JP2000182879A - Ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic electronic component with superior reliability that tends not to have cracks or chips easily in the ceramic element assembly, because it can effectively absorb external forces caused by deflection, etc., of a printed circuit board, when the component is mounted on the printed circuit board, etc. SOLUTION: In this electronic component, terminal electrodes 7, 8, having a structure wherein first electrode layers 7a, 8a and second electrode layers 7b, 8b made of conductive resin, are laminated. Corner portions of a ceramic element assembly 2 are rounded so as to have a round-surface shape with a radius of curvature R. When the length between the end part 8a1 of the covered portion of the first electrode layers 7a, 8a on the opposite side terminal electrode and the end surface 2b on which the first electrode layer 8a is formed, and the lengths of the ceramic element body are A and B, respectively, where A<=0.1B and R>=A. The ends of the covered portion of the second electrode layers 7b, 8b are extended from the ends of the covered portion of the first electrode layers 7a, 8a toward the opposite side electrodes by 50 μm or longer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic electronic component such as a ceramic capacitor, and more particularly, to a ceramic electronic component having an improved terminal electrode formed on an end face of a ceramic body.

[0002]

2. Description of the Related Art In recent years, ceramic electronic components which can be surface-mounted on a printed circuit board and the like have been widely used as electronic devices have been downsized. FIG. 4 shows a state in which this type of ceramic electronic component is mounted on a substrate.

[0003] The ceramic electronic component 51 has a structure in which terminal electrodes 53 and 54 are formed on both end surfaces of a ceramic body 52. The terminal electrodes 53 and 54 are electrically connected to electrodes (not shown) on the printed circuit board 57 by solders 55 and 56, and the ceramic electronic component 51 is fixed to the printed circuit board 57.

Incidentally, the printed circuit board 57 soldered by the solders 55 and 56 may bend as shown by a broken line X in FIG. When the printed circuit board 57 bends, an external force is applied to the mounted ceramic electronic component 51 to cause cracks in the ceramic body 52 or to prevent the ceramic electronic component 51 from being attached to the printed circuit board 57.
May be partially destroyed or the electrical characteristics may be degraded.

Therefore, the printed circuit board 5 as described above is used.
There has been proposed a ceramic electronic component capable of absorbing an external force caused by, for example, bending of the ceramic electronic component. For example, Japanese Patent Application Laid-Open No. 5-144
No. 665 or the like discloses a configuration capable of absorbing the above-mentioned external force by providing an electrode layer formed by mixing a metal powder with a thermosetting resin. This conventional ceramic electronic component will be described with reference to FIG.

In the ceramic electronic component 61 shown in FIG.
Internal electrodes 63a to 63d are arranged in a ceramic body 62 made of a ceramic sintered body so as to overlap with a ceramic layer interposed therebetween. Terminal electrodes 64 and 65 are formed on the facing end surfaces 62a and 62b of the ceramic body 62, respectively.

The terminal electrodes 64 and 65 have a structure in which first electrode layers 64a and 65a, second electrode layers 64b and 65b, and third electrode layers 64c and 65c are laminated, respectively. The first electrode layers 64a and 65a are formed by applying and baking a conductive paste. Second electrode layer 64
b and 65b are formed by applying and curing a material obtained by adding a thermosetting resin as a binder to a metal powder. The third electrode layers 64c and 65c are formed in order to enhance solderability, and the second electrode layers 64c and 65c are formed.
It is formed by plating Sn, solder or the like on b, 65b.

Since the second electrode layers 64b and 65b are made of a material obtained by adding a thermosetting resin to metal powder as described above, the thermosetting resin prevents the printed circuit board from bending. The resulting external force is absorbed. Also,
Since the thermosetting resin is used as a matrix, the second electrode layers 64b and 65b are non-porous, and can block intrusion of moisture from the outside during processing or during driving of the ceramic electronic component 61. Thereby, the electric characteristics can be stabilized.

[0009]

However, even in the above-described ceramic electronic component 61, when the printed circuit board is largely bent after being mounted on the printed circuit board, the applied external force cannot be sufficiently absorbed. There was something. That is, the second electrode layers 64b, 65
b absorbs the external force, but the electrode layers 64b,
The absorption of external force by 65b was limited.

