JP5046432B2 - Dielectric porcelain and multilayer electronic components - Google Patents

Description

【００４４】
高温負荷寿命は、誘電体層を薄層化する際に特に重要となるものである。試験条件の如何に関わらず、実施例は比較例よりも高い信頼性を有することが分かる。
【００４５】
結晶粒内の元素の濃度分布をエネルギー分散型Ｘ線検出器（ＥＤＳ）により測定した結果について、本発明の試料Ｎｏ．２を図２に、比較例の試料Ｎｏ．３を図３に示す。また、Ｎｏ．２について、結晶粒子の半径内におけるＹ濃度を図４に示す。
【００４６】
比較例では、Ｍｇの濃度が０になる距離と、Ｙ濃度が０になる距離が同じであるが、本実施例では、Ｍｇより、Ｙが結晶粒中央部側に存在していることが分かる。そのため、高い信頼性が発現することが判る。尚、試料は、Ｂａ、Ｔｉ、希土類元素、ＭｇおよびＭｎを含有するペロブスカイト型複合酸化物からなる結晶粒子と、Ｌｉ₂ＯとＳｉＯ₂とＣａＯからなる粒界相とから構成されていた。
【００４７】
【発明の効果】
以上のように構成された誘電体磁器では、誘電体層を構成する結晶粒子が、Ｂａ、Ｔｉ、希土類元素、Ｍｇ、Ｍｎを含有するペロブスカイト型複合酸化物から成るとともに、希土類元素がＭｇよりも結晶粒子の中央部側にまで存在することにより、高温負荷試験における信頼性を向上し、長寿命とすることができる。
【図面の簡単な説明】
【図１】本発明の積層型電子部品の概略断面図である。
【図２】本発明の試料Ｎｏ．２の結晶粒内におけるＹ、Ｍｇ、Ｍｎの濃度分布を表す図である。
【図３】比較例の試料Ｎｏ．３の結晶粒内におけるＹ、Ｍｇ、Ｍｎの濃度分布を表す図である。
【図４】本発明の試料Ｎｏ．２の結晶粒の半径内におけるＹ濃度分布を表す図である。
【符号の説明】
５・・・内部電極層
７・・・誘電体層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dielectric ceramic and a multilayer electronic component, and in particular, is used in a small and high-functional electronic device such as a mobile phone, and is a small-sized large-sized structure in which extremely thin dielectric layers and internal electrode layers are alternately stacked. The present invention relates to a dielectric ceramic and a multilayer electronic component which are preferably used for a multilayer ceramic capacitor having a capacity.
[0002]
[Prior art]
In recent years, with the miniaturization and high density of electronic devices, multilayer electronic components, such as multilayer ceramic capacitors, are required to have a small size and a large capacity. For this reason, an increase in the number of dielectric layers and the dielectric layer itself. Thinning of the layer is attempted.
[0003]
As such a dielectric ceramic for a multilayer ceramic capacitor or the like, for example, one disclosed in JP-A-10-330160 is known. In the dielectric ceramic disclosed in this publication, it is described that additive components such as Mn and V that improve reduction resistance are distributed almost uniformly over almost the entire crystal grains, thereby increasing the dielectric breakdown voltage. Has been.
[0004]
JP-A-5-144319 contains BaTiO ₃ powder, an organic compound soluble in organic solvents such as Dy and Co, and an organic compound soluble in organic solvents constituting the oxide glass component. The organic component is removed, and an additive component made of an oxide such as Dy or Co is coated on the surface of BaTiO ₃ , and a dielectric ceramic is manufactured using this raw material.
[0005]
And, in such a dielectric ceramic, for more effectively it can be uniformly attached to additional components in the BaTiO ₃ powder surface to form a uniform shell BaTiO ₃ powder surface with a small amount, the electrical characteristics It is described that a dielectric ceramic having excellent electrical characteristics such as dielectric characteristics and insulation characteristics and excellent sinterability can be obtained reliably by reducing the addition ratio of additive elements that cause deterioration of ing.
