JP6854593B2 - Multilayer ceramic capacitors - Google Patents

Description

The present invention relates to a ceramic capacitor, and more particularly to a multilayer ceramic capacitor having a structure in which an external electrode is formed on the surface of a laminate formed by laminating an internal electrode and a dielectric layer so as to be connected to the internal electrode.

In recent years, multilayer ceramic capacitors having a laminate in which an internal electrode and a dielectric layer are laminated and an external electrode formed on the surface of the laminate so as to connect to the internal electrode have been widely used in various applications. There is. One such multilayer ceramic capacitor is a multilayer ceramic capacitor (multilayer ceramic electronic component) as described in Patent Document 1.

As shown in FIG. 5, the multilayer ceramic capacitor 101 has a pair of end faces 108 of a laminate (ceramic laminate) 105 in which a plurality of internal electrodes 103 and 104 are laminated via a dielectric layer (ceramic layer) 102. The 109 has a structure in which a pair of external electrodes 112 and 113 are arranged so as to be conductive with the internal electrodes 103 and 104.

In the multilayer ceramic capacitor 101, the external electrodes 112 and 113 are provided with a brazing material containing Ti on at least a part of the surface on which the external electrode 104 should be formed, including the main surfaces 106 and 107 of the laminated body 110. The metal layer 119 containing Ti is formed by baking, and the plating films 114, 115, 116 are formed so as to cover the metal layer 119, and the metal layer 119 and the plating film (Cu plating film) 114 are formed. In between, as shown in FIG. 6 in which the region B of FIG. 5 is enlarged, it is formed by forming a mutual diffusion layer 120.

According to Patent Document 1, by providing the above-described configuration, the external electrodes 112 and 113 having excellent adhesion to the laminated body 105 are provided, and the laminated ceramic capacitor (multilayer ceramic electron) having good moisture resistance addition characteristics is provided. Parts) 101 is said to be obtained.

However, in the multilayer ceramic capacitor (multilayer ceramic electronic component) 101 of Patent Document 1 configured as described above, although the mutual diffusion layer 120 is formed between the metal layer 119 and the plating film 114, Ag- There is a problem that sufficient moisture resistance reliability cannot always be obtained due to mutual diffusion between the Cu—Ti alloy (metal layer) and Cu (plating film 114).

Further, since the plating film 114 completely covers the metal layer 119, the tip of the metal layer 119 closer to the end face 103 of the laminated body 110 when viewed in the direction along the pull-out direction of the internal electrodes 103 and 104. Has a problem that the thermomechanical strength (deflection strength) deteriorates when mutual diffusion of metals occurs on the tip side on the opposite side (central side in the longitudinal direction).

JP-A-2010-129621

The present invention solves the above problems, and an object of the present invention is to provide a highly reliable multilayer ceramic capacitor having excellent moisture resistance and high thermomechanical strength.

In order to solve the above problems, the multilayer ceramic capacitor of the present invention is used.
In a multilayer ceramic capacitor including a laminate in which an internal electrode and a dielectric layer are laminated, and an external electrode formed on the surface of the laminate so as to connect to the internal electrode.
The external electrode is formed on the main surface of the laminated body and contains a first external electrode layer containing Ni.
The end face from which the internal electrode of the laminated body is pulled out and the region including the tip of the first external electrode layer on the end face side are covered and joined to the first external electrode layer, and the internal electrode is formed. A second external electrode layer containing a glass component and Cu, which is formed so as to be conductive with the glass component, is provided.
In the region of the first external electrode layer located on the main surface of the laminated body, in the region near the ridge line formed by the main surface and the end surface, the first external electrode layer and the said. It is bonded to the second external electrode layer and
When looking at the pull-out direction of the internal electrode, the tip of the first external electrode layer opposite to the tip on the end face side of the laminated body is exposed without being covered by the second external electrode layer. While doing
Ni contained in the first external electrode layer diffuses into the second external electrode layer in the vicinity of the ridgeline and is solid-solved with Cu contained in the second external electrode layer .
The dimension in the pull-out direction of the internal electrode of the portion where the second external electrode layer covers the first external electrode layer is 3% of the dimension in the pull-out direction of the internal electrode of the first external electrode layer. It is characterized by being 50% or less.

The diffusion distance of Ni to the second external electrode layer is 10% of the thickness of the second external electrode layer in the portion where the second external electrode layer covers the first external electrode layer. It is preferably 100% or more and 100% or less.

