WO2012043207A1

WO2012043207A1 - Multilayer ceramic electronic component and method for producing multilayer ceramic electronic component

Info

Publication number: WO2012043207A1
Application number: PCT/JP2011/070711
Authority: WO
Inventors: 祥一郎鈴木; 将典中村; 伴野　晃一; 泰介神崎; 彰宏塩田; 大塚　正博
Original assignee: 株式会社村田製作所
Priority date: 2010-09-30
Filing date: 2011-09-12
Publication date: 2012-04-05
Also published as: JPWO2012043207A1; JP5429393B2

Abstract

The present invention provides a multilayer ceramic electronic component having excellent mechanical and electrical properties and having an excellent cost-performance ratio. The multilayer ceramic electronic component includes: a laminate that includes a plurality of laminated ceramic layers, and a plurality of internal electrodes each formed along the interface between said ceramic layers and containing Al as the main component thereof; and external electrodes formed on the outer surfaces of the laminate. The multilayer ceramic electronic component is characterized in that the internal electrodes contain flat Al particles.

Description

Multilayer ceramic electronic component and method of manufacturing multilayer ceramic electronic component

The present invention relates to a multilayer ceramic electronic component typified by a multilayer ceramic capacitor, and particularly relates to a component having an internal electrode mainly composed of Al.

Referring to FIG. 1, first, a multilayer ceramic capacitor 1 which is a typical example of the multilayer ceramic electronic component according to the present invention will be described.

The multilayer ceramic capacitor 1 includes a multilayer body 2 including a plurality of multilayered dielectric ceramic layers 3 and a plurality of

internal electrodes

4 and 5 formed along an interface between the dielectric ceramic layers 3. Yes.

In the multilayer ceramic capacitor 1 shown in FIG. 1, the first and second

external electrodes

8 and 9 are formed on the end faces 6 and 7 of the multilayer body 2 facing each other. The

internal electrodes

4 and 5 are a plurality of first internal electrodes 4 electrically connected to the first external electrode 8 and a plurality of second internal electrodes 5 electrically connected to the second external electrode 9. The first and second

internal electrodes

4 and 5 are alternately arranged in the stacking direction.

Since a multilayer ceramic capacitor is particularly required to be miniaturized, a method is employed in which a dielectric ceramic green sheet and an internal electrode layer are laminated and fired at the same time in the manufacturing process. In recent years, base metals such as Ni have been used for internal electrodes of multilayer ceramic capacitors in order to reduce costs.

However, since Ni is very easily oxidized during co-sintering with ceramics, it was necessary to control the temperature condition and oxygen partial pressure with a reducing atmosphere as the firing atmosphere. As a result, material design was greatly restricted. In addition, there were concerns about problems such as delamination and cracks due to non-uniform stress associated with co-firing.

Therefore, in order to increase the degree of freedom in designing the multilayer ceramic electronic component, it is preferable to consider internal electrodes of various metal types.

For example, Patent Document 1 describes a multilayer ceramic body that employs Al as an internal electrode material instead of Ni. However, since the melting point of Al is about 660 ° C., considering the conventional common sense, the ceramic must be able to be sufficiently sintered at 660 ° C., and the degree of freedom in designing ceramic materials is greatly limited. There was a problem.

German published patent publication DE19719174A1

However, in the multilayer ceramic electronic component disclosed in Patent Document 1, since the firing temperature is 1200 ° C., which is much higher than the melting point of Al, the Al internal electrode is spheroidized and sufficient conductivity cannot be ensured. When considered as a multilayer ceramic capacitor, sufficient electrostatic capacity cannot be obtained.

Furthermore, in the multilayer ceramic electronic component disclosed in Patent Document 1, since the firing atmosphere is a nitrogen atmosphere having an oxygen partial pressure of 10 ⁻⁵ atm, Al serving as the internal electrode is changed to aluminum nitride (AlN), and sufficient electrical conductivity is achieved. There was a problem that sex could not be secured. In this case, sufficient electrostatic capacity cannot be obtained.