[0006]
[Problems to be solved by the invention]
However, the dielectric ceramic disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 10-330160 has a problem of low reliability in a high temperature load test. That is, in recent years, there is a demand for a small size and high capacity, but in the above publication, since the rare earth element that improves the reliability exists only on the surface of the crystal particles, when the dielectric layer of the multilayer ceramic capacitor is thinned, There was a problem that the insulation resistance was frequently lowered and the reliability was lowered.
[0007]
In addition, the dielectric ceramic disclosed in Japanese Patent Laid-Open No. 5-144319 is manufactured using a raw material in which an additive component made of an oxide such as Dy or Co is coated on the surface of BaTiO ₃ . Since additive components containing rare earth elements are present on the surface of the crystal grains due to firing conditions and the like, there is a problem that when the dielectric layer is thinned, the insulation resistance is frequently reduced and the reliability is lowered.
[0008]
The present invention has been devised in view of the above-described problems, and an object thereof is to provide a dielectric ceramic and a multilayer electronic component that can improve reliability in a high-temperature load test and have a long life. Objective.
[0009]
[Means for Solving the Problems]
The dielectric ceramic of the present invention comprises a perovskite-type composite oxide containing Ba, Ti, rare earth elements, Mg and Mn as metal elements, an average grain size of 0.8 μm or less, and a grain boundary phase The ceramic is fired at a temperature rise rate from 500 ° C. of 40 to 80 ° C./h and a temperature of 1270 to 1300 ° C., and the rare earth element is more crystalline than Mg. It exists to the center part side of a particle | grain, and the abundance of the rare earth element in the crystal grain is decreasing toward the center part side of the crystal grain.
[0010]
In such a dielectric ceramic, the crystal particles are made of a perovskite complex oxide containing Ba, Ti, rare earth elements, Mg, and Mn, and the rare earth elements that improve the reliability are more central than the crystal grains than Mg. By being present to the side, the reliability in the high temperature load test can be improved and the life can be extended.
[0011]
In the dielectric ceramic according to the present invention, the abundance of the rare earth element in the crystal particles is
And it decreased gradually toward the center side of the crystal grains, it is desirable that the center portion of the crystal grains does not exist a rare earth element. According to such a configuration, a ferroelectric portion of only BaTiO ₃ remains, whereby high reliability can be obtained in a high temperature load test while maintaining a high dielectric constant.
[0012]
Further, the dielectric ceramic of the present invention, it is desirable that the Mn is present substantially uniformly in the crystal grains. In this way, Mn is present almost uniformly in the crystal particles, thereby generating a grain boundary phase while suppressing crystal growth of the crystal particles in the dielectric ceramic fired in a reducing atmosphere, By suppressing the reduction reaction of the dielectric, a highly insulating dielectric ceramic can be obtained.
[0013]
In the dielectric ceramic according to the present invention, it is desirable that the rare earth element is present from the crystal particle surface to the central portion side by 0.55 times or more of the radius. Thereby, since the rare earth element exists more to the center part side of the crystal grain, the reliability in the high temperature load test can be improved and the life can be extended.
[0014]
The multilayer electronic component of the present invention is obtained by alternately laminating dielectric layers made of the above dielectric ceramics and internal electrode layers.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
A multilayer ceramic capacitor which is the multilayer electronic component A of the present invention will be described in detail based on the schematic cross-sectional view of FIG. The multilayer electronic component A of the present invention is configured by forming external electrodes 3 at both ends of an electronic component body 1. The external electrode 3 is formed, for example, by baking Cu or an alloy paste of Cu and Ni.
[0016]
The electronic component main body 1 is configured by forming insulating layers 11 made of the same material as the dielectric layer 7 on both surfaces in the stacking direction of the capacitor portion 9 formed by alternately stacking the internal electrode layers 5 and the dielectric layers 7. ing. Further, on the surface of the external electrode 3, for example, a Ni plating layer 13, a Sn plating layer or a Sn—Pb alloy plating layer 15 is formed in this order.
