JP2000049032A - Laminated ceramic electronic component and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated ceramic electronic component, wherein tombstone effect at mounting to a printed circuit board is suppressed surely, even if it is miniaturized. SOLUTION: In a laminated capacitor 1, external electrodes 3-6 are so laminated as to be overlapped in the thickness direction in a ceramic sintered body 2 through a ceramic layer, and first and second external electrodes 7 and 8 are formed at first and second end surfaces 2c and 2d of the ceramic sintered body 2, with the end surfaces 2c and 2d recessed at intermediate height position, so that outer surfaces 7a and 8a of the external electrodes 7 and 8 are flattened.

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 a method of flattening an external electrode surface by devising a shape of a ceramic sintered body end face. And a method of manufacturing the same.

[0002]

2. Description of the Related Art In an electronic component such as a multilayer capacitor, external electrodes are formed at both ends of an electronic component body. FIG.
FIG. 3 is a cross-sectional view showing a state in which a conventional multilayer capacitor is mounted on a printed circuit board.

The multilayer capacitor 51 is made of dielectric ceramics and has a rectangular parallelepiped ceramic sintered body 52. Inside the ceramic sintered body 52, internal electrodes 53 to
56 are arranged so as to overlap with each other via the ceramic layer. The internal electrodes 53 and 55 are extended to the end face 52a, and the internal electrodes 54 and 56 are extended to the end face 52b. External electrodes 57 and 58 are formed to cover the end surfaces 52a and 52b.

The external electrodes 57 and 58 are formed by applying and baking a conductive paste. That is, the external electrodes 57 are formed by immersing the ceramic sintered body 52 in the conductive paste from the end face 52a side, applying the conductive paste, drying, and then baking. The external electrodes 58 are formed in a similar manner.

The external electrodes 57 and 58 formed by baking the conductive paste have a greater thickness at the central portions of the end faces 52a and 52b, and have an edge formed by the end faces 52a and 52b and the upper and lower surfaces 52c and 52d. Alternatively, the thickness of the external electrodes 57 and 58 tends to be reduced at the edge portions formed by the side surfaces (not shown) and the end surfaces 52a and 52b. That is, as shown by the arrow A in FIG. 3, the thickness of the external electrodes 57 and 58 tends to be small at the edge portions.

When the thickness of the external electrodes 57 and 58 becomes thin near the edges, when a plating layer is formed on the outside of the external electrodes 57 and 58, or when mounted on the printed circuit board 59, the plating solution, solder flux, etc. Sintered body 5
There is a risk of infiltration into the inside 2 and deterioration of characteristics.

[0007]

Therefore, conventionally, after obtaining the ceramic sintered body 52, the edge portion of the ceramic sintered body 52 is rounded by barrel polishing or the like as shown in FIG. A method of increasing the thickness of the external electrodes 57 and 58 at the edge portions is adopted. However, as shown in FIG. 3, even if the edge portion of the ceramic sintered body 52 is rounded by polishing, the thickness of the external electrodes 57 and 58 still does not become sufficiently large at the edge portion. In some cases, the properties may be degraded due to penetration of a plating solution, moisture, solder flux, or the like.

In recent years, electronic components such as multilayer capacitors have been further downsized. Therefore, the size of the ceramic sintered body 52 has been further reduced. As a result, for example, as shown in FIG. 3, when the multilayer capacitor 51 is mounted on the electrode lands 59 a and 59 b on the printed circuit board 59 using the solders 60 and 61, before the solders 60 and 61 solidify, Due to the surface tension of the solder 61, the ceramic sintered body 52 may rise as shown by the arrow B. In particular, when the end face portion of the ceramic sintered body 52 is rounded as described above,
The rising, that is, a phenomenon called a tombstone phenomenon was likely to occur.

An object of the present invention is to suppress the occurrence of the tombstone phenomenon even when the size is reduced,
An object of the present invention is to provide a multilayer ceramic electronic component capable of improving the reliability of electrical connection to a printed circuit board or the like when mounting using solder or the like, and a method for manufacturing the same.

