JP2004296936A - Ceramic electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic electronic component having an impact strength capability when surface-mounted onto a wiring board, and capable of preventing both excess creeping of solder up to an external electrode and a crack caused by an unnecessary stress. <P>SOLUTION: The ceramic component includes a component main body 1 of a rectangular parallelepiped, constituted of a ceramic member having internal conductors 3, 4 formed thereon; underlaying conductive layers 5a, 6a connected to the internal conductors 3, 4 and formed in such a way as bridging between the end surface and the main surface of the component main body 1; and external electrodes 5, 6 constituted of conductive resin layers 5b, 6b formed on a ridge between the end surface and the main surface of the component main body 1, so as to cover the underlaying conductive layers 5a, 6a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ceramic electronic component, and more particularly to a structure of an external electrode of a ceramic electronic component having a plurality of external electrodes on one end surface of a rectangular parallelepiped component body.
[0002]
[Prior art]
A description will be given of a multiple capacitor as an example of a typical ceramic electronic component.
[0003]
3A and 3B are views showing a conventional multiple capacitor, in which FIG. 3A is an external perspective view, and FIG. 3B is a sectional view taken along line XX.
[0004]
As shown in the figure, the multilayer body 31 (component body) of the multiple capacitor 30 is formed by laminating a plurality of dielectric layers 32.
[0005]
For example, a plurality of first and second internal electrodes (internal conductors) 33 and 34 are formed opposite to each other between the dielectric layers 32 of the multilayer body 31, and the first internal electrode 33 is provided on one end surface of the multilayer body 31. Further, the second internal electrode 34 extends to the other end surface of the multilayer body 31.
[0006]
Further, the plurality of external electrodes 35 and 36 are formed over the end surface of the multilayer body 31 and the main surface in contact with the end surface. Thereby, the end surfaces of the external electrodes 35 and 36 are connected to the first and second internal electrodes 33 and 34. The main surfaces (mounting surfaces) of the external electrodes 35 and 36 are securely mounted on the wiring board.
[0007]
A surface plating layer (not shown) is formed on the surfaces of the external electrodes 35 and 36 as necessary.
[0008]
Such a multiple capacitor 30 is surface-mounted on a wiring pattern on a wiring board with one main surface (mounting surface) down using a bonding material such as solder or a conductive adhesive.
[0009]
Here, in recent years, the demand for the multiple capacitors 30 for portable electronic devices such as portable telephones and portable computers has been increasing.
[0010]
However, in a portable electronic device, when used or carried, an impact due to a drop or the like is applied to the multiple capacitor 30 mounted on the wiring board inside the device, and as shown in FIG. 30 has a problem that a crack 38 is generated.
[0011]
Therefore, as shown in FIG. 4, a rectangular parallelepiped laminated body (component body) 41 in which internal electrodes (internal conductors) 43 and 44 are formed between a plurality of laminated dielectric layers 42 and internal electrodes 43 and 44 are connected. At the same time, the underlying conductor layers 45a and 46a formed so as to extend over the end surface and the main surface of the multilayer body 41, and the conductive layers formed so as to extend over the main surface portions of the underlying conductor layers 45a and 46a and the main surface of the multilayer body 41 Japanese Unexamined Patent Application Publication No. 2003-7567 discloses a multiple capacitor 40 including external electrodes 45 and 46 composed of conductive resin layers 45b and 46b.
[0012]
[Patent Document 1]
JP-A-2003-7567 (page 3-5, FIG. 1-13)
[0013]
[Problems to be solved by the invention]
However, in recent years, according to a study by the inventor, a crack 38 occurs starting from a portion where the ridge of the laminate 41 is in contact with the external electrodes 45 and 46 and the bonding material 13, and the crack 38 progresses to the side surface of the laminate 41. I know that. Therefore, in the multiple capacitor 40 shown in FIG. 4, there is a limit in preventing the occurrence of the crack 38 when the impact due to the drop or the like becomes severe.
[0014]
The present invention has been devised in view of the above problems, and an object of the present invention is to provide a ceramic electronic component having excellent impact resistance.
