Example 1-2 was prepared.

(Example 1-2)
A multilayer ceramic capacitor sample of Example 1-2 was produced in the same manner as Comparative Example 1-2, except that the firing conditions were changed to firing condition 1-B below.

[Baking condition 1-B]
Temperature rising rate: 5000 ° C./hour, holding temperature: 1220 ° C., temperature holding time: 6 minutes, cooling rate: 5000 ° C./hour, atmospheric gas: humidified (N ₂ + H ₂ ) mixed gas (oxygen partial pressure: 3 × ^10-15 MPa), followed by a heating rate: 200 ° C./hour, holding temperature: 800 ° C., temperature holding time: 200 hours, cooling rate: 200 ° C./hour, atmospheric gas: humidified N ₂ gas A heat treatment (oxygen partial pressure: 3 × 10 ⁻⁹ MPa) was performed.

(Example 1-3)
A multilayer ceramic capacitor sample of Example 1-3 was produced in the same manner as Comparative Example 1-1 except that the firing conditions were changed to firing conditions 1-C.

[Baking condition 1-C]
Temperature rising rate: 600 ° C./hour, holding temperature: 1200 ° C., temperature holding time: 2 hours, cooling rate: 600 ° C./hour, atmospheric gas: humidified (N ₂ + H ₂ ) mixed gas (oxygen partial pressure: 1 × 10 ⁻⁹ MPa), followed by heating rate: 200 ° C./hour, holding temperature: 1000 ° C., temperature holding time: 2 hours, cooling rate: 200 ° C./hour, atmospheric gas: humidified N ₂ gas (Oxygen partial pressure: 5 × 10 ⁻¹⁸ MPa) is heat-treated, heating rate: 200 ° C./hour, holding temperature: 800 ° C., temperature holding time: 200 hours, cooling rate: 200 ° C./hour, atmospheric gas: Heat treatment of humidified N ₂ gas (oxygen partial pressure: 3 × 10 ⁻⁹ MPa) was performed.

  For the obtained multilayer ceramic capacitor sample, dielectric particle size, segregation phase form, ratio of segregation Ni metal phase length to dielectric layer thickness in the dielectric layer thickness direction, adjacent segregation Ni metal phase and segregation The area ratio, relative dielectric constant (εs), and high temperature load reliability (HALT) of the Mg oxide phase were measured by the following methods. The results are shown in Table 2.

<Dielectric particle size>
First, a multilayer ceramic capacitor sample is cut in the stacking direction of the dielectric layer and the internal electrode layer, the average area of the dielectric particles is measured by a scanning electron microscope (SEM) in the cross section, and the diameter is calculated as the equivalent circle diameter. The value is multiplied by 27. Then, the crystal particle diameter was measured for 200 or more dielectric particles, and the value at which the accumulation was 50% from the cumulative frequency distribution of the obtained crystal particle diameter was defined as the average particle diameter (unit: μm). The dielectric average particle diameter in Experimental Example 1 was 0.4 μm.

<Segregation phase morphology>
By observing the dielectric layer 2 using a scanning electron microscope, the dielectric and the segregation phase are discriminated from the difference in contrast. Furthermore, the energy dispersive X-ray attached to the scanning transmission electron microscope (STEM) and the STEM is used. Using a spectroscopic device (EDS), point analysis of the central portion of the segregation phase was performed to determine the form of the segregation phase.

<Ratio of Segregated Ni Metal Phase Length to Dielectric Layer Thickness Length in Dielectric Layer Thickness Direction>
By observing the dielectric layer using a scanning electron microscope, the dielectric and the segregated phase are distinguished from the difference in contrast, and the ratio of the segregated Ni metal phase length to the dielectric layer thickness in the dielectric layer thickness direction. Was calculated.

<Area ratio between adjacent segregated Ni metal phase and segregated Mg oxide phase>
By observing the dielectric layer using a scanning electron microscope, the dielectric and the segregated phase are discriminated from the difference in contrast, the length of the segregated Ni metal phase and the adjacent segregated Ni metal phase and segregated Mg oxide phase. The area ratio was calculated.

<Relative permittivity εs>
The relative dielectric constant εs was determined by using a digital LCR meter (4274A manufactured by YHP) at a reference temperature of 25 ° C. for a capacitor sample that had been heat-treated at 150 ° C. for 1 hour in the atmosphere for 24 hours. Measurement voltage) It was calculated from the capacitance measured under the condition of 1.0 Vrms (no unit). It is preferable that the relative dielectric constant is high, and in this example, 6600 or more, which improves the dielectric constant by 10% or more compared with Comparative Example 1-1, was considered good.