Therefore, an object of the present invention is to provide a multilayer ceramic electronic component having an Al internal electrode excellent in smoothness and conductivity and excellent in mechanical properties and electrical properties.

That is, the present invention provides a laminate including a plurality of laminated ceramic layers and a plurality of Al-based internal electrodes formed along an interface between the ceramic layers, and an outer surface of the laminate. A multilayer ceramic electronic component including an external electrode formed on the substrate, wherein the internal electrode includes Al particles having a flat shape.

In the present invention, the surface layer portion of the internal electrode is preferably formed of an Al ₂ O ₃ layer. Particularly, the thickness of the Al ₂ O ₃ layer is 0.25 to 10% of the thickness of the internal electrode.

The present invention is also directed to a method for manufacturing a multilayer ceramic electronic component including an internal electrode mainly composed of Al. A step of preparing a raw laminate comprising a plurality of laminated ceramic green sheets and a plurality of layers containing a metal component mainly composed of Al formed along an interface between the ceramic green sheets; And firing the raw laminate, wherein the metal component containing Al as a main component includes Al particles having a flat shape.

According to the present invention, since the Al internal electrode is smooth and excellent in electrical conductivity, it is possible to provide a multilayer ceramic electronic component that is excellent in mechanical characteristics and electrical characteristics, and that is downsized and excellent in cost performance.

In addition, according to the present invention, since the Al ₂ O ₃ layer constituting the surface of the Al internal electrode adheres firmly to the ceramic layer having various compositions, the shrinkage in the surface direction during firing is suppressed, and high dimensional accuracy is achieved. It is possible to provide a multilayer ceramic electronic component having the following.

It is a figure which shows the multilayer ceramic capacitor which is an example of the multilayer ceramic electronic component of this invention. It is a SEM photograph of the layered product section in sample 1 which is a comparative example of the present invention. It is a SEM photograph of the layered product section in sample 2 which is an example of the present invention. It is an enlarged TEM photograph in the Al internal electrode vicinity of the laminated body cross section in the sample 2 which is an Example of this invention.

Hereinafter, an example of an embodiment of the present invention will be described using the multilayer ceramic capacitor of FIG. 1 as an example.

In the multilayer ceramic electronic component of the present invention, the main component of the internal electrode is Al. The internal electrode may be Al alone or an Al alloy, but when it is an Al alloy, the Al content is preferably 70 mol%, more preferably 90 mol% or more.

The internal electrode containing Al as a main component is formed of Al particles having many flat shapes (hereinafter referred to as “Al flat particles”). The flat particles herein are substantially plate-like particles, and the ratio (aspect ratio) between the average diameter (spherical conversion value) and the average thickness on the surface of the plate is 20 or more. When the plane direction (plane normal) of the flat particles is substantially parallel to the stacking direction, it is advantageous for thinning the internal electrode.

When flat Al particles are used for the internal electrode, a high capacitance is easily obtained even if there is no significant difference in coverage compared to the case where spherical Al particles are used. This is not seen in the conventional Ni internal electrode or Cu internal electrode, but seems to be an effect peculiar to the Al internal electrode.

Further, it is desirable that the surface layer portion of the internal electrode, that is, the portion in contact with the ceramic layer, is composed of a layer mainly composed of Al ₂ O ₃ . This is mainly due to the oxidation of the surface of the Al internal electrode. This Al ₂ O ₃ layer prevents the electrode breakage due to the spheroidization of the Al internal electrode, and keeps the conductivity of the Al internal electrode good. The Al ₂ O ₃ layer has a function of smoothing the Al internal electrode layer. As a result, delamination between the ceramic layer and the Al internal electrode is suppressed, and cracks in the laminate are also prevented. In order to exhibit this effect, the thickness of the Al ₂ O ₃ layer is preferably 0.25% or more of the thickness of the internal electrode.

