JPH11224828A - Ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a ceramics electronic component from being damaged mechanically due to solder contraction, when soldering a ceramics electronic component on a wiring substrate or due to the expansion/contraction of a wiring substrate in mounting state, without fitting a terminal member of metal plate. SOLUTION: For a peripheral part 8 of a terminal electrode 6 formed extending as far as the part of an adjoining surface 5 which adjoins each end surface 4, while covering the each end surface 4 of a ceramics electronic component main body 3, an angle α formed between an external surface extending along the end surface 4 and the external surface extending along the adjoining surface 5 is set as an acute angle. Thus, the peripheral part 9 can be easily deformed, so that stresses due to contraction, etc., of a solder 12 is prevented from affecting the electronic component main body 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic electronic component, and more particularly to an improvement in the shape of a terminal electrode of a ceramic electronic component having a chip-shaped ceramic electronic component body made of ceramic.

[0002]

2. Description of the Related Art Ceramic electronic components having a chip-shaped ceramic electronic component body made of ceramic, which are of interest to the present invention, include, for example, capacitors, resistors, inductors, filters and the like. Are often surface mounted on a suitable wiring board.

In the above-described ceramic electronic component to be surface-mounted, terminal electrodes are formed on at least each end face of the electronic component main body. Is soldered to a predetermined conductive land. At this time, due to the stress generated due to the shrinkage effect due to the solidification of the solder, the ceramic electronic component is subjected to stress attracted to each terminal electrode side. As a result, mechanical damage such as cracking of the electronic component body may be caused to the ceramic electronic component.

[0004] Such mechanical damage to ceramic electronic components is also likely to occur in the following situations. That is, this is a case where the ceramic electronic component is mounted on a wiring board made of, for example, aluminum having excellent heat dissipation. In this case, since the difference in thermal expansion between the aluminum substrate and the ceramic electronic component is relatively large, as a result of a temperature cycle in which the temperature rises and falls repeatedly, for example, cracks occur in the electronic component body or cracks occur in the solder fillet. May occur.

[0005] Mechanical damage in the electronic component body is particularly likely to occur when a high-capacity Pb-based multilayer ceramic capacitor is mounted on a wiring board, for example, because its bending strength is relatively low. In order to solve the above-mentioned problems, a ceramic electronic component in which a terminal member made of a metal plate is attached to a terminal electrode by soldering has been put to practical use. According to the ceramic electronic component having such a structure, much of the stress that can be caused by the shrinkage of the solder for mounting or the expansion and contraction of the wiring board is absorbed by the deformation of the terminal member, and is directly applied to the electronic component body. Can not be.

[0006]

However, the ceramic electronic component having the above-mentioned terminal member has the following problems. First, as the terminal members, those having various dimensions must be prepared according to the dimensions of the ceramic electronic component, and various molds are required to obtain such terminal members having various dimensions. As a result, the cost of the ceramic electronic component increases.

Further, the work of attaching the terminal member to the terminal electrode is relatively complicated. In the case of soldering, a thermal shock may be applied to the electronic component body during the soldering, and cracks may be formed. In addition, since the terminal member usually limits the direction in which the ceramic electronic component is mounted on the wiring board to one specific direction, the degree of freedom in the mounting direction of the ceramic electronic component is impaired.

Further, depending on the type of metal constituting the terminal member, an undesirable increase in equivalent series resistance may occur. Further, as described above, the terminal member has an action of absorbing the stress generated at the time of solidification of the solder due to its deformation. However, since this deformation of the terminal member usually occurs within the elastic limit, It is inevitable that stress remains in the terminal members. In addition, cracks may occur between the terminal electrode and the terminal member during the temperature cycle.

An object of the present invention is to provide a ceramic electronic component which can solve the above-mentioned various problems.

[0010]

SUMMARY OF THE INVENTION The present invention provides a ceramic electronic component body in the form of a chip, and extends to a part of an adjacent surface adjacent to each end surface while covering the opposing end surfaces of the electronic component body. The present invention is directed to a ceramic electronic component including a terminal electrode formed with a predetermined thickness, and is characterized by having the following configuration in order to solve the above-described technical problem.

That is, each terminal electrode forms a peripheral portion by a portion located outside the above-mentioned adjacent surface of the electronic component body, and an outer surface extending along the end surface of the electronic component body at this peripheral portion. An angle between the outer surface extending along the adjacent surface and the outer surface is an acute angle. In the present invention, the angle is preferably equal to or less than 60 degrees.