<High temperature acceleration reliability (HALT)>
The capacitor sample was held at 160 ° C. under an electric field of 10 V / μm and applied with a DC voltage, and the lifetime was measured to evaluate the high temperature accelerated lifetime (HALT). In this example, the time from the start of application until the insulation resistance drops by an order of magnitude was defined as the lifetime. Further, this high temperature accelerated life was performed for 10 capacitor samples. In this example, in the 10-hour test, “No” is indicated as “Poor” and “No” is indicated as “No”.

  Regardless of the addition method and the firing method, as the segregation phase, the segregated particles in which the Ni metal phase and the Mg oxide phase are adjacent to each other are precipitated, the high temperature load reliability is not deteriorated and the relative dielectric constant is improved by 10% or more. It was confirmed.

<Experimental example 2>
In Experimental Example 2, the main component of the dielectric layer was changed to BaTiO ₃ to produce a multilayer ceramic capacitor sample as shown in Table 3, and the influence of the type of segregation phase was examined.

(Comparative Example 2-1)
First, as the main component raw material, BaTiO ₃ produced by the oxalate method and having an average raw material particle size of 0.18 μm, MgO, Mn ₃ O ₄ , BaCO ₃ , CaCO ₃ , SiO ₂ , Y ₂ O ₃ , V ₂ O 5 was added and wet mixed by a ball mill for 16 hours, and the final composition was BaTiO ₃ with MgO: 1.0 mol%, MnO: 0.1 mol%, Y ₂ O ₃ : 0.5 mol%, (Ba, A dielectric material containing Ca) SiO ₃ : 0.5 mol% and V ₂ O ₅ : 0.1 mol% was obtained.

  Next, the obtained dielectric material: 100 parts by weight, polyvinyl butyral resin: 10 parts by weight, dibutyl phthalate (DBP) as a plasticizer: 5 parts by weight, and alcohol as a solvent: 100 parts by weight with a ball mill The mixture was pasted into a dielectric layer paste.

  Separately from the above, Ni particles: 45 parts by weight, terpineol: 52 parts by weight, and ethylcellulose: 3 parts by weight were kneaded with three rolls to form a slurry, thereby preparing an internal electrode layer paste.

  Then, using the dielectric layer paste prepared above, a green sheet was formed on the PET film so that the thickness after drying was 0.9 μm. Next, the electrode layer was printed in a predetermined pattern using the internal electrode layer paste thereon, and then the sheet was peeled off from the PET film to produce a green sheet having the electrode layer. Next, a plurality of green sheets having electrode layers were laminated and pressure-bonded to form a green laminate, and this green laminate was cut into a predetermined size to produce a green chip.

  Next, the obtained green chip was subjected to binder removal processing, firing and annealing under the following conditions to produce a multilayer ceramic fired body.

  The binder removal treatment conditions were temperature rising rate: 25 ° C./hour, holding temperature: 240 ° C., temperature holding time: 16 hours, and atmosphere: in the air.

[Firing condition 2-A]
Temperature rising rate: 2000 ° C./hour, holding temperature: 1180 ° C., temperature holding time: 1 hour, cooling rate: 2000 ° C./hour, atmospheric gas: humidified (N ₂ + H ₂ ) mixed gas (oxygen partial pressure: 1 × 10 ⁻¹¹ MPa), followed by heating rate: 200 ° C./hour, holding temperature: 1000 ° C., temperature holding time: 2 hours, cooling rate: 200 ° C./hour, atmospheric gas: humidified N ₂ gas A heat treatment (oxygen partial pressure: 5 × 10 ⁻⁸ MPa) was performed.

  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 produce a sample of the multilayer ceramic capacitor shown in FIG. The size of the obtained capacitor sample is 2.0 mm × 1.2 mm × 0.5 mm, the thickness of the dielectric layer is 0.8 μm, the thickness of the internal electrode layer is 0.7 μm, and the dielectric sandwiched between the internal electrode layers The number of layers was 200, and the counter electrode area per layer was 1.7 mm 2.

(Comparative Example 2-2)
First, composite particles were produced. MgCO3 and NiO powders are weighed so as to have a molar ratio of 1: 1, then mixed by a ball mill, heat-treated at a temperature of 1000 ° C. in air, and Mg—Ni—O composite oxide particle powders are obtained. Obtained. The average particle size of the composite oxide particle powder was 0.05 μm.

  Next, Comparative Example 2-1 except that 0.1% by weight of the composite oxide particles was added to the dielectric material paste similar to Comparative Example 2-1: 100% by weight to the dielectric layer paste. Similarly to the above, a sample of the multilayer ceramic capacitor of Comparative Example 2-2 was produced.