Further, when the thickness of the Al ₂ O ₃ layer exceeds 10% of the thickness of the internal electrode, more than 20% of the total thickness of the internal electrode layer is composed of Al ₂ O ₃ , and there is a concern about a decrease in conductivity. The Therefore, the thickness of the Al ₂ O ₃ layer is preferably 10% or less of the thickness of the internal electrode.

Next, the manufacturing method of the multilayer ceramic electronic component of the present invention will be described taking a multilayer ceramic capacitor as an example.

First, ceramic raw materials are prepared. This ceramic raw material is mixed with an organic binder component in a solvent as necessary to form a ceramic slurry. A ceramic green sheet is obtained by sheet-forming this ceramic slurry.

Next, an internal electrode mainly composed of Al is formed on the ceramic green sheet. As a forming method, a method of screen printing an Al paste containing Al flat particles and an organic vehicle in a desired pattern is simple.

In this way, a large number of ceramic green sheets and Al internal electrode layers are stacked and pressed to obtain a raw laminate before firing.

This raw laminate is fired in a firing furnace, for example, at a predetermined atmosphere and temperature. For example, when the oxygen partial pressure during firing is 1 × 10 ⁻⁴ MPa or more and the firing temperature is 600 ° C. or more, preferably 670 ° C. or more, the oxidation of the surface of the Al internal electrode proceeds and Al having an appropriate thickness is obtained. _{A 2} O ₃ layer is formed. For example, when the firing temperature is 1000 ° C. or less, the spheroidization of the Al internal electrode is effectively prevented. Regarding the oxygen partial pressure, atmospheric pressure is most preferable in consideration of the simplicity of the process.

Further, if the rate of temperature increase from room temperature to TOP temperature in the firing process is 100 ° C./min or more, even if there are various changes in the ceramic material composition, etc., the surface layer of the Al internal electrode can be more reliably applied to the surface layer of Al ₂ O _3. Layers are easily formed.

By firing under the above conditions, the surface Al ₂ O ₃ layer is used for protection of the internal electrode. On the other hand, if the oxidation of the Al internal electrode proceeds to the inside, there arises a problem that the capacitance decreases. However, in the present invention, since flat Al particles are used for the Al internal electrode, oxidation between adjacent Al particles is prevented as much as possible, and as a result, the oxidation of the Al internal electrode does not easily proceed to the inside. Therefore, although the Al ₂ O ₃ layer that is an oxide film exists on the surface layer, the Al ₂ O ₃ abundance ratio as a whole can be minimized and the decrease in capacitance can be minimized. For this reason, multilayer ceramic electronic components having Al internal electrodes using flat Al particles are more advantageous in terms of capacitance than those having Al internal electrodes using spherical Al particles. .

Although the melting point of Al is about 660 ° C., according to the manufacturing method of the present invention, it can be co-fired with ceramic even at a temperature of 660 ° C. or higher. This is considered to be due to the Al ₂ O ₃ layer formed in the surface layer portion of the Al internal electrode. For this reason, a great degree of freedom arises in the material composition design of the ceramic used, and it can be applied to various applications.

The ceramic composition in the multilayer ceramic electronic component of the present invention is not particularly limited. Barium titanate (including those substituted with Ca, Sr, Zr, etc.), lead titanate or lead zirconate titanate, alumina glass ceramic, ferrite, transition element oxide semiconductor ceramic, etc. Various materials can be applied as long as the object of the invention is not impaired.

The multilayer ceramic electronic component of the present invention is not limited to a multilayer ceramic capacitor, and can be applied to various electronic components such as a multilayer piezoelectric element, a multilayer thermistor element, a multilayer chip coil, and a ceramic multilayer substrate.

[Example 1] In this example, in a multilayer ceramic electronic component having an Al internal electrode, the difference between the one using spherical Al particles and the one using flat Al particles is observed.

First, BaTiO ₃ powder and Pb (Ti, Zr) O ₃ powder were prepared as ceramic main components. Further, Bi ₂ O ₃ and CuO powders, and Li ₂ CO ₃ and Bi ₂ O ₃ powders were prepared as subcomponents. These powders were mixed so as to satisfy the content ratios of Samples 1 to 3 in Table 1.

