KR20110134866A - Multiplayer ceramic capacitor - Google Patents

Abstract

PURPOSE: A multilayer ceramic capacitor is provided to arrange the thickness of an inner electrode in the upper part and lower part of an effective layer thinner than other inner electrodes in the inside of the effective layer, thereby effectively preventing cracking and dielectric breakdown phenomena. CONSTITUTION: An effective layer(20) is arranged by alternatively laminating a dielectric layer(6) and an inner electrode(4). The effective layer is comprised of an outer part(24) and an inner part(22). The thickness of the inner electrode of the outer part is 0.7 to 0.95 times of the thickness of the inner electrode of the inner part. A protection layer(10) is arranged in the lower surface and upper surface of the effective layer. The thickness of the outer part is 0.1 to 0.5 times of the thickness of the protection layer.

Description

Multilayer Ceramic Capacitors {MULTIPLAYER CERAMIC CAPACITOR}

The present invention relates to a multilayer ceramic capacitor capable of stably securing capacitance and preventing cracks and dielectric breakdown due to thermal shock.

In general, a multilayer ceramic capacitor includes a plurality of ceramic dielectric sheets and internal electrodes inserted between the plurality of ceramic dielectric sheets. Such multilayer ceramic capacitors are widely used as capacitive components of various electronic devices because of their small size, high capacitance, and easy mounting on a substrate.

Recently, as electronic products are miniaturized and multifunctional, chip components are also miniaturized and highly functionalized, and thus, multilayer ceramic capacitors are required to have high capacity and large capacity. Therefore, in recent years, multilayer ceramic capacitors having a thickness of at least 2 μm and having a laminated number of at least 500 layers have been manufactured.

However, the thinning and high lamination of the ceramic dielectric layer increases the proportion of the volume occupied by the internal electrode layer, thereby causing cracks or insulation on the ceramic laminate due to thermal shock applied in a circuit board mounting process such as firing and reflow soldering. There is a problem that destruction occurs.

Specifically, cracks are caused by stresses caused by the difference in thermal expansion coefficients of the materials forming the ceramic layer and the internal electrode layer acting on the ceramic laminate, and are particularly generated at both edges of the upper and lower portions of the multilayer ceramic capacitor.

In addition, a stress is generated at the top and bottom of the dielectric material due to the thermal change, and when voltage is applied, dielectric breakdown of the dielectric layer may occur.

An object of the present invention is to provide a multilayer ceramic capacitor that can effectively prevent cracks and dielectric breakdown of a ceramic laminate due to thermal shock while ensuring a stable capacitance.

According to the first technical aspect of the present invention, there is provided an effective layer in which internal electrodes and dielectric layers are alternately stacked, and a protective layer formed by stacking dielectric layers on top and bottom surfaces of the effective layer, wherein the effective layer is disposed in a stacking direction. The outer portion, the inner portion, and the outer portion in order, the thickness of the inner electrode of the outer portion is formed thinner than the thickness of the inner electrode of the inner portion, the thickness of the inner electrode of the outer portion is 0.7 of the thickness of the inner electrode of the inner portion We propose a multilayer ceramic capacitor that is from 0.95 times.

In addition, the thickness of the outer portion proposes a multilayer ceramic capacitor of 0.1 to 0.5 times the thickness of the protective layer.

On the other hand, according to the second technical aspect of the present invention, the internal electrode and the dielectric layer includes an effective layer alternately stacked, and a protective layer formed by laminating a dielectric layer on the upper and lower surfaces of the effective layer, the effective layer is laminated A multilayer ceramic capacitor including a plurality of internal electrodes having an outer portion, an inner portion, and an outer portion in order in a direction, wherein the outer portion has a thickness of 0.7 to 0.95 times the thickness of the inner electrode of the inner portion.

In addition, the thickness of the outer portion including the plurality of internal electrodes proposes a multilayer ceramic capacitor having a thickness of 0.1 to 0.5 times the thickness of the protective layer.

According to a third technical aspect of the present invention, there is provided an effective layer in which internal electrodes and dielectric layers are alternately stacked, and a protective layer formed by stacking dielectric layers on top and bottom surfaces of the effective layer, wherein the effective layer is disposed in a stacking direction. The outer portion is composed of an outer portion, an inner portion, and an outer portion in order, wherein the outer portion includes a plurality of inner electrodes having a thickness of 0.7 to 0.95 times the thickness of the inner electrode of the inner portion, and a thickness of the outer portion including the plurality of inner electrodes. Proposes a multilayer ceramic capacitor that is 0.1 to 0.5 times the thickness of the protective layer.

In the multilayer ceramic capacitor according to the present invention, the thickness of the internal electrodes of the upper and lower effective layers in which the dielectric layers and the internal electrodes are alternately stacked is thinner than other internal electrodes in the effective layer, so that cracks are likely to occur in the upper and lower effective layers. And insulation breakdown can be prevented.

In addition, by controlling the thickness of the inside of the effective layer to form a thinner internal electrode, it is possible to effectively prevent cracks and breakdown while ensuring a stable capacitance.