[0017]
On the other hand, the internal electrode layer 5 is made of a metal film obtained by sintering a conductive paste film. As the conductive paste, for example, a base metal such as Ni, Co, or Cu is used. The internal electrode layer 5 is mainly composed of a base metal and is a substantially rectangular conductor film. The odd-numbered internal electrode layers 5 of the first layer, the third layer, the fifth layer,. One end of the capacitor body 1 is exposed at one end surface, and the second, fourth, sixth,... Internal electrode layers 5 from the top end of the electronic component body 1 have one end. The other end surface is exposed. The external electrode 3 and the internal electrode layer 5 do not necessarily need to be made of the same material.
[0018]
In the multilayer electronic component A of the present invention, the crystal particles of the dielectric layer 7 made of dielectric porcelain are composed of a perovskite complex oxide containing Ba, Ti, rare earth elements, Mg, and Mn as metal elements. ing. At grain boundaries of crystal grains, for example, grain boundary phases containing Li, Si, and Ca as components exist mainly as glass.
[0019]
The rare earth element exists in the center part of the crystal grain rather than Mg. The presence of the rare earth element to the center of the crystal grain rather than Mg means that the rare earth element concentration is substantially zero than the position where the Mg concentration by the energy dispersive X-ray detector (EDS) is substantially zero. Means that it is on the center side of the crystal grains. Further, although it is desirable for all the crystal particles in the dielectric ceramic to have the rare earth element even closer to the center of the crystal particles than Mg, there may be particles that do not have such a structure.
[0020]
In addition, the abundance of rare earth elements in the crystal grains gradually decreases toward the center of the crystal grains. This means that the rare earth element has a continuous concentration distribution from the crystal grain boundary (particle surface), and it does not have to be a constant concentration gradient. Examples of rare earth elements include Y, Sc, Ce, Pr, Nd, Sm, En, Gd, Tb, Dy, Ho, Er, Tm, Yb, and La. Among these, Y is desirable.
[0021]
Furthermore, it is desirable that the rare earth element is present from the surface of the crystal grain to the center part side by 0.55 times or more of the radius thereof, but it is desirable that there is a region where the rare earth element is not present in the center part of the crystal grain. . Further, Mn is present almost uniformly in the crystal grains.
[0022]
FIG. 2 shows the abundances of rare earth elements, Mg, and Mn in crystal grains having a particle diameter of 0.8 μm. From FIG. 2, the rare earth element is present up to the center of the crystal grain rather than Mg, the abundance of the rare earth element in the crystal grain gradually decreases toward the center of the crystal grain, and Mn is the crystal grain. It can be seen that it exists almost uniformly inside. FIG. 4 shows the Y concentration in a crystal particle having a particle diameter of 0.8 μm. From FIG. 4, Y exists on the center side from the crystal particle surface to about 0.7 times its radius. You can see that
[0023]
The thickness of one sheet-like dielectric layer composed of these crystal particles is 3 μm or less. To increase the capacity of the multilayer electronic component A, for example, the capacity of the multilayer ceramic capacitor, it is an effective means to reduce the thickness of the dielectric layer, in order to construct a recent small size and high capacity multilayer ceramic capacitor. The dielectric layer thickness is preferably 1 to 3 μm.
[0024]
The average particle size of the crystal particles is preferably 1 μm or less, and particularly preferably 0.8 μm or less. As described above, in order to make the dielectric layer 3 μm or less, the average particle size needs to be 1 μm or less, and by using such fine crystal particles, the rare earth element can reach the center of the crystal particles. Can exist.
[0025]
(Manufacturing method)
In the multilayer electronic component A of the present invention, first, a green sheet to be a dielectric layer is produced. This green sheet can be formed using, for example, BaTiO ₃ raw material powder, and the synthesis method of the main raw material BaTiO ₃ powder is solid phase method, liquid phase method (method of passing oxalate, etc.), water There are thermal synthesis methods, among which hydrothermal synthesis method is desirable because of its narrow particle size distribution and high crystallinity.