[0010]

According to a first aspect of the present invention, there is provided a multilayer ceramic electronic component comprising: a ceramic sintered body;
A plurality of internal electrodes arranged so as to overlap in the thickness direction via the ceramic layer in the ceramic sintered body, and formed on the opposed first and second end faces of the ceramic sintered body, respectively, and First and second external electrodes electrically connected to any of the internal electrodes, wherein the first and second end surfaces of the ceramic sintered body are concave surfaces concave at an intermediate height position. It is characterized by being.

Preferably, the outer surfaces of the first and second external electrodes are flatter than the end surface of the ceramic sintered body. According to a third aspect of the present invention, there is provided a method for manufacturing a multilayer ceramic electronic component, comprising preparing a plurality of ceramic green sheets having an internal electrode formed on one main surface, and a plain ceramic green sheet having no internal electrode formed. And laminating the ceramic green sheet and the plain ceramic green sheet on which the internal electrode is formed so that the plain ceramic green sheet is positioned above and below the plurality of ceramic green sheet laminated portions on which the internal electrode is formed. A step of obtaining a laminate;
Baking the laminate to obtain a ceramic sintered body, using a ceramic green sheet softer than a plain ceramic green sheet as the ceramic green sheet on which the internal electrodes are formed, and prior to the baking. The method further comprises the step of polishing the end face of the laminate with an abrasive.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a multilayer ceramic electronic component, comprising: a plurality of ceramic green sheets having an internal electrode formed on one main surface; and a plain ceramic green sheet having no internal electrode formed. And a step of preparing a ceramic green sheet and a plain ceramic green sheet on which internal electrodes are formed such that the plain ceramic green sheets are positioned above and below a plurality of ceramic green sheet laminated portions on which the internal electrodes are formed. The method includes a step of obtaining a laminated body by laminating, and a step of firing the laminated body to obtain a ceramic sintered body, wherein, as the plain ceramic green sheet, a shrinkage rate during firing is such that an internal electrode is formed. Use a ceramic green sheet that is smaller than the shrinkage of the ceramic green sheet And it features.

According to the fifth aspect of the present invention, a ceramic green sheet having a higher glass frit content ratio than a plain ceramic green sheet is used as the ceramic green sheet on which the internal electrodes are formed.

In the invention according to claim 6, as the ceramic green sheet on which the internal electrodes are formed, a ceramic green sheet having a higher plasticizer content ratio than a plain ceramic green sheet is used.

[0015]

FIG. 1 is a sectional view showing a multilayer capacitor as one embodiment of a multilayer ceramic electronic component according to the present invention.

The multilayer capacitor 1 has a ceramic sintered body 2 made of a dielectric ceramic. The ceramic sintered body 2 has a substantially rectangular parallelepiped shape. That is, the ceramic sintered body 2 has an upper surface 2a, a lower surface 2b, a pair of end surfaces 2c and 2d facing each other, and a pair of side surfaces (not shown).

However, the first and second end faces 2c, 2d
Are concave concave surfaces at the intermediate height position. In addition, the edges formed by the end surfaces 2c and 2d of the ceramic sintered body 2, the upper surface 2a, the lower surface 2b, and the pair of side surfaces are rounded. That is, as shown by arrow A in FIG.
For example, an edge portion formed by the end surface 2c and the upper surface 2a is rounded.

In the ceramic sintered body 2, a plurality of internal electrodes 3 to 6 are arranged so as to overlap in the thickness direction via a ceramic layer. The internal electrodes 3, 5 are connected to the end face 2c.
It is pulled out to be exposed. On the other hand, the internal electrodes 4 and 6 are drawn out so as to be exposed on the second end face 2d.

In order to cover the end faces 2c and 2d,
First and second external electrodes 7 and 8 are formed. The external electrodes 7 and 8 are formed so as to reach not only the end surfaces 2c and 2d but also the upper surface 2a, the lower surface 2b, and a pair of side surfaces of the ceramic sintered body 2.

