JPH11111553A - Laminated ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated ceramic capacitor which can improve electrostatic capacity, prevent deterioration of dielectric characteristic, restrains cracks during a surface-mounting step, and improve the reliability of capacitor. SOLUTION: A capacitor body C comprises an effective laminate A, which is formed by alternately laminating a first conductor layer 12 having an oxidized region on one end and a second conductor layer 13 having an oxidized region on the other end with a dielectric layer 11 (11a, 11b) in between, and a non-effective laminate B which is formed by alternately laminating a third conductor layer 14 having an oxidized are on both ends and a dielectric layer. Furthermore the dielectric layer 11 of the non-effective laminate B is made to be smaller by just 4-10×10<-7> / deg.C in coefficient of thermal expansion than that of the effective laminate A, and a ratio of the thickness of the non-effective laminate B to that of the capacitor body C is set to 2.5 to 25%.

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 an outer peripheral portion of an internal electrode except for a portion electrically connected to an external electrode, which is electrically insulated by a metal oxide forming the internal electrode. To a laminated ceramic capacitor.

[0002]

2. Description of the Related Art Conventionally, as a laminated ceramic capacitor, a dielectric layer and one kind of internal electrode layer are alternately laminated, and a part of the internal electrode layer is alternately exposed at a different place on the surface of the laminated body. The structure is such that a terminal electrode is formed in the portion.

Hereinafter, a general method for manufacturing such a multilayer ceramic capacitor will be described. First, a ceramic slurry in which dielectric ceramic powder is dispersed in an organic binder is formed into a sheet to form a ceramic green sheet, and an internal electrode pattern is printed on the ceramic green sheet with a conductive paste by a screen printing method or the like. I do. Then, the ceramic green sheets on which the internal electrode patterns are printed are stacked, and a plurality of ceramic green sheets on which the internal electrode patterns are not printed are stacked on both sides thereof.

[0004] The laminate thus obtained is cut into chips in such a manner that the internal electrodes are exposed at the end faces, and the chips are fired. And by polishing this sintered laminate,
A desired multilayer chip capacitor has been manufactured by exposing an internal electrode to the end face, further applying a conductive paste to the end face, and baking this to form an external electrode.

[0005] As another method of manufacturing a multilayer ceramic capacitor, there is a manufacturing method in which a conductive paste is applied in advance to the end portion of a ceramic laminate before firing, and firing is performed simultaneously. Further, as a method for obtaining a laminate, a so-called printing method in which a ceramic paste and a conductive paste are alternately printed is used in addition to a so-called sheet method using ceramic green sheets.

By the way, such a multilayer capacitor is
In recent years, there has been a demand for large capacity as well as miniaturization. In order to meet this demand, the dielectric ceramic layers are made thinner to enable a higher lamination. However, when the number of laminations increases, the difference in lamination thickness between the portion where the internal electrodes overlap via the ceramic layer inside the laminate and the other margin portion increases due to the thickness of the internal electrodes. When the side margin is narrowed in order to obtain a large capacity, the adhesion between the ceramics located above and below the internal electrode is impaired, and delamination tends to occur.

As a means for solving such a problem,
For example, Japanese Unexamined Patent Publication No. Hei 3-82005 proposes a multilayer ceramic capacitor in which the side ends of internal electrodes are oxidized. FIG. 5 is a cross-sectional view of each layer (odd layer, even layer) of the internal electrode layer of the multilayer ceramic capacitor.
According to the structure of this capacitor, since the side edges of the internal electrode layer 1 are oxidized to form the oxide 2, the internal electrode layer 1 and the dielectric layers located above and below the internal electrode layer 1 are strongly bonded to each other. Lamination is suppressed and a high capacity capacitor is obtained. In the drawing, reference numeral 6 indicates an external electrode, and reference numeral 8 indicates an end margin area.

Further, for example, Japanese Unexamined Patent Publication No. Hei. 8-180332 discloses a multilayer ceramic capacitor having a non-effective laminated body in which a conductor layer having the same composition as an internal electrode layer not electrically connected to an external electrode is formed. ing. According to this, the difference in firing shrinkage between the effective laminate in which the internal electrode layers are laminated and the other ineffective laminate is reduced, the occurrence of delamination is suppressed, and a highly reliable multilayer ceramic capacitor is obtained. It has been.