(Comparative Example 2-2)
Comparative Example 2 except that 0.05% by weight of Ni metal powder having an average particle size of 0.05 μm was added to the dielectric layer paste with respect to 100% by weight of the dielectric material of Comparative Example 1-1. Similarly to -1, a sample of the multilayer ceramic capacitor of Comparative Example 2-3 was produced.

(Example 2-1)
First, composite particles were produced. MgCO3 and Ni metal powder are weighed so as to have a molar ratio of 1: 1, then mixed by a ball mill, and heat-treated at a temperature of 1000 ° C. in a reducing atmosphere to obtain a powder of composite particles of Ni metal and Mg oxide. Got. The average particle size of the composite particle powder was 0.05 μm.

  Next, the composite particles were the same as in Comparative Example 2-1, except that 0.1% by weight was added to the dielectric layer paste with respect to 100% by weight of the same dielectric material as in Comparative Example 2-1. A sample of the multilayer ceramic capacitor of Example 2-1 was prepared.

(Example 2-2)
A multilayer ceramic capacitor sample of Example 2-2 was produced in the same manner as in Comparative Example 2-2, except that the firing conditions were changed as in firing condition 2-B below.

[Baking condition 2-B]
Temperature rising rate: 5000 ° C./hour, holding temperature: 1200 ° C., temperature holding time: 6 minutes, cooling rate: 5000 ° C./hour, atmospheric gas: humidified (N ₂ + H ₂ ) mixed gas (oxygen partial pressure: 3 × ^10-15 MPa), followed by a heating rate: 200 ° C./hour, holding temperature: 800 ° C., temperature holding time: 200 hours, cooling rate: 200 ° C./hour, atmospheric gas: humidified N ₂ gas A heat treatment (oxygen partial pressure: 3 × 10 ⁻⁹ MPa) was performed.

(Example 2-3)
A multilayer ceramic capacitor sample of Example 2-3 was produced in the same manner as Comparative Example 2-1, except that the firing conditions were changed to firing conditions 2-C.

[Firing condition 2-C]
Temperature rising rate: 800 ° C./hour, holding temperature: 1180 ° C., temperature holding time: 2 hours, cooling rate: 800 ° C./hour, atmosphere gas: humidified (N ₂ + H ₂ ) mixed gas (oxygen partial pressure: 1 × 10 ⁻⁹ MPa), followed by a heating rate: 200 ° C./hour, holding temperature: 1000 ° C., temperature holding time: 2 hours, cooling rate: 400 ° C./hour, atmospheric gas: humidified N ₂ gas (Oxygen partial pressure: 5 × 10 ⁻¹⁸ MPa) is heat-treated, temperature rising rate: 400 ° C./hour, holding temperature: 800 ° C., temperature holding time: 200 hours, cooling rate: 200 ° C./hour, atmospheric gas: Heat treatment of humidified N ₂ gas (oxygen partial pressure: 3 × 10 ⁻⁹ MPa) was performed.

  About the obtained multilayer ceramic capacitor sample, dielectric particle size, segregation phase form, ratio of segregation Ni metal phase length to dielectric layer thickness in the dielectric layer thickness direction, adjacent segregation Ni metal phase and Mg oxide phase The area ratio, relative dielectric constant (εs), and high temperature load reliability (HALT) were measured by the following methods. The results are shown in Table 4. Regarding the dielectric particle size, the form of the segregation phase, the ratio of the segregation Ni metal phase length to the dielectric layer thickness in the dielectric layer thickness direction, and the area ratio of the adjacent segregation Ni metal phase and Mg oxide phase, Evaluation was performed in the same manner. The average dielectric particle size in Experimental Example 2 was 0.23 μm.

<Relative permittivity εs>
The relative dielectric constant εs was evaluated in the same manner as in Experimental Example 1. In Experimental Example 2, compared with Comparative Example 2-1, as a preferable range, 4400 or more that improves the dielectric constant by 10% or more is preferable, and as a more preferable range, 4600 or more that improves the dielectric constant by 15% or more is further preferable. It was good.

<High temperature acceleration reliability (HALT)>
In Experimental Example 2, evaluation was performed in the same manner as in Experimental Example 1 while maintaining a DC voltage applied to the capacitor sample at 125 ° C. under an electric field of 10 V / μm. In Experimental Example 2, 100 capacitor samples were used. In Experimental Example 2, “x” indicates that there is a defect in the test for 1000 hours, “◯” indicates that there is no defect, and “◎” indicates that there is no defect in the test for 2000 hours.

