JP2015043424A - Multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer ceramic capacitor having an external electrode which has high resistance against impacts from outside and deflection of a substrate after mounting on the substrate and also has excellent moisture resistance.SOLUTION: A multilayer ceramic capacitor 50 includes: a ceramic element body 10 including a dielectric layer 1 and a plurality of internal electrodes 2 disposed on a plurality of borders between the dielectric layers; and an external electrode 5 conducting with the internal electrodes, and is configured so that the external electrode includes a first sinter metal layer 12, a second sinter metal layer 22, and a plating layer 32; the first sinter metal layer is directly formed only on a first and second end surfaces 21a, 21b of the ceramic element body; the second sinter metal layer 22 covers the first sinter metal layer and is formed so as to wrap around a first and second principal surfaces 11a, 11b and a first and second side surfaces 31a, 31b of the ceramic element body; and the plating layer 32 is formed so as to cover the whole second sinter metal layer.

Description

  The present invention relates to a multilayer ceramic capacitor, and more particularly to a multilayer ceramic capacitor having a structure in which an external electrode is disposed on a surface of a ceramic body having an internal electrode so as to be electrically connected to the internal electrode.

  One typical ceramic electronic component is, for example, a multilayer ceramic capacitor as disclosed in Patent Document 1.

As shown in FIG. 3, the multilayer ceramic capacitor includes a dielectric layer 106, an element body (ceramic element body) 102 including internal electrodes 107 and 108, and external electrodes 103 and 104.
The external electrodes 103 and 104 are disposed on the end faces 102a and 102b side of the element body 102, and are formed to cover the end faces 102a and 102b, part of the main faces 102c and 102d, and part of the side faces.
Further, the external electrodes 103 and 104 are formed so as to cover the baking electrodes 131a and 141a formed on the end faces 102a and 102b, the plating layers 131b and 141b, a part of the main faces 102c and 102d, and a part of the side face. Formed so as to cover the thin film electrodes 132 and 142, the first plating layers 133 and 143 made of Ni or Ni alloy, and the first plating layers 133 and 143, And plating layers 134 and 144 made of Sn or Sn alloy.

  However, the external electrode disclosed in Patent Document 1 has a structure in which one layer of baking electrodes (sintered metal) 131a and 141a is disposed on the end faces 102a and 102b of the ceramic body 102, and one layer of baking is performed. In order to secure the connection reliability between the electrodes (sintered metal) 131a and 141a and the internal electrodes 107 and 108, the bonding between the ceramic body 102 and the baked electrodes (sintered metal) 131a and 141a is ensured. For this purpose, for example, it is necessary to contain a lot of glass components in the baked electrode (sintered metal), and the formed baked electrode (sintered metal) is hard and resistant to external impacts, etc. However, there is a problem that sufficient reliability cannot be ensured.

  Further, in order to improve characteristics such as impact resistance, for example, it is necessary to form voids in the baked electrodes (sintered metal) 131a and 141a to alleviate the bending stress. If the electrode is formed, the connection reliability with the internal electrodes 107 and 108 is lowered, or the plating solution used when plating the external electrodes 103 and 104 or the cleaning water used for cleaning after plating enters, and the characteristics and reliability are reduced. There is a problem of lowering.

JP 2013-165180 A

  The present invention solves the above-mentioned problems, and has high resistance to external impacts, flexure of the substrate after mounting on the substrate, and the like, and has a highly reliable external electrode having excellent moisture resistance. An object is to provide a multilayer ceramic capacitor.

In order to solve the above problems, the multilayer ceramic capacitor of the present invention is
A ceramic body comprising a dielectric layer made of a dielectric ceramic, and a plurality of internal electrodes disposed at a plurality of interfaces between the dielectric layers, wherein the first main surface and the first main surface A second main surface opposite to the first main surface, a second end surface orthogonal to the first main surface, a second end surface opposite to the first end surface, and a first side surface orthogonal to the first end surface And a ceramic body having a rectangular parallelepiped shape including a first side surface and a second side surface opposite to the first side surface, wherein the plurality of internal electrodes are alternately drawn to the first end surface and the second end surface;
A multilayer ceramic capacitor comprising a pair of external electrodes disposed on the ceramic body so as to be electrically connected to the internal electrodes drawn out to the first end surface and the second end surface;
The external electrode includes a first sintered metal layer, a second sintered metal layer, and a plating layer,
The first sintered metal layer is directly formed only on the first and second end faces of the ceramic body,
The second sintered metal layer covers the first sintered metal layer and wraps around the first and second main surfaces and the first and second side surfaces of the ceramic body. Formed,
The plating layer is formed so as to cover the entire second sintered metal layer.

In the multilayer ceramic capacitor of the present invention,
The first sintered metal layer and the second sintered metal layer contain a glass component, and
The glass component content is preferably different between the first sintered metal layer and the second sintered metal layer.

  Both the first sintered metal layer and the second sintered metal layer contain a glass component, and by making the contents of the glass components different, the first sintered metal layer and the second sintered metal layer By making the characteristics of the sintered metal layer different, it is possible to impart intended characteristics to the first sintered metal layer and the second sintered metal layer. For example, giving excellent adhesion and moisture resistance to the first sintered metal layer, or adding a lot of voids to the second sintered metal layer to give excellent resistance to external impact Is possible.

  Moreover, it is preferable that the first sintered metal layer contains more glass components than the second sintered metal layer.

  When the first sintered metal layer contains more glass components than the second sintered metal layer, the adhesion of the first sintered metal layer to the ceramic body is improved, It is possible to obtain sufficient connection reliability with the internal electrode or to form a dense first sintered metal layer to improve moisture resistance, and to contain a glass component A large amount of voids are included in the second sintered metal layer having a small amount to form a sintered metal layer excellent in impact resistance or a sintered metal layer that does not apply a large compressive stress to the ceramic body. This makes it possible to make the present invention more effective.

  In addition, when the second sintered metal layer includes more voids than the first sintered metal layer, the second sintered metal layer that does not apply a large compressive stress to the ceramic body is provided. It is possible to form the second sintered metal layer having excellent resistance to external impact, and the present invention can be more effectively realized.

  In the multilayer ceramic capacitor of the present invention, the first sintered metal layer directly formed only on the end surface of the ceramic body, the first sintered metal layer, and the main surface and side surfaces of the ceramic body are covered. Since the second sintered metal layer is formed so as to wrap around, and two sintered metal layers are formed on the end face of the ceramic body, the outer surface of the ceramic element body is external as compared with the case where only one layer exists. It is possible to improve resistance to impacts from water and to improve resistance to intrusion of moisture and plating solution. Moreover, since the 1st sintered metal layer is formed only in the end surface, it can suppress that a compressive stress is applied to a ceramic body.

  Furthermore, the multilayer ceramic capacitor of the present invention uses the first sintered metal layer and the second sintered metal layer in combination as described above, and the first sintered metal layer is formed only on the end face. For example, the first sintered metal layer contains a large amount of glass component and has a large adhering force to the end face of the ceramic element body, so that the inner electrode and the inner electrode Even when a high-density sintered metal layer with excellent conduction reliability and moisture resistance is formed, the ceramic body is prevented from cracking due to the compressive stress of the first sintered metal layer. It becomes possible. Further, the second sintered metal layer is formed so as to cover the first sintered metal layer and to wrap around the first and second main surfaces and the first and second side surfaces of the ceramic body. For example, by mounting a low-density sintered metal layer with a low density, voids, and excellent impact resistance, for example, when mounting on a mounting land on a substrate A highly reliable multilayer ceramic capacitor with an external electrode that is highly resistant to impacts from the outside and bending of the substrate after mounting on the substrate, while ensuring an electrode shape with excellent ease and certainty It becomes possible.