[0009]

In a multilayer ceramic capacitor, one end of an internal electrode layer is connected to an external electrode and the other end is insulated from the external electrode. In the multilayer ceramic capacitor thus manufactured, as shown in FIG. 5, the internal electrode forming area is controlled by a printing pattern so that the other end of the internal electrode layer 1 is not connected to the external electrode 6, so that a so-called end margin region 8 is formed. ing. For this reason, in order to prevent short circuit and delamination due to printing accuracy, it is necessary to form a large end margin region 8, and there is a limit in increasing the effective electrode area.

When the dielectric layer is made thinner and more highly laminated using this technique, the difference in the laminated thickness between the portion where the internal electrode 1 overlaps and the other end margin region 8 becomes large, There is still a problem that distortion due to the thickness difference is large.

In the multilayer ceramic capacitor disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-180332, a conductor layer is formed inside an ineffective laminate. For this reason, in order to prevent the conductor layer from being exposed due to printing accuracy, it is necessary to form a large end margin region and a side margin region, and the lamination of the portion where the conductor layer overlaps and the other end and side margin regions There is a problem that the difference in thickness is larger than that in which the conductor layer is not formed, and the strain due to the difference in thickness is large.

Further, in any of the above techniques, the internal stress generated in the capacitor increases due to the difference in the shrinkage rate and the coefficient of thermal expansion during firing of the metal and ceramic contained in the internal electrode layer, and the distortion increases. Become. Due to this distortion, even if the thickness of the dielectric layer is the same, the dielectric characteristics are deteriorated due to an increase in the number of stacked layers, and thermal stress and mechanical stress generated in the surface mounting process, as well as cracks in the capacitor due to thermal shock, etc. There is a problem that causes a decrease in sex.

The present invention solves the above-mentioned conventional problems, increases the effective electrode area to improve the capacitance, and reduces the thickness of the dielectric layer.
It is an object of the present invention to provide a multilayer ceramic capacitor capable of preventing deterioration of dielectric properties due to high stacking, suppressing cracks in a surface mounting process, and improving reliability as a capacitor.

[0014]

Means for Solving the Problems As a result of diligent studies on the above problems, the present inventors have found that the internal electrode layers in the effective laminated body of the multilayer ceramic capacitor are formed of two types of internal electrode layer paste mainly composed of different metals. When the portion of the internal electrode layer in contact with the external electrode is electrically insulated by a metal oxide constituting the internal electrode layer every other layer, the effective electrode area can be increased, Knowing that there is no thickness difference due to the location of the capacitor because the internal electrode region is formed on the entire surface, furthermore, in the ineffective laminate where the internal electrode layer is not formed, the same composition as the base metal part of the internal electrode layer By forming the conductor layer over the entire surface, it has been found that the difference in shrinkage between the effective laminate and the ineffective laminate during firing can be reduced, and furthermore, the dielectric layer of the ineffective laminate has 4~10 × 10 ^-7 / ℃ only smaller than the expansion coefficient of the thermal expansion coefficient of the dielectric layer of the effective stack,
In addition, by setting the ratio of the thickness of the non-effective laminate to the entire thickness to be 2.5 to 25%, the metal and ceramic contained in the internal electrode layer may have different shrinkage rates and thermal expansion coefficients during firing. The present inventors have found that the internal stress generated in the capacitor can be reduced, and have reached the present invention.

