JP2001052950A - Laminated ceramic electronic part and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent f cracking an a ceramic sintered body by, related to a part of internal electrode which is drawn out of the external surface of the ceramic sintered body, controlling the porosity against, each internal electrode exposed area to a specified percentage or below. SOLUTION: In a ceramic sintered body 2 of a laminated ceramic electronic part, a plurality of internal electrodes 3-8 are so arranged as to overlap each other in the thickness direction through a ceramic layer. The internal electrodes 3, 5, and 7 are drawn out of an end surface 2a of the ceramic sintered body 2 while the internal electrodes 4, 6, and 8 are drawn out of an end surface 2b on the side opposite to the end surface 2a, forming external electrodes 9 and 10 so as to cover the end surfaces 2a and 2b. The external electrodes 9 and 10 are so formed as to reach the upper surface 2c, the lower surface 2d, and side surfaces 2e and 2f as well as the end surfaces 2a and 2b. The porosity against an internal electrode area which is exposed to the end surfaces 2a and 2b of the internal electrodes 3-8 is controlled to 30% or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic electronic component such as a multilayer capacitor and a method of manufacturing the same, and more particularly, to an internal electrode drawn to an outer surface of a ceramic sintered body. TECHNICAL FIELD The present invention relates to a multilayer ceramic electronic component in which the structure of a part is improved and a method of manufacturing the same.

[0002]

2. Description of the Related Art When manufacturing a multilayer ceramic electronic component such as a multilayer capacitor, a ceramic sintered body is obtained by firing a laminate formed by alternately laminating internal electrodes and ceramics. Then, the ceramic sintered body is subjected to barrel polishing or the like to expose the internal electrodes to the end surface of the sintered body. next,
External electrodes are formed on the outer surface of the ceramic sintered body so as to be electrically connected to the internal electrodes.

[0003] In ordinary dielectric ceramics mainly composed of BaTiO ₃ , noble metals such as palladium and platinum are used as internal electrodes. However, when such a noble metal is used as the internal electrode material, there is a problem that the cost of the multilayer ceramic electronic component increases.

Therefore, in order to solve the above-mentioned problems, it has been proposed to use an inexpensive base metal material such as nickel as the internal electrode. However, if a base metal is used as the internal electrode material and firing is performed under the conventional conditions, the internal electrode made of the base metal is oxidized and no longer functions as an electrode.

Therefore, when a base metal is used as an internal electrode, it is necessary to use a ceramic which does not turn into a semiconductor even when fired in a neutral or reducing atmosphere having a low oxygen partial pressure. As a ceramic material satisfying such conditions, barium titanate-based ceramics having various compositions have been proposed (for example, see Japanese Unexamined Patent Publication No.
2-256422, JP-A-63-103861, etc.).

[0006]

In a multilayer ceramic electronic component, upon firing, residual stress is generated at the interface between the internal electrode and the ceramic due to the difference in the contraction rate and the difference in thermal expansion between the internal electrode and the ceramic. In a multilayer capacitor and the like, when the thickness of the ceramic layer between the internal electrodes is small and the number of internal electrodes stacked is large, the influence of the residual stress increases. Therefore, cracks may occur in the ceramic sintered body due to heat generated when the external electrodes are baked on the obtained ceramic sintered body.

[0007] In the production of multilayer ceramic electronic components, after a ceramic sintered body is obtained, wet barrel polishing is performed to ensure that the internal electrodes are exposed at the end faces of the ceramic sintered body. However, in this case, at the initial stage of barrel polishing, water used for barrel polishing enters through holes in exposed portions of the internal electrodes on the end surfaces of the ceramic sintered body, and water is trapped in the ceramic sintered body by the end of barrel polishing. is there. Therefore, a sudden vaporization of the trapped water during the subsequent baking of the external electrode is also considered to be one of the causes of the crack.

An object of the present invention is to provide a multilayer ceramic electronic component in which cracks in a ceramic sintered body due to heat during baking of an external electrode and the like are less likely to occur, and a method of manufacturing the same.

[0009]

According to the present invention, there is provided a ceramic sintered body, a plurality of internal electrodes disposed in the ceramic sintered body, drawn out to the outer surface of the ceramic sintered body, and the ceramic sintered body. An external electrode formed on the outer surface of the sintered body and electrically connected to any one of the internal electrodes; The ratio of voids in the exposed portion of the internal electrode to the electrode exposed area is not more than 30%.

[0010] In the present invention, preferably, the percentage of the vacancies is 10% or less. According to a specific aspect of the present invention, the internal electrode is formed using Ni or a Ni alloy.