Further, in the present invention, the electronic component body has an inner conductor, and the terminal electrodes are formed on the inner layer formed on the electronic component body so as to be electrically connected to the inner conductor, and on the inner layer. It is preferable to have at least a two-layer structure having an outer layer. Preferably, the cross-sectional shape of the above-mentioned peripheral portion is substantially triangular. In this case, more preferably, in the cross-sectional shape of the peripheral portion, the dimension projecting from the adjacent face is substantially equal to the dimension measured in the direction in which the adjacent face extends.

[0013] In the cross-sectional shape of the peripheral portion, it is preferable that the size of the protrusion from the adjacent surface is 0.3 mm or more. Further, the outer surface of the terminal electrode extending along the end face may have a quadrilateral shape defined by four inwardly curved curved sides. Further, the peripheral portion may have a jagged edge.

[0014]

FIG. 1 is a sectional view schematically showing a ceramic electronic component 1 according to one embodiment of the present invention. Referring to FIG. 1, ceramic electronic component 1 constitutes a multilayer ceramic capacitor. The ceramic electronic component 1 includes a chip-shaped ceramic electronic component body 3 having a plurality of laminated dielectric ceramic layers 2, and covers adjacent end faces 4 of the electronic component body 3 and is adjacent to each end face 4. The terminal electrodes 6 are each formed with a predetermined thickness so as to extend to a part of the surface 5.

Inside the electronic component body 3, a plurality of internal electrodes 7 as internal conductors are formed in a laminated shape. The internal electrodes 7 are arranged such that those electrically connected to one of the pair of terminal electrodes 6 and those electrically connected to the other are alternately arranged. Each terminal electrode 6 forms a peripheral portion 8 by a portion located outside the adjacent surface 5. The form of the peripheral portion 8 is a characteristic configuration of the present invention, and the angle α between the outer surface extending along the end surface 4 and the outer surface extending along the adjacent surface 5 in the peripheral portion 8.
Is sharp. This angle α is preferably 6
0 degrees or less.

In this embodiment, the sectional shape of the peripheral portion 8 is substantially triangular. In such a cross-sectional shape of the peripheral portion 8, it is preferable that the dimension “a” protruding from the adjacent face 5 is substantially equal to the dimension “b” measured in the direction in which the adjacent face 5 extends. Further, in the cross-sectional shape of the peripheral portion 8, it is preferable that the dimension a projecting from the adjacent surface 5 is 0.3 mm or more.

In this embodiment, the terminal electrode 6 has an inner layer 9 formed on the electronic component body 3 so as to be electrically connected to the inner electrode 7, and an outer layer 10 formed on the inner layer 9. It has at least a two-layer structure. As described above, by forming the terminal electrode 6 into at least a two-layer structure, the inner layer 9 is formed to be relatively thick in the outer layer 10 while ensuring electrical conduction with the inner electrode 7. Thereby, the characteristic shape of the peripheral portion 8 as described above can be easily provided.

The ceramic electronic component 1 is surface-mounted on a wiring board 11 in a state as shown in FIG. In this mounting state, the terminal electrodes 6 are soldered to conductive lands (not shown) on the wiring board 11,
A solder fillet 12 is formed over the conductive land and the terminal electrode 6. At the time of soldering, a force in a direction away from each other is exerted on both terminal electrodes 6 as the solder constituting the solder fillet 12 solidifies, and this force deforms the peripheral portion 8 by bending, for example, about 10 to 25 μm. Therefore, the stress applied to the electronic component body 3 is reduced. In addition, when the wiring board 11 is, for example, an aluminum board, a dimensional change due to thermal expansion and contraction on the wiring board 11 side which is relatively large can be dealt with by deforming the peripheral portion 8.

As described above, the angle α of the peripheral portion 8 is 60
By setting the peripheral portion 8 to be equal to or smaller than 0.3 degrees or the dimension a of the peripheral portion 8 to be 0.3 mm or more, the above-described operation based on the characteristic form of the peripheral portion 8 is more effectively exhibited. In addition, as described above, when the dimension a and the dimension b are substantially equal in the cross-sectional shape of the substantially triangular peripheral portion 8, the direction in which the outer surface of the solder fillet 12 extends and the terminal electrode 6 It is likely that the extending direction of the rising surface 13 is substantially parallel to the extending direction. This is effective not only for exerting the action based on the form of the peripheral portion 8 as described above, but also for the solder fillet 12 to be cracked. This is also effective in preventing the occurrence of the following.

The terminal electrode 6 of the ceramic electronic component 1 as described above can be formed, for example, as follows. First, as shown in FIG. 2A, an adjacent surface 5 adjacent to each end surface 4 while covering each end surface 4 of the electronic component body 3.
The inner layer 9 is formed by applying and drying a conductive paste so as to extend to a part of the inner layer 9. Inner layer 9
It is sufficient that the electrical conduction with the internal electrode 7 (see FIG. 1) can be ensured, and the wall thickness is preferably made as small as possible.

Next, as shown in FIG.
On top, a conductive paste to be the outer layer 10 is applied by dipping. Next, as shown in FIG. 2 (3), the above-mentioned conductive paste to be the outer layer 10 is pressed against a mold 14 having a surface parallel to the end surface 4. As a result, the conductive paste serving as the outer layer 10 is given the characteristic form as described above. This conductive paste is shown in FIG.
It is dried while maintaining the state shown in (3). The mold 14 may be heated to a temperature of about 100 ° C. in order to easily fix the form of the conductive paste.

After the above-described drying of the conductive paste, the electronic component body 3 is pulled up from the mold 14, and the same operation is repeated on the other end face 4. Note that at least a surface of the mold 14 that is in contact with the conductive paste, in order to facilitate the release of the mold 14 from the conductive paste to be the outer layer 10,
For example, it is preferable to use a material that facilitates mold release, such as a fluorine resin or polyimide.

Next, the above-described conductive paste for forming the inner layer 9 and the outer layer 10 is baked, whereby the terminal electrode 6 is formed. These terminal electrodes 6 may be plated with nickel, solder, or tin as needed. FIG. 3 shows an alternative example of the mold 14 used in the process shown in FIG. 2 (3). The mold 14a shown in FIG. 3 has split molds 17 and 18 that can be divided in the directions of arrows 15 and 16, respectively. Split molds 17 and 1
8 form a cavity 19 having a shape which can be more adapted to the outer shape of the terminal electrode 6 having a characteristic form when they are integrated.

According to such a mold 14a, the terminal electrode 6
Can be more reliably and reproducibly provided. In addition, since the mold 14a can be divided into the split molds 17 and 18, the form of the terminal electrode 6 is not damaged when the mold is released. FIG. 4 is an end view of a ceramic electronic component 1a according to another embodiment of the present invention. FIG. 4 shows one terminal electrode 6 of the ceramic electronic component 1a.
a, more specifically, the outer surface of the terminal electrode 6a extending along the end face 4 of the electronic component body 3 (see FIG. 1).

The above-described ceramic electronic component 1 shown in FIG.
In FIG. 4, the outer surface of the terminal electrode 6 extending along the end face 4 forms a quadrilateral defined by four substantially linear sides. However, in the ceramic electronic component 1a shown in FIG. Has a quadrilateral defined by four curved sides that curve inward. According to the embodiment shown in FIG. 4, the peripheral portion 8 of the terminal electrode 6a is formed.
a is more likely to occur, so that the action based on the characteristic form of the peripheral portion 8a as described above can be more effectively exerted.

FIG. 5 is for explaining still another embodiment of the present invention, and corresponds to an enlarged view of a portion V in FIG. FIG. 5 shows the peripheral portion 8 of the terminal electrode 6b.
b is shown. As shown in FIG. 5, the peripheral portion 8b of the terminal electrode 6b has a jagged edge. The jagged shape acts to increase the area of the terminal electrode 6b in contact with air, and the solder fillet 12
In portions where no jagged shape is formed (see FIG. 1), a higher radiation fin effect can be exhibited as compared with a case where the jagged shape is not provided.

The jagged edge shown in FIG. 5 is formed along an inwardly curved side as shown in FIG. 4 and a linear side as shown in the embodiment of FIG. May be formed along. As described above, the present invention has been described with reference to the illustrated embodiment. However, the present invention relates to a chip-shaped electronic component main body and an adjacent surface adjacent to each end surface while covering each of the opposed end surfaces of the electronic component main body. Can be applied to any ceramic electronic component having any structure or function as long as it has a terminal electrode formed with a predetermined thickness so as to extend to a part of the ceramic electronic component. .

[0028]

As described above, according to the present invention, the outer surface extending along the end surface of the ceramic electronic component body and the outer surface extending along the adjacent surface adjacent to the end surface at the peripheral portion of the terminal electrode. Is formed at an acute angle, so that the stress exerted during soldering to the wiring board or due to expansion and contraction of the wiring board is advantageously absorbed by the deformation of the peripheral portion of the terminal electrode, and is applied to the electronic component body. The applied stress can be effectively reduced. Therefore, it is possible to advantageously prevent mechanical damage such as cracks from occurring in the electronic component body and the terminal electrodes.

The operation based on the characteristic form of the peripheral portion of the terminal electrode described above is performed when the above-mentioned angle is 60 degrees or less, or when the sectional shape of the peripheral portion is substantially triangular. In the cross-sectional shape of the above, when the dimension extending from the adjacent surface is substantially equal to the dimension measured in the direction in which the adjacent surface extends, or when the dimension extending from the adjacent surface is 0.3 mm or more. Or, when the outer surface of the terminal electrode extending along the end face of the electronic component main body forms a quadrilateral defined by four sides curved inward, the effect is more effectively exhibited.

According to the present invention, it is not necessary to attach a terminal member made of a metal plate to the terminal electrode. For this reason, the operation and cost related to the terminal member are not bothered. Also, the problem of an increase in equivalent series resistance due to the attachment of the terminal member is not encountered. In addition, a problem that may occur in attaching the terminal member to the terminal electrode, particularly in soldering,
For example, it eliminates all problems such as cracks in the electronic component main body due to thermal shock applied at the time of soldering, generation of flux residues, and the necessity of a cleaning step using an organic solvent or the like for removing flux. be able to.

Further, since the mounting on the wiring board is performed by the terminal electrode itself without depending on the terminal member, the degree of freedom of the mounting posture of the ceramic electronic component can be increased. In addition, since the peripheral portion of the terminal electrode has the above-described characteristic form, it has a fin effect for radiating heat of the electronic component body. Therefore, the allowable voltage can be increased. This effect is more remarkably exhibited particularly when the jagged edge is formed at the peripheral edge of the terminal electrode.

When the electronic component body provided in the ceramic electronic component according to the present invention has an internal conductor, the terminal electrodes
Having at least a two-layer structure having an inner layer formed on the electronic component body and an outer layer formed on the inner layer so as to be electrically connected to the inner conductor,
The outer layer makes it easier to give a characteristic shape of the peripheral portion of the terminal electrode while ensuring the electrical conduction between the inner conductor and the terminal electrode.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a ceramic electronic component 1 according to an embodiment of the present invention.
This shows the mounting state above.

FIG. 2 is a sectional view schematically showing steps for forming a terminal electrode 6 of the ceramic electronic component 1 shown in FIG.

FIG. 3 is a sectional view schematically showing a modification of the step shown in FIG. 2 (3).

FIG. 4 is an end view of a ceramic electronic component 1a according to another embodiment of the present invention.

FIG. 5 is for explaining still another embodiment of the present invention, and corresponds to an enlarged view of a portion V in FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 1a Ceramic electronic component 3 Ceramic electronic component main body 4 End surface 5 Adjacent surface 6, 6a, 6b Terminal electrode 7 Internal electrode (internal conductor) 8, 8a, 8b Peripheral edge 9 Inner layer 10 Outer layer 11 Wiring board 12 Solder fillet α Terminal electrode The angle between the outer surface extending along the end surface of the electronic component body and the outer surface extending along the adjacent surface of the electronic component body at the peripheral edge of a a Dimension extending from the adjacent surface b Dimension measured in the direction in which the adjacent surface extends

Claims (8)

[Claims] A ceramic electronic component body in the form of a chip;
A terminal electrode formed to have a predetermined thickness so as to extend to a part of an adjacent surface adjacent to each of the end surfaces while covering each of the end surfaces facing each other of the electronic component body. The terminal electrode forms a peripheral portion by a portion located outside the adjacent surface, and an angle formed between an outer surface extending along the end surface and an outer surface extending along the adjacent surface in the peripheral portion. A ceramic electronic component characterized by having an acute angle. 2. The ceramic electronic component according to claim 1, wherein the angle is equal to or less than 60 degrees. 3. The electronic component body includes an internal conductor,
2. The terminal electrode according to claim 1, wherein the terminal electrode has at least a two-layer structure including an inner layer formed on the electronic component body and an outer layer formed on the inner layer so as to be electrically connected to the inner conductor. 3. 3. The ceramic electronic component according to 2. 4. The ceramic electronic component according to claim 1, wherein a cross-sectional shape of said peripheral portion is substantially triangular. 5. The ceramic electronic component according to claim 4, wherein, in the cross-sectional shape of the peripheral portion, a dimension extending from the adjacent surface is substantially equal to a size measured in a direction in which the adjacent surface extends. . 6. The ceramic electronic component according to claim 1, wherein in the cross-sectional shape of the peripheral portion, a dimension protruding from the adjacent surface is 0.3 mm or more. 7. The terminal according to claim 1, wherein an outer surface extending along the end face of the terminal electrode forms a quadrilateral defined by four curved sides curved inward. Ceramic electronic components. 8. The ceramic electronic component according to claim 1, wherein the peripheral portion has a jagged edge.