KR100541091B1 - Multilayered ceramic chip capacitor having superior accelerated life of insulation resistration - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic capacitor composed of a nonmetal internal electrode and a reducing resistant dielectric layer which is reoxidized. The multilayer ceramic capacitor is a multilayer ceramic having a first sintered electrode and a second external electrode facing the outer side of the sintered sintered body and the outer layer of the sintered dielectric layer in which a non-metal internal electrode pattern is alternately stacked and reoxidized. The internal electrode pattern is formed in a non-connected state with the first internal electrode 11 and the first internal electrode 11 for capacitance formation in the same layer of the dielectric, so that the diffusion passage of oxygen in the reoxidation process The second internal electrode 21 is formed.

Multilayer Ceramic Capacitor, Internal Electrode, Oxygen Diffusion, Reoxidation Treatment

Description

MULTILAYERED CERAMIC CHIP CAPACITOR HAVING SUPERIOR ACCELERATED LIFE OF INSULATION RESISTRATION}

1 is a cross-sectional view of a multilayer ceramic capacitor having a conventional internal electrode pattern.

2 is a cross-sectional view of a multilayer ceramic capacitor having an internal electrode pattern of the present invention;

3 is an internal electrode pattern of the multilayer ceramic capacitor according to the first embodiment of the present invention,

4 is an internal electrode pattern of the multilayer ceramic capacitor according to the second embodiment of the present invention,

5 is an internal electrode pattern of the multilayer ceramic capacitor according to the third embodiment of the present invention,

6 is an example of a pattern of a printing plate for forming an internal electrode according to the present invention.

The present invention relates to a multilayer ceramic capacitor composed of a non-metal internal electrode and a reducing dielectric layer, and more particularly, to a multilayer ceramic capacitor having an internal electrode, which is an oxygen diffusion path, during the reoxidation process, and thus having an accelerated insulation resistance. It is about.

With the miniaturization of information and communication equipments represented by computer portable telephones, high-density mounting of electronic components has progressed, leading to the demand for miniaturization and large capacity in multilayer ceramic capacitors.

An example of a conventional multilayer ceramic capacitor is shown in FIG. The multilayer ceramic capacitor includes a multilayer sintered body in which dielectric layers 2 having an internal electrode 1 pattern are alternately stacked, and a first external electrode 13 and a second external electrode 23 facing the outer side of the multilayer sintered body. have.

The internal electrode adopts Ag, Pd, which is a precious metal, but uses inexpensive Ni, Cu, or an alloy thereof. Since internal electrodes of nonmetals such as Ni are oxidized when co-fired with dielectric layers in the air, they should be fired in a reducing atmosphere. However, in the reducing component crisis, since the dielectric layer is reduced to lower the specific resistance, a reducing-resistant dielectric magnetic composition such as (Ca, Sr) (Zr, Ti) O ₃ is used.

When the laminated ceramic capacitor of the reduction resistant dielectric self composition is fired in a reducing atmosphere, oxygen vacancies remain in the dielectric after firing. Oxygen vacancies reduce the accelerated life of insulation resistance, resulting in poor reliability. Therefore, the laminated sintered body is calcined in a reducing atmosphere and then reoxidized in a weak oxidation atmosphere.

However, in the same dielectric layer, oxygen diffusion is delayed in the margin region where the internal electrode is not printed as shown in FIG. Oxygen vacancies have a +2 charge in the lattice and are moved to the electrode where the cathode is caught during reliability evaluation or practical use, causing localized semiconductorization. The semiconductor part becomes the main communication path of the leakage current, which lowers the reliability.

An object of the present invention is to solve the deterioration of the acceleration life of the insulation resistance caused by the diffusion delay of oxygen in the multilayer ceramic capacitor subjected to reoxidation.

Laminated ceramic capacitor of the present invention for achieving the above object,

A multilayer ceramic capacitor comprising a laminated sintered body in which a non-metallic internal electrode pattern is formed by alternately stacking and reoxidizing a laminated sintered body and a first external electrode and a second external electrode facing the outer side of the laminated sintered body. The pattern consists of a first internal electrode for capacitive formation and a second internal electrode which is formed in a non-connected state with the first internal electrode in the same layer of the dielectric and becomes a diffusion passage of oxygen in the reoxidation process.

An example of the internal electrode pattern in the multilayer ceramic capacitor of the present invention,

When the first inner electrode is connected to the first outer electrode, the second inner electrode is connected to the second outer electrode that faces the second inner electrode, and the second inner electrode is in a non-connected state with the first inner electrode over the entire width direction of the dielectric layer. It is formed to connect with the second external electrode.

Another example of the internal electrode pattern in the multilayer ceramic capacitor of the present invention,

When the first internal electrode is connected to the first external electrode, the second internal electrode is connected to an opposing second external electrode, and the second internal electrode is disconnected from the first internal electrode and is connected to the first internal electrode. It is formed with the same electrode width and is not connected with the 2nd external electrode in the both ends in the width direction.