[0015]
[Means for Solving the Problems]
The present invention provides a rectangular parallelepiped component body made of a ceramic member having an internal conductor formed thereon, and a base conductor layer connected to the internal conductor and formed so as to extend over an end surface and a main surface of the component main body, An external electrode comprising a conductive resin layer formed on a ridge line between the end surface and the main surface of the component body is provided.
[0016]
[Action]
According to the ceramic electronic component of the present invention, a rectangular parallelepiped component body made of a ceramic member having an internal conductor formed thereon, and a base conductor connected to the internal conductor and formed so as to straddle the end surface and the main surface of the component main body And an external electrode formed of a conductive resin layer formed on a ridge line between the end surface and the main surface of the component body so as to cover the base conductor layer. That is, it is formed so that the central portion of the end face underlying conductor layer is exposed. For this reason, cracks can be reduced even if an impact due to dropping or the like is applied to the ceramic electronic component in a state where the ceramic electronic component is surface-mounted on a wiring board with a bonding material such as solder.
[0017]
That is, in many cases, a stress in the torsional direction is applied to the ceramic electronic component due to an impact due to a drop or the like. Then, at this time, cracks are generated from the part where the ridge line of the component body and the external electrode are in contact with the bonding material, and it is considered that the crack proceeds and proceeds to the side surface of the component body. Since the conductive resin layer is formed on the ridge line between the end face and the main surface, the thickness of the external electrode covering the ridge line of the component body is increased, and the component body is protected from torsional stress. It is considered that the occurrence of cracks can be reduced. In addition, since the conductive resin layer is appropriately deformed, it is possible to prevent the stress in the torsional direction from being transmitted to the starting point, and it is considered that this can also reduce the occurrence of cracks.
[0018]
In addition, since the conductive resin layer is formed only on the ridgeline between the end surface and the main surface of the component body, when the ceramic electronic component is surface-mounted on a wiring board with a bonding material, the solder is opposite to the mounting surface. Does not climb over the conductive resin layer, and the position where the stress is generated in the laminate is lowered. Further, dimensional variations of the ceramic electronic component can be suppressed.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a ceramic electronic component of the present invention will be described with reference to the drawings.
[0020]
A description will be given of a multiple capacitor as an example of a typical ceramic electronic component.
[0021]
1A and 1B are views showing a multiple capacitor of the present invention, wherein FIG. 1A is an external perspective view, and FIG. 1B is a longitudinal sectional view. FIG. 2 is a sectional view showing a state in which the multiple capacitor of FIG. 1 is surface-mounted on a wiring board.
[0022]
In the figure, 10 is a multiple capacitor (ceramic electronic component), 1 is a laminated body (component body) made of dielectric ceramic, 2 is a dielectric layer, 3 and 4 are internal electrodes, and 5 and 6 are external electrodes. Reference numeral 11 denotes a wiring board, 12 denotes a wiring pattern, and 13 denotes a solder (joining material).
[0023]
As shown in FIG. 1, the multilayer body 1 of the multiple capacitor 10 is formed by laminating a plurality of dielectric layers 2.
[0024]
The dielectric layer 2 is made of a non-reducing dielectric material containing barium titanate (BaTiO ₃ ) as a main component and a dielectric material containing a glass component, and has a shape of 2.0 mm × 1.2 mm or the like. The thickness is set to 1 to 5 μm to increase the capacity. The dielectric layer 2 is stacked in the upward direction in the drawing to form the laminate 1. The shape, thickness, and number of layers of the dielectric layer 2 can be arbitrarily changed according to the capacitance value.
[0025]
For example, a plurality of internal electrodes 3, 4 are formed facing each other between the dielectric layers 2 of the multilayer body 1, and extend to both end surfaces of the multilayer body 1, respectively. The internal electrodes 3 and 4 are made of, for example, a material mainly containing Ni, and have a thickness of 1 to 2 μm.