The diffusion distance of Ni to the second external electrode layer is in the range of 10% or more and 100% or less of the thickness of the second external electrode layer in the portion where the second external electrode layer covers the first external electrode layer. When this is done, a sufficient diffusion distance of Ni can be secured to improve the moisture resistance.

In the multilayer ceramic capacitor of the present invention, as described above,
(A) The first external electrode layer containing Ni formed on the main surface of the laminated body, the end face from which the internal electrode of the laminated body is drawn out, and the end face side of the first external electrode layer. It covers the region including the tip, is bonded to the first external electrode layer, and is provided with a second external electrode layer containing a glass component and Cu, which is formed so as to be conductive with the internal electrode.
(B) In the region of the first external electrode layer located on the main surface of the laminated body, in the region near the ridge line formed by the main surface and the end surface, the first external electrode layer and the second Bonded with the external electrode layer
(D) When looking at the pull-out direction of the internal electrode, the tip of the first external electrode layer opposite to the tip on the end face side of the laminate is exposed without being covered by the second external electrode layer.
(E) Ni contained in the first external electrode layer diffuses into the second external electrode layer in the vicinity of the ridgeline, and has a structure in which it is solid-dissolved with Cu contained in the second external electrode layer. It is possible to obtain a highly reliable multilayer ceramic capacitor having excellent moisture resistance and high thermomechanical strength.

That is, Ni contained in the first external electrode layer diffuses into the second external electrode layer in the vicinity of the ridgeline and is solid-dissolved with Cu contained in the second external electrode layer. Moisture resistance and reliability are improved.

Further, since the tip of the first external electrode layer opposite to the tip on the end face side of the laminated body is exposed without being covered by the second external electrode layer, the first external electrode layer is formed. It is possible to improve the thermomechanical strength by suppressing the influence of stress generated by the diffusion and solid dissolution of Ni in the second external electrode layer.
Further, the dimension of the portion where the second external electrode layer covers the first external electrode layer in the pull-out direction of the internal electrode is 3% or more and 50% of the dimension in the pull-out direction of the internal electrode of the first external electrode layer. By the following, it becomes possible to sufficiently form a solid solution layer in which Ni is solid-dissolved in Cu, which is necessary for ensuring moisture resistance, and the present invention can be made more effective.

Further, since the second external electrode layer contains a glass component, the adhesion to the laminated body is improved, and the moisture resistance reliability is also improved from this point as well.

It is a front sectional view which shows the structure of the multilayer ceramic capacitor which concerns on one Embodiment (Embodiment 1) of this invention. It is a perspective view which shows the appearance structure of the multilayer ceramic capacitor which concerns on Embodiment 1 of this invention. A schematic cross section of a main part for explaining the shape of the first external electrode layer and the second external electrode layer and the dimensions of the main part in the multilayer ceramic capacitor according to another embodiment of the present invention (Embodiment 2). It is a figure shown in. (A) is a schematic cross-sectional view showing the configuration of the first external electrode layer and the second external electrode layer in the multilayer ceramic capacitor according to still another embodiment (Embodiment 3) of the present invention, and (b) is a schematic cross-sectional view. , (A) is an enlarged view showing the diffusion distance D2 of Ni constituting the first external electrode layer to the second external electrode layer containing Cu, and the second external electrode. It is a figure which shows the thickness V of. It is a front sectional view which shows the structure of the conventional multilayer ceramic capacitor. FIG. 5 is an enlarged view showing a region B of the monolithic ceramic capacitor of FIG.

Hereinafter, embodiments of the present invention will be shown, and the features of the present invention will be described in more detail.
[Embodiment 1]
FIG. 1 is a front sectional view showing a configuration of a multilayer ceramic capacitor 50 according to an embodiment (Embodiment 1) of the present invention, and FIG. 2 is a perspective view showing an external configuration of the multilayer ceramic capacitor 50.

As shown in FIGS. 1 and 2, the multilayer ceramic capacitor 50 is a laminate having a structure in which a plurality of dielectric layers 1 made of a dielectric ceramic and a plurality of internal electrodes 2 (2a, 2b) are laminated. The ceramic body) 10 and a pair of external electrodes 5 (5a, 5b) arranged so as to be conductive with the internal electrodes 2 (2a, 2b) are provided on the outer surface of the laminated body 10. Further, the external electrodes 5 (5a, 5b) are provided with a plating film 18 on the surface thereof, and the plating film 18 has a two-layer structure composed of a Ni plating film 16 and a Sn plating film 17, respectively. ..

