JP2002299147A - Laminated ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated ceramic capacitor, in which a bonding property to a terminal electrode is improved and whose capacitance accuracy is superior. SOLUTION: First dummy-electrodes 5a to 5d connected to a first terminal electrode 7 are situated between dielectric layers adjacent to first internal electrodes 3a to 3c, and they are formed in positions corresponding to both ends, in the width direction in connection-side end parts of at least the internal electrodes. Second dummy-electrodes 6a to 6d, connected to a second terminal electrode 8, are situated between dielectric layers adjacent to second internal electrodes 4a to 4c, and they are formed at positions corresponding to both ends in the width direction of connection-side end parts of at least the internal electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic capacitor, and more particularly to a multilayer ceramic capacitor having excellent capacitance accuracy.

[0002]

2. Description of the Related Art A multilayer ceramic capacitor generally has a ceramic dielectric layer 22 and internal electrodes 23 and 24 alternately stacked as shown in FIG. 3 as a sectional view in the stacking direction. The other end is formed so as to be alternately exposed on both sides of the laminate 20, and the internal electrodes 23, 23 (and 24, 24) having the same potential are connected to the terminal electrodes 27 (or 28) on the side surface of the laminate 20. ). The outer surface of the terminal electrode is also used for connection and fixing to an external circuit.

[0003] Such a multilayer ceramic capacitor includes:
It is manufactured through the following steps. First, a slurry containing a ceramic powder to be a dielectric layer and an organic binder is formed into a sheet, and a paste containing metal powder is printed on the surface of the obtained green sheet in an internal electrode pattern.
A plurality of green sheets printed in this manner are stacked, and an unprinted green sheet is stacked on the uppermost surface and / or lowermost surface. Then, after cutting in the laminating direction so as to have a predetermined size, the remaining binder is degreased and subsequently fired. Then, by applying and baking a metal powder-containing paste to be a terminal electrode on the side surface of the laminate,
It becomes a multilayer ceramic capacitor.

[0004]

In the above degreasing step,
The surface oxygen of the metal powder oxidized in the previous process such as printing is also reduced by the carbon in the remaining binder, and is taken into the atmosphere at the same time as the binder.

[0005] However, if the amount of the remaining binder is large relative to the internal electrodes, oxygen on the surface of the metal powder is excessively deprived.
According to the study results of the inventors, the phenomenon is particularly remarkable in a portion of the internal electrode exposed from the side surface of the laminate, oxygen in the exposed portion is deprived, and the portion is over-sintered. As a result, it was found that the bondability with the terminal electrode was degraded, resulting in a defect such as loss of capacitance. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a multilayer ceramic capacitor which has improved jointability with a terminal electrode and has excellent capacitance accuracy.

[0006]

In order to solve the problem, the present invention is directed to a first internal electrode having first and second internal electrodes having different potentials alternately stacked with a ceramic dielectric layer interposed therebetween. In a multilayer ceramic capacitor in which a first terminal electrode connecting them is formed on one side surface of the laminate and a second terminal electrode connecting the second internal electrodes is formed on the other side surface, The first pseudo electrode connected to the first terminal electrode is a dielectric layer adjacent to the dielectric layer on which the first internal electrode is formed, and at least a connection side of the internal electrode to the first terminal electrode. A second pseudo electrode formed at a position corresponding to both ends in the width direction of the end and connected to the second terminal electrode is a dielectric layer adjacent to the dielectric layer on which the second internal electrode is formed. And at least a first of its internal electrodes Characterized in that it is formed at a position corresponding to both widthwise ends of the connecting end portion of a child electrodes.

[0007] Since the pseudo electrode is formed in this manner, oxygen that is about to be deprived during degreasing is also supplied from the pseudo electrode. Accordingly, excessive deprivation of oxygen from the internal electrodes is prevented, and the bondability between the internal electrodes and the terminal electrodes is improved. On the other hand, the pseudo electrode is connected to a terminal electrode on the same side as the internal electrode immediately above or below it and has the same potential as the internal electrode, and therefore does not originally function as a capacitor electrode of the capacitor. Therefore, the capacitance value is not affected in design. Therefore, as a result of the improvement of the joining property between the internal electrode and the terminal electrode, the capacitance accuracy is improved by the amount corresponding to the prevention of the capacitance loss.