[0026]
The external electrodes 5 and 6 are attached to the pair of long side end surfaces of the multilayer body 1 and are connected to the internal electrodes 3 and 4, respectively. Further, a surface plating layer (not shown) is formed on the surfaces of the external electrodes 5 and 6. The surface plating layer can be exemplified by, for example, Ni plating, Sn plating, solder plating, and the like. A feature of the present invention is that the external electrodes 5 and 6 are connected to the internal electrodes 3 and 4 and are connected to the end surfaces of the laminate 1. The base conductor layers 5a and 6a formed so as to straddle the main surface, and the center portions of the end face base conductor layers 5a and 6a formed on the end faces of the laminate 1 so as to cover the base conductor layers 5a and 6a. It consists of conductive resin layers 5b and 6b which are exposed and formed on the ridge line between the end surface and the main surface of the laminate 1.
[0027]
The base conductor layers 5a and 6a are made of a base metal component such as Cu, Ni, or an alloy thereof, and a glass component, and have an end surface on the long side and two main surfaces adjacent to the end surface (one of which is a mounting surface). Formed over the surface.
[0028]
The conductive resin layers 5b and 6b are formed by mixing a thermosetting resin such as an epoxy resin, a phenol resin, and an acrylic resin with a conductive powder such as Cu, Ni, and Ag.
[0029]
Here, the amount yb of each of the conductive resin layers 5b and 6b wrapping around from the main surface of the multilayer body 1 to the end face of the multilayer body 1 is 0.05 ≦ when the dimension in the height direction of the multiple capacitor 10 is T. It is desirable that yb / T ≦ 0.3. That is, when yb / T is less than 0.05, the effect of reducing the occurrence of cracks 38 when impact due to dropping or the like is applied to the multiple capacitor 10 is not sufficiently exhibited. On the other hand, when yb / T is less than 0.3, a pair of conductive resin layers 5b and 6b on the mounting surface side (or the opposite side) are formed, and then a pair of conductive resin layers on the opposite side (or the mounting surface side). According to the method of forming the conductive resin layers 5b and 6b, the conductive resin layers 5b and 6b cannot be formed with high accuracy, and the dimensional variation in the W direction of the multiple capacitor 10 increases.
[0030]
In addition, in order to effectively reduce the occurrence of cracks 38, when the thickness of the external electrodes 5 and 6 covering the ridge line is rt and the radius of curvature of the ridge line portion of the multilayer body 1 is r1, rt / The r1 ratio is desirably 0.25 or more.
[0031]
Hereinafter, a method for manufacturing the multiple capacitor 10 of the present invention will be described. Each code is not distinguished before and after firing.
[0032]
First, a conductive paste is formed on a ceramic green sheet 2 serving as a dielectric layer by screen printing, and conductive films 3 and 4 serving as internal electrodes are formed.
[0033]
Then, after stacking a predetermined number of such ceramic green sheets 2 so that the conductor films 3 and 4 face each other and the conductor films 3 and 4 extend to different end faces, the ceramic green sheets 2 are cut and each capacitor is cut. The unfired laminate 1 including the unit N is fired under a predetermined atmosphere, temperature and time. Thus, the internal electrodes 3 and 4 are exposed on the pair of end surfaces of the multilayer body 1 for each capacitor unit N.
[0034]
Then, in order to electrically connect each capacitor unit N to the outside, the conductor films 5a and 6a serving as the base conductor layers of the external electrodes are formed on the end face of the laminate 1 and two faces adjacent thereto by a screen printing method and a roller. It is applied by a transfer method or the like. Then, the conductive films 5a and 6a are formed by removing the binder components in the air at 250 ° C. to 400 ° C. and then baking at 800 to 900 ° C. in a neutral or reducing atmosphere to form the base conductor layers 5a and 6a. .