1 is a perspective view of a multilayer ceramic capacitor according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1;
3 is a cross-sectional view taken along line BB ′ of FIG. 1.

DETAILED DESCRIPTION The following detailed description of the invention refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention, if properly described, is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. Like reference numerals in the drawings refer to the same or similar functions throughout the several aspects.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

1 is a perspective view of a multilayer ceramic capacitor according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a multilayer ceramic capacitor according to an exemplary embodiment of the present invention may include a capacitor body 1 and an external electrode 2.

In the capacitor body 1, a plurality of dielectric layers may be stacked therein, and an internal electrode may be inserted between the plurality of dielectric layers. In this case, the dielectric layer may be formed using barium titanate (Ba ₂ TiO ₃ ), and the internal electrode may be formed using nickel (Ni), tungsten (W), or cobalt (Co).

The external electrode 2 may be formed on both side surfaces of the capacitor body 1. The external electrode 2 may serve as an external terminal by being electrically connected to the internal electrode exposed on the outer surface of the capacitor body 1. In this case, the external electrode 2 may be formed using copper (Cu) or the like.

2 is a cross-sectional view taken along line AA ′ of FIG. 1, and FIG. 3 is a cross-sectional view taken along line B-B ′ of FIG. 1.

2 and 3, a multilayer ceramic capacitor according to an exemplary embodiment of the present invention may include an effective layer 20 in which a dielectric layer 6 and an internal electrode 4 are alternately stacked therein. In addition, the upper and lower surfaces of the effective layer 20 may include a protective layer 10 formed by stacking dielectric layers.

The effective layer 20 is composed of an outer portion 24, an inner portion 22, and an outer portion 24 in order in the stacking direction.

The protective layer 10 may be formed by sequentially stacking a plurality of dielectric layers on the upper and lower surfaces of the effective layer 20 to protect the effective layer 20 from external shocks and the like.

When the internal electrode 4 of the effective layer 20 is formed of nickel (Ni), its thermal expansion coefficient is about 13 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the dielectric layer 6 formed of ceramic is about 8 × 10 ^{−. 6} / ° C. Due to the difference in the coefficient of thermal expansion between the dielectric layer 6 and the internal electrode 4, a stress is applied to the dielectric layer 6 when thermal shock is applied in a process such as firing and reflow soldering to a circuit board. Therefore, a crack may occur in the dielectric layer 6 due to stress during thermal shock, or an insulation breakdown may occur when a voltage is applied while the stress is applied. In particular, the crack and the dielectric breakdown phenomenon is likely to occur in the upper and lower portions of the effective layer 20, that is, the outer portion 24.

Therefore, in the multilayer ceramic capacitor according to the exemplary embodiment of the present invention, as illustrated in FIGS. 2 and 3, the thickness t ₁ of the inner electrode of the outer part 24 of the effective layer 20 is determined by the inside of the inner part 22. By forming a thickness thinner than the thickness t ₂ of the electrode, such cracks and dielectric breakdown can be prevented.

On the other hand, when the thickness of the internal electrode 4 is formed thin, it is highly likely that pores are included in the internal electrode 4, so that the capacitance of the multilayer ceramic capacitor may be reduced. Therefore, as the thickness t ₁ of the inner electrode of the outer part 24 is thinner than the thickness t ₂ of the inner electrode of the inner part 22, the capacitance of the multilayer ceramic capacitor decreases. In addition, as the overall thickness of the outer part 24 forming the thickness of the inner electrode 4 becomes thicker, the capacitance of the multilayer ceramic capacitor is reduced.

It is important to stably secure the capacitance and prevent cracks and dielectric breakdown due to thermal shock, so that the thickness t ₁ of the inner electrode of the outer part 24 is compared to the thickness t ₂ of the inner electrode of the inner part 22. Appropriate numerical values can be set through experiments on how thin it is and how much the overall thickness of the outer part 24 is to be formed in proportion to the thickness of the protective layer 10.

Example Thickness ratio of internal electrode (t ₁ / t ₂ ) Thickness ratio of outer part to protective layer (Y / X) Capacitance
(uF) Thermal shock test
Number of cracks One 1.22 0.3 10.3 23/300 2 1.00 0.3 10.2 11/300 3 0.97 0.3 10.2 5/300 4 0.95 0.3 10.2 0/300 5 0.89 0.3 10.2 0/300 6 0.83 0.3 10.1 0/300 7 0.70 0.3 10.1 0/300 8 0.68 0.3 9.9 0/300 9 0.65 0.3 9.6 0/300

Table 1 shows the results of experiments on cracks and capacitances against thermal shock while varying the ratio (t ₁ / t ₂ ) to the thickness of the internal electrode of the multilayer ceramic capacitor. At this time, the thickness ratio of the outer portion to the protective layer (Y / X, where X is the thickness of the protective layer 10 in the lamination direction, and Y is the thickness of the outer portion 24 in the lamination direction) is constant at 0.3. Implemented.

