JP3267067B2 - Ceramic electronic components - Google Patents

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 multilayer capacitor, and more particularly to a ceramic electronic component having an improved external electrode structure.

[0002]

2. Description of the Related Art A multilayer capacitor as an example of a conventional ceramic electronic component will be described with reference to FIG.

A multilayer capacitor 1 is formed using a ceramic sintered body 2 made of a dielectric ceramic such as barium titanate. In the ceramic sintered body 2, a plurality of internal electrodes 3 to 7 are formed so as to overlap with a ceramic layer interposed therebetween. Also, one end face 2 of the sintered body 2
An external electrode 8 is formed on “a” so as to be electrically connected to the internal electrodes 4 and 6. Ceramic sintered body 2
On the other end surface 2b, an external electrode 9 is formed so as to be electrically connected to the internal electrodes 3, 5, 7.

The internal electrodes 3 to 7 are usually made of Pd or Ag-
It is made of a noble metal material such as a Pd alloy. On the other hand, when the external electrodes 8 and 9 are formed, Ag or A is used as the lowermost layer in order to increase the reliability of electrical connection with the internal electrodes 3 to 7.
First electrode layers 8a and 9a are formed by applying and baking a conductive paste containing a g-Pd alloy.

When mounting the multilayer capacitor 1 on a printed circuit board or the like, the external electrodes 8 and
9 is electrically connected to the wiring electrodes on the printed circuit board. However, the first electrode layers 8a and 9a are mainly made of a material such as Ag which is apt to cause solder erosion. Therefore, when soldering is performed using only the first electrode layers 8a and 9a as an external electrode material, the external electrodes partially disappear due to the solder erosion phenomenon, and the multilayer capacitor 1 can function reliably. become unable.

Therefore, in order to prevent solder erosion, the first electrode layers 8a and 9a are plated with a material such as Ni that is unlikely to cause solder erosion, thereby plating the second electrode layers 8b and 9a.
9b is formed. In addition, since materials such as Ni that are unlikely to cause solder erosion do not have sufficient solderability, by plating a material excellent in solderability, such as Sn or Sn-Pb alloy, in order to enhance solderability. Three electrode layers 8c and 9c are formed.

[0007]

In the conventional multilayer capacitor 1, the first to third electrode layers 8a to 8c, 9a to 9
The external electrodes 8 and 9 were constituted by c. When this type of multilayer capacitor 1 is mounted on a printed circuit board or the like by soldering the external electrodes 8 and 9, in some cases, a considerably large external force is applied to the multilayer capacitor 1 due to bending of the substrate. For example, when the printed circuit board on which the multilayer capacitor 1 is mounted is inserted into the mounting portion of the electronic device, the printed circuit board is bent, and thus an external force is applied to the mounted multilayer capacitor 1 or the surroundings. In some cases, the printed circuit board expands and contracts due to a temperature change or the like, causing the board to be distorted.

In particular, as shown in FIG. 2, when the substrate 10 on which the multilayer capacitor 1 is mounted is bent so as to protrude toward the multilayer capacitor 1, the external electrodes 8 and 9 are separated from the ceramic sintered body 2. A large force is applied in the direction of separation. However, the first electrode layers 8a and 9a are firmly adhered to the ceramic sintered body 2, and the first to third electrode layers 8a to 8c and 9a to 9c are also firmly adhered.
Therefore, when the external force as described above is applied, a crack indicated by an arrow A occurs in the ceramic sintered body 2, and as a result, the multilayer capacitor 1 may not function.

On the other hand, if the adhesion of the external electrodes 8 and 9 to the ceramic sintered body 2 is reduced, the external electrodes 8 and 9 are peeled off from the ceramic sintered body 2 when the above-described external force is applied. It is considered that the above-mentioned external force can be absorbed and the occurrence of cracks in the ceramic sintered body 2 can be prevented. However, when the external electrodes 8 and 9 are peeled off from the ceramic sintered body 2, it is no longer possible to operate the multilayer capacitor 1.