The materials used for the pseudo electrode include:
A metal having the same or higher ionization tendency than the material used for the internal electrode is preferable. This is because the metal oxide formed on the surface of the pseudo electrode made of such a metal by oxidation in the atmosphere or the like releases oxygen more easily than the internal electrode.

Further, the first pseudo electrode is provided between all the dielectric layers adjacent to the dielectric layer on which the first internal electrode is formed, and between the dielectric layer on which the second internal electrode is formed. It is preferable that the second pseudo electrode is formed between all adjacent dielectric layers. This is because all bonding between the internal electrode and the terminal electrode is improved.

The distance between the first or second pseudo electrode and the first or second internal electrode in the stacking direction is A,
Alternatively, when the length from the connection side end to the non-connection side end of the second pseudo electrode is B, it is preferable that A is 30 μm or less and B is 5 A or more. When A is 30 μm or less,
This is because part of the oxygen that is about to be deprived from the internal electrode is efficiently replaced by oxygen from the pseudo electrode, and is sufficiently replaced when B is 5 A or more.

Furthermore, it is preferable that the first or second pseudo electrode is formed separately at positions corresponding to both ends in the width direction of the first or second internal electrode. This is because the surface oxygen at both end portions in the width direction among the internal electrodes is most easily deprived, and by providing the pseudo electrode only at a position corresponding to that portion, the material used for the pseudo electrode can be saved. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1 FIG. 1 is a sectional view in the lamination direction showing an embodiment of a multilayer ceramic capacitor according to the present invention. The multilayer ceramic capacitor 1 has a large number (9 in the drawing, for convenience) of dielectric layers 2a to 2c.
2i are laminated, and the first internal electrodes 3a-3
c, second internal electrodes 4a to 4c, first pseudo electrodes 5a to 5c
The laminate 10 has a laminated structure in which 5d or the second pseudo electrodes 6a to 6d are formed. The first terminal electrode 7 is formed on one side of the laminated body 10 and the second terminal electrode is formed on the other side.

The internal electrodes 3a to 3c are provided every other one of the eight dielectric layers starting from between the dielectric layers 2c and 2d, and are connected to the terminal electrode 7 on one side of the laminated body 10,
It extends long from there to the other side. The other internal electrode 4
a to 4c are provided alternately and in reverse directions with the internal electrodes 3a to 3c. No internal electrode is formed between the lowermost dielectric layers 2a and 2b and between the uppermost dielectric layers 2h and 2i.

In addition, the pseudo electrodes 5a to 5d are
b and 2c, and alternately with the internal electrodes 3a to 3c until reaching between the dielectric layers 2h and 2i.
If any one of the internal electrodes 4a to 4c is present in the same plane, it is formed so as to overlap a connection portion between the terminal electrodes 7a and 3c and a predetermined insulating region. The other pseudo electrodes 6a to 6d also have the dielectric layers 2a and 2b.
Between the dielectric layers 2g and 2h and alternately with the internal electrodes 4a to 4c and in plan view.
If any one of the internal electrodes 3a to 3c is present in the same plane, it is formed so as to overlap a connection portion with the terminal electrode 8 of c.

The dielectric layer is mainly composed of a ceramic dielectric material such as barium titanate. Each of the internal electrode, the pseudo electrode, and the terminal electrode is made of nickel, copper, or an alloy thereof. However, the relationship between the pseudo electrode and the internal electrode is preferably selected from the viewpoint of the oxygen supply capability during degreasing so that the ionization tendency of the metal forming the pseudo electrode is not lower than that of the metal forming the internal electrode. For example, when the internal electrode is made of nickel, the pseudo electrode may be formed of magnesium or chromium oxide.