That is, a multilayer ceramic capacitor according to the present invention is a multilayer ceramic capacitor comprising a capacitor body and a pair of external electrodes disposed at both ends of the capacitor body, wherein the capacitor body has an oxidized region at one end. And a second conductor layer having an oxidized region on the other end side alternately laminated with a dielectric layer interposed therebetween, and disposed on both sides of the effective laminate, respectively. And
A third conductor layer having oxidized regions at both ends and a non-effective laminate formed by alternately laminating dielectric layers,
The first conductor layer of the effective laminate is connected to one external electrode, the second conductor layer is connected to the other external electrode, and the coefficient of thermal expansion of the dielectric layer of the non-effective laminate is determined by the effective laminate. Wherein the coefficient of thermal expansion of the dielectric layer is smaller by 4 to 10 × 10 ⁻⁷ / ° C., and the ratio of the thickness of the ineffective laminate to the thickness of the capacitor body is 2.5 to 25%. And

Here, the first conductor layer and the second conductor layer of the effective laminated body may be composed of a noble metal portion mainly containing a noble metal and a base metal portion mainly containing a metal other than the noble metal. desirable. Further, the third conductor layer of the ineffective laminate has a main component of a metal other than the noble metal, that is, the third conductor layer has the same composition as the base metal portion. The number of conductor layers is one or more.

[0017]

The multilayer ceramic capacitor of the present invention has an internal electrode layer in which a first conductive layer and a second conductive layer of internal electrode layers are formed with a dielectric layer interposed therebetween, and are electrically connected to external electrodes. Except for one end portion of the inner electrode layer, the outer peripheral portion of the internal electrode layer is oxidized and the oxide is formed, so that it can be electrically insulated from the outside and insulated between the other end of the internal electrode and the external electrode. The distance (end margin) can be minimized, whereby the effective electrode area can be increased, and the capacitance can be increased.

That is, in the multilayer ceramic capacitor disclosed in Japanese Patent Laid-Open Publication No. Hei 3-82005, the internal electrode formation area is controlled by the printing pattern so that the other end of the internal electrode is not connected to the external electrode. Although a large end margin area had to be formed, in the present invention, it is possible to insulate the external electrode by oxidizing the end of the internal electrode layer without controlling the printing pattern for forming the internal electrode layer. Therefore, the effective electrode area can be increased.

Further, in the multilayer ceramic capacitor disclosed in Japanese Patent Application Laid-Open No. 8-181332, since the conductor layer is formed inside the non-effective laminate, a large end and a large end are required to prevent the conductor layer from being exposed due to printing accuracy. Although it was necessary to form the side margin region, in the present invention, without controlling the printing pattern for forming the internal electrode layer, it is possible to insulate the external electrode by oxidizing the end of the internal electrode layer, The difference in shrinkage during sintering between the effective laminate and the non-effective laminate can be further reduced.

Further, since the area of the internal electrode and the conductor layer formed between the dielectric layers is the same as the area of the dielectric layer,
There is no thickness difference depending on the location of the capacitor. Thereby, it is possible to prevent the occurrence of delamination due to the internal stress caused by the thickness difference.

Further, the internal electrode layer is composed of a noble metal region mainly composed of palladium formed on the side electrically connected to the external electrode and another base metal region mainly composed of nickel, for example. When manufacturing the capacitor body, a region mainly composed of palladium is formed at one end of the internal electrode layer so as to be electrically connectable to an external electrode, and a region mainly composed of a base metal is formed in other portions. You.

Therefore, by oxidizing the capacitor body, the outer peripheral portion of the region containing the base metal as a main component is oxidized to form an oxide of the base metal. One end and the external electrode are electrically connected, the other end of the internal electrode layer is insulated from the external electrode, and the side surface of the internal electrode layer is oxidized and insulated from the outside. become.

Further, in the multilayer ceramic capacitor of the present invention, the coefficient of thermal expansion of the dielectric layer of the non-effective laminated body is smaller than the coefficient of thermal expansion of the dielectric layer of the effective laminated body by a predetermined amount, and the non-effective laminated body has a non-effective thickness. Since the thickness ratio of the effective laminate is set to 2.5 to 25%, tensile stress is accumulated in the effective laminate and compressive stress is accumulated in the non-effective laminate during the cooling process after sintering. The dielectric ceramic layers of the laminate can exhibit the original characteristics.

That is, for example, as shown in FIG. 8, when a pair of external electrodes 6 of the multilayer ceramic capacitor of the present invention are mounted on a substrate 17 made of glass epoxy or the like with copper wiring by solder 18, The tensile stress due to thermal stress, mechanical stress, thermal shock (due to bending stress applied to the board, thermal load during soldering, etc.) generated during the mounting process acts on the capacitor body during this period. The stress is absorbed by the compressive stress of the ineffective laminate, and as a result, no stress is generated between the ineffective laminate and the effective laminate, thereby preventing cracks from occurring.