An object of the present invention is to provide a ceramic electronic component having excellent reliability, in which cracks in a ceramic sintered body and exfoliation of external electrodes hardly occur even when a substrate on which a ceramic electronic component is mounted is bent. Is to provide.

[0011]

The present invention is a ceramic electronic component in which an external electrode is formed on the outer surface of a ceramic sintered body having an internal electrode, and has the following configuration.

That is, the ceramic electronic component of the present invention includes a ceramic sintered body, an internal electrode formed in the ceramic sintered body, and an external electrode formed on an outer surface of the ceramic sintered body.

Further, the external electrode is formed by applying and baking a conductive paste to the outer surface of the sintered body.
And a conductive material is formed inside a through hole formed in the thickness direction of the resin layer having a higher elasticity than the other electrode layers formed on the outside and the inside of the first electrode layer and located inside and outside. It has a buried conductive resin layer and a second electrode layer formed outside the conductive resin layer.

As the material constituting the first electrode layer, there can be used various conductive pastes which have been conventionally used for forming external electrodes of ceramic electronic components. Examples of such a conductive paste include Ag, Cu, and Ag.
A material mainly composed of a material powder having excellent conductivity such as a Pd alloy is used. The conductive paste is obtained by kneading a glass resin binder and a solvent into the conductive powder as described above, and the first electrode layer is formed by applying the conductive paste on the outer surface of the ceramic sintered body and baking the paste. Is formed. The steps of applying and baking this conductive paste can be performed in the same manner as the conventional method of forming external electrodes of a ceramic electronic component.

The conductive resin layer formed outside the first electrode layer is formed of a resin layer having a smaller breaking strength than the inside and outside, that is, the first electrode layer and the second electrode layer. You. The resin layer has a through hole penetrating in the thickness direction, and a conductive material is embedded in the through hole. With such a configuration, conduction between the first electrode layer and the second electrode layer is ensured, and the effect of an external force applied to the external electrode is reduced by utilizing the elastic property of the resin. ing.

The second electrode layer is made of, for example, Ni, Cu, S
n, Sn-Pb or the like. The thickness of the second electrode layer may not be so large, and therefore, preferably,
The second electrode layer is formed by a plating method that is easy to form.

Further, the second electrode layer may be a laminate of a plurality of electrode layers. For example, an electrode layer such as Ni or Cu which is hard to be eroded by solder is formed first, and then Sn or Sn is further formed thereon to improve solderability.
-An electrode layer made of a material having excellent solderability such as a Pb alloy may be formed. Since the electrode layer made of such a material having excellent solderability is provided only for enhancing the solderability, the thickness of the electrode layer does not need to be so large, and is preferably easy to form. It is formed by a suitable plating method.

Further, in the present invention , the conductive resin layer is formed by embedding a metal material inside the open cells of the thermosetting resin layer in which the open cells are formed.
And the second electrode layer is electrically connected. As such a thermosetting resin, an epoxy resin, an acrylic resin, a silicone resin, a phenol resin, or the like is used. When these thermosetting resins are subjected to a foaming treatment, open cells are formed in the thickness direction. Therefore, a metal material is buried in the interior by using these open cells, and the elasticity and conductivity of the entire layer are secured.

[0019]

According to the ceramic electronic component of the present invention, a conductive resin layer is provided between the first and second electrode layers of the external electrode. The first and second conductive resin layers are made of a conductive material embedded in through holes therein.
Conductivity between the electrode layers. Further, due to the property of the resin layer, that is, the property of having a higher elasticity than other electrode layers, when an external force is applied to the external electrode in a direction away from the ceramic sintered body, the conductive resin layer is deformed. Or the effect of an external force can be absorbed, for example, by causing a partial crack. Thereby, it is possible to effectively prevent a crack from being generated in the ceramic sintered body due to the external force acting directly on the ceramic sintered body.

As described above, according to the present invention, even if the mounted substrate is bent due to an external temperature change or an external force at the time of mounting, cracks in the ceramic sintered body are hardly generated. In addition, it is possible to provide a highly reliable ceramic electronic component capable of stably exhibiting its characteristics.