To each of these ceramic raw materials, an ethanol-based organic solvent and a polyvinyl butyral-based binder were added and wet-mixed with a ball mill to obtain a ceramic slurry. This ceramic slurry was formed into a sheet to obtain a ceramic green sheet.

Meanwhile, a powder made of spherical Al particles having an average particle diameter of 1 μm and a powder made of flat Al particles having an average diameter of 10 μm and an average thickness of 0.3 μm were prepared. Each of these Al powders was mixed with an organic vehicle, an organic solvent and the like to obtain an Al paste.

Next, an Al paste was applied on the ceramic green sheet by screen printing to form an Al paste layer. Sample 1 used spherical Al particles, and

samples

2 and 3 used flat Al particles. The ceramic green sheets after the application of the Al paste were laminated so that the sides from which the Al paste layers were drawn were alternated and pressed to obtain a raw laminate.

This raw laminate was heated in the atmosphere at 270 ° C. to remove the binder. Thereafter, the temperature was increased at a rate of temperature increase of 100 ° C./min, and firing was performed at 725 ° C. for 1 minute under an oxygen partial pressure of 2 × 10 ⁻² MPa. An Ag resin paste having an Ag powder and an epoxy resin was applied to both end faces of the obtained laminate and cured at 180 ° C. in the atmosphere, and this was used as an external electrode connected to the internal electrode.

The multilayer ceramic capacitor obtained as described above has a length of 2.0 mm, a width of 1.0 mm, and a thickness of 1.0 mm, a ceramic layer thickness of 50 μm, an internal electrode layer thickness of 5 μm, and an effective number of layers of 5. there were. The area facing the internal electrode per layer was 1.7 × 10 ⁻⁶ m ² .

The electrostatic capacity of the obtained sample was measured under the conditions of 1 Vrms and 1 KHz using an automatic bridge type measuring device. The results are shown in Table 1.

When Sample 1 and Sample 2 were compared, a higher capacitance was obtained with a multilayer ceramic capacitor using flat Al particles than with a multilayer ceramic capacitor using spherical Al particles. Also, in Sample 3 using flat Al particles, a relatively high capacitance was obtained.

Moreover, the cross section by FIB processing was observed by SEM, and the cross-sectional photographs of

Samples

1 and 2 are shown in FIGS. 2 and 3, respectively. Furthermore, in the thin piece processed sample of Sample 2, a cross section near the Al internal electrode was observed by TEM, and an enlarged photograph is shown in FIG.

3 and 4, it can be seen that the Al flat particles yielded a thin Al internal electrode with high continuity.

The multilayer ceramic electronic component of the present invention can be applied to multilayer ceramic capacitors, multilayer piezoelectric elements, multilayer thermistors, multilayer chip coils, ceramic multilayer substrates, and the like.

DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 2 Laminated body 3 Dielectric

ceramic layer

4, 5 Internal electrode 6, 7

End surface

8, 9

External electrode

10, 11

1st plating layer

12, 13 2nd plating layer

Claims

A laminate comprising a plurality of laminated ceramic layers, and a plurality of Al-based internal electrodes formed along the interface between the ceramic layers;
An external electrode formed on the outer surface of the laminate;
A multilayer ceramic electronic component comprising:
A multilayer ceramic electronic component, wherein the internal electrode has Al particles having a flat shape.
The multilayer ceramic electronic component according to claim 1, wherein a surface layer portion of the internal electrode is formed of an Al 2 O 3 layer.
The multilayer ceramic electronic component according to claim 2, wherein the thickness of the Al 2 O 3 layer is 0.25 to 10% of the thickness of the internal electrode.
Preparing a raw laminate comprising a plurality of laminated ceramic green sheets and a plurality of layers containing a metal component mainly composed of Al formed along an interface between the ceramic green sheets;
Firing the raw laminate;
A method for producing a multilayer ceramic electronic component comprising:
The method for producing a multilayer ceramic electronic component, wherein the metal component containing Al as a main component includes Al particles having a flat shape.