Hereinafter, each part constituting the monolithic ceramic capacitor will be described in more detail.
(1) Laminated body The laminated body 10 has a first main surface 11a, a second main surface 11b facing the first main surface 11a, and a first end surface 21a and a first surface orthogonal to the first main surface 11a. It has a rectangular parallelepiped shape including a second end surface 21b facing the end surface 21a of 1, a first side surface 31a orthogonal to the first end surface 11a, and a second side surface 31b facing the first side surface 31a. There is.
The laminated body 10 preferably has rounded corners and ridges.

The dimensions of the laminated body 10 are not particularly limited, but when the thickness dimension of the laminated body 10 is T, the length dimension is L, and the width dimension is W, T <W <L, (1/5) W ≦ T. It may be a thin one that satisfies the requirement of ≦ (1/2) W or T <0.3 mm. Specifically, 0.05 mm ≦ T <0.3 mm, 0.4 mm ≦ L ≦ 1 mm, and 0.3 mm ≦ W ≦ 0.5 mm may be used.
However, in the present invention, the shape and dimensions of the laminated body 10 are not particularly limited, and other shapes and dimensions can be used.

Further, the dielectric layer 1 constituting the laminated body 10 is made of a ceramic material. As the ceramic material, for example, _{a dielectric ceramic containing Badio 3} , CaTIO ₃ , SrTIO ₃ , CaZrO _3, or the like as a main component can be used. Further, those in which sub-components such as Mn compound, Fe compound, Cr compound, Co compound and Ni compound are added to these main components may be used. The thickness of the dielectric layer 1 is usually preferably 0.5 μm or more and 10 μm or less.

In the multilayer ceramic capacitor according to the first embodiment, the internal electrode 2 is configured such that a capacitance is formed in an effective portion which is a region facing the dielectric layer 1 via the dielectric layer 1.

(2) Internal Electrodes Inside the laminated body 10, a plurality of substantially rectangular first and second internal electrodes 2a and 2b are alternately arranged at equal intervals along the thickness direction T.
The ends of the first and second internal electrodes 2a and 2b are exposed on the end faces of the laminated body 10. Specifically, one end of the first internal electrode 2a is pulled out to the first end surface 21a of the laminated body 10 and is exposed. One end of the second internal electrode 2b is pulled out and exposed on the second end surface 21b of the laminated body 10.

The first and second internal electrodes 2a and 2b are arranged in parallel with the first and second main surfaces 11a and 11b, respectively. The main portions of the first and second internal electrodes 2a and 2b face each other via the dielectric layer 1 in the thickness direction T.
The thickness of the first and second internal electrodes 2a and 2b is not particularly limited, but is usually preferably 0.2 μm or more and 2 μm or less.

The first and second internal electrodes 2a and 2b can be made of various conductive materials. Specifically, the first and second internal electrodes 2a and 2b include, for example, metals such as Ni, Cu, Ag, Pd and Au, and alloys such as Ag-Pd alloys containing one of these metals. Can be configured by

(3) External Electrodes The external electrodes 5 (5a, 5b) provided on the surface of the laminated body 10 are arranged so as to cover the exposed regions of the first and second internal electrodes 2a, 2b of the laminated body 10. Has been done. Specifically, the external electrodes 5 (5a, 5b) are
(A) While covering the first and second end faces 21a and 21b of the laminated body 10,
(B) Regions on both ends of the first and second main surfaces 11a and 11b of the laminated body 10 in the length direction (L direction) of the laminated body 10 (direction along the pull-out direction of the internal electrodes 2a and 2b). Cover and
(C) The first and second side surfaces 31a and 31b of the laminated body 10 are arranged so as to cover the regions on both ends of the laminated body 10 in the length direction (L direction).

The external electrode 5 (5a, 5b) includes a first external electrode layer 15 (15a, 15b) and a second external electrode layer 25 (25a, 25b).
The first external electrode layer 15 (15a, 15b) is an electrode layer containing Ni, and is formed on the main surfaces 11a, 11b of the laminated body 10. In the multilayer ceramic capacitor according to this embodiment, the first external electrode layers 15 (15a, 15b) are formed on the main surfaces 11a, 11b of the laminate 10, but the side surfaces 31a, 31b of the laminate 10 are formed. Can also be formed.

The second external electrode layers 25 (25a, 25b) constituting the external electrode 5 are electrode layers containing a glass component and Cu, and the end faces 21a and 21b of the laminated body 10 and the first external electrode layer 15 The regions of (15a, 15b) on both ends in the length direction (L direction) of the laminate 10 are covered and joined to the first external electrode layer 15 (15a, 15b), and the side surfaces 31a, 31b of the laminate 10 are formed. Is formed so as to cover the regions on both ends in the length direction (L direction) of the laminated body 10. A second external electrode layer 25 (25a, 25b) containing a glass component and Cu is provided.