In particular, when the content ratio of the metal powder is increased in order to increase the conductivity of the second electrode layers 64b and 65b, the external force absorbing effect tends to be considerably reduced. An object of the present invention is to be able to effectively absorb such external force even when an external force caused by bending of the printed circuit board or the like is applied when mounted on a printed circuit board or the like,
It is an object of the present invention to provide a ceramic electronic component having excellent reliability, in which cracks and cracks of a ceramic body are less likely to occur and electrical characteristics are less likely to deteriorate.

[0011]

SUMMARY OF THE INVENTION The present invention provides a ceramic body having a pair of opposed end faces, an upper face, a lower face, and a pair of side faces connecting the pair of end faces. In a ceramic electronic component in which a terminal electrode is formed so as to have a lower surface and a cover portion extending to a pair of side surfaces, the terminal electrode includes a first electrode layer formed by baking or plating a metal paste; A second electrode layer formed on the electrode layer, the second electrode layer being made of a conductive resin; and an edge formed by an end face of the ceramic body, an upper face, a lower face, and a pair of side faces having a radius of curvature R. And a length between a terminal electrode side end of the terminal electrode on the other side of the covering portion of the first electrode layer of the terminal electrode and an end face on which the first electrode layer is formed. Dimension A, connect the pair of opposing end faces When the length of the ceramic body is B, A ≦ 0.1B and R ≧ A, and the terminal electrode side end of the counterpart of the covering portion of the second electrode layer is The one electrode layer extends at least 50 μm or more toward the counterpart terminal electrode from the counterpart terminal electrode side end.

In the ceramic electronic component according to the present invention, a third electrode layer may be further formed on the second electrode layer, and the third electrode layer may be formed to improve solderability. Those containing a plating film of Sn or a Sn alloy are preferably used.

The ceramic electronic component according to the present invention may be a multilayer ceramic electronic component having external electrodes. In this case, a plurality of internal electrodes are arranged in the ceramic body, and a plurality of internal electrodes are provided. The electrode is drawn out to one of the pair of end faces, and is electrically connected to the terminal electrode. However, the present invention can be applied not only to a multilayer ceramic electronic component but also to a ceramic electronic component having no internal electrode.

[0014]

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

FIG. 1A is a sectional view showing a multilayer capacitor as a ceramic electronic component according to one embodiment of the present invention. The multilayer capacitor 1 has a ceramic body 2 made of a substantially rectangular parallelepiped ceramic sintered body. The ceramic body 2 includes a pair of end faces 2a and 2b facing each other,
It has upper surfaces 2c and 2d connecting the end surfaces 2a and 2b, and both side surfaces (not shown). Internal electrodes 3 to 6 are formed in the ceramic body 2 so as to overlap with each other via a ceramic layer. The internal electrodes 3 and 5 are extended to the end face 2a, and the internal electrodes 4 and 6 are extended to the end face 2b.

In the ceramic body 2, the corners are rounded. That is, the end faces 2a, 2b
1 and the upper surface 2c, the lower surface 2d, and both edges are rounded so as to form a curved surface having a radius of curvature R (FIG. 1).
(B)).

The ceramic body 2 is obtained according to a well-known method for manufacturing a laminated ceramic electronic component. That is, a ceramic green sheet on which the internal electrodes 3 to 6 are printed is laminated, an appropriate number of plain ceramic green sheets are laminated vertically, and a laminate is obtained by pressing in the thickness direction. This laminate is fired to obtain a ceramic sintered body. The obtained ceramic sintered body is polished by barrel polishing or the like, and the end surfaces 2a and 2b, the upper surface 2c and the lower surface 2 are polished.
The ceramic body 2 is obtained by rounding the edges forming d and both side surfaces.

Terminal electrodes 7 and 8 are formed so as to cover the end surfaces 2a and 2b of the ceramic body 2. Each of the terminal electrodes 7 and 8 has a structure in which first electrode layers 7a and 8a, second electrode layers 7b and 8b, and third electrode layers 7c and 8c are sequentially stacked.

The first electrode layers 7a and 8a are formed by applying and baking a metal paste such as an Ag paste on the end faces 2a and 2b of the ceramic body 2.
However, the first electrode layers 7a and 8a may be formed by so-called metal dry plating instead of applying and baking a conductive paste.

The second electrode layers 7b, 8b formed on the first electrode layers 7a, 8a are made of, for example, a conductive resin in which an epoxy resin contains Ag as a filler. That is, the conductive resin is applied to the first electrode layers 7a, 8a.
a on the second electrode layer 7
b, 8b are formed.

The third electrode layers 7c and 8c are formed by forming a Ni plating film and / or a Sn or Sn alloy plating film on the second electrode layers 7b and 8b, whereby the terminal electrodes 7c and 8c are formed. , 8 are improved in solderability.

In the ceramic electronic component 1 of the present embodiment, the terminal electrode side ends of the terminal electrodes 7 and 8 on the opposite side of the covering portions of the first electrode layers 7a and 8a and the first electrode layers 7a and 8a.
When the length between the end faces 2a and 2b in which is formed is A and the length of the ceramic body is B, A ≦ A
0.1B.

The length A will be described with reference to FIG. 1A, taking the terminal electrode 8 as an example. The first electrode layer 8a of the terminal electrode 8 includes not only the end face 2b but also the upper face 2c and the lower face 2d.
And it is formed so as to reach both side surfaces, that is, to have a covering portion. Here, as those with the terminal electrode side end portion 8a ₁ of the mating fog portion of the first electrode layer 8a, of the wearing portion of the first electrode layer 8a, refer to the end 8a ₁ of the terminal electrode 7 side I do. A terminal electrode side end 8a ₁ of the other side of the covering portion.
A is a distance along the length direction of the ceramic body 2 between the first electrode layer 8a and the end face 2b on which the first electrode layer 8a is formed.

The length B of the ceramic body refers to the outer dimension of the ceramic body along the direction connecting the pair of end faces 2a and 2b. In this embodiment, the end surfaces 2a and 2b of the ceramic body 2 and the upper surface 2c and the lower surface 2d
And an edge formed by the pair of side surfaces is rounded so as to have a curved surface with a radius of curvature R, and R ≧ A.

Further, the covering portions of the second electrode layers 7b, 8b
Of the other terminal electrode side is the phase of the covering portion of the first electrode layer.
Towards the other terminal electrode from the end of the hand terminal electrode side
It is extended at least 50 μm or more. This is shown in FIG.
The terminal electrode 8 will be described as an example with reference to FIG. Second
Terminal electrode side end 8b of the other side of the covering portion of the electrode layer 8b ₁
And an end of the first electrode layer 8a on the counterpart terminal electrode side
8a₁Is at least 50 μm or more.
Have been.

In this embodiment, as described above, A ≦ 0.1
B, R ≧ A, the distance C is 50 μm or more, and the second electrode layers 7b, 8b are made of conductive resin. Even if the printed circuit board is largely bent when mounted on the surface of the printed circuit board, the external force caused by the bending can be effectively absorbed, thereby effectively preventing chipping or cracking of the ceramic body 2. Can be suppressed.

Next, specific experimental examples will be described. 80 layers of internal electrodes 3 to 6 using relaxor ceramics
Was formed, and a ceramic sintered body having an outer dimension of 2.0 mm × 1.2 mm was prepared. The edges formed by the end surfaces 2a and 2b of the ceramic sintered body, the upper surface 2c, the lower surface 2d, and the pair of side surfaces were polished by barrel polishing, and the edge portions were rounded. In this manner, a ceramic body 2 having a curved surface having a radius of curvature R of 120 μm was obtained.

An Ag paste is applied to the ceramic body 2 and baked to form a 30 μm thick first paste.
Of the electrode layers 7a and 8a were formed. Next, the first electrode layer 7
a, 8a is coated with a conductive epoxy resin and has a thickness of 12
Second electrode layers 7b and 8b made of a conductive resin of 0 μm were formed. Further, Ni is deposited on the second electrode layers 7b and 8b.
A plating layer and a solder plating layer were sequentially formed, and third electrode layers 7c and 8c having a two-layer structure were formed.

In order to obtain a multilayer capacitor as described above, the end portions of the first electrode layers 7a, 8a on the opposite terminal electrode side and the end surfaces 7a, 8a on which the terminal electrodes 7, 8 are formed are formed. The length A is varied between 0.04B, 0.07B, 0.14B and 0.21.
The multilayer capacitors of B were obtained.

The radius of curvature is R = 170 μm, R = 2
Using a ceramic body different from 00 μm, the length dimension A was A = 0.05B to 0.30B, A = 0.06B to
Various multilayer capacitors of 0.35B were obtained.

As shown in FIG. 2A, each of the multilayer capacitors obtained as described above was surface-mounted on a glass epoxy substrate 11 having a thickness of 2 mm using solder. Thereafter, the upper surface of the glass epoxy substrate 11 is moved to the position shown in FIG.
As shown in the figure, the surface on which the multilayer capacitor 1 is mounted is bent so as to protrude. In this case, the end faces 2a, 2b
The glass epoxy substrate 11 was bent so that the upper surface of the glass epoxy substrate 11 protruded upward by 5 mm at the center of the direction connecting the two.

As described above, the glass epoxy substrate 11
The occurrence of cracks and cracks in the ceramic body 2 when was bent was visually observed. The results are shown in Table 1 below.
3 are shown.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

As is apparent from Tables 1 to 3, the length A
Is 10% or less of the length dimension B of the ceramic body 2,
Further, it can be seen that by setting the length dimension A so as to be equal to or less than the radius of curvature R of the portion that has been curved by polishing, chipping and cracking of the ceramic body 2 in the ceramic electronic component 1 can be prevented.

On the other hand, if the length A exceeds 10% of the length B of the ceramic body 2, regardless of the relationship between the length A and the radius of curvature R of the curved surface of the corner portion. In addition, cracks and cracks of the ceramic body 2 occurred at a considerable rate. Even when the length dimension A is set to 10% or less of the length dimension B, when the length dimension A of the covering portion is larger than the radius of curvature R of the corner portion, the ceramic body still remains. Chipping and cracking of No. 2 occurred at a considerable rate.

As described above, it is considered that cracking and chipping of the ceramic body 2 can be suppressed by setting A ≦ 0.1B and R ≧ A for the following reasons.
That is, when the glass epoxy substrate 11 bends, the stress caused by the bend is caused by the mating terminal electrode side ends 7a ₁ , 1b of the _first electrode layers 7a, 8a formed by baking.
To concentrate on 8a _1. Therefore, the external force F is partially concentrated on the ceramic sintered body 2 as schematically shown in FIG.

However, the end face 2 of the ceramic body 2
In the case where the edges formed by a, 2b, the upper surface 2c, the lower surface 2d, and the pair of side surfaces are rounded and R ≧ A, FIG.
As shown in (a), it is considered that the external F force is dispersed in the curved surface portion, whereby the external force applied to the ceramic body 2 is suppressed, so that cracking and chipping of the ceramic body 2 are suppressed. The degree of dispersion of the stress depends on the relationship between the length A and the length B of the ceramic body 2,
In addition, since it depends on the relationship between the radius of curvature R of the curved surface portion and the length A of the electrode covering portion of the first electrode layer, A ≦ 0.1
It is considered that by setting B and R ≧ A, cracking and chipping of the ceramic body 2 can be suppressed.

Next, in the same manner as in the above-mentioned experimental example, except that the end portions of the second electrode layers 7b and 8b on the opposite side of the terminal electrode and the opposite end portions of the first electrode layer on the opposite terminal electrode side. The distances C between the ends were variously varied to obtain various multilayer capacitors. Note that in the second experimental example, R = 120 μ
m and A = 0.07B. The various multilayer capacitors obtained as described above were subjected to a bending test in the same manner as in the first experimental example, and it was visually confirmed whether or not cracks and cracks had occurred in the ceramic body 2. The results are shown in Table 4 below.

[0041]

[Table 4]

As is apparent from Table 4, R = 120 μm
When m and A = 0.07B and the distance C is less than 50 μm, it can be seen that cracking and chipping of the ceramic body 2 occur at a considerable rate even if R ≧ A. . On the other hand, when the distance C is 50 μm or more, when A ≦ 0.1B and R ≧ A are satisfied, it can be seen that cracking and chipping of the ceramic body 2 can be reliably suppressed.

Therefore, as in the present invention, the length A in the electrode covering portion of the first electrode layer is set to 10% or less of the length B of the ceramic body, and the end of the ceramic body 2 The radius of curvature R of the rounded portion is defined as length A
By setting the distance C to 50 μm or more, the external force caused by the deflection of the printed circuit board or the like when mounted on the printed circuit board can be effectively absorbed. It can be seen that cracking and chipping can be reliably suppressed.

In the above embodiment, the second electrode layer 7
b, 8b to improve the plating and soldering properties
Third electrode layer 7 composed of i-plated layer and Sn-plated layer
Although c and 8c are formed, the third electrode layer may be formed by a single plating film, and the third electrode layer may not be particularly formed.