Another example of the internal electrode pattern in the multilayer ceramic capacitor of the present invention,

When the first inner electrode is connected to the first outer electrode, the second inner electrode is connected to the opposing second outer electrode, and the second inner electrode is connected to the second outer electrode over the entire width direction of the dielectric layer. The electrode width of the second internal electrode is extended while being reduced in the inward direction of the dielectric to be in a non-connected state with the first internal electrode.

In another example of the internal electrode pattern in the multilayer ceramic capacitor of the present invention, when the first internal electrode is connected to the first external electrode, the second internal electrode is connected to the opposing second external electrode, and the second internal electrode is connected. Is formed in a tea (T) shape.

In the multilayer ceramic capacitor of the present invention, the closest distance t between the first internal electrode and the second internal electrode is represented by the following relationship, 1.0T ≦ t ≦ 4.0T (T is the thickness of the dielectric layer on which the internal electrode is formed). I'm satisfied. In addition, the internal electrode is composed of Ni, Cu, or an alloy thereof.

Hereinafter, the present invention will be described in detail.

The inventors noticed that oxygen diffusion is delayed in the margin region where no internal electrode is formed because oxygen is preferentially diffused through the internal electrode layer in the reoxidation process of the dielectric layer. It is characterized by.

This invention will be described with reference to FIGS. 2 to 6.

As shown in Fig. 2, the multilayer ceramic capacitor of the present invention includes a laminated sintered body in which a dielectric layer 3 having a pattern of internal electrodes is alternately stacked, and an external electrode 3 provided outside the laminated sintered body.

The internal electrode is provided with the first internal electrode 11 for capacitance formation and the second internal electrode 21 for oxygen diffusion passage in the same dielectric layer 2, and the first internal electrode 11 is the first external electrode ( 13, the second inner electrode 21 is connected to the second outer electrode 23. In FIG. The pattern of the first internal electrode 11 and the second internal electrode 21 is rotated by 180 ° for each dielectric layer, and thus the connection with the external electrode is also changed for each dielectric layer. In addition, in the present invention, the length of the first internal electrode 11 is longer than that of the second internal electrode 21.

In the present invention, preferred examples of the printing pattern provided with the second internal electrode 21 for the oxygen diffusion passage are shown in FIGS. 3 to 4.

In FIG. 3A, when the first inner electrode 11 is connected to the first outer electrode, the second inner electrode 21 is formed when the second inner electrode 21 is connected to an opposing second outer electrode. 1 is a case where it is formed in a state in which it is connected to a second external electrode over the entire width direction of the dielectric layer in a non-connected state with the internal electrode 11. Of course, as shown in FIG. 3B, the second inner electrode 21 is formed to have the same electrode width as that of the first inner electrode 11, so that the second inner electrode 21 is not connected to the second outer electrode at both ends in the width direction. Do.

Since the second inner electrode serves as a diffusion passage for oxygen, it is preferable that the second inner electrode is formed over the entire width direction of the dielectric layer. In the case where the second internal electrodes are not formed at both ends of the width as shown in FIG. 3 (b), the ratio of direct bonding between molded sheets during stacking increases, so that bonding strength between dielectric layers is enhanced. This is because the junction between the dielectric layer and the internal electrode is not good.

In FIG. 4, when the first inner electrode 11 is connected to the first outer electrode, the second inner electrode 21 is connected to an opposing second outer electrode, and the second inner electrode 21 is a dielectric layer. Is connected to the second external electrode 23 over the entire width direction of the second electrode, and the electrode width of the second internal electrode 21 is reduced as it extends in the inward direction of the dielectric and is not connected to the first internal electrode 11. This is the case. In this case, it is possible to increase the bonding strength between the external electrode and the internal electrode while increasing the bonding strength between sheets while ensuring a wide diffusion path of oxygen.

In FIG. 5, when the first inner electrode 11 is connected to the first outer electrode, the second inner electrode 21 is connected to an opposing second outer electrode, and the second inner electrode 21 is a tee (T). It is a case where it is formed in the When the second internal electrode 21 is formed in a tee shape, the second internal electrode 21 may be modified as shown in FIGS. 5A to 5D. That is, the case where the head of the tee T is adjacent to the first internal electrode 11 (FIGS. 5A and B), and the case where the head of the tee T is adjacent to the external electrode (FIGS. 5C and D). At this time, there is a case where the head of the tee T is formed over the entire width direction of the dielectric layer (FIGS. 5A and C) and not formed at both ends of the dielectric layer in the width direction (FIGS. 5B and D).

In the present invention, the closest distance t between the first internal electrode and the second internal electrode satisfies the following relationship, 1.0T ≦ t ≦ 4.0T (T is the thickness of the dielectric layer on which the internal electrode is formed). If the closest distance (t) is less than 1.0T, the distance between the first internal electrode and the second internal electrode is too small, which may shorten the lifespan, and in excess of 4,0T, the dielectric may be excessive to diffuse oxygen. The region can be formed and short lived.