The external electrodes 7 and 8 are formed by applying and baking a conductive paste after obtaining the ceramic sintered body 2. That is, the ceramic sintered body 2
Is immersed in the conductive paste from the end face 2c side and pulled up, so that the conductive paste is applied so as to cover the end face 2c, and thereafter, the conductive paste is similarly applied to the end face 2d. Thereafter, the external electrodes 7 and 8 are formed by baking the conductive paste.

The feature of the multilayer capacitor 1 is that the end faces 2c, 2
d is a concave concave surface at the intermediate height position, whereby the end surfaces 2 of the external electrodes 7 and 8 are formed.
The outer surfaces 7a and 8a of the portions covering c and 2d are flat. Preferably, the outer surfaces 7 of the external electrodes 7 and 8
a, 8a are flatter than the end faces 2c, 2d of the ceramic sintered body 2.

That is, when forming the external electrodes 7 and 8, the conductive paste is applied so as to cover the end faces 2c and 2d as described above. In this case, when the end face is flat, as in the case of the conventional multilayer capacitor 51 shown in FIG. 3, when the ceramic sintered body is pulled up from the conductive paste, the thickness of the conductive paste is at the center of the end face. It gets thicker.

On the other hand, in this embodiment, the end faces 2c,
Since 2d is a concave surface, the end face 2
c or the end face 2d is immersed and pulled up.
The conductive paste adheres thickly at the intermediate height position between c and 2d, but the outer surface of the conductive paste is flattened by the concave surface. Therefore, the flatness of the outer surfaces 7a, 8a of the external electrodes 7, 8 after baking is improved.

Therefore, the above-mentioned tombstone phenomenon is likely to occur with the miniaturization. However, in the multilayer capacitor 1 of this embodiment, the outer surfaces 7a and 8a of the external electrodes 7 and 8 are flattened, so that the tombstone phenomenon occurs. Can be effectively suppressed.

The degree of the concave surface is as follows.
Since it depends on the adhesive force of the conductive paste, it cannot be uniquely determined. However, in order to effectively suppress the tombstone phenomenon, it is preferable that the external electrode 7 be provided at the portion where the internal electrodes 3 to 6 are stacked. , 8 are determined to be flat.

Further, the specific degree of the concave shape of the concave surface cannot be uniquely determined because it varies depending on the dimensions of the ceramic sintered body 2 and the like. In the case where a size of × 0.8 × 0.8 mm or less is used, the innermost end of the end faces 2 c and 2 d is indented 3 μm or more, more preferably 5 μm or more inward than the outermost end. Preferably, the outer surfaces 7a and 8a of the external electrodes 7 and 8 can be made flatter.

As described above, the method for forming the end surfaces 2c and 2d into concave surfaces concave at the intermediate height is not particularly limited, but the following various methods can be exemplified. As a first method, in obtaining the ceramic sintered body 2, plain ceramics which are arranged above and below a portion where the internal electrodes 3 to 6 are laminated as ceramic green sheets having internal electrodes formed on the upper surface. There is a method in which a ceramic green sheet softer than the green sheet is used and the end face of the laminate is polished with an abrasive prior to firing. That is, when the laminate is polished by sand blasting or the like, the middle ceramic green sheet on which the internal electrodes are laminated is relatively soft, so the intermediate height position portion of the laminate end surface is more than the upper and lower portions. Polished a lot. Therefore, after firing, the end surfaces 2c and 2d can be made the concave surfaces.

As described above, various methods can be used to make the ceramic green sheet on which the internal electrode is laminated softer than the plain ceramic green sheet. For example, the ceramic green sheet on which the internal electrode is formed can be used. A method of relatively increasing the content of the plasticizer in the green sheet may be used.