The multilayer ceramic capacitor 1 is manufactured through the following steps. First, a slurry containing a ceramic powder to be a dielectric layer and an organic binder is formed into a sheet, and a paste containing a metal powder is printed on the surface of the obtained green sheet in an internal electrode pattern and a pseudo electrode pattern. Eight green sheets printed in this manner are stacked, and one unprinted green sheet is stacked on the uppermost surface. Then, after cutting in the laminating direction so as to have a predetermined size, the remaining binder is degreased and subsequently fired. Then, by applying and baking a metal powder-containing paste to be a terminal electrode on the side surface of the laminate,
It becomes a multilayer ceramic capacitor.

In the multilayer ceramic capacitor 1,
Since pseudo electrodes 5a to 5d are formed so as to sandwich each connection portion of internal electrodes 3a to 3c with terminal electrode 7 from above and below, oxygen which is about to be deprived during degreasing is reduced to pseudo electrodes 5a to 5d.
It is also supplied from 5d. Accordingly, excessive deprivation of oxygen from the internal electrodes 3a to 3c is prevented, and the bonding between the internal electrodes and the terminal electrodes 7 is improved. Internal electrode 4
The same applies to the bondability between a to 4c and the terminal electrode 8. Since the pseudo electrodes 5a to 5d are connected to the terminal electrode 7 and have the same potential as the internal electrodes 3a to 3c immediately above or below the terminal electrodes 7, they do not form a capacitance component with the internal electrodes 3a to 3c. Therefore, the capacitance value is not affected in design. The same applies to the pseudo electrodes 6a to 6d. Therefore, as a result of the improvement of the joining property between the internal electrode and the terminal electrode, the capacitance accuracy is improved by the amount corresponding to the prevention of the capacitance loss.

Embodiment 2 FIG. 2 is a plan view showing a dielectric layer used in a multilayer ceramic capacitor according to a second embodiment of the present invention. In the first embodiment, the pseudo electrode is formed so as to overlap the entire connection portion between the internal electrode and the terminal electrode in a plan view. In the second embodiment, the pseudo electrode is formed separately at both ends in the width direction of the connection portion.

That is, the first surface of the dielectric layer 12 shown in FIG.
Are formed starting from one end connected to a first terminal electrode (not shown) and extending to near the other end. From the other end, pseudo electrodes 16 and 16 'connected to a second terminal electrode (not shown) are formed up to a position separating the internal electrode 13 from a predetermined insulating region. Pseudo electrode 1
6 and the pseudo electrode 16 ′ are separately arranged at locations corresponding to both ends in the width direction of the internal electrode 13.

A dielectric layer having the same shape and the same quality as the dielectric layer 12 is stacked immediately above the dielectric layer 12. However, the first internal electrode 13 and the pseudo electrodes 16, 16 'are provided on the main surface of the dielectric layer.
Are rotated 180 degrees in plan view to form a second internal electrode and a pseudo electrode. Since the surface oxygen of the internal electrode is most easily deprived during degreasing at both ends of the connection portion with the terminal electrode, the separated pseudo electrodes 16, 16 ′ are separated.
Deoxygenation of the internal electrode is sufficiently prevented by the oxygen supplied from. Moreover, the material consumed for the pseudo electrode can be saved.

[0021]

EXAMPLES Example 1 A multilayer ceramic capacitor having a shape shown in FIG. 1 and a target capacitance value of 10 nF having the following specifications was manufactured and evaluated.

[Specifications] Size in plan view: 3.2 × 1.6 mm Dielectric layer: dielectric constant 2700, total number 19, thickness 40 μm Internal electrode: nickel, total number 8 of first and second internal electrodes Pseudo-electrode: nickel, total number of first and second pseudo-electrodes 10
Sheet distance C: 30 μm

[Evaluation] A capacity loss of 20% or more lower than the target capacity value was determined as a capacity loss, and a capacity loss occurrence rate was calculated from 10,000 measured values. Table 1 shows the evaluation results. The interval A is the interval between the internal electrode and the pseudo electrodes immediately above and below the internal electrode, and the length B
Is the length from the connection end to the non-connection end of the pseudo electrode,
The occurrence rate P indicates the occurrence rate of capacity loss.