[0026]
The specific surface area of the BaTiO ₃ powder is preferably 1.7 to 6.6 (m ² / g). The main raw material is a BaTiO ₃ powder coated with a rare earth element oxide on its surface. Examples of the coating method include a solid phase method, a liquid phase method, and a gas phase method, but the method is not particularly limited. By using BaTiO ₃ powder having a surface coated with a rare earth element oxide, the rare earth element tends to exist up to the center of BaTiO ₃ .
[0027]
Next, an electrode pattern of an internal electrode layer made of a conductive paste is printed on the green sheet and dried. Next, a plurality of green sheets on which this electrode pattern is formed are stacked and thermocompression bonded. Thereafter, the laminate is cut into a lattice shape to obtain a molded body of the electronic component main body 1. The end portions of the electrode pattern of the internal electrode layer 5 are alternately exposed at both end faces of the molded body of the electronic component body 1.
[0028]
Next, the molded body of the electronic component body 1 is debindered at 400 to 500 ° C. at a temperature rising rate of 40 to 80 ° C./h in the air, and then heated from 500 ° C. in a reducing atmosphere. Baked at a temperature of 1270-1300 ° C. for 2-5 hours at a rate of 40-80 ° C./h, then cooled at a temperature drop rate of 80-120 ° C./h, and reoxidized at 750-850 ° C. in an air atmosphere I do.
[0029]
In particular, the heating rate from 500 ° C. is 40 to 80 ° C./h, and firing is performed at a temperature of 1270 to 1300 ° C., so that the coated rare earth element is present in the BaTiO ₃ to the center side. .
[0030]
Thereafter, the external electrode 3 is formed by applying an external electrode paste on both end faces of the fired capacitor body and baking it in nitrogen.
[0031]
Further, the surface of the external electrode 3 is degreased, acid washed, and washed with pure water, and then plated by a barrel method.
[0032]
In the present invention, the crystal particles are composed of a perovskite complex oxide containing Ba, Ti, rare earth elements, Mg, and Mn, and the rare earth elements that improve the reliability are present up to the center of the crystal grains rather than Mg. By doing so, the reliability in the high temperature load test can be improved and the life can be extended.
[0033]
【Example】
A multilayer ceramic capacitor, which is one of the multilayer electronic components, was produced as follows. First, as the dielectric material cost, a BaTiO ₃ powder having a specific surface area becomes ^{3.2 (m 2 / g),} BaTiO 3 coated with Y ₂ O ₃ of 1 part by weight with respect to BaTiO ₃ 100 parts by weight Using powder, with respect to 100 parts by weight of BaTiO ₃ , 0.2 parts by weight of MgO, 0.1 parts by weight of MnCO ₃ , and 0.5 parts by weight of grain boundary phase components composed of Li ₂ O, SiO ₂ and CaO The raw material powder as a part was prepared by wet pulverization in a ball mill using ZrO ₂ balls having a diameter of 5 mmφ.
[0034]
As a comparative example, 1 part by weight of Y ₂ O ₃ and 0.2 part by weight of MgO with respect to 100 parts by weight of BaTiO ₃ having a specific surface area of 3.2 (m ² / g) as a dielectric material. A raw material powder containing 0.1 part by weight of MnCO ₃ and 0.5 part by weight of a grain boundary phase component composed of Li ₂ O, SiO ₂ and CaO was prepared.
[0035]
Next, an organic binder was mixed to prepare a slurry, and a green sheet was produced using a doctor blade.
[0036]
Next, an internal electrode paste was screen-printed on the green sheet. The effective area of this internal electrode layer was 2.1 mm ² .
[0037]
Next, 100 green sheets printed with the internal electrode paste were laminated, and 20 green sheets not printed with the internal electrode paste were laminated on the upper and lower surfaces, respectively, and integrated using a press machine. Obtained.
[0038]
Thereafter, the laminate was cut into a lattice shape to produce a molded body of the electronic component main body 1 having a size of 2.3 mm × 1.5 mm × 1.5 mm.