The method for manufacturing a multilayer ceramic electronic component according to the present invention includes a step of obtaining a multilayer ceramic electronic component unit having a structure in which a plurality of internal electrode patterns made of a conductive paste are laminated via a ceramic layer. A firing step of firing the laminate to obtain a ceramic sintered body, a barrel polishing step of barrel polishing the ceramic sintered body, and an external step of forming an external electrode on an outer surface of the barrel-polished ceramic sintered body. An electrode forming step, wherein in the step of obtaining the laminated body, the ratio of voids in the exposed portion of the internal electrode to the exposed area of the internal electrode on the outer surface of the sintered body after firing is 30% or less. It is characterized in that an internal electrode pattern made of paste is formed.

In a specific aspect of the method for manufacturing a multilayer ceramic electronic component according to the present invention, the internal electrode is made of Ni or a Ni alloy.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

FIGS. 1A and 1B are a vertical sectional view of a multilayer capacitor as a multilayer ceramic electronic component according to an embodiment of the present invention and a cross-sectional view schematically showing an end face of a sintered body of the multilayer capacitor. It is.

The multilayer capacitor 1 includes a ceramic sintered body 2
Having. The ceramic sintered body 2 has a rectangular parallelepiped shape, and is made of a dielectric ceramic such as a barium titanate-based ceramic.

In the ceramic sintered body 2, a plurality of internal electrodes 3 to 8 are arranged so as to overlap in the thickness direction via a ceramic layer. The internal electrodes 3, 5, 7 are drawn out to the first end face 2a of the ceramic sintered body 2, and the internal electrodes 4, 6, 8 are connected to the second end face 2a opposite to the first end face 2a.
Is drawn out to the end face 2b.

External electrodes 9 are provided so as to cover the end faces 2a and 2b.
10 are formed. The external electrodes 9 and 10 are connected to the end face 2
a, 2b, the upper surface 2c of the ceramic sintered body 2;
It is formed so as to reach the lower surface 2d and the side surfaces 2e and 2f (see FIG. 1B).

The external electrodes 9 and 10 have a structure in which second and third external electrode layers are laminated by plating on the surface of a first external electrode layer formed by applying and baking a conductive paste. The second external electrode layer is formed by plating Ni or Cu, and the third external electrode layer is formed by plating a metal material having excellent solderability such as solder or tin.

The feature of the multilayer capacitor 1 of this embodiment is that the area occupied by the holes in the internal electrodes is larger than the exposed area of the internal electrodes 3 to 8 at the end faces 2a and 2b. A ratio (hereinafter abbreviated as a void area ratio) of 30% or less;
Preferably, it is set to 10% or less.

That is, as shown in FIGS. 1B and 2, the internal electrodes 3, 5, and 7 are exposed on the end face 2a. Taking the internal electrode 3 as an example, when the area of the exposed part of the internal electrode 3 is S, and the total area of the holes 11 appearing in the part exposed on the end face 2a of the internal electrode 3 is A , Void area ratio = A / S × 100 (%) is 30%
Hereinafter, it is preferably 10%.

In the multilayer capacitor 1, the above-mentioned hole area ratio is set to 30% or less, so that a conductive paste is applied and baked when forming the external electrodes 9 and 10 as will be apparent from an experimental example described later. As the ceramic sintered body 2
Cracks are less likely to occur.

The material constituting the internal electrodes 3 to 8 is not particularly limited, and any of a base metal such as Ni or a Ni alloy or a noble metal such as Ag, Pd or an alloy thereof can be used. it can.

However, as described above, conventionally, when a base metal such as Ni or a Ni alloy is used as an internal electrode material, cracks are easily generated in ceramics. On the other hand, in the multilayer capacitor 1 of the present embodiment, the void area ratio is set to 30% or less, so that even if Ni or a base metal such as Ni is used as the internal electrode material, the ceramic firing is performed. The generation of cracks in the consolidated body can be suppressed. Therefore, Ni or a Ni alloy can be suitably used.

Next, specific experimental examples will be described. (Example 1) First, a ceramic slurry mainly composed of barium titanate-based ceramic powder was prepared. Next, the ceramic slurry was formed by a doctor blade method to obtain a rectangular ceramic green sheet having a thickness of 11 μm.

On one side of the ceramic green sheet,
In order to form the internal electrodes, a conductive paste mainly composed of Ni was screen-printed. Thereafter, a plurality of ceramic green sheets on which the conductive paste is printed are stacked such that the side from which the conductive paste is drawn is alternately opposite, and an appropriate number of plain ceramic green sheets are stacked on top and bottom. Thus, a laminate was obtained.

The above laminated body is placed in a nitrogen atmosphere at 350
After heating to a temperature of 0 ° C. and burning the binder, H ₂ ,
It was fired in a reducing atmosphere consisting of a mixed gas of N ₂ and H ₂ O to obtain a ceramic sintered body. In addition, firing is 1
This was performed by maintaining the temperature at 300 ° C. for 2 hours. Further, the temperature raising rate and the cooling rate were both 200 ° C./h.