[0035]
Thereafter, conductive epoxy-based thermosetting conductive resin layers 5b and 6b are applied on the ridge line between the end surface and the main surface of the laminate 1 so as to cover the base conductor layers 5a and 6a, respectively, and dried and cured. Are sequentially formed. As a coating method, a screen printing method, a dropping method from a dispenser, or the like is used. At this time, in the method of forming the conductive resin layer 5b (or 6b) on one end surface of the laminate 1 and then forming the conductive resin layer 6b (or 5b) on the other end surface of the laminate 1, Since the conductive resin layers 5b and 6b are formed on the inclined surface due to the variation in the formation of the layers 5a and 6a, the conductive resin layers 5b and 6b cannot be formed accurately. After forming the resin layers 5b and 6b, the conductive resin layers 5b and 6b are formed on a flat surface by a method of forming a pair of conductive resin layers 5b and 6b on the opposite side (or the mounting surface side) from the mounting surface. Therefore, it can be formed with high accuracy.
[0036]
In this way, the external electrodes 5, 6 composed of the base conductor layers 5a, 6a and the conductive resin layers 5b, 6b are formed.
[0037]
Thereafter, surface plating layers (not shown) are formed on the external electrodes 5 and 6 by electrolytic plating or electroless plating.
[0038]
Thus, the multiple capacitor 10 of the present invention is obtained.
[0039]
Thus, according to the multiple capacitor 10 of the present invention, the external electrodes 5, 6 are connected to the internal electrodes 3, 4, and are formed so as to extend over the end surface and the main surface of the multilayer body 1. 5a, 6a, and conductive resin layers 5b, 6b formed on the ridges between the end surfaces and the main surface of the laminate 1 so as to cover the base conductor layers 5a, 6a. For this reason, in a state where the multiple capacitor 10 is surface-mounted on the wiring pattern 12 on the wiring board 11 by the solder 13, the occurrence of cracks 38 can be reduced even if an impact due to a drop or the like is applied to the multiple capacitor 10.
[0040]
That is, in many cases, a stress in the torsional direction is applied to the multiple capacitor 10 by an impact due to a drop or the like. At this time, it is considered that a crack 38 occurs starting from a portion where the ridge line of the laminate 1 is in contact with the external electrodes 5 and 6 and the solder 13 and proceeds to the side surface of the laminate 1, but the conductive resin layer 5b, It is thought that the presence of 6b increases the thickness rt of the external electrodes 5 and 6 covering the ridge line of the laminated body 1 and protects the laminated body 1 from the stress in the torsional direction, so that the occurrence of cracks 38 can be reduced. Can be In addition, since the conductive resin layer is appropriately deformed, it is possible to prevent the stress in the torsional direction from being transmitted to the starting point, and it is considered that the generation of the cracks 38 can be reduced also by this.
[0041]
Further, since the conductive resin layers 5 b and 6 b are formed only on the ridge line between the end surface and the main surface of the multilayer body 1, the multiple capacitors 10 are connected to the wiring pattern 12 on the wiring board 11 by the solder 13. In the case of surface mounting, the solder 13 does not climb over the conductive resin layers 5b and 6b on the side opposite to the mounting surface, and the position where the stress occurs in the laminate 1 is reduced.
[0042]
Furthermore, a method of forming a pair of conductive resin layers 5b and 6b on the mounting surface side (or the opposite side), and then forming a pair of conductive resin layers 5b and 6b on the opposite side (or the mounting surface side) of the mounting surface. Therefore, the conductive resin layers 5b and 6b can be formed with high accuracy, and the dimensional variation of the multiple capacitor 10 can be suppressed.
[0043]
It should be noted that the present invention is not limited to the above embodiments, and various changes and improvements may be made without departing from the spirit of the present invention.
[0044]
For example, in the above embodiment, the description has been made using the multiple capacitor 10 as the ceramic electronic component. However, in the present invention, the external electrodes 5 and 6 extend from the end surface of the component main body 1 to three or four surfaces adjacent thereto. The present invention can also be applied to ordinary multilayer ceramic capacitors formed in the above. Further, the present invention can be applied to a ceramic electronic component in which the external electrodes 5 and 6 are formed so as to extend from the end face of the component body 1 to only one face adjacent thereto. Further, the present invention can be applied to other electronic components and other ceramic electronic components such as semiconductor components.
[0045]
Further, in the above embodiment, the width na of the underlying conductor layers 5a and 6a formed on the main surface of the laminate 1 and the width nb of the conductive resin layers 5b and 6b are substantially the same, and the underlying conductor layers 5a and 6a are formed. The distances xa and xb between the end surfaces of the conductive resin layers 5b and 6b and the portions formed on the main surface of the multilayer body 1 are substantially the same, but na <nb or xa <xb. You may make it. As a result, the bonding strength between the conductive resin layers 5b, 6b and the laminate 1 is greater than the bonding strength between the base conductor layers 5a, 6a and the laminate 1, so that the external electrodes 5 formed on the main surface of the laminate 1 are formed. , 6 can be reduced. Conversely, na> nb or xa> xb may be satisfied. As a result, the material cost of the expensive conductive resin can be reduced, and the conductive resin layers 5b, 6b can be formed accurately even when the surfaces of the base conductor layers 5a, 6a have irregularities. Here, the nb / na ratio is desirably 0.2 ≦ nb / na ≦ 2, preferably 0.5 ≦ nb / na ≦ 1.25, and the xb / xa ratio is 0.1 ≦ xb / It is desirable that xa ≦ 4, preferably 0.3 ≦ xb / xa ≦ 2. That is, when the nb / na ratio is less than 0.2 or the xb / xa ratio is less than 0.1, the generation of the crack 38 when an impact due to a drop or the like is applied to the multiple capacitor 10 is reduced. The effect of reducing does not appear sufficiently. On the other hand, if nb / na is larger than 2, unnecessary conduction between adjacent capacitor units (NN) becomes a problem due to soldering. If the xb / xa ratio is larger than 4, unnecessary conduction between the external electrodes (5-6) of different polarities due to the soldering 13 becomes a problem.
[0046]
As shown in FIG. 1, the present inventor produced a multiple capacitor 10 in which the external electrodes 5 and 6 were composed of the underlying conductor layers 5a and 6a and the conductive resin layers 5b and 6b, as shown in FIG. Here, the dimensions of the multiple capacitor 10 were 2.0 mm × 1.2 mm.
[0047]
As a comparative example, as shown in FIG. 3, external capacitors 35 and 36 are formed of multiple capacitors 30 composed of only underlying conductor layers 35a and 35b, and as shown in FIG. And conductive resin layers 45b and 46b formed so as to extend over the main surfaces of the base conductor layers 45a and 46a and the main surface of the laminated body 41. The multiple capacitor 40 composed of In addition, as shown in FIG. 5, the external electrodes 55 and 56 cover the base conductor layers 55a and 56a formed so as to extend over the end surface and the main surface of the multilayer body 1, and cover the entire base conductor layers 55a and 56a. The multiple capacitor 50 including the conductive resin layers 55b and 56b formed as described above was also manufactured. In FIG. 5, 52 is a dielectric layer, and 53 and 54 are internal electrodes.
[0048]
About the obtained sample, the measurement of the dimension of W direction and the drop test were performed.
[0049]
Regarding the dimension in the width direction, ten samples were measured with calipers, and the largest value was obtained.
[0050]
In the drop test method, as shown in FIG. 2, 100 samples were surface-mounted on a wiring pattern 12 on a 1.6 mm thick glass epoxy substrate (wiring board) 11 by soldering. Then, the substrate 11 was set in a resin case, dropped on a concrete plate from a height of 2 m, and the incidence of cracks 38 was determined by a metallographic microscope.
[0051]
As a result of the measurement, as shown in FIG. 1, the external electrodes 5, 6 are connected to the internal electrodes 3, 4, and the underlying conductor layers 5a, 6a formed so as to extend over the end face and the main face of the laminate 1. In the tenth embodiment, the conductive resin layers 5b and 6b formed on the ridge line between the end surface and the main surface of the laminate 1 so as to cover the base conductor layers 5a and 6a. The size was 1.4 mm or less, and the incidence of cracks 38 when dropped on a concrete plate from a height of 2 m was 0% or less.
[0052]
On the other hand, as shown in FIG. 3, in the comparative example 30 in which the external electrodes 35 and 36 consist only of the base conductor layers 35a and 35b, when dropped on a concrete plate from a height of 2 m, cracks 38% occur. did.