Even when the main component is BaTiO ₃ , the segregated particles in which the segregated Ni metal phase and the segregated Mg oxide phase are adjacent to each other are precipitated, so that the high temperature load reliability is not deteriorated and the relative dielectric constant is improved by 20% or more. It was confirmed. Further, in Experimental Example 1 (Ba, Ca) (Ti , Zr) effect it has been found greater than _{O 3.}

<Experimental example 3>
In Experimental Example 3, the particle size of the composite particles of Ni metal and Mg oxide was adjusted, and the influence of the size of the segregated Ni metal phase on the dielectric layer thickness was examined.

  A multilayer ceramic capacitor sample was prepared and evaluated under the same conditions as in Comparative Example 2-1, except that the particle diameter of the composite particles of Ni metal and Mg oxide was changed as shown in Table 5. The results are shown in Table 5.

  It was found that the ratio of the segregated Ni metal phase length to the dielectric layer thickness in the dielectric layer thickness direction is in the range of 0.06 to 0.40, and both a 10% increase in relative permittivity and high temperature load reliability are compatible. . When the thickness ratio is out of the above range, it is considered that the effect of residual stress for increasing the relative dielectric constant is reduced.

<Experimental example 4>
In Experimental Example 4, the compounding ratio of the composite particles of Ni metal and Mg oxide was adjusted, and the influence of the area ratio between the adjacent segregated Ni metal phase and the segregated Mg oxide phase was examined.

  A multilayer ceramic capacitor sample was prepared and evaluated under the same conditions as in Comparative Example 2-1, except that the compounding ratio of the composite particles of Ni metal and Mg oxide was changed as shown in Table 6. The results are shown in Table 6.

  When the area ratio of the adjacent segregated Ni metal phase and segregated Mg oxide phase is in the range of 0.20 to 2.0, the high temperature load reliability is not deteriorated, and the relative permittivity is improved by 15%, which has a greater effect. I found out. When the area ratio is out of the above range, it is considered that the effect of the residual stress for increasing the relative dielectric constant is reduced.

<Experimental example 5>
In Experimental Example 5, particles in which other oxides were combined with Mg oxide were prepared, and the influence of the composition of the segregated Mg oxide phase was examined.

  A multilayer ceramic capacitor sample was prepared and evaluated under the same conditions as in Comparative Example 2-1, except that the composition of the segregated Mg oxide phase was changed as shown in Table 7. The results are shown in Table 7.

Even when the segregated Mg oxide phase in contact with the segregated Ni metal phase contains Mn, Cr, Ti, Ba, Ni, etc., it is found that the relative permittivity is improved by 20% and the high temperature load reliability is compatible. It was.

<Experimental example 6>
In Experimental Example 6, the composition of the dielectric material was changed and the influence of the dielectric composition was examined.

A multilayer ceramic capacitor sample was prepared and evaluated under the same conditions as in Comparative Example 2-1, except that the additive composition in the dielectric material was changed as shown in Table 8. The results are shown in Table 8.

It has been found that even if the additive composition in the dielectric material is changed, a 20% increase in relative dielectric constant and high temperature load reliability are compatible. It was confirmed from Experimental Examples 1, 2, and 6 that the dielectric characteristics (relative permittivity and high-temperature load reliability) can be improved regardless of the content of the components contained in the dielectric ceramic constituting the dielectric layer.

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 10 ... Element main body 2 ... Dielectric layer 20 ... Dielectric particle 22 ... Grain boundary 27 ... Segregation area | region 28 ... Segregation Ni metal phase 29 ... Segregation Mg oxide phase 3 ... Internal electrode layer 4 ... External electrode

Claims (4)

  A multilayer ceramic capacitor in which dielectric layers and internal electrode layers mainly composed of Ni are alternately stacked, wherein a metal phase mainly composed of Ni and Mg in contact with the metal phase are disposed inside the dielectric layer. A monolithic ceramic capacitor comprising an oxide phase containing as a main component. The multilayer ceramic capacitor according to claim 1, wherein the dielectric layer contains BaTiO ₃ as a main component.   The ratio of the length in the thickness direction of the first dielectric layer of the metal phase mainly composed of Ni contained in the dielectric layer to the length in the thickness direction of the dielectric layer is 0.06 or more and 0.40 or less. The multilayer ceramic capacitor according to claim 1 or 2, wherein:   The area ratio (metal phase / oxide phase) of the metal phase mainly composed of Ni contained in the dielectric layer and the oxide phase mainly composed of Mg in contact with the metal phase is 0.2 or more The multilayer ceramic capacitor according to claim 3, wherein the multilayer ceramic capacitor is 2.0 or less.

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