In the second method, a plain ceramic green sheet having a smaller shrinkage ratio during firing is used as compared with the ceramic green sheet on which the internal electrodes are formed. In this case, at the stage where the laminate is obtained prior to firing, the end face is flat, but firing causes the intermediate surface of the end faces 2c and 2d to be dented due to the difference in shrinkage, and the end face 2c , 2d are concave surfaces.

As described above, various methods can be used for differentiating the contraction rate. For example, the glass frit content in the ceramic green sheet on which the internal electrode is formed is made higher than the glass frit content of the plain ceramic green sheet, or the plasticizer content of the ceramic green sheet on which the internal electrode is formed is reduced. And a method of increasing the plasticizer content ratio of the plain ceramic green sheet.

As a third method, after the ceramic sintered body 2 is obtained, the end faces 2c and 2d of the ceramic sintered body 2 are obtained.
Are selectively polished at intermediate height positions of the end faces 2c and 2d.
May be a concave surface. Note that the above-described various methods of forming the end surfaces 2c and 2d as concave surfaces may be appropriately used in combination.

Next, the method of manufacturing the multilayer capacitor will be clarified by describing specific experimental examples, and the fact that the tombstone phenomenon is effectively suppressed will be specifically described.

A ceramic powder containing barium titanate as a main component, a polyvinyl butyral-based binder, an organic solvent and dioctyl phthalate as a plasticizer are mixed, and the content ratio of dioctyl phthalate is 2.5 parts by weight with respect to 100 parts by weight of the ceramic powder. , A first ceramic slurry was obtained.

Next, in the same manner as in the first ceramic slurry, except that the content ratio of dioctyl phthalate is 3.0 parts by weight with respect to 100 parts by weight of the ceramic powder.
Was prepared.

Using the first ceramic slurry, a first ceramic green sheet was formed by a doctor blade method. Similarly, a second ceramic green sheet was formed using the second ceramic slurry.
An internal electrode was formed on the upper surface of the first ceramic green sheet by screen printing a conductive paste.

Next, each of the first and second data shown in FIGS.
The second ceramic green sheets were laminated and pressed in the thickness direction to obtain a ceramic laminate. That is, the first ceramic green sheets 11, 13 on which the internal electrodes 12, 14 shown in FIGS. 2B and 2C are printed.
Are alternately laminated, and the upper and lower plain second ceramic green sheets 15 and 16 shown in FIGS.
Were laminated on each other to obtain a ceramic laminate.

The first and second end faces (the end faces from which the internal electrodes are drawn out) of the ceramic laminate obtained as described above were ground by sandblasting. As a result, the first dioctyl phthalate having a high content of
The intermediate height position portion where the ceramic green sheets are laminated is shaved more than the upper portion and the lower portion, and the end surface is a concave surface.

As described above, the ceramic laminate having the concave end face was fired to obtain the ceramic sintered body 2 shown in FIG. After that, the end face 2 of the ceramic sintered body 2
The ceramic sintered body 2 was immersed in the conductive paste layer from the c side and pulled up, so that the conductive paste was applied so as to cover the end face 2c. Subsequently, the ceramic sintered body 2 was immersed in the conductive paste layer from the end face 2d side and pulled up to form a conductive paste layer so as to cover the end face 2d.

Thereafter, the first and second external electrodes 7 and 8 are formed by baking the conductive paste attached so as to cover the end surfaces 2c and 2d.
I got The external dimensions of the multilayer capacitor 1 are 1.6 × 0.
It is 8 × 0.8 mm.

In obtaining the multilayer capacitor 1 described above, by changing the grinding conditions by the sand blast method,
As shown in Table 1 below, the dent amounts of the end faces 2c and 2d are set to 0.
μm, 1 μm, 3 μm and 5 μm to obtain various multilayer capacitors. Then, the various multilayer capacitors thus obtained were mounted on a printed circuit board by a reflow soldering method, and it was confirmed whether or not the tombstone phenomenon occurred. The results are shown in Table 1 below.

The above-mentioned dent amount is defined as the end faces 2c and 2d.
Means the horizontal distance from the outermost end to the innermost end of the concave portion.