[0045]

According to the ceramic electronic component of the present invention,
A terminal electrode having a first electrode layer formed by baking a metal paste or dry plating of a metal, and a second electrode layer made of a conductive resin;
The edge formed by the upper surface, the lower surface, and the pair of side surfaces has a radius of curvature R
And a length dimension A between an end of the first electrode layer on the opposite side of the terminal electrode and the end surface on which the first electrode layer is formed. Is 10% or less of the length B of the ceramic body, and R ≧ A, and the terminal electrode side end of the counterpart of the second electrode layer is covered with the first electrode layer. Is extended at least 50 μm or more toward the counterpart terminal electrode from the end of the counterpart terminal electrode side, so that even when the printed circuit board is bent due to a change in the ambient temperature or the like when mounted on a printed circuit board or the like, In addition, cracking and chipping of the ceramic body can be reliably prevented. Therefore, it is possible to reduce the failure of the ceramic body during processing and use, and to provide a ceramic electronic component having stable electric characteristics and excellent reliability.

In the case where a third electrode layer having a plating film formed by plating Sn or a Sn alloy on the second electrode layer is formed, solder for mounting on a printed circuit board or the like may be used. The attachment property can be improved.

In the present invention, the ceramic body may have no internal electrode or may have an internal electrode. If you have internal electrodes,
The plurality of internal electrodes are drawn out to a pair of end surfaces and are electrically connected to the terminal electrodes.By using a ceramic body having such internal electrodes, the present invention is suitable for a conventionally known multilayer capacitor and the like. It is possible to provide a multilayer ceramic electronic component having excellent reliability.

[Brief description of the drawings]

FIGS. 1A and 1B are a longitudinal sectional view and a partially cutaway longitudinal sectional view showing a ceramic electronic component according to an embodiment of the present invention in an enlarged manner and an upper portion thereof.

FIGS. 2A and 2B are schematic diagrams for explaining a state in which a ceramic electronic component according to an embodiment of the present invention is mounted on a glass epoxy board and a state in which the glass epoxy board is bent. Side view.

FIGS. 3A and 3B are diagrams for explaining stress applied to a ceramic body when a substrate is bent;
(A) is a partially cutaway sectional view for explaining a state in which stress is applied to a conventional ceramic electronic component, and (b) is for explaining a state in which stress is applied in a ceramic electronic component according to one embodiment of the present invention. FIG.

FIG. 4 is a side view for explaining a conventional ceramic electronic component.

FIG. 5 is a longitudinal sectional view illustrating an example of a conventional ceramic electronic component.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ceramic electronic component 2 ... Ceramic body 2a, 2b ... End surface 2c ... Upper surface 2d ... Lower surface 3-6 ... Internal electrode 7, 8 ... Terminal electrode 7a, 8a ... First electrode layer 7b, 8b ... Second electrode layer 7c, 8c ... third electrode layer 8a ₁ ... mating terminal electrode side end portion of the electrode layer overburden portion of the first electrode layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasunobu Yoneda 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. BC33 BC38 EE04 EE35 EE42 FG06 FG26 FG52 FG54 GG10 GG11 GG26 GG28 HH43 HH51 JJ03 JJ05 JJ12 JJ21 JJ23 LL02 MM22 MM24 PP09

Claims (3)

[Claims] 1. A ceramic body having a pair of opposed end surfaces and an upper surface, a lower surface, and a pair of side surfaces connecting the pair of end surfaces, covers not only the end surfaces but also the upper surface, the lower surface, and the pair of side surfaces. In a ceramic electronic component in which a terminal electrode is formed so as to have a portion, the terminal electrode is formed on a first electrode layer formed by baking or plating of a metal paste, and on the first electrode layer. And a second electrode layer made of a conductive resin, wherein the end surface of the ceramic body, and the upper surface, the lower surface, and a pair of side edges are rounded so as to form a curved surface having a radius of curvature R. The length dimension between the terminal electrode side end of the counter electrode covered with the first electrode layer and the end face on which the first electrode layer is formed is A, Ceramic element along the direction connecting the pair of end faces When the length of the body is B,
A ≦ 0.1B and R ≧ A, and the terminal electrode side end of the counterpart of the covering portion of the second electrode layer is connected to the terminal electrode side of the counterpart of the covering portion of the first electrode layer. A ceramic electronic component extending at least 50 μm or more toward an opposite terminal electrode from an end. A second electrode layer formed on the second electrode layer;
The ceramic electronic component according to claim 1, further comprising a third electrode layer including a Sn or Sn alloy plating film. 3. The semiconductor device according to claim 1, further comprising: a plurality of internal electrodes disposed in the ceramic body, wherein the plurality of internal electrodes are drawn out to one of a pair of end surfaces and are electrically connected to the terminal electrodes. 3. The ceramic electronic component according to 1 or 2.