The ceramic sintered body obtained as described above was put into a barrel pot together with water and an abrasive, and wet barrel polishing was performed to expose the internal electrodes to the end faces of the ceramic sintered body. Thereafter, a Cu paste is applied to both end surfaces of the ceramic sintered body, and the paste is applied in a nitrogen atmosphere.
Baking was performed at a temperature of 0 ° C. to form a first external electrode layer.

Thereafter, a Ni plating film and a solder plating film were laminated in this order on the first external electrode layer. As described above, the multilayer capacitor 1 shown in FIG. 1A was obtained. The external dimensions of the obtained multilayer capacitor 1 are 1.6 mm in width × 3.2 mm in length × 1.2 mm in thickness.
The thickness of the ceramic layer between the internal electrodes is 6 μm, and the total number of ceramic layers sandwiched between the internal electrodes is 150.

In the above manufacturing method, the thickness of the conductive paste for forming the internal electrode by screen printing is set to 0.5, 0.7, 1.0, and 1.5 μm, so that the empty space in the internal electrode is reduced. Change the percentage of holes and change the sample number 1
To 4 were obtained. That is, the thickness of the conductive paste applied to form the internal electrodes is 0.5,
By setting the pore area ratio to 0.7, 1.0, and 1.5 μm, the above-mentioned hole area ratio of 50%, 30%, 10%, and 0%
Various types of multilayer capacitors were prepared. In addition, the said hole area ratio was calculated | required by observing the end face of a ceramic sintered compact after wet barrel polishing using a scanning electron microscope.

External electrodes were formed on the outer surfaces of the four types of ceramic sintered bodies as described above, and after obtaining multilayer capacitors, the rate of occurrence of cracks in each multilayer capacitor was evaluated. The results are shown in Table 1 below.

[0031]

[Table 1]

As is clear from Table 1, the sample No. 1 had a void area ratio of 50%, and thus cracks occurred in many multilayer capacitors. Since the hole area ratio is 30% or less, the number of occurrences of cracks is extremely small. In particular, cracks hardly occur in the multilayer capacitors of Sample Nos. 3 and 4 in which the hole area ratio is 10% or less. Was.

After the wet barrel polishing is performed after the ceramic sintered body is obtained, even if the end face of the ceramic sintered body is observed, it is difficult to determine the size of the above-mentioned pores. It is desirable to determine the hole area ratio by observing the end face of the sintered body. Further, the applied thickness of the conductive paste for forming the internal electrode may be adjusted as described above so that the hole area ratio obtained in this manner is 30% or less.

Of course, not only the adjustment of the thickness of the conductive paste applied but also the ratio of the void area in the exposed portion of the internal electrode may be adjusted by another method. For example, Example 2 described later
As described above, the particle size of the metal particles forming the internal electrode may be adjusted, or the wettability of the conductive paste forming the internal electrode to the ceramic green sheet, the application density of the conductive paste, and the like may be adjusted.

Example 2 In the same manner as in Example 1, a ceramic slurry was prepared using a barium titanate-based ceramic slurry. This ceramic slurry was formed into a sheet by a doctor blade method to obtain a rectangular ceramic green sheet having a thickness of 11 μm.

On one side of the ceramic green sheet obtained as described above, a conductive paste mainly composed of Ni for forming an internal electrode was screen-printed in the same manner as in Example 1.

However, at the time of printing, 1.0 μm, 0.5 μm, 0.3 μm and 0.1 μm are used so that the hole area ratio is finally 50%, 30%, 10% and 0%.
Samples Nos. 5 to 8 were prepared by preparing Ni powders having four different particle sizes of m and using a conductive paste composed of the Ni powders having the respective particle sizes.

On one side of the ceramic green sheet,
Example 1 Screen printing of any conductive paste
Were laminated in the same manner as in the above to obtain a laminate. This laminate was fired in the same manner as in Example 1 to obtain a sintered body.

With respect to the obtained ceramic sintered body, 10
The re-oxidation treatment was performed by holding in the atmosphere at 00 ° C. for 0.5 hour. Thereafter, the ceramic sintered body was put into a barrel pot together with water and an abrasive, and barrel polishing was performed to expose an internal electrode on the end face of the ceramic sintered body.

Next, external electrodes were formed on both end surfaces of the ceramic sintered body in the same manner as in Example 1. Thus, the width is 1.6 mm × the length 3.2 mm × the thickness 1.2 mm, the thickness of the ceramic layer between the internal electrodes is 6 μm, and the total number of ceramic layers sandwiched between the internal electrodes is 150. Various kinds of multilayer capacitors were obtained.

As described above, multilayer capacitors of Sample Nos. 5 to 8 using conductive pastes having different particle diameters of Ni powder were obtained. The void area ratio in each of the multilayer capacitors of Sample Nos. 5 to 8 was observed and evaluated by a scanning electron microscope immediately after obtaining the ceramic sintered body.