[0039]
Next, the molded body of the electronic component main body was debindered at 500 ° C. in the atmosphere at a temperature rising rate of 50 ° C./h, and the temperature rising rate from 500 ° C. was 50 ° C./h. 1270 ° C. to 1300 ° C. (oxygen partial pressure 10 ⁻¹¹ atm) for 2 hours, followed by cooling to 800 ° C. at a cooling rate of 100 ° C./h, and reoxidation treatment at 800 ° C. for 4 hours in the air atmosphere. The electronic component main body was manufactured by cooling at a temperature decrease rate of 200 ° C./h. The thickness of the dielectric layer was 2.5 μm.
[0040]
Next, after barrel-polishing the fired electronic component body 1, an external electrode paste containing Cu powder and glass was applied to both ends of the electronic component body, and baked in nitrogen at 850 ° C. to form external electrodes. . Thereafter, using an electrolytic barrel machine, Ni and Sn plating were sequentially performed on the surface of the external electrode to produce a multilayer electronic component.
[0041]
The high temperature load life test of the multilayer capacitor was performed for each of the present example and the comparative example. The test conditions were a DC voltage applied twice the rated voltage at 125 ° C, a DC voltage applied three times the rated voltage at 125 ° C, and a DC voltage twice the rated voltage applied at 150 ° C. I went in three ways.
[0042]
Evaluation was made by measuring the number of short-circuited capacitors after 1000 hours of test time. The results are shown in Table 1.
[0043]
[Table 1]

[0044]
The high temperature load life is particularly important when the dielectric layer is thinned. It can be seen that the examples have higher reliability than the comparative examples regardless of the test conditions.
[0045]
Regarding the result of measuring the concentration distribution of elements in the crystal grains with an energy dispersive X-ray detector (EDS), the sample No. 2 is shown in FIG. 3 is shown in FIG. No. 4, the Y concentration within the radius of the crystal grains is shown in FIG.
[0046]
In the comparative example, the distance at which the Mg concentration is 0 and the distance at which the Y concentration is 0 are the same. However, in this example, it can be seen that Y is present on the crystal grain center side from Mg. . Therefore, it turns out that high reliability expresses. The sample was composed of crystal particles made of a perovskite complex oxide containing Ba, Ti, rare earth elements, Mg and Mn, and a grain boundary phase made of Li ₂ O, SiO ₂ and CaO.
[0047]
【Effect of the invention】
In the dielectric ceramic constructed as described above, the crystal particles constituting the dielectric layer are composed of a perovskite complex oxide containing Ba, Ti, rare earth element, Mg, Mn, and the rare earth element is more than Mg. By being present up to the center of the crystal grains, the reliability in the high temperature load test can be improved and the life can be extended.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a multilayer electronic component of the present invention.
[Fig. 2] Sample No. of the present invention. It is a figure showing the density | concentration distribution of Y, Mg, and Mn in 2 crystal grains.
3 is a sample No. of a comparative example. 3 is a diagram illustrating a concentration distribution of Y, Mg, and Mn in three crystal grains.
4 is a sample No. of the present invention. It is a figure showing Y concentration distribution within the radius of 2 crystal grains.
[Explanation of symbols]
5 ... Internal electrode layer 7 ... Dielectric layer

Claims (3)

A dielectric ceramic comprising a perovskite type complex oxide containing Ba, Ti, rare earth elements, Mg and Mn as metal elements, and comprising crystal grains having an average grain size of 0.8 μm or less and a grain boundary phase. The temperature rise rate from 500 ° C. is 40 to 80 ° C./h, and is fired at a temperature of 1270 to 1300 ° C., and the rare earth element is present from the Mg to the center of the crystal grain. The dielectric ceramic is characterized in that the abundance of the rare earth element in the crystal grains decreases toward the center of the crystal grains.   The dielectric ceramic according to claim 1, wherein the Mn exists substantially uniformly in the crystal grains.   A multilayer electronic component comprising a dielectric layer comprising the dielectric ceramic according to claim 1 and an internal electrode layer alternately laminated.

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