When the width and thickness of the multilayer ceramic capacitor are the same, it is difficult to distinguish the mounting direction. However, since the corner where the stress is concentrated is an ineffective laminate having the specified thermal expansion coefficient, Can absorb most of the tensile stress.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing an example of the multilayer ceramic capacitor C1 of the present invention.

As shown in FIG. 1, the multilayer ceramic capacitor C1 includes a dielectric layer 11 and an internal electrode layer (the first conductor layer 1).
2, the second conductor layer 13) are alternately laminated, and further, a part of the conductor layer (the first conductor layer 12 having an oxidized region on one end side, and an oxidized region on the other end side) are provided at both ends of the capacitor body C. External electrode 16 to which the second conductive layer 13) is electrically connected
The capacitor body C1 includes an effective laminated body A in which dielectric layers 11a and internal electrode layers (first conductor layer 12, second conductor layer 13) are alternately laminated, A non-effective laminate B is provided on both sides of the effective laminate A, and the dielectric layer 11b and the third conductor layers 14 having oxidized regions at both ends 14a are alternately laminated.

FIG. 2 shows each of the internal electrode layers (the first conductive layer 1).
2 is a cross-sectional view of the second conductor layer 13), and FIG.
2A shows a cross section of an odd-numbered layer (first conductor layer 12) counted from below the effective laminated body A, and FIG. 2B shows a cross-section of an even-numbered layer (second conductor layer 13).

As shown in FIGS. 2A and 2B, in the effective laminate A, one ends 12a and 13a of the first and second conductor layers 12 and 13 located at the external electrodes 16 are made of a noble metal (gold, Silver and platinum groups (Ru, Rh, Pd, Os, I
r, Pt)) as a precious metal portion, and other outer portions 12b, 13b and inner regions 12c, 13c as metals other than noble metals (metals having a lower ionization tendency than noble metals).
Is a base metal portion whose main component is, for example, the outer peripheral portions 12b and 13b are oxidized regions as shown in FIG. Here, metals constituting the base metal portion include Ni, Co, Fe, and C.
Although u or the like is preferable, it is preferable that Pd is used as the noble metal portion and nickel is used as the base metal portion. This is because Pd and Ni are inexpensive, have melting points close to each other, and are optimal as a combination that does not produce a low melting point compound such as eutectic.

The third conductor layer 14 in the ineffective laminate B
It is preferable for fabrication to have the same composition as the base metal portion of the internal electrode layer, and the outer peripheral portion 14a of the third conductor layer 14 is oxidized.

The first to third conductor layers 12 to 14 only need to be mainly composed of a metal, and contain metal oxides, glass, and the same ceramic material as that of the dielectric layer in addition to the metal. May be.

Then, the dielectric layer 11b of the ineffective laminate B
1 is smaller than that of the dielectric layer 11a of the effective laminate A by 4 to 10 × 10 ⁻⁷ / ° C., and FIG.
, The ratio of the thickness of the ineffective laminate B to the thickness (A + 2B) of the capacitor body C (B / (A + 2
B)) is 2.5 to 25%, respectively.

The reason why the difference between the thermal expansion coefficients of the dielectric layers of the ineffective laminate B and the effective laminate A and the ratio of the thickness of the ineffective laminate B on one side to the thickness of the capacitor body C is specified as described above is as follows. When the difference in expansion coefficient is less than 4 × 10 ⁻⁷ / ° C.,
Insufficient compressive stress cannot be applied to the effective laminated body A to apply tensile stress for preventing the deterioration of the dielectric properties to the effective laminated body A and sufficient to absorb thermal stress, mechanical stress and thermal shock generated in the surface mounting process. This is because it cannot be applied to the laminate and cracks tend to occur from the surface.