The first external electrode layer and the second external electrode layer are regions of the first external electrode layer 15 (15a, 15b) located on the main surfaces 11a, 11b of the laminated body 10. , The main surfaces 11a and 11b and the end surfaces 21a and 21b are joined to each other in the region near the ridgeline.

The tip of the first external electrode layer 15 (15a, 15b) on the central portion side in the longitudinal direction (L direction) of the laminated body 10, that is, the tip opposite to the tip on the end faces 21a, 21b side of the laminated body 10 , It is exposed from the second external electrode layer 25 (25a, 25b) without being covered with the second external electrode layer 25 (25a, 25b).

Then, Ni contained in the first external electrode layer 15 (15a, 15b) diffuses to the second external electrode layer 25 (25a, 25b) near the ridgeline, and the second external electrode layer 25 (25a, 25a, It is completely solid-solved with Cu contained in 25b).

Next, the first external electrode layer 15 (15a, 15b) and the second external electrode layer 25 (25a, 25b) will be described.
(3-1) First External Electrode Layer As the conductive component constituting the first external electrode layer 15 (15a, 15b), for example, Ni or an alloy containing Ni can be used.
Further, it is desirable that the first external electrode layer 15 (15a, 15b) contains an inorganic binder. The inorganic binder is a component for increasing the adhesion strength to the laminate 10.

When the first external electrode layer 15 (15a, 15b) is formed by co-fired with the laminate 10, it is the same as the ceramic material contained in the dielectric layer constituting the laminate 10 as an inorganic binder. It is preferable to use the ceramic material of the above or a ceramic material having the same main component. The content of the inorganic binder in the first external electrode layer is preferably in the range of 40% by volume or more and 60% by volume or less.

Further, the thickness (thickest portion) of the first external electrode layer 15 (15a, 15b) is preferably 1 μm or more and 20 μm or less.

Further, the first external electrode layer 15 (15a, 15b) can be formed by a method (cofire) of simultaneous firing with the internal electrode.

(3-2) Second External Electrode Layer As the conductive component constituting the second external electrode layer 25 (25a, 25b), for example, Cu or an alloy containing Cu can be used.

The second external electrode layer 25 (25a, 25b) preferably contains an inorganic binder. The inorganic binder is a component for increasing the adhesion strength to the laminate 10. As the inorganic binder, for example, a glass component can be used.
The content of the inorganic binder in the second external electrode layer 25 (25a, 25b) is preferably in the range of 15% by volume or more and 35% by volume or less.

The thickness (thickest portion) of the second external electrode layer 25 (25a, 25b) is preferably 1 to 20 μm.

The second external electrode layer 25 (25a, 25b) can be formed by applying a conductive paste and baking it.
The second external electrode layer can be formed, for example, by applying a conductive paste to the fired laminate (ceramic element body) 10 and baking it at about 700 ° C. to 900 ° C.

(3-3) Plating film The external electrode 5 (5a, 5b) is a plating film formed on the surfaces of the first external electrode layer 15 (15a, 15b) and the second external electrode layer 25 (25a, 25b). It is preferable to have.
As described above, the external electrodes 5 (5a, 5b) of the multilayer ceramic capacitor according to the first embodiment include a two-layered plating film 18 composed of a Ni plating film 16 and a Sn plating film 17.

The material (plating metal) constituting the plating film is not limited to the above-mentioned example, and other than Ni and Sn, for example, Sn, Ag, Pd, Ag—Pd alloy, Au and the like can be used. it can.

Further, the plating film may have a two-layer structure (multi-layer structure) or a single-layer structure as in the above example. Further, it is possible to have a multi-layer structure having three or more layers.

When the plating film has a single-layer structure, the thickness of the single layer is preferably in the range of 1 μm or more and 10 μm or less. In the case of a multi-layer structure, it is preferable that the thickness of each plating film constituting the multi-layer structure is in the range of 1 μm or more and 10 μm or less.

Further, when the plating film 18 is provided, a conductive resin layer for stress relaxation is formed between the first external electrode layers 15a and 15b and the second external electrode layers 25a and 25b and the plating film 18. May be good.

Next, a method for manufacturing the monolithic ceramic capacitor according to the first embodiment of the present invention will be described.
(1) Ceramic green sheet for dielectric layer, conductive paste for internal electrode, conductive paste (including Ni) for first external electrode layer, and conductive paste for second external electrode layer (1) (Including Cu) is prepared.
The ceramic green sheet and each conductive paste include a binder and a solvent, but the binder and the solvent are not particularly limited, and various known organic binders and organic solvents can be used.