[0042]

[Table 1]

As is clear from Table 1, the end faces 2c and 2d
When the dent amount was 0 μm, that is, on the surface that was not a concave surface, a tombstone phenomenon occurred in five multilayer capacitors out of 1,000 multilayer capacitors.

On the other hand, when the dent amount is 1 μm or more and the end surfaces 2 c and 2 d are concave surfaces, the occurrence ratio of the tombstone phenomenon can be effectively suppressed, and particularly, the dent amount is 3 μm or more. In this case, no tombstone phenomenon occurred.

Accordingly, by making the end surfaces 2c and 2d concave, the outer surfaces 7a and 8a of the external electrodes 7 and 8 formed by applying and baking the conductive paste are flattened,
This shows that the occurrence of the tombstone phenomenon can be effectively suppressed.

Although the above embodiments have been described by taking a multilayer capacitor as an example, the multilayer ceramic electronic component according to the present invention is not limited to a multilayer capacitor, but may be various types such as a multilayer thermistor, a multilayer varistor, and a multilayer piezoelectric ceramic electronic component. The present invention can be generally applied to multilayer ceramic electronic components.
The external dimensions of the multilayer ceramic electronic component are 1.6 ×
It is more effective when applied to a member having a size of 0.8 × 0.8 mm or less.

[0047]

In the multilayer ceramic electronic component according to the first aspect of the present invention, since the first and second end faces of the ceramic sintered body are concave at the intermediate height,
Even if the first and second external electrodes are formed by applying and baking a conductive paste, the surfaces of the first and second external electrodes are flattened. Therefore, the tombstone phenomenon when mounted on a printed circuit board or the like by, for example, the reflow soldering method can be effectively suppressed, and the reliability and stability of the mounting operation of the multilayer ceramic electronic component can be improved.

According to the second aspect of the present invention, the first and second end surfaces are the concave surfaces, whereby the outer surfaces of the external electrodes are made flat. Therefore, the tombstone phenomenon at the time of mounting the multilayer ceramic electronic component on the printed circuit board can be suppressed, and the mounting reliability and stability of the multilayer ceramic electronic component can be improved.

In the method for manufacturing a multilayer ceramic electronic component according to the third aspect of the present invention, the ceramic green sheet on which the internal electrodes are formed is a ceramic green sheet that is softer than a plain ceramic green sheet, and is laminated before firing. When the body end face is polished with an abrasive, the edge of the ceramic green sheet on which the internal electrodes are formed is greatly polished, whereby the end face can be made concave. Therefore, it is possible to reliably obtain a ceramic sintered body in which the first and second end surfaces are concavely concave at the intermediate height position by firing, and the multilayer ceramic electronic component according to claim 1 or 2. Can be provided.

According to the fourth aspect of the present invention, since a ceramic green sheet having a contraction rate during firing smaller than that of the ceramic green sheet on which the internal electrodes are formed is used as the plain ceramic green sheet,
In the ceramic sintered body obtained by firing,
In the second end face, the middle height position where the internal electrodes are stacked is dented, and the first and second end faces are concave.
Therefore, the multilayer ceramic electronic component according to claim 1 or 2 can be provided.

According to the fifth aspect of the present invention, a ceramic green sheet having a higher glass frit content ratio than a plain ceramic green sheet is used as a ceramic green sheet on which internal electrodes are formed.
The shrinkage rate of the plain ceramic green sheet during firing is made smaller than the shrinkage rate of the ceramic green sheet on which the internal electrodes are formed. Therefore, after firing, the first and second end surfaces are surely made concave, and the multilayer ceramic electronic component according to claim 1 or 2 can be provided.

According to the sixth aspect of the present invention, since the ceramic green sheet on which the internal electrodes are formed is a ceramic green sheet having a higher plasticizer content ratio than a plain ceramic green sheet, the first and second ceramic green sheets are formed before firing. When the second end face is polished, the intermediate height position where the internal electrodes are stacked is polished larger than the upper and lower portions, thereby ensuring that the first and second end faces are concave. it can. Further, the shrinkage rate of the plain ceramic green sheet when firing is made smaller than the shrinkage rate of the ceramic green sheet on which the internal electrodes are formed. Therefore, after firing, the first and second end surfaces are surely made concave. Therefore, the multilayer ceramic electronic component according to claim 1 or 2 can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a multilayer capacitor according to one embodiment of the present invention.

FIGS. 2A to 2D are plan views illustrating a ceramic green sheet prepared for obtaining a multilayer capacitor according to an embodiment and internal electrode shapes formed thereon;

FIG. 3 is a longitudinal sectional view for explaining a tombstone phenomenon when a conventional multilayer capacitor is mounted on a printed circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Multilayer capacitor 2 ... Ceramic sintered body 2c, 2d ... 1st, 2nd end surface 3-6 ... Internal electrode 7, 8 ... 1st, 2nd external electrode 7a, 8a ... Outer surface 11, 13, 15 , 16 ... ceramic green sheet 12, 14 ... internal electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E001 AB03 AC03 AD03 AE00 AE02 AE03 AE04 AF06 AH00 AH05 AH09 AJ02 5E082 AA01 AB03 BC40 EE04 EE35 FG06 FG25 FG26 FG27 FG32 FG52 FG54 GG10 GG28 HH43LL01

Claims (6)

[Claims] 1. A ceramic sintered body; a plurality of internal electrodes arranged so as to overlap in a thickness direction via a ceramic layer in the ceramic sintered body; And first and second external electrodes respectively formed on the end faces of the ceramic sintered body and electrically connected to any of the internal electrodes, wherein the first and second end faces of the ceramic sintered body are intermediate. A multilayer ceramic electronic component having a concave concave surface at a height position. 2. The multilayer ceramic electronic component according to claim 1, wherein outer surfaces of said first and second external electrodes are flatter than end faces of said ceramic sintered body. 3. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein the plurality of ceramic green sheets having an internal electrode formed on one main surface thereof, and a plain green color having no internal electrode formed thereon. A step of preparing a ceramic green sheet; and a ceramic green sheet and a plain ceramic having an internal electrode formed thereon such that the plain ceramic green sheet is positioned above and below a plurality of laminated ceramic green sheets on which the internal electrode is formed. A step of stacking green sheets to obtain a laminate; and a step of firing the laminate to obtain a ceramic sintered body, wherein the ceramic green sheets on which the internal electrodes are formed are formed from plain ceramic green sheets. Also use a soft ceramic green sheet and prior to the firing And further comprising the step of polishing with the polishing slurry an end surface of the lamina, the method of production of a multilayer ceramic electronic component. 4. The method for manufacturing a multilayer ceramic electronic component according to claim 1, wherein a plurality of ceramic green sheets having an internal electrode formed on one main surface thereof, and a plain green color having no internal electrode formed thereon. A step of preparing a ceramic green sheet; and a ceramic green sheet and a plain ceramic having an internal electrode formed thereon such that the plain ceramic green sheet is positioned above and below a plurality of laminated ceramic green sheets on which the internal electrode is formed. A step of obtaining a laminated body by laminating green sheets; and a step of obtaining a ceramic sintered body by firing the stacked body. Use a ceramic green sheet smaller than the shrinkage of the formed ceramic green sheet. It characterized Rukoto, the method of production of a multilayer ceramic electronic component. 5. The ceramic green sheet according to claim 3, wherein the ceramic green sheet on which the internal electrode is formed is a ceramic green sheet having a higher glass frit content ratio than a plain ceramic green sheet. A method for manufacturing a multilayer ceramic electronic component. 6. The ceramic green sheet on which the internal electrodes are formed is a ceramic green sheet having a higher plasticizer content ratio than a plain ceramic green sheet. A method for manufacturing a multilayer ceramic electronic component.