Further, if the ratio of the ineffective laminate B to the thickness of the capacitor body C is less than 2.5%, a tensile stress for preventing deterioration of the dielectric properties cannot be applied to the effective laminate A. On the other hand, the thermal expansion coefficient difference is 10 × 10 ⁻⁷ /
° C. or when the ratio of the thickness of the ineffective laminate B to the thickness of the capacitor body C is greater than 25%,
This is because the tensile stress applied to the effective laminate A becomes too large, and cracks are easily generated from the effective laminate A.

The difference in the coefficient of thermal expansion between the dielectric layers of the ineffective laminate B and the effective laminate A prevents the dielectric properties from deteriorating,
In order to reduce the compressive stress generated in the surface mounting step or the like, it is desirable that the effective laminated body A is larger by 6 to 10 × 10 ⁻⁷ / ° C. because the optimum tensile stress is applied to the effective laminated body A.

The ratio of the thickness of the non-effective laminate B on one side to the thickness of the capacitor body C is 7.5 to 20 because the optimum laminate A is given an optimal tensile stress.
% Is desirable.

From the viewpoint of improving the dielectric properties, the dielectric layer
It is preferable that the dielectric ceramic is mainly composed of a dielectric ceramic mainly containing a titanate such as barium titanate, lanthanum titanate, calcium titanate, neodymium titanate and magnesium titanate. In this case, by adjusting the dielectric layer of the ineffective laminate to contain 5 to 15 mol% more zirconate than the dielectric layer of the effective laminate, the thermal expansion between the ineffective laminate and the effective laminate is adjusted. The difference between the coefficients can be set as described above. When the excess content of zirconate in the ineffective laminate is less than 5 mol%, the difference in thermal expansion coefficient is less than 4 × 10 ⁻⁷ / ° C.,
Conversely, if it exceeds 15 mol%, the difference in thermal expansion coefficient is 10 × 1.
0 ^-7 / ° C.

Although zirconate is not used as a raw material for the dielectric layer, it may be inevitably contained in the raw material, and zirconate is later used as one constituent material of the dielectric layer. Since zirconate was added in some cases, the ineffective laminate was described as containing 5 to 15 mol% more. As described above, it is desirable to add zirconate as a raw material of the dielectric layer, because the ceramic strength of the capacitor increases.

The multilayer ceramic capacitor C1 of the present invention
Can be obtained, for example, by first preparing a green sheet to be a dielectric layer. The green sheet contains, for example, barium titanate as a main component, yttrium oxide, a dielectric powder to which manganese carbonate and magnesium oxide are added, water and a dispersant, and after mixing and grinding in a ball mill, an organic binder is mixed. The obtained slurry is formed into a tape having a predetermined thickness.

As a material of the dielectric layer of the effective laminate, barium titanate is used as a main component, and 0.5 to 8 mole parts of magnesium oxide and 0.05% of manganese carbonate are added to 100 mole parts of the main component. It is desirable to use a material containing 0.5 to 0.5 mol part of yttrium oxide and 0.3 to 4 mol part of yttrium oxide in terms of improving properties such as dielectric constant.

The raw material powder for the dielectric layer of the effective laminate is made of a zirconate such as calcium zirconate (CaZr
O ₃ ) and barium zirconate (BaZrO ₃ ) powder
１５15 mol% to make a material for an ineffective laminate.

As the conductor paste, for example, a paste in which an organic plasticizer is added to nickel powder and a paste in which an organic plasticizer is added to palladium powder are prepared. Note that nickel and palladium are contained in the paste, for example, at about 40 to 60% by weight.

As shown in FIG. 3, a conductive paste of nickel and a conductive paste of palladium are applied to the upper surface of the green sheet 31 of the dielectric layer for the effective laminate by, for example, a screen printing method. The green sheets 31 coated with the conductive paste are laminated so that the electrode regions 33 and the palladium internal electrode regions 35 are alternately arranged to form an effective laminated body.

On the other hand, a plurality of dielectric green sheets for an ineffective laminate in which the same nickel conductive paste as the internal electrodes is applied to both surfaces of the effective laminate by a screen printing method are laminated to form an ineffective laminate.

Then, after cutting the obtained laminated molded body to a predetermined size, for example, the oxygen partial pressure is 3 × 10 ⁻⁸ to 3 × 10 ^−8.
-3 Pa, firing at a temperature of 1150-1300 ° C for 0.5-3 hours, and thereafter, a temperature of 800-1150 ° C in the air.
For 30 minutes to 5 hours to oxidize the nickel exposed on the surface of the sintered body to produce a capacitor body. This capacitor body is shown in FIG.

Next, a paste in which an organic plasticizer is added to copper powder is prepared, and this paste is baked on both ends of the capacitor body so as to be electrically connected alternately with the internal electrode layers, thereby preparing a multilayer ceramic capacitor. I do.

In the above example, the internal electrodes made of a combination of nickel and palladium are formed, but the present invention is not limited to the above example. Furthermore, the effective electrode area can be further increased by forming the external electrodes on the sintered body so as to be electrically connected alternately with the internal electrode layers by using a thin film forming technique such as a sputtering method.

[0049]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a dielectric material containing barium titanate as a main component, 1 mole portion of yttrium oxide, 2 mole portions of magnesium oxide and 0.1 mole portion of manganese oxide was added to 100 mole portions of the main component. Water and a dispersant are added to the powder, mixed and pulverized by a ball mill using ZrO ₂ balls, and then an organic binder is mixed. The resulting slurry is formed into a tape having a thickness of 8 μm, and the slurry is used for an effective laminated body A dielectric green sheet of the effective laminate was obtained.

On the other hand, a paste in which an organic plasticizer was added to nickel powder and a paste in which an organic plasticizer was added to palladium powder were prepared as internal electrodes, each of which was placed on the tape for the effective laminate as shown in FIG. Then, nickel and palladium were alternately arranged by screen printing, and tapes were laminated.

Next, in order to fabricate a conventional general capacitor as shown in FIG. 6, a green sheet having nickel and an end and a side margin region formed by screen printing is laminated using nickel as an internal electrode to form a molded body. In order to manufacture the capacitor as shown in FIG. 5, a green body having nickel and nickel as an internal electrode and having an end margin 8 formed by screen printing was laminated to form a molded body.

In FIGS. 5 and 6, reference numeral 1 denotes an internal electrode, reference numeral 6 denotes an external electrode, reference numeral 8 denotes an end margin area,
Reference numeral 9 denotes a side margin area. Further, a capacitor having an ineffective laminated body as shown in FIG.
-181032), a molded body was prepared in which the end and side margin regions were formed by screen printing using nickel for the internal conductor layer in the ineffective laminate. The internal electrode layers of the effective laminate are the same as those in FIG. After cutting the obtained molded body, the oxygen partial pressure was 1 × 10
Calcination was performed at ^-6 Pa and a temperature of 1260 ° C. for 2 hours, and then heat treatment was performed at an oxygen partial pressure of 1 × 10 1 Pa and a temperature of 1000 ° C. for 1 hour.

After barrel polishing the sintered body, a copper paste was applied to both end surfaces of the capacitor where the internal electrodes were exposed,
Baking at 0 ° C., and further performing Ni plating and Sn plating thereon, with a dielectric layer thickness of 5 μm and an effective dielectric layer number of 15
0 layer, external dimensions 3.2mm x 1.6mm x 0.96 ~
2.1 mm, effective electrode area 4.38 (3.04 × 1.4)
4) A multilayer capacitor of mm ² was obtained.

Next, these samples were transferred to the LCR meter 42
The capacitance at + 25 ° C. was measured using 84A at a frequency of 1.0 kHz and an input signal level of 1.0 Vrms.

As a result, the capacitance of the conventional general capacitor of FIG. 6 and FIG. 7 was 3350 nF, and the capacitance of the capacitor as shown in FIG. In the case of the present invention in which nickel and palladium are formed so as to be alternately arranged, and the part of the internal electrode layer that is in contact with the external electrode is electrically insulated by a metal oxide constituting the internal electrode every other layer, the capacitance is 45
00 nF. Therefore, it can be seen that a multilayer ceramic capacitor having a large capacitance can be manufactured.

Next, the state of occurrence of delamination of these capacitors was confirmed. As a result, in the conventional capacitor (FIG. 6), delamination or crack occurs in 49 out of 50 capacitors, and when no metal is provided in the ineffective laminate (FIG. 5), 20 out of 50 capacitors have delamination. Occurs, and a conductor layer is formed in the effective laminate (FIG. 7).
When delamination occurred in 17 of the 50 laminates, and when the metal layer was formed such that the outer peripheral portion was exposed in the effective laminate of the present invention, cracks and delamination did not occur. This indicates that the multilayer ceramic capacitor of the present invention has no delamination and no cracks as compared with the conventional multilayer ceramic capacitor, and high reliability can be obtained.

Next, calcium zirconate (CaZrO ₃ ) and / or barium zirconate (BaZrO ₃ ) powder was added to the above-mentioned dielectric material powder in an amount shown in Table 1.
A green sheet for an ineffective laminated body was obtained by treating in the same manner as the slurry for the dielectric ceramic, and a laminated ceramic capacitor was produced in the same manner as above.

Then, the thickness of the ineffective laminate, CaZrO
Table 1 shows the ratio between the thickness B of the non-effective laminated body on one side and the thickness (A + 2B) of the capacitor body shown in FIG. 1 for the samples in which the addition amounts of ₃ and BaZrO ₃ were changed. In addition, a value Δα obtained by subtracting the thermal expansion coefficient of the dielectric layer of the ineffective laminate from the thermal expansion coefficient of the dielectric layer of the effective laminate is measured and calculated, and the residual stress (compressive stress of the ineffective laminate, effective laminate Tensile stress) was determined by FEM analysis.

The sample was measured using an LCR meter 4284A at a frequency of 1 kHz and an input signal level of 1.0 Vrm.
The capacitance at −55 to 125 ° C. was measured at s, and +
The change ratio TCC of the capacitance at each temperature with respect to the capacitance at 25 ° C. was calculated.

The above capacitor was soldered on a glass epoxy board with copper wiring, and the board was placed on a support having a spacing of 90 mm. The board was pressed from the back side of the board to determine the amount of flexure deformation until a crack was formed in the capacitor. (Based on the Japan Electronic Machinery Manufacturers Association standard RC-3402).

The polished cross section of the sintered body was examined with a stereo microscope (× 4
Observation was performed in 0) to check for the presence of internal cracks.

Ineffective laminate thickness, CaZrO ₃ and B
aZrO ₃ addition amount, thermal expansion coefficient α of ineffective laminate, difference Δα in thermal expansion coefficient between ineffective laminate and effective laminate, residual stress, dielectric properties, flexural deformation before cracking, and internal crack Tables 1 and 2 collectively show the observation results of the presence / absence of.

[0063]

[Table 1]

[0064]

[Table 2]

In Tables 1 and 2, the sample No. 3
Since the compressive stress of the non-effective laminate is larger than the tensile stress of the effective laminate, the amount of deformation until cracks are formed by the test method of the above-mentioned standard RC-3402 is reduced. It is understood that it is large enough to withstand the tensile stress during surface mounting. Further, the tensile stress of the effective laminate is less than 5 kg / mm ² , so that there is no internal crack.

On the other hand, the sample No. Nos. 1 and 17 have no difference in the thermal expansion coefficient between the non-effective laminate and the effective laminate.
Compressive stress is not accumulated in the ineffective laminate, so that the amount of deformation before cracking is small, and cracking may occur due to tensile stress during surface mounting.

Sample No. In No. 13, since the ratio of the ineffective laminate to the total thickness of the multilayer ceramic capacitor was large, the tensile stress of the effective laminate was large, and cracks occurred inside the sintered body.

Conversely, for sample no. No. 10 has a tensile stress of the effective laminate of 0.5 kg / m because the ratio of the non-effective laminate is small.
smaller than m ² and cannot improve TCC. Sample N
o. In No. 2, since the difference in the coefficient of thermal expansion is small, the tensile stress of the effective laminate is smaller than 0.5 kg / mm ² and the TCC cannot be improved. Further, the sample No. In No. 16, the tensile stress of the effective laminate was 5 kg / mm ² because of a large difference in the coefficient of thermal expansion.
Sample no. As in the case of No. 13, internal cracks occurred.

In the above description, a method of adding zirconate to the dielectric material of the effective laminated body was adopted as a means for reducing the coefficient of thermal expansion of the ineffective laminated body, but other methods were excluded. is not.

[0070]

The multilayer ceramic capacitor of the present invention has the following features.
An internal electrode layer is formed on the entire surface of the dielectric layer, and except for one end of the internal electrode layer electrically connected to an external electrode,
Since the outer peripheral portion of the internal electrode layer is oxidized and the oxide is formed, it can be insulated from the outside, the effective electrode area can be increased, and the capacitance can be increased.

Further, since the metal layer is formed on the ineffective laminate, stress due to sintering shrinkage of the effective laminate and the ineffective laminate is reduced. The coefficient of thermal expansion of the ineffective laminate is smaller than that of the effective laminate by a predetermined amount, and the ratio of the thickness of the ineffective laminate to the thickness of the capacitor body is 2.5 to 2%.
Because of 5%, after sintering, tensile stress accumulates and remains in the effective laminate, dielectric characteristics do not deteriorate even in high lamination, and compressive stress accumulates and remains in the non-effective laminate, resulting in surface mounting. The tensile stress is absorbed, cracks are suppressed, and the reliability of the capacitor is maintained. A multilayer ceramic capacitor having the above excellent characteristics can be obtained reliably.

The practical value of the present invention having such remarkable effects is extremely large.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a multilayer ceramic capacitor of the present invention.

FIGS. 2A and 2B are cross-sectional views of FIG. 1, and FIGS. 2A and 2B are cross-sectional views of respective internal electrode layers.

FIG. 3 is a perspective view schematically showing a state in which green sheets coated with a conductive paste are stacked.

FIG. 4 is a perspective view of a capacitor body.

FIG. 5 is a cross-sectional view of a conventional multilayer ceramic capacitor formed by oxidizing a side end of an internal electrode.

FIG. 6 is a cross-sectional view of a conventional general multilayer ceramic capacitor.

FIG. 7 is a cross-sectional view showing a non-effective laminated body of a multilayer ceramic capacitor in which a conductor layer is formed on a conventional ineffective laminated body.

FIG. 8 is a longitudinal sectional view showing surface mounting of the multilayer ceramic capacitor on a substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Dielectric layer 12 ... 1st conductor layer 13 ... 2nd conductor layer 14 ... 3rd conductor layer 16 ... External electrode 12a, 13a ... Noble metal part 12b, 13b, 13c , 14a: base metal portion A: effective laminate B: ineffective laminate C: capacitor body C1: multilayer ceramic capacitor

Claims (3)

[Claims] 1. A multilayer ceramic capacitor comprising a capacitor main body and a pair of external electrodes disposed at both ends of the capacitor main body, wherein the capacitor main body is provided with a first conductor layer having an oxidized region on one end side. An effective laminated body obtained by alternately laminating a second conductor layer having an oxidized region on an end side with a dielectric layer interposed therebetween, and having an oxidized region at both ends disposed on both surfaces of the effective laminated body, respectively; A third conductor layer and a non-effective laminate obtained by alternately laminating dielectric layers, wherein the first conductor layer of the effective laminate is used as one external electrode, and the second conductor layer is used as the other. Connected to an external electrode, and further having the coefficient of thermal expansion of the dielectric layer of the non-effective laminate be 4 to 10 × 10 ⁻⁷ more than the coefficient of thermal expansion of the dielectric layer of the effective laminate.
/ C, and the ratio of the thickness of the ineffective laminate to the thickness of the capacitor body is set to 2.5 to 25%. 2. The method according to claim 1, wherein the first conductor layer and the second conductor layer of the effective laminate are composed of a noble metal portion mainly containing a noble metal and a base metal portion mainly containing a metal other than the noble metal. The multilayer ceramic capacitor according to claim 1, wherein 3. The multilayer ceramic capacitor according to claim 1, wherein the third conductor layer of the ineffective laminate has a main component of a metal other than a noble metal.