(2) The conductive paste for the internal electrode is printed on the ceramic green sheet so as to have a predetermined pattern by a method such as screen printing or gravure printing to form the internal electrode pattern.

(3) A predetermined number of ceramic green sheets for the outer layer on which the internal electrode pattern is not printed are laminated, and ceramic green sheets on which the internal electrode pattern is printed are sequentially laminated on the ceramic green sheets, and then the internal electrode pattern is printed on the ceramic green sheets. A predetermined number of ceramic green sheets for outer layers that have not been printed are laminated to prepare a mother laminate.

(4) The first external electrode constituting the external electrode by printing the conductive paste (including Ni) for the first external electrode layer on both the upper and lower main surfaces of the mother laminate by screen printing or the like. Form a layered external electrode pattern.

(5) The mother laminate is cut at a predetermined position, and a raw (unfired) laminate of a predetermined size is cut out. At this time, the corners and ridges of the laminate may be rounded by barrel polishing or the like.

(6) Then, the unfired laminate is fired. The firing temperature depends on the ceramic material and the conductive material used, but is usually preferably 900 ° C. or higher and 1300 ° C. or lower. As a result, the ceramic green sheet, the conductive paste for the internal electrode and the conductive paste for the first external electrode layer are co-fired and sintered, and the laminate (ceramic element) provided with the first external electrode layer. Body) is obtained.

(7) A conductive paste (including Cu) for the second external electrode layer is applied and baked on both end faces of the fired laminate by, for example, a dip method or the like. As a result, the second external electrode layer is formed on both end faces of the laminated body.

(8) After that, a plating treatment is performed to form a base plating film (for example, a Ni plating film) on the surfaces of the first external electrode layer and the second external electrode layer. As the plating method, either electrolytic plating or electroless plating may be used. However, when electroless plating is performed, pretreatment with a catalyst or the like is required in order to improve the plating precipitation rate, which tends to complicate the process. Therefore, it is usually preferable to use electroplating. Further, as the plating method, it is preferable to use the barrel plating method.

(9) Then, if necessary, one or more upper layer plating films (for example, Sn plating film) are formed on the base plating film.

By the above-mentioned method, the multilayer ceramic capacitor of the present invention can be reliably manufactured. However, there are no particular restrictions on the manufacturing method of the multilayer ceramic capacitor of the present invention, and various known construction methods can be applied using the multilayer ceramic electronic component as the manufacturing method.

<Evaluation>
A moisture-resistant load test was performed on a monolithic ceramic capacitor (sample of Example 1) having the requirements of the present invention produced by the above method, and the IR defect rate was measured.
The configuration (conditions) of the multilayer ceramic capacitor used for the evaluation and the evaluation method are as follows. Further, the dimensions and the like of each part of the multilayer ceramic capacitor are all for a laminated ceramic capacitor provided with a fired laminate and an external electrode.

(Conditions for multilayer ceramic capacitor (sample) used for evaluation)
-Device thickness (thickness of the dielectric layer in the opposite region of the pair of internal electrodes): 1.2 μm
-Ceramic material that constitutes the dielectric layer: BaTIO ₃
-Number of laminated dielectric layers: 23-Thickness of ceramic layer (outer layer) outside the inner electrode of the outermost layer: 30 μm
(25 layers x 1.2 μm)
・ Capacity: 0.1 μF
-Rated voltage: 6.3V
-Dimensions: L x W x T (1.0 mm x 0.5 mm x 0.15 mm)
-Thickness of the first external electrode layer: 5 μm (thickness on the main surface)
-Thickness of the second external electrode layer: 15 μm (thickness at the end face)
-Thickness of base plating film (Ni plating film): 3 μm
-Thickness of upper plating film (Sn plating film): 3 μm
-Baking temperature of the laminate: Keep at 1200 ° C for 2 hours

(Sample for comparison)
The requirements of the present invention are provided by different types of metals contained in the first external electrode layer and the second external electrode layer in the multilayer ceramic capacitor (sample of Example 1) having the above-mentioned requirements of the present invention. The multilayer ceramic capacitors (samples) of Comparative Examples 1 to 3 which were not used were prepared. Then, the samples of Comparative Examples 1 to 3 were also subjected to a moisture resistance load test in the same manner as the multilayer ceramic capacitor having the above-mentioned requirements of the present invention, and the IR defect rate was measured.

The moisture resistance load test was performed under the conditions of 125 ° C., 95% RH, 3.2 V, and 72 h. Then, after the test, the insulation resistance at room temperature was measured, and the one having 1 MΩ or less was judged to be defective.
In the moisture resistance load test, the number of samples was 20 (n = 20), and the IR defect rate was determined from the number of samples used in the test and the number of samples determined to be defective.

Further, identification of the metal materials (Ni, Cu) constituting the first and second external electrode layers and analysis of the alloy state (total rate solid dissolution, etc.) of each sample of Examples 1 and Comparative Examples 1 to 3 are performed. , FE-WDX was used under the following conditions.

FE-WDX (Device name: JEOL JXA-8500F)
Acceleration voltage: 15.0kV
Irradiation current: 5 × 10-8A
(Conditions for qualitative analysis)
Beam diameter: φ0 μm
DwellTime (capture time): 200 ms
Qualitative analysis of the selected metal is performed by FE-WDX.

The intermetallic alloy state was evaluated with reference to the intermetallic alloy phase diagram in the "Metal Handbook" (published by the Japan Institute of Metals).
Table 1 shows the results of alloy state analysis, IR defect rate, and comprehensive evaluation of the sample of Example 1 and the samples of Comparative Examples 1 to 3 performed as described above.

As shown in Table 1, in the case of the sample of Example 1 of the present invention in which the first external electrode layer is Ni and the second external electrode layer is Cu, the alloy state is a total solid solution type and IR is defective. It was confirmed that the occurrence of was not observed.

On the other hand, in the case of the sample of Comparative Example 1 in which the first external electrode layer is Ag and the second external electrode layer is Cu, the alloy state is eutectic and the IR defect rate is as high as 30%. confirmed.

Further, in the case of the sample of Comparative Example 2 in which the first external electrode layer is Ti and the second external electrode layer is Cu, an intermetallic compound is generated at the junction between the first and second external electrode layers. , It was confirmed that the IR defect rate was as high as 25%.

Further, in the case of the sample of Comparative Example 3 in which the first external electrode layer and the second external electrode layer are both Cu, the joint portion between the first and second external electrode layers is a bond between the same types of metals. Therefore, it was confirmed that no alloy was formed at the joint and the IR defect rate was as high as 10%.

From these results, when Ni is used for the first external electrode layer and Cu is used for the second external electrode layer as in the present invention, Ni in the first external electrode layer is the second external. It diffuses into the electrode layer and dissolves in Cu, forming a 100% solid solution type diffusion layer (alloy layer) at the joint between the first and second external electrode layers, which contributes to the improvement of moisture resistance. Was confirmed.

Further, in the multilayer ceramic capacitor according to the first embodiment of the present invention, as shown in FIG. 1, the central portion of the laminated body 10 in the length direction (L direction) in the first external electrode layer 15 (15a, 15b). Since the tip on the side, that is, the tip on the side opposite to the tip on the end faces 21a, 21b side of the laminated body 10, is exposed from the second external electrode layer 25 (25a, 25b), the first external electrode layer In the exposed portion of the metal, stress due to mutual diffusion of metals is not generated, and deterioration of thermomechanical strength (deflection strength) is suppressed.

Therefore, by satisfying the requirements of the present invention, it is possible to obtain a highly reliable multilayer ceramic capacitor having excellent moisture resistance and high thermomechanical strength.

[Embodiment 2]
In the second embodiment, the first external electrode layer 15 (see FIG. 3) in which the dimension of the second external electrode layer 25 (25a, 25b) in the length direction (L direction) of the laminated body 10 is E (see FIG. 3). Examples 2-1, 2-2, in which the dimension D1 (see FIG. 3) of the laminated body 10 in the length direction (L direction) of the portion covering 15a, 15b) is set to the value shown in Table 2. Samples of 2-3, 2-4 and 2-5 and samples of Comparative Examples 4 and 5 were prepared.

Then, these samples were subjected to a moisture resistance load test, and the IR defect rate was measured. The moisture resistance load test was carried out by the same method and conditions as in the case of the first embodiment.

Moreover, the thermal shock cycle test was performed by the method described below, and the crack occurrence rate of each Example and each Comparative Example was measured.

In conducting the thermal shock cycle test, first, each sample is solder-mounted on the substrate under the following conditions.
Evaluation board: FR44 layer board 0.8 mm thick Solder thickness: 100 μm
Reflow temperature: 255 ° C

Then, for each of the above-mentioned samples, a cycle of holding for 30 minutes at each temperature condition of −55 ° C./80 ° C. is repeated 200 times.
After that, for each sample, the surface (LT surface) defined in the length L direction and the thickness T direction was polished to the central portion in the width W direction, and the exposed polished surface was observed, and cracks were observed. The number of samples was examined to determine the crack occurrence rate. The number of samples was 10 (n = 10).

For each sample (multilayer ceramic capacitor),
(A) Dimension E of the second external electrode layer in the length direction of the laminated body and (b) The portion of the second external electrode layer covering the first external electrode layer in the length direction of the laminated body. Dimension D1
The measuring method of is as follows.

First, the surface (LT surface) defined by the length L direction and the thickness T direction of each sample (multilayer ceramic capacitor) (n = 5) is polished to the central portion in the width W direction.
The first external electrode layer 15 on the polished surface is observed by SEM at a magnification of 3000, and from one end located on the end face side of the laminated body 10 to the other end located on the central portion side in the length L direction of the laminated body 10. The distance was measured, and the average value (n = 5) of this measurement result was defined as the length E of the first external electrode layer 15.

Similarly, the second external electrode layer 25 on the polished surface is observed by SEM at a magnification of 3000, and is located on the end faces 21a and 21b of the laminated body 10, and is located on the end faces 21a and 21b of the laminated body 10 in the thickness T direction of the laminated body 10. The distance was measured from the portion overlapping with the electrode layer 15 to the other end located on the central portion side in the length L direction of the laminated body 10, and the average value (n = 5) of the measurement results was defined as D1.

Table 2 shows the values of E and D1, the values of D1 / E, the IR defect rate in the moisture resistance load test, and the crack occurrence rate in the thermal shock cycle test measured as described above.

As shown in Table 2, the dimension D1 of the portion covering the first external electrode layer in the direction along the pull-out direction of the internal electrode is the dimension E in the direction along the pull-out direction of the internal electrode of the first external electrode layer. In the case of the samples of Examples 2-1, 2-2 and 2-3, which are 3% or more and 50% or less (that is, D1 / E: 3% or more and 50% or less), the IR defect rate and the crack occurrence rate are 0. It was confirmed that it was%.
It was also confirmed that the IR defect rate and the crack occurrence rate were 0% in the samples of Example 2-4 having D1 / E: 15% and Example 2-5 having D1 / E: 45%. Was done.

On the other hand, in the sample of Comparative Example 4 having D1 / E: 0% (the present invention in which the region of the first external electrode layer including the tip on the end face side of the laminated body is covered with the second external electrode layer. The crack generation rate in the thermal shock cycle test was 0%, but the IR defect rate in the moisture resistance load test was 10%, which was confirmed to be unfavorable.

Further, the sample of Comparative Example 5 having D1 / E: 100% (the tip of the first external electrode layer opposite to the tip on the end face side of the laminate is exposed without being covered by the second external electrode layer. In the sample that does not have the basic requirement of the present invention, that is, the IR defect rate in the moisture resistance load test was 0%, but it was confirmed that the crack occurrence rate of 30% in the thermal shock cycle test was not preferable. Was done.

From the results of the second embodiment, it was confirmed that it is preferable to obtain favorable results regarding the IR defect rate and the crack occurrence rate in the range of D1 / E of 3% or more and 50% or less.
That is, in the case of Comparative Example 4 in which the second external electrode layer does not cover the first external electrode layer at all, IR failure occurs in the moisture resistance load test, and the second external electrode layer is the first. In the case of Comparative Example 5 which covers the entire external electrode layer (a part of the first external electrode layer is not exposed), cracks were generated in the thermal shock cycle test, and it was confirmed that it was not preferable. ..

[Embodiment 3]
At the joint between the first external electrode layer and the second external electrode layer, the diffusion distance D2 of Ni constituting the first external electrode layer to the second external electrode layer containing Cu was different. Samples of Examples 3-1, 3-2, 3-3 and 3-4 and samples of Comparative Example 6 were prepared. Each sample was prepared by a method according to the method of the first embodiment (see FIG. 4).

However, in order to make the diffusion distance D2 different, the temperature at which the second external electrode layer is baked is changed in the range of 300 ° C. to 700 ° C. to change the Cu of Ni constituting the first external electrode layer. The diffusion distance D2 to the second external electrode layer including was changed.

Note that FIG. 4A is a schematic cross-sectional view showing the configuration of the first external electrode layer 15 and the second external electrode layer 25 in the multilayer ceramic capacitor according to the third embodiment, and FIG. 4B is a schematic cross-sectional view showing the configuration of the first external electrode layer 15 and the second external electrode layer 25. FIG. 4A is an enlarged view showing the region A of FIG. 4A, in which the diffusion distance D2 of Ni constituting the first external electrode layer to the second external electrode layer containing Cu and the second external electrode layer are shown. It is a figure which shows the thickness V of the electrode 25.

Then, a moisture resistance load test was performed on each of the prepared samples, and the IR defect rate of the sample of each example and the sample of the comparative example was measured. The moisture resistance load test was carried out under the same method and conditions with 20 samples as in the case of the first embodiment.

It should be noted that the second external electrode layer is formed so as to cover the first external electrode layer located on the main surface of the laminated body from the wraparound portion to the first external electrode layer, that is, the end surface of the laminated body. The thickness of the second external electrode layer of the region (joint portion), and the second outer surface containing Cu of Ni constituting the first external electrode layer at the joint portion of the first and second external electrode layers. The diffusion distance D2 to the electrode layer was determined by performing mapping analysis using the following device.

FE-WDX (Device name: JEOL JXA-8500F)
Acceleration voltage: 15.0kV
Irradiation current: 5 × 10 ^-8 A
Analytical depth: 1-2 μm
Measurable elements: B to U <Mapping analysis>
Number of pixels (number of pixels): 256 x 256
Pixel size: 0.1303 (3000 times)
Dwell Time (capture time in one pixel): 40 ms
Scan method: Beam

Table 3 shows the thickness V of the second external electrode layer at the joint, the diffusion distances D2 and D2 / V of Ni and Cu, and the IR defect rate in the moisture resistance load test.

As shown in Table 3, the value of the ratio (D2 / V) of the diffusion distance D2 of Ni to the thickness V of the second external electrode layer at the junction of the first and second external electrode layers is 10% or more. In the case of the samples of Examples 3-1, 3-2, 3-3 and 3-4 of 100% or less, the IR defect rate was confirmed to be 0%.

On the other hand, in the sample of Comparative Example 6 having D2 / V: 0% (a sample that does not have the basic requirement of the present invention that Ni is diffused in the second external electrode layer), the moisture resistance load test is performed. It was confirmed that the IR defect rate was 10%, which was not preferable.

The present invention is not limited to each of the above embodiments, and various applications and modifications can be added within the scope of the invention.

1 Capacitor layer 2 (2a, 2b) Internal electrode 5 (5a, 5b) External electrode layer 10 Laminated body 11a First main surface of the laminated body 11b Second main surface of the laminated body 15 (15a, 15b) First External electrode layer 16 Ni plating film 17 Sn plating film 18 Plating film 21a First end face of laminated body 21b Second end face of laminated body 25 (25a, 25b) Second external electrode layer 31a First end face of laminated body Side surface 31b Second side surface of the laminate 50 Multilayer ceramic capacitor L Length of multilayer ceramic capacitor T Height of multilayer ceramic capacitor W Width of multilayer ceramic capacitor D1 Covers the first external electrode layer of the second external electrode layer Dimensions in the length direction (L direction) of the laminated body of the part D2 Ni diffusion distance V Thickness of the second external electrode

Claims (2)

In a multilayer ceramic capacitor including a laminate in which an internal electrode and a dielectric layer are laminated, and an external electrode formed on the surface of the laminate so as to connect to the internal electrode.
The external electrode is formed on the main surface of the laminated body and contains a first external electrode layer containing Ni.
The end face from which the internal electrode of the laminated body is pulled out and the region including the tip of the first external electrode layer on the end face side are covered and joined to the first external electrode layer, and the internal electrode is formed. A second external electrode layer containing a glass component and Cu, which is formed so as to be conductive with the glass component, is provided.
In the region of the first external electrode layer located on the main surface of the laminated body, in the region near the ridge line formed by the main surface and the end surface, the first external electrode layer and the said. It is bonded to the second external electrode layer and
When looking at the pull-out direction of the internal electrode, the tip of the first external electrode layer opposite to the tip on the end face side of the laminated body is exposed without being covered by the second external electrode layer. While doing
Ni contained in the first external electrode layer diffuses into the second external electrode layer in the vicinity of the ridgeline and is solid-solved with Cu contained in the second external electrode layer .
The dimension in the pull-out direction of the internal electrode of the portion where the second external electrode layer covers the first external electrode layer is 3% of the dimension in the pull-out direction of the internal electrode of the first external electrode layer. A monolithic ceramic capacitor characterized by being 50% or more and 50% or less. The diffusion distance of Ni to the second external electrode layer is 100% or more of 10% or more of the thickness of the second external electrode layer in the portion where the second external electrode layer covers the first external electrode layer. multilayer ceramic capacitor according to claim 1, wherein the% or less.

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