An example of a method of forming the internal electrode pattern of the present invention will be described with reference to FIG. 6. 6 is a pattern diagram of a printing plate for screen printing a pattern of an internal electrode of the present invention on a dielectric layer. Using the printing plate of the pattern shown in FIG. 6 on the dielectric layer, the metal paste which mainly consists of nonmetallic electroconductive powders, such as Ni, is formed as an internal electrode by the screen printing method. The dielectric layers thus obtained are laminated, the laminate is cut and separated, and then a multilayer ceramic capacitor is manufactured according to a conventional method.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

In order to form the internal electrode patterns as shown in FIGS. 3 and 4 on the X7R dielectric, Ni internal electrodes were printed on the molded sheet using a screen pattern having internal electrodes repeated, and a plurality of printed sheets were stacked and pressed. The laminate laminated as described above was cut to a certain size, debindered, and the molded body was sintered at 1200 to 1350 ° C. in an H ₂ -H ₂ ON ₂ atmosphere. After sintering, it was reoxidized. An external electrode mainly composed of copper was formed on both ends of the sintered chip to manufacture a laminated ceramic capacitor. The obtained chip samples were 2.0 mm x 1.2 mm x 1.0 mm in size, composed of 6um of dielectric layers and 10 layers.

The accelerated life of the insulation resistance for the multilayer ceramic capacitor was measured as the average life time by measuring the time until the resistance became less than the reference under the condition of 150 ° C. and 20 V / um. The measurement results are shown in Table 1.

Sample classification Life expectancy (hr) Conventional multilayer ceramic capacitor (FIG. 1) 23 Multilayer Ceramic Capacitor with Internal Electrode Pattern of FIG. > 72 Multilayer Ceramic Capacitor with Internal Electrode Pattern of FIG. > 72 Multilayer Ceramic Capacitor with Internal Electrode Pattern of FIG. > 72

As shown in Table 1, it can be seen that the average life span is improved when the internal electrode 21 for diffusion path of oxygen is formed in the internal electrode pattern.

Example 2

In order to form an internal electrode pattern as shown in FIG. 3A on the X7R dielectric, a Ni internal electrode was printed on a molded sheet using a screen pattern in which the internal electrodes were repeated, and a plurality of printed sheets were stacked and pressed. The laminate laminated as described above was cut to a certain size, debindered, and the molded body was sintered at 1200 to 1350 ° C. in an H ₂ -H ₂ ON ₂ atmosphere. It was then reprocessed. An external electrode mainly composed of copper was formed on both ends of the sintered chip to manufacture a laminated ceramic capacitor. The obtained chip samples were 2.0 mm x 1.2 mm x 1.0 mm in size, composed of 6um of dielectric layers and 10 layers.

The accelerated life of the insulation resistance for the multilayer ceramic capacitor was measured as the average life time by measuring the time until the resistance became less than the reference under the condition of 150 ° C. and 20 V / um. The measurement results are shown in Table 2.

Nearest distance t between the first internal electrode and the second internal electrode t Life expectancy (hr) t = 0.5T 2 t = 1.0T > 72 t = 2.0T > 72 t = 4.0T > 72 t = 6.0T 39

As shown in Table 2, the closest distance t between the first (11) internal electrode and the second internal electrode 21 satisfies 1.0T to 4.0T with respect to the dielectric layer thickness T on which the internal electrode is formed. The average life expectancy was highest.

According to the present invention, the average lifetime can be increased by at least three times in the accelerated life evaluation by reinforcing a weak reliability in the margin of the multilayer ceramic capacitor made of a non-metal internal electrode such as nickel or copper. In addition, since the unprinted layer of the margin can be compensated, there is a useful effect to increase the durability and reliability of the chip.

Claims (7)

Laminated ceramics having alternately laminated and reoxidized resistive dielectric layers having non-metal internal electrode patterns formed thereon, and laminated ceramics provided with a first external electrode 13 and a second external electrode 23 facing the outer portion of the laminated sintered body. And the internal electrode pattern is formed over the entire width direction of the dielectric layer in a non-connected state with the first internal electrode 11 and the first internal electrode 11 for capacitance formation in the same layer of the dielectric material. A multilayer ceramic capacitor having an accelerated life of insulation resistance composed of a second internal electrode 21 serving as an oxygen diffusion passage in a chemical treatment. 2. The dielectric layer according to claim 1, wherein the closest distance t between the first internal electrode 11 and the second internal electrode 21 is as follows: 1.0T ≦ t ≦ 4.0T (where T is an internal electrode formed thereon). Multilayer ceramic capacitors having excellent acceleration life of insulation resistance. 2. The multilayer ceramic capacitor according to claim 1, wherein the nonmetal is Ni or Cu. delete delete The second external electrode 23 according to any one of claims 1 to 3, wherein the second internal electrode 21 faces the second internal electrode 21 when the first internal electrode 11 is connected to the first external electrode 13. Access The second internal electrode 21 is connected to the second external electrode 23, and the electrode width of the second internal electrode 21 is reduced in the inward direction of the dielectric layer. Ceramic capacitors. The second external electrode 23 according to any one of claims 1 to 3, wherein the second internal electrode 21 faces the second internal electrode 21 when the first internal electrode 11 is connected to the first external electrode 13. Access The second internal electrode 21 is a multilayer ceramic capacitor having excellent acceleration life of the insulation resistance, characterized in that formed in the T-shaped (T) type.

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