  That is, in the present invention, as described above, the first sintered metal layer formed only on the end face of the ceramic body, the first sintered metal layer, and the first and second ceramic body bodies are covered. Since the external electrode having desired characteristics is formed by combining the two main surfaces and the second sintered metal layer that goes around the first and second side surfaces, the connection to the internal electrode is possible. It is possible to provide a highly reliable multilayer ceramic capacitor with high reliability, excellent moisture resistance, and high resistance to external impacts and substrate deflection.

It is a front sectional view showing the composition of the multilayer ceramic capacitor concerning one embodiment of the present invention. 1 is a perspective view showing an external configuration of a multilayer ceramic capacitor according to an embodiment of the present invention. It is front sectional drawing which shows the structure of the external electrode of the conventional multilayer ceramic capacitor.

  Embodiments of the present invention will be described below to describe the features of the present invention in more detail.

  FIG. 1 is a front sectional view showing a configuration of a multilayer ceramic capacitor 50 according to one 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 FIG. 1, the multilayer ceramic capacitor 50 includes a dielectric layer 1 made of a dielectric ceramic, and a plurality of internal electrodes 2 (2a, 2b) disposed at a plurality of interfaces between the dielectric layers 1. And a pair of external electrodes 5 (5a, 5b) disposed on the outer surface of the ceramic body 10 so as to be electrically connected to the internal electrodes 2 (2a, 2b).

The dielectric layer 1 constituting the ceramic body 10 is made of a BaTiO ₃ -based or CaZrO ₃ -based ceramic dielectric.
The internal electrode 2 is a metal layer mainly composed of a base metal such as Ni or Cu.

  The ceramic body 10 has a rectangular parallelepiped shape, and includes a first main surface 11a, a second main surface 11b facing the first main surface 11a, and a first main surface 11a orthogonal to the first main surface 11a. An end surface 21a, a second end surface 21b facing the first end surface 21a, a first side surface 31a orthogonal to the first end surface 21a, and a second side surface 31b facing the first side surface 31a are provided. .

  When the direction connecting the first main surface 11a and the second main surface 11b is the height direction, the height direction is the stacking direction of the dielectric layer 1 and the internal electrodes 2 (2a, 2b). .

  In this embodiment, the ceramic body 10 is chamfered, the first and second end faces 21a and 21b, the first and second main faces 11a and 11b, the first and second side faces 31a and 31b, The ridge formed between the chamfers is chamfered and rounded.

  A plurality of internal electrodes 2 (2a, 2b) are alternately drawn out from the first end face 21a and the second end face 21a, the internal electrode 2a is drawn out from the first end face 21a, and the second end face The internal electrode 2b is drawn out to 21b.

  In the multilayer ceramic capacitor 50, the external electrode 5 (5a, 5b) includes the first sintered metal layer 12 (12a, 12b), the second sintered metal layer 22 (22a, 22b), and plating. The structure includes the layer 32 (32a, 32b).

The first sintered metal layer 12 (12a, 12b) is directly formed only on the first end surface 21a and the second end surface 21b of the ceramic body 10. Here, the 1st end surface 21a and the 2nd end surface 21b say the flat area | region which does not cover the roundish area | region of a ridgeline part.
In addition, about the 1st sintered metal layer 12, it is comprised from the viewpoint of ensuring fixed adhesion and moisture resistance so that it may contain more glass components than the below-mentioned 2nd sintered metal layer 22. FIG. Preferably, the number of voids is smaller than that of the second sintered metal layer 22.

The second sintered metal layer 22 (22a, 22b) covers the first sintered metal layer 12 (12a, 12b), and the first and second main surfaces 11a, 11b of the ceramic body 10. , And the first and second side surfaces 31a and 31b.
The second sintered metal layer 22 preferably contains more voids than the first sintered metal layer 12 described above, particularly from the viewpoint of ensuring flexibility and impact resistance. More preferably, the glass component is contained less than the first sintered metal layer 12.

Furthermore, the plating layer 32 (32a, 32b) is formed so as to cover the entire second sintered metal layer 22 (22a, 22b).
In this embodiment, the plating layer 32 (32a, 32b) has a two-layer structure including the Ni plating layer 33 (33a, 33b) and the Sn plating layer 34 (34a, 34b) formed thereon. It is a plating layer.

The first and second sintered metal layers 12 and 22 are sintered metal layers formed by baking a conductive paste containing Cu or Ni as a conductive component.
The first sintered metal layer 12 and the second sintered metal layer 22 may have the same main conductive component or may be different.

In this embodiment, as the multilayer ceramic capacitor 50,
(A) Multi-layer ceramic capacitor having dimensions including an external electrode: length (L): 0.6 mm, width (W): 0.3 mm, height (T): 0.3 mm;
(B) A monolithic ceramic capacitor having the dimensions including the external electrode, length (L): 0.4 mm, width (W): 0.2 mm, and height (T): 0.2 mm was produced.
However, the present invention is not limited to the monolithic ceramic capacitor having the dimensions as described above, and can be applied to monolithic ceramic capacitors having different dimensions.

In the case of the multilayer ceramic capacitor having the dimensions as described above, the thickness of the first sintered metal layer 12 is usually in the range of 0.5 μm to 10 μm, and the thickness of the second sintered metal layer 22 is 0.00. It is desirable to be in the range of 5-20 μm.
However, the thickness of the 1st sintered metal layer 12 and the 2nd sintered metal layer 22 is not restricted to the above-mentioned range, It is also possible to set it as another thickness.

Next, a method for manufacturing the multilayer ceramic capacitor 50 will be described.
First, a ceramic raw material slurry in which a binder and a solvent are mixed and dispersed in a dielectric ceramic powder mainly composed of BaTiO ₃ or CaZrO ₃ is thinly stretched on a resin film such as a PET film and formed into a sheet shape. A ceramic green sheet is prepared. Note that Dy is added in an amount of 1.0 mol and Mg is added in an amount of 1.3 mol with respect to 100 mol of Ti in BaTiO ₃ .

  Then, a conductive paste is printed on the ceramic green sheet using a method such as screen printing or gravure printing to form an internal electrode pattern. Then, a predetermined number of ceramic green sheets on which internal electrode patterns are formed and ceramic green sheets on which no internal electrode patterns are formed (ceramic green sheets for outer layers) are stacked in a predetermined order.

  And the obtained laminated block is pressed and each ceramic green sheet is crimped | bonded. In pressing the laminated block, for example, the pressure-bonding block is sandwiched between resin films and pressed by a method such as isostatic pressing.

  Thereafter, the pressed laminated pressure-bonded body is divided into rectangular parallelepiped-shaped chips (pieces) using a method such as pressing and cutting, and then barrel polishing is performed.

  The barrel-polished chip (the piece that becomes the ceramic body 10 (FIG. 1) after firing) is heated to a predetermined temperature to remove the binder, and then fired at, for example, 900 to 1000 ° C. to obtain a rectangular parallelepiped. A shaped ceramic body is obtained. Dy diffuses into the internal electrode by performing the main baking.

  Then, one end face of the ceramic body is immersed in a conductive paste layer formed by holding the other end face side of the ceramic body and applying the conductive paste on a surface plate. In addition, after applying the conductive paste that becomes the first sintered metal layer through the baking process, unnecessary portions of the conductive paste (for example, portions that wrap around the main surface and side surfaces of the ceramic body) are removed and dried. To do.

  Next, again, the other end face side of the ceramic body is held, and the conductive paste serving as the first sintered metal layer is applied to the conductive paste layer formed on the surface plate, and dried. By immersing the one end face on which the conductive paste layer is formed, the conductive paste film serving as the first sintered metal layer on the one end face of the ceramic body is covered and the main face and side surfaces of the ceramic body are wrapped around. Then, a conductive paste to be the second sintered metal layer is applied through a baking step and dried.

  Thereafter, the other end face of the ceramic body is also coated with the conductive paste to be the first sintered metal layer and the conductive paste to be the second sintered metal layer by the same method and dried.

  Then, by baking the conductive paste to be the first sintered metal layer and the conductive paste to be the second sintered metal layer at the one end and the other end applied as described above, the first baking is performed. A sintered metal layer and a second sintered metal layer are formed. By baking, the first sintered metal layer component diffuses into the internal electrode drawn to the end face, and a diffusion layer of Cu, Dy, and Ni is formed.

  As described above, when forming the first sintered metal layer and the second sintered metal layer, Cu powder is used as a conductive component as a conductive paste, and a glass component, an organic binder, and a solvent are added thereto. A kneaded conductive paste was used.

  In this embodiment, as the conductive paste for forming the first sintered metal layer and the second sintered metal layer, a conductive paste having the same composition and the same glass component content was used. The glass components may be different.

Next, Ni plating and Sn plating are performed in this order on the second sintered metal layer to form a Ni plated layer covering the second sintered metal layer and an Sn plated layer covering the Ni plated layer. .
Thereby, the multilayer ceramic capacitor 50 according to the embodiment of the present invention having the structure as shown in FIGS. 1 and 2 is obtained.
The voids can be observed by the following method. First, the multilayer ceramic capacitor is polished to a depth of about ½ of the width or thickness so that the cross section of the external electrode is exposed. Remove sagging due to polishing. Next, the sintered metal part and the other part of the cross section of the external electrode are imaged by SEM. Further, the same cross section is subjected to composition analysis by WDX, and a portion including a glass component is specified by image processing. By superimposing the image captured by the SEM and the image processed by the WDX, the portion containing the glass component and the gap are distinguished. Similarly, different glass components are also distinguished from the composition analysis by WDX.

<Test>
In order to confirm the effect of the present invention, a multilayer ceramic capacitor was produced by the method described below, and the following test was performed using the obtained multilayer ceramic capacitor as a sample.

  First, a conductive paste was printed on a ceramic green sheet having a predetermined thickness so that the thickness of the dielectric layer after firing was 1.6 μm and the thickness of the internal electrode was 0.85 μm. Then, 200 layers of this ceramic green sheet were laminated.

  Further, the outer layer ceramic green sheet on which the inner electrode was not formed was laminated so that an outer layer having a thickness of 30 μm was formed after firing, and a laminated crimped body having an outer layer portion was formed by pressure bonding. .

Then, the laminated pressure-bonded body is cut and divided so that the dimensions of the fired ceramic body are length: 1.0 mm, width: 0.5 mm, height: 0.5 mm. A test multilayer ceramic capacitor (sample as an example) having a structure as shown in FIG. 1 was produced in the same manner as shown.
In addition, the thickness of the 1st sintered metal layer was 10 micrometers, and the thickness of the 2nd sintered metal layer was 20 micrometers.

  Further, for comparison, the first sintered metal layer is formed so as to wrap around from the end surface side to the main surface side and the side surface side, and the second sintered metal layer is covered so as to cover the first sintered metal layer. A multilayer ceramic capacitor (sample) as a comparative example was produced under the same method and conditions as in the case of the multilayer ceramic capacitor as an example described above, except that was formed.

  When the multilayer ceramic capacitors (samples) of Examples and Comparative Examples manufactured as described above were observed by applying a voltage having a steep voltage waveform, the 20 multilayer ceramic capacitors (samples) of Comparative Examples were manufactured. It was confirmed that cracks occurred in the ceramic body for three of the samples.

  On the other hand, in the case of the multilayer ceramic capacitor (sample) of the example, no crack was observed in any of the 20 samples.

  In addition, each of the multilayer ceramic capacitors (samples) of the example manufactured as described above and the multilayer ceramic capacitor of the comparative example (samples in which no cracks were observed) were soldered on the land of the substrate. After mounting, the substrate was bent and examined for cracks.

As a result, in the case of the comparative example, the occurrence of cracks was observed for 6 out of 20 samples.
This is because both the first sintered metal layer and the second sintered metal layer are formed so as to wrap around from the end surface side to the main surface side and the side surface side. This is considered to be caused by a large stress applied to the element body via the external electrode.

  On the other hand, in the case of the sample according to the example of the present invention, no crack was observed in any of the 20 samples.

  From the above results, it was confirmed that according to the present invention, it is possible to obtain a highly reliable monolithic ceramic capacitor in which cracks due to compressive stress of the external electrodes and cracks due to substrate bending are unlikely to occur. .

  In the above test, the glass component content is not different between the first sintered metal layer and the second sintered metal layer, but the glass component content is controlled (first By increasing the glass component content of the sintered metal layer and decreasing the glass component content of the second sintered metal layer), the adhesion of the first sintered metal layer to the ceramic body It is possible to improve the moisture resistance, suppress the compressive stress of the second sintered metal layer, or further improve the impact resistance, so that a more reliable multilayer ceramic capacitor can be obtained.

  In addition, this invention is not limited to the said embodiment, A various application and deformation | transformation are possible within the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Dielectric layer 2 (2a, 2b) Internal electrode 5 (5a, 5b) External electrode 10 Ceramic body 11a The 1st main surface of a ceramic body 11b The 2nd main surface 12 of a ceramic body 12 (12a, 12b) First sintered metal layer 21a First end face 21b of ceramic body Second end face 22 of ceramic body 22 (22a, 22b) Second sintered metal layer 31a First side face 31b of ceramic body 31b Ceramic body Second side surface 32 (32a, 32b) Plating layer 33 (33a, 33b) Ni plating layer 34 (34a, 34b) Sn plating layer 50 Multilayer ceramic capacitor L Multilayer ceramic capacitor length T Multilayer ceramic capacitor height W Multilayer ceramic capacitor width

Claims (4)

A ceramic body comprising a dielectric layer made of a dielectric ceramic, and a plurality of internal electrodes disposed at a plurality of interfaces between the dielectric layers, wherein the first main surface and the first main surface A second main surface opposite to the first main surface, a second end surface orthogonal to the first main surface, a second end surface opposite to the first end surface, and a first side surface orthogonal to the first end surface And a ceramic body having a rectangular parallelepiped shape including a first side surface and a second side surface opposite to the first side surface, wherein the plurality of internal electrodes are alternately drawn to the first end surface and the second end surface;
A multilayer ceramic capacitor comprising a pair of external electrodes disposed on the ceramic body so as to be electrically connected to the internal electrodes drawn out to the first end surface and the second end surface;
The external electrode includes a first sintered metal layer, a second sintered metal layer, and a plating layer,
The first sintered metal layer is directly formed only on the first and second end faces of the ceramic body,
The second sintered metal layer covers the first sintered metal layer and wraps around the first and second main surfaces and the first and second side surfaces of the ceramic body. Formed,
The multilayer ceramic capacitor, wherein the plating layer is formed so as to cover the whole of the second sintered metal layer. The first sintered metal layer and the second sintered metal layer contain a glass component, and
2. The multilayer ceramic capacitor according to claim 1, wherein the glass component content is different between the first sintered metal layer and the second sintered metal layer.   The multilayer ceramic capacitor according to claim 2, wherein the first sintered metal layer contains more glass components than the second sintered metal layer.   The multilayer ceramic capacitor according to claim 1, wherein the second sintered metal layer includes a larger number of voids than the first sintered metal layer.

Images