As a conductive paste for forming the internal electrode 4, nickel (Ni) powder having a particle size of 0.1 to 0.2 um was used, and the nickel powder content was made to be 40 to 50%. The thickness t ₁ of the inner electrode of the outer part 24 of the multilayer ceramic capacitor thus formed was about 0.5 to 0.9 μm, and the thickness t ₂ of the inner electrode of the inner part 22 was about 0.7 to 0.8 μm. In addition, the thermal shock test was made by immersing in a 320 ° C lead bath for 2 seconds.

Referring to Table 1, it can be seen that the number of cracks has decreased since the ratio (t ₁ / t ₂ ) to the thickness of the internal electrode is 0.95 or less, and the capacitance decreases below 0.70.

Therefore, it can be seen that it is appropriate to set the ratio (t ₁ / t ₂ ) to the thickness of the internal electrode to 0.70 to 0.95 in order to stably secure the capacitance and prevent the occurrence of cracks.

Example Thickness ratio of internal electrode (t ₁ / t ₂ ) Thickness ratio of outer part to protective layer (Y / X) Capacitance
(uF) Thermal shock test
Number of cracks One 0.95 0.095 10.2 2/300 2 0.95 0.1 10.2 0/300 3 0.95 0.3 10.2 0/300 4 0.95 0.4 10.1 0/300 5 0.95 0.5 10.0 0/300 6 0.95 0.6 9.8 0/300

Table 2 shows the thickness ratio of the outer portion of the multilayer ceramic capacitor (Y / X, where X is the thickness of the protective layer 10 in the lamination direction, and Y is the thickness of the outer portion 24 in the lamination direction). The table shows the results of experiments on crack and capacitance against thermal shock. At this time, the ratio (t ₁ / t ₂ ) to the thickness of the internal electrode was constantly implemented as 0.95.

As a conductive paste for forming the internal electrode 4, nickel (Ni) powder having a particle size of 0.1 to 0.2 um was used, and the nickel powder content was made to be 40 to 50%. The thickness t ₁ of the inner electrode of the outer part 24 of the multilayer ceramic capacitor thus formed was about 0.5 to 0.9 μm, and the thickness t ₂ of the inner electrode of the inner part 22 was about 0.7 to 0.8 μm. In addition, the thermal shock test was made by immersing in a 320 ° C lead bath for 2 seconds.

Referring to Table 2, when the thickness ratio (Y / X) of the outer portion to the protective layer is less than 0.1, it can be seen that the number of cracks is increased and the insulation breakdown voltage is lowered.

Therefore, it can be seen that it is appropriate to set the thickness ratio (Y / X) of the outer part to the protective layer to 0.1 to 0.5 in order to stably secure the capacitance and to prevent cracking.

Although the present invention has been described by specific embodiments such as specific components and the like, but the embodiments and the drawings are provided to assist in a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations can be made from these descriptions.

Accordingly, the spirit of the present invention should not be limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the appended claims, fall within the scope of the spirit of the present invention. I will say.

1: capacitor body 2: external electrode
4: internal electrode 6: dielectric layer
10: protective layer 20: effective layer
22: inner part 24: outer part

Claims (5)

An effective layer in which internal electrodes and dielectric layers are alternately stacked; And
A protective layer formed by stacking a dielectric layer on top and bottom surfaces of the effective layer; Including;
The effective layer is composed of an outer portion, an inner portion, and an outer portion in order in the stacking direction, and the thickness of the inner electrode of the outer portion is thinner than that of the inner electrode of the inner portion.
The thickness of the inner electrode of the outer portion is a multilayer ceramic capacitor of 0.7 to 0.95 times the thickness of the inner electrode of the inner portion.
The method of claim 1,
The thickness of the outer portion is a multilayer ceramic capacitor of 0.1 to 0.5 times the thickness of the protective layer.
An effective layer in which internal electrodes and dielectric layers are alternately stacked; And
A protective layer formed by stacking a dielectric layer on top and bottom surfaces of the effective layer; Including;
The effective layer is composed of an outer side, an inner side, and an outer side in order in the stacking direction,
And the outer portion includes a plurality of inner electrodes having a thickness of 0.7 to 0.95 times the thickness of the inner electrode of the inner portion.
The method of claim 3,
The thickness of the outer portion including the plurality of internal electrodes is 0.1 to 0.5 times the thickness of the protective layer multilayer ceramic capacitor.
An effective layer in which internal electrodes and dielectric layers are alternately stacked; And
A protective layer formed by stacking a dielectric layer on top and bottom surfaces of the effective layer;
Including;
The effective layer includes an outer portion, an inner portion, and an outer portion in order in the stacking direction, and the outer portion includes a plurality of inner electrodes having a thickness of 0.7 to 0.95 times the thickness of the inner electrode of the inner portion. The thickness of the outer portion including the electrode is a multilayer ceramic capacitor of 0.1 to 0.5 times the thickness of the protective layer.

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