It should be noted that the present invention provides, in addition to the multilayer capacitor,
The present invention can be generally applied to ceramic electronic components having external electrodes. For example, it can be used for a ceramic inductor, a laminated piezoelectric resonance component, a ceramic multilayer substrate, and the like.

[0022]

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

FIG. 3 is a sectional view showing a chip type multilayer capacitor according to one embodiment of the present invention, and FIG. 4 is a partially enlarged sectional view of an external electrode. The multilayer capacitor 21 is configured using a ceramic sintered body 22. The ceramic sintered body 22 is made of a dielectric ceramic such as barium titanate, and has internal electrodes 23 to 27 formed therein. The internal electrodes 23 to 27 are arranged so as to overlap via the ceramic layer. In addition, the internal electrode 2
4 and 26 are exposed on one end face 22a of the sintered body 22, while the internal electrodes 23, 25 and 27 are exposed on the other end face 22b.
It is exposed to.

External electrodes 28 and 29 are formed on the end faces 22a and 22b. In the present embodiment, each of the external electrodes 28 and 29 has the first to third electrode layers 28a to 28
c, 29 a to 29 c and conductive resin layers 30 and 31.

First, the first electrode layers 28a, 29a
It is formed by applying and baking a conductive paste containing a metal powder such as g, Ag-Pd, or Cu. Therefore, the first electrode layers 28a and 29a
The end face 22 of the sintered body 22 having a thickness of about
a, 22b.

The conductive resin layers 30, 31 are formed by applying a foaming thermosetting resin on the surfaces of the first electrode layers 28a, 29a and performing a thermosetting process. As the thermosetting resin, a foamable epoxy resin is preferably used, and an acrylic resin, a silicone resin, a phenol resin, or the like is used. Many open cells are formed in the resin layer subjected to the thermosetting treatment. Then, an ultraviolet-curing plating resist is applied between the terminal electrodes and cured, and then the surface of the thermosetting resin is subjected to electroless Ni plating to deposit Ni in the mesh-like resin voids (open cells). After filling, the plating resist was peeled off. As a result, conductive resin layers 30 and 31 are formed. This conductive resin layer 3
Reference numerals 0 and 31 function to reduce the effect of an external force applied to the external electrode by the elasticity of the resin portion 30a, and the first electrode layers 28a and 28a are formed by metal-filled portions 30b such as Ni formed inside the open cells. 29a and the second electrode layer 2
8b and 29b. In addition, as a method of filling the metal material into the resin void portion, a molten metal may be filled therein by using a press-fitting method.

Outside the conductive resin layers 30, 31, second electrode layers 28b, 29b are formed to prevent solder erosion. In the present embodiment, the second electrode layers 28b and 29b are formed by plating a metal material such as Ni or Cu to a thickness of about 2 to 4 μm.
Alternatively, Sn-Pb may be used. But Sn or Sn-P
When b is formed as the second electrode layer, the third electrode layer described below becomes unnecessary.

Further, the third electrode layers 28c and 29c
It is formed on the second electrode layers 28b and 29b.
The third electrode layers 28c and 29c are made of Sn or Sn-Pb.
It is formed by plating an alloy or the like to a thickness of about 2 to 4 μm, and is formed to enhance the solderability when mounting the external electrodes 28 and 29.

The multilayer capacitor 21 of this embodiment is mounted on a printed circuit board by soldering and joining the external electrodes 28 and 29 to the printed circuit board. In this case, when the printed circuit board is bent so as to protrude toward the multilayer capacitor side as shown in FIG. 2, for example,
External force acts in a direction in which the external electrodes 28 and 29 are moved away from the ceramic sintered body 22. However, the conductive resin layers 30 and 31 are elastically deformed in response to an external force due to the elasticity of the resin portion, thereby absorbing the external force. Therefore, the application of external force directly to the ceramic sintered body 22 is reduced, and the occurrence of cracks in the ceramic sintered body 22 is prevented.