[0053]
Also, as shown in FIG. 4, the external conductors 45 and 46 are formed so as to extend over the end surface and the main surface of the multilayer body 41, and the main surfaces of the base conductor layers 45a and 46a and In Comparative Example 40 including the conductive resin layers 45b and 46b formed so as to straddle the main surface of the laminate 41, when dropped on a concrete plate from a height of 2 m, cracks 38% occurred.
[0054]
On the other hand, as shown in FIG. 5, the external electrodes 55 and 56 cover the base conductor layers 55a and 56a formed so as to extend over the end face and the main face of the multilayer body 51, and cover the entire base conductor layers 55a and 56a. In Comparative Example 50 including the conductive resin layers 55b and 56b formed as described above, after the conductive resin layer 55b (or 56b) is formed, the external resin is formed by a method of forming the conductive resin layer 56b (or 55b). Since the electrodes 55 and 56 were formed, the dimensional variation in the W direction became large, and the maximum value of the dimension in the W direction became larger than 1.47 mm.
[0055]
From these results, the multiple capacitor 10 of the present invention is characterized in that the external electrodes 5 and 6 are connected to the internal electrodes 3 and 4 and the base conductor formed so as to extend over the end face and the main face of the multilayer body 1. It is composed of the layers 5a and 6a and the conductive resin layers 5b and 6b formed on the ridge line between the end surface and the main surface of the laminate 1 so as to cover the base conductor layers 5a and 6a. The cracks 38 can be reduced even if an impact due to a drop or the like is applied during surface mounting on the wiring board 11 while suppressing the dimensional variation, and the excessive rise of the solder 13 to the external electrodes 5 and 6 can be prevented. It was found that cracks 38 due to unnecessary stress can be prevented.
[0056]
【The invention's effect】
According to the ceramic electronic component of the present invention, the external electrode is connected to the internal conductor, and the base conductor layer formed so as to straddle the end surface and the main surface of the component body, so as to cover the base conductor layer. Since it is made of the conductive resin layer formed on the ridge line between the end face and the main face of the component body, it has excellent impact resistance.
[0057]
In addition, since the conductive resin layer is formed only on the ridgeline between the end surface and the main surface of the component body, when the ceramic electronic component is surface-mounted on a wiring board with a bonding material, the solder is opposite to the mounting surface. Does not climb over the conductive resin layer, and the position where the stress is generated in the laminate is lowered. Further, dimensional variations of the ceramic electronic component can be suppressed.
[Brief description of the drawings]
FIG. 1 is a view showing a multiple capacitor of the present invention, wherein (a) is an external perspective view and (b) is a cross-sectional view taken along line XX.
FIG. 2 is a cross-sectional view showing a state where the multiple capacitor of the present invention is surface-mounted on a wiring board.
3A and 3B are views showing a conventional multiple capacitor, in which FIG. 3A is an external perspective view, and FIG. 3B is a sectional view taken along line XX.
FIGS. 4A and 4B are diagrams showing another conventional multiple capacitor, in which FIG. 4A is an external perspective view, and FIG. 4B is a sectional view taken along line XX.
5A and 5B are diagrams illustrating a multiple capacitor of a comparative example, in which FIG. 5A is an external perspective view, and FIG. 5B is a cross-sectional view taken along line XX.
[Explanation of symbols]
10 Multiple capacitors (ceramic electronic components)
1 laminated body (part body)
2 Dielectric layers 3, 4 Internal electrode (internal conductor)
5, 6 External electrodes 5a, 6a Base conductor layers 5b, 6b Conductive resin layer 11 Wiring board 12 Wiring pattern 13 Solder

Claims (1)

A rectangular parallelepiped component body made of a ceramic member having an internal conductor formed thereon,
A base conductor layer connected to the internal conductor and straddling the end face and the main surface of the component main body; and a conductive layer formed on a ridge line between the end face and the main face of the component main body. A ceramic electronic component, comprising: an external electrode comprising a resin layer.

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