In each of the multilayer capacitors of Sample Nos. 5 to 8, the rate of occurrence of cracks after forming the external electrodes was evaluated in the same manner as in Example 1. The results are shown in Table 2 below.

[0043]

[Table 2]

As is clear from Table 2, the sample 5 had a very high cracking rate because the hole area ratio was 50%, whereas the sample Nos. 6 to 8 had the hole area ratio of 50%. Since the ratio is 30% or less, the occurrence of cracks is extremely small.
Since the content was 0% or less, almost no cracks were observed.

In the first and second embodiments, the method for manufacturing a multilayer capacitor has been described as an example. However, the present invention can be applied to other multilayer ceramic electronic components such as a multilayer varistor.

[0046]

In the multilayer ceramic electronic component according to the present invention, the ratio of the porosity to the exposed area of the internal electrode in the portion where the ceramic sintered body of the internal electrode is drawn out to the surface is 30% or less. Therefore, even if the internal electrodes are formed by applying and baking a conductive paste, or even if the heat of solder at the time of mounting on a printed circuit board is applied, cracks are not easily generated in the ceramic sintered body. Therefore, the yield rate of the multilayer ceramic electronic component can be increased, and a multilayer ceramic electronic component having excellent reliability can be provided.

In particular, when the proportion of the vacancies is 10% or less, it is possible to more effectively suppress the occurrence of the cracks and to provide a more reliable multilayer ceramic electronic component. Can be.

When the internal electrodes are made of Ni or a Ni alloy, cracks have conventionally been liable to occur, but according to the present invention, cracks can be effectively suppressed. Therefore, a multilayer ceramic electronic component that is inexpensive and has excellent reliability can be stably provided.

In the method for manufacturing a multilayer ceramic electronic component according to the present invention, the internal electrode pattern is formed so that the ratio of voids to the internal electrode exposed area is 30% or less. And a multilayer ceramic electronic component according to the present invention, in which cracks hardly occur during mounting on a printed circuit board, can be stably provided.

In the method for manufacturing a multilayer ceramic electronic component according to the present invention, when Ni or a Ni alloy is used as the internal electrode, not only is it inexpensive, but also the reliability in which cracks are unlikely to occur as described above. It is possible to provide a multilayer ceramic electronic component having excellent characteristics.

[Brief description of the drawings]

1A and 1B are a longitudinal sectional view of a multilayer capacitor according to an embodiment of the present invention and a sectional view schematically showing an end face of a ceramic sintered body of the multilayer capacitor shown in FIG.

FIG. 2 is a partially cutaway cross-sectional view showing an enlarged main part of the multilayer capacitor shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Multilayer capacitor 2 ... Ceramic sintered body 2a, 2b ... End surface 3-8 ... Internal electrode 9, 10 ... External electrode 11 ... Void

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 5E001 AB03 AC03 AC04 AC09 AD03 AE02 AE03 AF00 AF06 AH01 AH09 AJ01 5E082 AA01 AB03 BC33 BC38 BC40 EE04 EE23 EE35 EE42 FG06 FG26 FG27 FG52 FG54 GG10 GG11 GG11 GG23 LL35 MM24 PP10

Claims (5)

[Claims] 1. A ceramic sintered body, a plurality of internal electrodes disposed in the ceramic sintered body, drawn out on an outer surface of the ceramic sintered body, and formed on an outer surface of the ceramic sintered body. And an external electrode electrically connected to any one of the internal electrodes, wherein the internal electrode occupies each internal electrode exposed area in a portion of the internal electrode that is drawn to the outer surface of the ceramic sintered body. A multilayer ceramic electronic component, characterized in that the proportion of holes in the exposed portion is 30% or less. 2. The multilayer ceramic electronic component according to claim 1, wherein the proportion of the holes is 10% or less. 3. The multilayer ceramic electronic component according to claim 1, wherein the internal electrode is made of Ni or a Ni alloy. 4. A step of obtaining a multilayer ceramic electronic component unit having a structure in which a plurality of internal electrode patterns made of a conductive paste are laminated via a ceramic layer, and firing the multilayer body to perform ceramic sintering. A firing step of obtaining a body, a barrel polishing step of barrel polishing the ceramic sintered body, and an external electrode forming step of forming an external electrode on an outer surface of the barrel polished ceramic sintered body, and sintering after firing. In the step of obtaining the laminate, an internal electrode pattern made of a conductive paste is formed such that a ratio of voids in the exposed portion of the internal electrode to an exposed area of the internal electrode on the external surface of the body becomes 30% or less. A method for manufacturing a multilayer ceramic electronic component, which is characterized by the following. 5. The method according to claim 4, wherein the internal electrode contains Ni or a Ni alloy.