[0024]

[Table 1] Note) No. 1 is a case where no pseudo electrode was formed.

As can be seen from Table 1, it is clear that the provision of the pseudo electrode prevents the loss of capacitance. Moreover, it was also found that when A is 30 μm or less and B is 5 times or more than A, the loss of capacity is most effectively prevented.

Example 2 Example 1 was repeated except that the material of the pseudo electrode was changed to that shown in Table 2. A multilayer ceramic capacitor having the same shape and the same quality as that of No. 9 was manufactured, and the rate of occurrence of capacity loss was measured. Table 2 shows the measurement results.

[0027]

[Table 2]

As can be seen from Table 2, the material of the pseudo electrode is Mg and C which have a higher ionization tendency than that of the internal electrode.
In the case of r, the capacity loss occurrence rate was small, and in the case of Ag and Pd, which have a small ionization tendency, the capacity loss occurrence rate was relatively large. In the case of Co, since the ionization tendency is equal to that of Ni, it is recognized that the rate of occurrence of capacity loss is similar.

[0029]

As described above, in the multilayer ceramic capacitor of the present invention, since the pseudo electrode is provided between the dielectric layers immediately above or immediately below the connection side end of the internal electrode, deoxygenation of the internal electrode is reduced. As a result, the bonding accuracy with the terminal electrode is improved, so that the capacitance accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view in the lamination direction showing a multilayer ceramic capacitor of a first embodiment.

FIG. 2 is a plan view showing a dielectric layer used in the multilayer ceramic capacitor of Embodiment 2.

FIG. 3 is a sectional view in the lamination direction showing a conventional multilayer ceramic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 2a-2i, 12,22 Dielectric layer 3a-3c, 13,23 1st internal electrode 4a-4c, 24 2nd internal electrode 5a-5d 1st pseudo electrode 6a-6d, 16, 16 'Second pseudo electrode 7,27 First terminal electrode 8,28 Second terminal electrode 10,20 Stack

Claims (4)

[Claims] A first and a second internal electrode having different potentials are alternately laminated with a ceramic dielectric layer interposed therebetween, and a first terminal electrode connecting the first internal electrodes is formed on one side of the laminated body. And a second terminal electrode connecting the second internal electrodes to each other is formed on the other side surface, wherein the first pseudo electrode connected to the first terminal electrode is: A first internal electrode formed between adjacent dielectric layers and a dielectric layer adjacent to the dielectric layer, and formed at positions corresponding to at least both ends in the width direction of the connection side end of the internal electrode with the first terminal electrode; The second pseudo electrode connected to the second terminal electrode is located between the dielectric layer on which the second internal electrode is formed and the adjacent dielectric layer, and at least the internal electrode and the first terminal electrode are connected to each other. Positions corresponding to both ends in the width direction of the connection side end Multilayer ceramic capacitor, characterized in that it is formed. 2. The method according to claim 1, wherein the first pseudo electrode is provided between all of the dielectric layers adjacent to the dielectric layer on which the first internal electrode is formed, and the dielectric layer on which the second internal electrode is formed. 2. The multilayer ceramic capacitor according to claim 1, wherein said second pseudo electrode is formed between all adjacent dielectric layers. 3. The distance between the first or second pseudo electrode and the first or second internal electrode in the laminating direction is A, and the connection end of the first or second pseudo electrode to the non-connection side. 3. The multilayer ceramic capacitor according to claim 1, wherein when the length up to the end is B, A is 30 μm or less and B is 5 A or more. 4. 4. The method according to claim 1, wherein the first or second pseudo electrode comprises the first or second pseudo electrode.
4. The multilayer ceramic capacitor according to claim 1, wherein the multilayer ceramic capacitor is formed separately at positions corresponding to both ends in the width direction of the second internal electrode. 5.