Next, specific experimental examples will be described. 4.5 × in which a plurality of internal electrodes 23 to 27 are internally formed
A ceramic sintered body 22 having a size of 3.2 × 2.0 mm was prepared. The first electrode layers 28a and 29a were formed by applying a conductive paste containing Ag as a main component so as to have a thickness of 50 μm after drying, and firing at 800 ° C. Next, a foaming epoxy resin was applied on the first electrode layers 28a and 29a, and a curing treatment was performed at a temperature of 150 ° C. for 1 hour. Next, an ultraviolet-curing plating resist is applied between the terminal electrodes and cured, and then subjected to electroless Ni plating to deposit Ni on the surface and in a mesh-like resin void portion, thereby forming a conductive resin layer 30 and a conductive resin layer 30. 31 was formed.

Further, on the conductive resin layers 30 and 31, second electrode layers 28b and 29b made of a Ni plating layer having a thickness of 2 to 4 μm are formed by electrolytic plating, and further formed thereon by electrolytic plating. The third electrode layers 28c and 29c made of the Sn plating layer were formed, and the multilayer capacitor of the example was manufactured.

For comparison, a multilayer capacitor of the comparative example was manufactured in the same manner as in the example except that the conductive resin layer was not formed in the step of manufacturing the multilayer capacitor of the above example.

Using each of the 36 multilayer capacitors of the embodiment and the comparative example prepared as described above, they were mounted by soldering on wiring electrodes formed on an alumina substrate. And
With the multilayer capacitor mounted on an alumina substrate,
Maintain at a temperature of 55 ° C. for 0.5 hour,
The heating / cooling temperature cycle test was performed with the step of maintaining the time as one cycle. The results are shown in Table 1 below. In Table 1, the number of defectives indicates the number of multilayer capacitors in which the decrease in the capacitance has become 10% or more after the heating / cooling temperature cycle test is performed.

[0034]

[Table 1]

As is clear from Table 1, the number of defects was zero in the multilayer capacitor of the embodiment even when the cooling / heating temperature cycle was repeated 500 cycles, whereas in the multilayer capacitor of the comparative example, 50 cycles were performed. At the elapse of time, the occurrence of two defective products is observed, and it can be seen that the number of defective products increases as the number of cooling / heating temperature cycles increases.

The reason why no failure occurs in the multilayer capacitor of the embodiment is that the conductive resin layer between the first electrode layers 28a and 29a and the second electrode layers 28b and 29b is elastically deformed. It is considered that the external force applied to the multilayer capacitor by the cooling / heating temperature cycle was absorbed by the above.

A test was also conducted on the mounting strength of the multilayer capacitor of the example and the multilayer capacitor of the comparative example on the substrate. As a result, as shown in Table 1, it was found that both had substantially the same mounting strength. As a result, even when the conductive resin layer was formed in the external electrode, no remarkable decrease in the mounting strength was observed, and it was found that the mounting strength without practical problems could be secured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a conventional multilayer capacitor.

FIG. 2 is a cross-sectional view illustrating a conventional multilayer capacitor.

FIG. 3 is a sectional view showing a multilayer capacitor according to one embodiment of the present invention.

4 is a partially enlarged view of an external electrode 28 of the multilayer capacitor shown in FIG.

DESCRIPTION OF SYMBOLS 21 ... Multilayer capacitor 22 ... Ceramic sintered body 23-27 ... Internal electrode 28, 29 ... External electrode 28a, 29a ... First electrode layer 28b, 29b ... Second electrode layer 28c, 29c ... 3 electrode layers 30, 31 ... conductive resin layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-17619 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 4/00-4/40

Claims (1)

(57) [Claims] A ceramic sintered body; an internal electrode formed in the ceramic sintered body; and an external electrode formed on an outer surface of the ceramic sintered body. Apply conductive paste on the surface
A first electrode layer formed by baking, and penetrating in a thickness direction of a resin layer formed outside the first electrode layer and having a higher degree of elasticity than other electrode layers located inside and outside. possess an inner conductive material is embedded the conductive resin layer of the through hole, and a second electrode layer formed on the outside of the conductive resin layer, the conductive resin layer, the continuous bubble formation Heat hardened
A metal material is embedded in the open cells of the plasticizable resin layer.
The first electrode layer and the second electrode layer
And a ceramic electronic component, wherein the ceramic electronic component is electrically connected to: