Patent Publication Number: US-8988854-B1

Title: Multilayer ceramic electronic component

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a multilayer ceramic electronic component and particularly relates to a multilayer ceramic electronic component including a ceramic element body, in which internal electrodes are provided, and external electrodes arranged on end surfaces of the ceramic element body so as to be electrically connected to respective ones of the internal electrodes. For example, the present invention relates to a multilayer ceramic capacitor, a multilayer ceramic inductor, a multilayer ceramic thermistor, or a multilayer ceramic piezoelectric component. 
     2. Description of the Related Art 
     For example, as disclosed in Japanese Unexamined Patent Application Publication No. 10-284343, a generally known multilayer electronic component includes external electrodes formed on both end surfaces of a ceramic element body in which internal electrodes are provided to be exposed in the surfaces of the ceramic element body, the external electrodes each including a sintered electrode layer containing a metal as a main component, a conductive resin electrode layer formed on the surface the sintered electrode layer and containing metal particles, and a plating layer formed on the surface of the conductive resin electrode layer. In the multilayer ceramic electronic component, the conductive resin electrode layer is formed between the sintered electrode layer and the plating layer, thereby resolving to some extent the problem of cracks being caused in the ceramic element body due to a temperature cycle during use and the problem of weakening resistance to deflection of a substrate when the multilayer ceramic electric component is mounted on the substrate. 
     However, the general multilayer ceramic electronic component described above has low adhesive force between the conductive resin electrode layer containing a large amount of resin and the sintered electrode layer composed of a metal. Therefore, deflection of a substrate on which the multilayer ceramic electronic component is mounted is absorbed by the conductive resin electrode layer, but the low adhesive force between the conductive resin electrode layer and the sintered electrode layer causes the problem of separation between the conductive resin electrode layer and the sintered electrode layer. 
     SUMMARY OF THE INVENTION 
     Accordingly, preferred embodiments of the present invention provide a multilayer ceramic electronic component having strong adhesive force between a conductive resin electrode layer and a sintered electrode layer. 
     According to a preferred embodiment of the present invention, a multilayer ceramic electronic component includes a ceramic element body in which internal electrodes are provided and which includes a first main surface, a second main surface facing the first main surface, a first side surface connected to the first main surface and the second main surface, a second side surface facing the first side surface, a first end surface connected to the first main surface, the second main surface, the first side surface, and the second side surface, and a second end surface facing the first end surface; and external electrodes arranged on the end surfaces and at least a portion of the first main surface or the second main surface of the ceramic element body so as to be electrically connected to respective ones of the internal electrodes. The external electrodes are provided on the end surfaces and at least the first main surface or the second main surface of the ceramic element body, and each of the external electrodes includes a sintered metal layer, a conductive resin layer, and a plating layer which are arranged in that order from the ceramic element body, the conductive resin layer including resin and metal particles. When a cross section including an interface between the sintered metal layer and the conductive resin layer is viewed from any one of the first main surface, the second main surface, the first side surface, and the second side surface, the sintered metal layer includes a plurality of recesses each including an inlet extending along the interface and an inner portion extending from the interface into the sintered metal layer, each of the recesses having a shape in which a dimension of the inner portion is larger than a dimension of the inlet measured along the interface. A material of the conductive resin layer is disposed in at least some of the recesses. 
     According to a preferred embodiment of the present invention, in another aspect, a multilayer ceramic electronic component includes a ceramic element body in which internal electrodes are provided and which includes a first main surface, a second main surface facing the first main surface, a first side surface connected to the first main surface and the second main surface, a second side surface facing the first side surface, a first end surface connected to the first main surface, the second main surface, the first side surface, and the second side surface, and a second end surface facing the first end surface; and external electrodes arranged on the end surfaces and at least a portion of the first main surface or the second main surface of the ceramic element body so as to be electrically connected to respective ones of the internal electrodes. The external electrodes are provided on the end surfaces and at least the first main surface or the second main surface of the ceramic element body and each of the external electrodes includes a sintered metal layer, a conductive resin layer, and a plating layer which are arranged in that order from the ceramic element body, the conductive resin layer including resin and metal particles. The metal particles are Cu powder particles and include flat particles (first particles) having a flat shape and spherical particles (second particles) having a spherical shape, and a ratio of the number of the spherical particles to the number of the flat particles preferably is about 3/7 to about 7/3, for example. When a cross section including an interface between the sintered metal layer and the conductive resin layer is viewed from any one of the first main surface, the second main surface, the first side surface, and the second side surface, the sintered metal layer includes a plurality of recesses having a shape in which a dimension of the inner portion is larger than a dimension of the inlet measured along the interface, and a material of the conductive resin layer is disposed in at least some of the recesses, and the number of the recesses in which the material of the conductive resin layer is present is two or more within a length range of about 70 μm along the interface, for example. When a cross section including another interface between the conductive resin layer and the plating layer is viewed from any one of the first main surface, the second main surface, the first side surface, and the second side surface, the plating layer at the another interface includes a plurality of projections preferably having a height of about 1.0 μm to about 7.0 μm and projecting toward the conductive resin layer, and the number of the projections is two or more within a length range of about 80 μm along the interface, for example. 
     In a multilayer ceramic electronic component according to a preferred embodiment of the present invention, the metal powder of the conductive resin layer preferably contains Cu or Ag. 
     In a multilayer ceramic electronic component according to a preferred embodiment of the present invention, the sintered metal layer preferably includes Cu. 
     In a multilayer ceramic electronic component according to a preferred embodiment of the present invention, the plating layer preferably includes a Ni plating layer. 
     In a multilayer ceramic electronic component, a sintered metal layer is formed preferably by applying a conductive paste to the end surfaces of a ceramic element body and baking the paste. In this case, many recesses are formed in the surface of the sintered metal layer. When a material of a conductive resin layer enters the recesses, a strong adhesive force between the conductive resin layer and the sintered metal layer is obtained. However, in some cases, the material of the conductive resin layer does not sufficiently enter the recesses. When the material of the conductive resin layer does not enter many recesses, the adhesive force between the conductive resin layer and the sintered metal layer is decreased, thus easily causing separation between the conductive resin layer and the sintered metal layer. 
     In a multilayer ceramic electronic component according to a preferred embodiment of the present invention, observation of a section of the conductive resin layer revealed that when the material of the conductive resin layer does not enter the recesses within a length range of about 70 μm along the interface between the conductive resin layer and the sintered metal layer, satisfactory adhesive force between the conductive resin layer and the sintered metal layer is achieved. 
     Therefore, in a multilayer ceramic electronic component according to various preferred embodiments of the present invention, satisfactory adhesive force between the conductive resin layer and the sintered metal layer is achieved. 
     According to various preferred embodiments of the present invention, multilayer ceramic electronic components having good adhesive force between a conductive resin layer and a sintered metal layer are provided. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating an example of a multilayer ceramic capacitor according to a preferred embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the multilayer ceramic capacitor shown in  FIG. 1 , taken along line II-II in  FIG. 1 . 
         FIG. 3  is a diagram illustrating an interface between a conductive resin layer and a sintered metal layer in which recesses are present. 
         FIG. 4  is an enlarged partial view illustrating a cross section of a central portion of the multilayer ceramic capacitor shown in  FIG. 1  in the width direction thereof. 
         FIG. 5  is a diagram illustrating an interface between a conductive resin layer and a Ni plating layer in which projections extend from the Ni plating layer to the conductive resin layer. 
         FIG. 6  is a diagram illustrating the size of the projections shown in  FIG. 5 . 
         FIG. 7  is a diagram, similar to  FIG. 3 , illustrating an interface between a conductive resin layer and a sintered metal layer in which recesses are present. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A multilayer ceramic electronic component  10  shown in  FIG. 1  includes a ceramic element body  12 , for example, preferably having a substantially rectangular parallelepiped shape. The ceramic element body  12  includes a plurality of stacked ceramic layers  14  and also includes a first main surface  12   a  and a second main surface  12   b  which face each other, a first side surface  12   c  and a second side surface  12   d  which face each other, and a first end surface  12   e  and a second end surface  12   f  which face each other. The first side surface  12   c  and the second side surface  12   d  are each connected to the first main surface  12   a  and the second main surface  12   b . The first end surface  12   e  and the second end surface  12   f  are each connected to the first main surface  12   a , the second main surface  12   b , the first side surface  12   c , and the second side surface  12   d . The ceramic element body  12  preferably includes rounded corners and edges. In addition, the ceramic element body  12  may be formed to have other sizes and shapes. 
     Examples of a ceramic material which can be used for the ceramic layers  14  of the ceramic element body  12  include dielectric ceramics composed of BaTiO 3 , CaTiO 3 , SrTiO 3 , CaZrO 3 , or the like as a main component. An accessory component such as a Mn compound, a Fe compound, a Cr compound, a Co compound, a Ni compound, or the like may be added to the main component. The thickness of each of the ceramic layers  14  of the ceramic element body  12  preferably is, for example, about 0.5 μm to about 10 μm. 
     As shown in  FIG. 2 , a plurality of first and second internal electrodes  16   a  and  16   b  preferably having, for example, a substantially rectangular shape are provided in the ceramic element body  12  so as to be alternately arranged at equal or substantially equal intervals along the thickness direction of the ceramic element body  12 . 
     The first and second internal electrodes  16   a  and  16   b  include exposed end portions  18   a  and  18   b  exposed at the first and second end surfaces  12   e  and  12   f , respectively, of the ceramic element body  12 . Specifically, the exposed portions  18   a  at the ends of the first internal electrodes  16   a  are exposed at the first end surface  12   e  of the ceramic element body  12 . Also, the exposed portions  18   b  at the ends of the second internal electrodes  16   b  are exposed at the second end surface  12   f  of the ceramic element body  12 . 
     Further, the first and second internal electrodes  16   a  and  16   b  are parallel or substantially parallel with the first and second main surfaces  12   a  and  12   b  of the ceramic element body  12 . In addition, the first and second internal electrodes  16   a  and  16   b  face each other with the ceramic layers  14  disposed therebetween in the thickness direction of the ceramic element body  12 . 
     The thickness of each of the first and second internal electrodes  16   a  and  16   b  preferably is, for example, about 0.2 μm to about 2 μm. However, the thickness of each of the first and second internal electrodes  16   a  and  16   b  is not particularly limited. 
     The first and second internal electrodes  16   a  and  16   b  include, for example, a base metal Ni as a conductive material. The first and second internal electrodes  16   a  and  16   b  may be composed of a metal, such as Ni, Cu, Ag, Pd, Au, or the like, or an alloy containing one of these metals, such as an Ag—Pd alloy or the like. 
     Further, first and second external electrodes  20   a  and  20   b  are provided on the first and second end surfaces  12   e  and  12   f , respectively, of the ceramic element body  12 . 
     The first external electrode  20   a  extends from the first end surface  12   e  to the first and second main surfaces  12   a  and  12   b  and the first and second side surfaces  12   c  and  12   d  of the ceramic element body  12 . In this case, the first external electrode  20   a  is electrically connected to the exposed portions  18   a  of the first internal electrodes  16   a.    
     The second external electrode  20   b  extends from the second end surface  12   f  to the first and second main surfaces  12   a  and  12   b  and the first and second side surfaces  12   c  and  12   d  of the ceramic element body  12 . In this case, the second external electrode  20   b  is electrically connected to the exposed portions  18   b  of the second internal electrodes  16   b.    
     The external electrode  20   a  includes a sintered metal layer  22   a , a conductive resin layer  24   a , and a plating layer  26   a  which are arranged in that order from the ceramic element body  12 . Similarly, the external electrode  20   b  includes a sintered metal layer  22   b , a conductive resin layer  24   b , and a plating layer  26   b  which are arranged in that order from the ceramic element body  12  side. 
     The sintered metal layers  22   a  and  22   b  include a base metal Cu as a main component and are provided on the outer surfaces of the ceramic element body  12 , that is, on the first and second end surfaces  12   e  and  12   f , etc. to be physically and electrically connected to the first and second internal electrodes  16   a  and  16   b , respectively. The sintered metal layers  22   a  and  22   b  are formed preferably by applying a conductive paste containing a Cu powder and glass powder to the outer surfaces of the ceramic element body  12  and then baking the paste. Each of the sintered metal layers  22   a  and  22   b  preferably has a thickness of, for example, about 10 μm to about 30 μm. 
     Each of the conductive resin layers  24   a  and  24   b  contains metal particles as a conductive material. The conductive resin layers  24   a  and  24   b  are arranged on the sintered metal layers  22   a  and  22   b  so as to cover the sintered metal layers  22   a  and  22   b , respectively. Each of the conductive resin layers  24   a  and  24   b  is a layer formed preferably by heat-curing a mixture containing a first metal powder of Cu or Ag which forms metal particles, a second metal powder having a predetermined average particle diameter, and a resin. 
     The sintered metal layers  22   a  and  22   b  are preferably formed by applying the conductive paste to the end surfaces of the ceramic element body and then baking the paste. In this case, as shown in  FIGS. 3 and 7 , a plurality of recesses  25  are formed in the surfaces of the sintered metal layers  22   a  and  22   b  along an interface between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b . When the conductive resin layers  24   a  and  24   b  are formed on the sintered metal layers  22   a  and  22   b , respectively, a material of the conductive resin layers  24   a  and  24   b  may or may not enter the recesses  25  in the surfaces of the sintered metal layers  22   a  and  22   b , respectively. That is, the recesses  25  include filled recesses  25   a  in which a material of the conductive resin layers  24   a  and  24   b  has entered, and empty recesses  25   b  in which a material of the conductive resin layers  24   a  and  24   b  has not entered. It should be noted that the filled recesses  25   a  may be completely or only partially filled with the material of the conductive resin layers  24   a  and  24   b . When the material of the conductive resin layers  24   a  and  24   b  enters the filled recesses  25   a  of the sintered metal layers  22   a  and  22   b , an adhesive strength between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b  is enhanced by an anchor effect. Therefore, in order to prevent separation between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b , it is preferred to decrease the number of the empty recesses  25   b  which the material of the conductive resin layers  24   a  and  24   b  does not enter. 
     The recesses  25  in the surfaces of the sintered metal layers  22   a  and  22   b  are observed preferably by using a section of a central portion in the width direction of the multilayer ceramic capacitor  10 , that is, a surface defined in the length direction and the thickness direction of the multilayer ceramic capacitor  10  and exposed by grinding up to the central portion in the width direction. In this case, surface treatment is performed to avoid sagging due to grinding, and the interfaces between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b  are observed at a 1000 times magnification by using an SEM. The recesses  25  are located on the sintered metal layer side and opened toward the conductive resin layer side. Each of the recesses  25  is configured such that a dimension d2 of an inner portion extending from the interface into the sintered metal layer is larger than a dimension d1 of an inlet extending along the interface. The inlet of each of recess  25  is located at the portion of the recess  25  that is located along interface between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b  and opens to the surface of the conductive resin layers  24   a  and  24   b . The dimension d1 is defined as a distance along the interface between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b  from one edge of the inlet to an opposite edge of the inlet in a cross-section of the inlet as shown in  FIGS. 3 and 7 . In other words, a dimension of the inlet is defined by d1. The dimension d2 of the inner portion is defined as a maximum dimension of the recess  25  extending in a direction parallel to the direction along which the dimension d1 is measured in a cross section of the recesses  25  as shown in  FIGS. 3 and 7 . 
     As noted above, a material of the conductive resin layers  24   a  and  24   b  enters some of the recesses  25  so as define filled recesses  25   a . For example, the resin of the conductive resin layers  24   a  and  24   b  enters and is disposed in at least some of the recesses  25  to define the filled recesses  25   a , and some of metal particles of the conductive resin layers  24   a  and  24   b  enter and are disposed in at least some of the recesses  25  to define the filled recesses  25   a.    
     It should be noted that  FIG. 3  shows a straight or substantially straight interface between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b  along which the recesses  25   a  and  25   b  are located, and  FIG. 7  shows a meandering or non-straight interface between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b  along which the recesses  25   a  and  25   b  are located. 
     In addition, in order to achieve high adhesive strength between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b , the number of the filled recesses  25   a  within a length range of about 70 μm along the interface is preferably about 2 or more, for example. In this case, the dimension d1 of the inlet of the filled recesses  25   a  is preferably about 1 μm to about 3 μm in a section including the sintered metal layers  22   a  and  22   b , for example. In addition, the filled recesses  25   a  are preferably present at  5  positions or more at the interface in the width direction or the thickness direction, for example. 
     Each of the recesses  25  has a depth measured along a line of maximum length within the respective recess  25  extending perpendicular to the direction along which the dimension d1 is measured. The depth of the recesses  25  is preferably within a range of about 3 μm to about 5 μm, for example. A depth out of this range has difficulty in achieving the desired anchor effect. 
     The metal particles contained in the conductive resin layers  24   a  and  24   b  include flat particles with a flat shape and spherical particles with a spherical shape. Whether the metal particles are the flat particles or the spherical particles is determined by observing a cross section of a central portion in the width direction of the multilayer ceramic capacitor  10 , which is a cross section of the conductive resin layers  24   a  and  24   b . When the ratio of a long side to a short side in each of the metal particles contained in the conductive resin layers  24   a  and  24   b  is about 5/1 or more, the metal particle is regarded as a flat particle. When the ratio of a long side to a short side is less than about 5/1, the metal particle is regarded as a spherical particle. For example, a substantially flat shape is a shape which has at least one flat surface. The flat particles in the metal particles contained in the conductive resin layers  24   a  and  24   b  relaxes the stress applied to the external electrodes  20   a  and  20   b , and the spherical particles in the metal particles contained in the conductive resin layers  24   a  and  24   b  secure electric connection. 
     Further, the ratio of the number of the spherical particles to the number of the flat particles in the metal particles contained in the conductive resin layers  24   a  and  24   b  preferably is about 3/7 to about 7/3, for example. The ratio is determined by observing a cross section of a central portion in the width direction of the multilayer ceramic capacitor  10 , which is a cross section including the conductive resin layers  24   a  and  24   b . The ratio of the flat particles to the number of the spherical particles in the section of the conductive resin layers  24   a  and  24   b  is regarded as the ratio of the number of the spherical particles to the number of the flat particles. 
     The section of a central portion in the width direction of the multilayer ceramic capacitor  10  observed as described above is a surface defined in the length direction and the thickness direction of the multilayer ceramic capacitor  10  and the section is exposed by fixing the multilayer ceramic capacitor  10  with a resin and grinding a portion including the internal electrodes  16   a  and  16   b  and the external electrodes  20   a  and  20   b  up to the central portion in the width direction of the multilayer ceramic capacitor  10 . In addition, surface treatment is performed to avoid sagging due to grinding, and the section including the conductive resin layers  24   a  and  24   b  is observed at, for example, a 1000 times magnification by using SEM.  FIG. 4  is an enlarged partial view showing the section. 
     The reason for the ratio of about 3/7 to about 7/3 of the number of the spherical particles to the number of the flat particles in the metal particles contained in the conductive resin layers  24   a  and  24   b  is that a ratio larger than about 7/3 causes a state having a small number of the flat particles and a large number of the spherical particles, and electric connection is secured, but the ceramic element body is easily cracked by deflection stress due to insufficient stress relaxation. On the other hand, a ratio smaller than about 3/7 causes a state having a large number of the flat particles and a small number of the spherical particles, and stress relaxation is secured, but electric connection cannot be secured to increase equivalent series resistance. 
     In addition, a base metal Ni or Sn preferably is used as the second metal powder contained in the conductive resin layers  24   a  and  24   b . The second metal powder may have a spherical shape or a fish-scale-shaped configuration, and the second metal powder preferably has an average particle diameter of about 10 μm to about 50 μm, for example, and is a very fine powder. 
     Examples of the resin contained in the conductive resin layers  24   a  and  24   b  include, but are not limited to, thermosetting resin such as phenol resins, acrylic resins, silicone resins, epoxy resins, polyimide resins, and the like. 
     When a section containing an interface between the sintered metal layer  22   a  and the conductive resin layer  24   a  in the external electrode  20   a  is observed, glass is present on the surface of the sintered metal layer  22   a  at the interface, and a ratio L1/L2 preferably is about 0.2 or more and about 1.5 or less, for example, where L1 is the length of the glass along the interface and L2 is the length of a metal portion other than glass in the sintered metal layer  22   a  along the interface. Similarly, when a section including an interface between the sintered metal layer  22   b  and the conductive resin layer  24   b  in the external electrode  20   b  is observed, glass is present on the surface of the sintered metal layer  22   b  at the interface, and a ratio L1/L2 preferably is about 0.2 or more and about 1.5 or less, for example, where L1 is the length of the glass along the interface and L2 is the length of a metal portion other than glass in the sintered metal layer  22   b  along the interface. 
     Like the section described above, the section of the multilayer ceramic capacitor  10  observed as described is a surface defined in the length direction and the thickness direction of the multilayer ceramic capacitor  10  and the section is exposed by fixing the multilayer ceramic capacitor  10  with a resin and grinding a portion including the internal electrodes  16   a  and  16   b  and the external electrodes  20   a  and  20   b  up to the central portion in the width direction of the multilayer ceramic capacitor  10 . In addition, as described above, surface treatment is performed to avoid sagging due to grinding, and the section including the external electrodes  20   a  and  20   b  is observed at, for example, a 1000 times magnification by using SEM.  FIG. 4  is an enlarged partial view showing the section. 
     When a section containing an interface between the sintered metal layer  22   a  ( 22   b ) and the conductive resin layer  24   a  ( 24   b ) in the external electrode  20   a  ( 20   b ) is observed, glass is present on the surface of the sintered metal layer  22   a  ( 22   b ) at the interface, and a ratio L1/L2 preferably is about 0.2 or more and about 1.5 or less, for example, where L1 is the length of the glass along the interface and L2 is the length of a metal portion other than glass in the sintered metal layer  22   a  ( 22   b ) along the interface. This is because when the ratio L1/L2 is larger than about 1.5, the amount of glass at the interface is increased, and thus the resistance value between the sintered metal layer  22   a  ( 22   b ) and the conductive resin layer  24   a  ( 24   b ) is increased. On the other hand, when the ratio L1/L2 is smaller than about 0.2, the amount of glass in the sintered metal layer  22   a  ( 22   b ) is decreased, and thus the adhesive strength between the sintered metal layer  22   a  ( 22   b ) and the ceramic element body  12  is decreased. 
     Also, in order to enhance the adhesive strength between the sintered metal layer  22   a  ( 22   b ) and the ceramic element body  12 , it is necessary to incorporate a predetermined amount of glass into the sintered metal layer  22   a  ( 22   b ). In this case, when the sintered metal layer  22   a  ( 22   b ) is baked to the ceramic element body  12 , the glass is precipitated on the surface of the sintered metal layer  22   a  ( 22   b ). That is, the glass is precipitated at the interface between the sintered metal layer  22   a  ( 22   b ) and the conductive resin layer  24   a  ( 24   b ), and the length of glass along the interface 50 μm is preferably about 10 μm or more and about 30 μm or less, for example. When the length of glass is less than about 10 μm, the glass is not sufficiently contained, and thus the adhesive strength between the sintered metal layer  22   a  ( 22   b ) and the ceramic element body  12  is weakened. When the length of glass exceeds about 30 μm, a contact area between the conductor of the sintered metal layer  22   a  ( 22   b ) and the conductor of the conductive resin layer  24   a  ( 24   b ) cannot be secured, and thus the resistance value therebetween is increased, resulting in the tendency to increase equivalent series resistance. The plating layer  26   a  preferably includes a Ni plating layer  28   a  and a Sn plating layer  30   a , for example. Similarly, the plating layer  26   b  preferably includes a Ni plating layer  28   b  and a Sn plating layer  30   b , for example. 
     The Ni plating layers  28   a  and  28   b  are formed preferably by electroplating the surfaces of the conductive resin layers  24   a  and  24   b  with Ni, and a thickness of each of the Ni plating layers  28   a  and  28   b  preferably is, for example, about 1 μm to about 5 μm. The Ni plating layers  28   a  and  28   b  are configured to define and function as barrier layers. 
     The conductive resin layers  24   a  and  24   b  are formed preferably by applying resin and metal particles on the sintered metal layers  22   a  and  22   b  and then thermally curing the resin. In this case, a plurality of recesses can be formed in the surfaces of the conductive resin layers  24   a  and  24   b  by adjusting the curing conditions of the resin. After the conductive resin layers  24   a  and  24   b  are formed, the recesses may be formed in the surfaces of the conductive resin layers  24   a  and  24   b  by applying a physical external force, such as, for example, performing sand blasting. 
     The Ni plating layers  28   a  and  28   b  are formed on the conductive resin layers  24   a  and  24   b , respectively, in which the recesses have been formed. Since the recesses have been formed in the surfaces of the conductive resin layers  24   a  and  24   b , the Ni plating layers  28   a  and  28   b  enter at least some of the recesses to form projections  29  at additional interfaces between the conductive resin layers  24  and  24   b  and the plating layers  28   a  and  28   b  so that the projections  29  project from the Ni plating layers  28   a  and  28   b  to the conductive resin layer side as shown in  FIG. 5 . In this case, the projections  29  projecting from the Ni plating layers  28   a  and  28   b  on the surfaces of the conductive resin layers  24   a  and  24   b  into the recesses of the conductive resin layers  24   a  and  24   b  preferably have a depth within a range of about 1.0 μm to about 7.0 μm, for example. When the depth of two or more projections  29  present within a length along the additional interface of about 80 μm is less than about 1.0 μm, for example, entering of the Ni plating layers  28   a  and  28   b  into the conductive resin layers  24   a  and  24   b  is insufficient, and thus a satisfactory anchor effect cannot be obtained. When the depth of the projections  29  exceeds about 7.0 μm, Ni plating is captured by the conductive resin layers  24   a  and  24   b , and thus the surfaces of the Ni plating layers  28   a  and  28   b  are concaved, thus deteriorating mountability of the multilayer ceramic capacitor  10  on a substrate. In order to remove the recess of the surfaces of the Ni plating layers  28   a  and  28   b , it is considered to sufficiently thicken the Ni plating, but this is undesirable for the efficiency of production because a longer time is required for thickening the Ni plating. Further, the projections  29  are preferably present at three or more positions along the additional interface in the width direction or the thickness direction. 
     The projections  29  projecting from the Ni plating layers  28   a  and  28   b  to the conductive resin layer side are observed with a section of the multilayer ceramic capacitor  10 . The section is a surface defined in the length direction and the thickness direction of the multilayer ceramic capacitor  10  and a section exposed by grinding the multilayer ceramic capacitor  10  up to a central portion in the width direction is used. In addition, surface treatment is performed to avoid sagging due to grinding, and the additional interfaces between the conductive resin layers  24   a  and  24   b  and the Ni plating layers  28   a  and  28   b  are observed at a 1000 times magnification by using an SEM. Among the depth of each projection  29  measured from the Ni plating layer on both sides of the projection, as shown in  FIG. 6 , a large value is regarded as the size of the projection  29 . 
     Further, the Sn plating layers  30   a  and  30   b  are formed preferably by electroplating the surfaces of the Ni plating layers  28   a  and  28   b  with Sn, and the thickness of each of the Sn plating layers  30   a  and  30   b  preferably is, for example, about 1 μm to about 5 μm, for example. The Sn plating layers  30   a  and  30   b  are configured to function to improve solderability. 
     When a section including the additional interface between the conductive resin layer  24   a  and the plating layer  26   a  in the external electrode  20   a  is observed, the number of the metal particles exposed from the conductive resin layer  24   a  is preferably 50 to 250 per a length of about 1 mm at the additional interface between the conductive resin layer  24   a  and the plating layer  26   a , for example. Similarly, when a section including the additional interface between the conductive resin layer  24   b  and the plating layer  26   b  in the external electrode  20   b  is observed, the number of the metal particles exposed from the conductive resin layer  24   b  preferably is 50 to 250 per a length of about 1 mm at the additional interface between the conductive resin layer  24   b  and the plating layer  26   b.    
     The section of the multilayer ceramic capacitor  10  observed as described above is a surface defined in the length direction and the thickness direction of the multilayer ceramic capacitor  10  and the section is exposed by fixing the multilayer ceramic capacitor  10  with a resin and grinding a portion including the internal electrodes  16   a  and  16   b  and the external electrodes  20   a  and  20   b  up to the central portion in the width direction of the multilayer ceramic capacitor  10 . In addition, as described above, the section is surface-treated to avoid sagging due to grinding, and the section including the conductive resin layers  24   a  and  24   b  is observed at, for example, a 1000 times magnification by using SEM.  FIG. 4  is an enlarged partial view showing the section. 
     When a section including the additional interface between the conductive resin layer  24   a  ( 24   b ) and the plating layer  26   a  ( 26   b ) in the external electrode  20   a  ( 20   b ) is observed, the number of the metal particles exposed from the conductive resin layer  24   a  ( 24   b ) preferably is 50 to 250 per a length of 1 mm at the interface between the conductive resin layer  24   a  ( 24   b ) and the plating layer  26   a  ( 26   b ). This is because when the number of metal particles exposed from the conductive resin layer  24   a  ( 24   b ) is less than 50, concentration of electrolysis occurs in a small number of the exposed metal particles, and thus water is electrolyzed to produce hydrogen, which may cause defects in the plating layer  26   a  ( 26   b ). When the number of metal particles exposed from the conductive resin layer  24   a  ( 24   b ) is larger than 250, the amount of the resin in the conductive resin layer  24   a  ( 24   b ) is decreased, and thus when the multilayer ceramic capacitor  10  is mounted on a substrate, the resistance strength of the multilayer ceramic capacitor  10  against deflection of the substrate may be decreased. 
     The multilayer ceramic capacitor  10  preferably has, for example, a substantially rectangular parallelepiped shape having a length L of about 1 mm, a width W of about 0.5 mm, and a thickness T of about 0.55 mm. 
     In the multilayer ceramic capacitor  10 , the internal electrodes  16   a  and  16   b  preferably have a layer shape and are stacked in a direction connecting the main surfaces  12   a  and  12   b  of the ceramic element body  12 . 
     In the multilayer ceramic capacitor  10 , the ratio of the number of the spherical particles to the number of the flat particles in the metal particles contained in the conductive resin layers  24   a  and  24   b  preferably is about 3/7 to about 7/3, for example, and thus the relaxation of stress and electric connection are balanced. Therefore, the multilayer ceramic capacitor  10  has good resistance and good electric characteristics. 
     Further, in a section of the multilayer ceramic capacitor  10 , the number of recesses within a length along the interface of about 70 μm at each of the interfaces between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b  preferably is 2 or less, and thus adhesion between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b  is greatly increased. 
     In the multilayer ceramic capacitor  10 , a ratio of L1/L2 preferably is about 0.2 more and about 1.5 or less, and thus the resistance value between the sintered metal layers  22   a  and  22   b  and the conductive resin layers  24   a  and  24   b  is suppressed, and adhesive strength between the sintered metal layers  22   a  and  22   b  and the ceramic element body  12  becomes satisfactory. Therefore, in the multilayer ceramic capacitor  10 , equivalent series resistance is significantly reduced or suppressed. 
     In addition, when the section including the additional interface between the conductive resin layer  24   a  ( 24   b ) and the plating layer  26   a  ( 26   b ) in the multilayer ceramic capacitor  10  is observed, the metal particles are preferably present in a number of 50 to 250 per a length along the additional interface of about 1 mm on the conductive rein layer  24   a  ( 24   b ) at the additional interface. Therefore, a concentration of electrolysis does not occur in the metal particles, and thus the occurrence of hydrogen is significantly reduced or prevented, and defects in the plating layer  26   a  ( 26   b ) are prevented. In addition, when mounted on a substrate, the multilayer ceramic capacitor  10  has satisfactory resistance strength against deflection of the substrate. 
     Further, in the multilayer ceramic capacitor  10 , the projections are configured to project from the Ni plating layers  28   a  and  28   b  to the conductive resin layers  24   a  and  24   b , respectively, and thus separation between the conductive resin layers  24   a  and  24   b  and the Ni plating layers  28   a  and  28   b  is significantly reduced or prevented from occurring due to the anchor effect. Therefore, even when reflow soldering is performed to mount the multilayer ceramic capacitor  10  on a substrate, moisture contained in the conductive resin layers  24   a  and  24   b  is not ejected, and thus solder popping is prevented. 
     In the multilayer ceramic capacitor  10 , t1&gt;t2 is preferably satisfied, and each of t1 and t2 preferably is about 10 μm or more and about 40 μm or less, for example. 
     Therefore, in the multilayer ceramic capacitor  10 , each of the external electrodes  20   a  and  20   b  preferably is configured to include a convex central portion, and an amount of convexity in the central portion is smaller than that near the external layers. 
     Therefore, in the multilayer ceramic capacitor  10 , the external electrodes  20   a  and  20   b  preferably has a thin flat configuration, and thus equivalent series resistance is significantly reduced or prevented. 
     When in the multilayer ceramic capacitor  10 , the amount of convexity of the external electrodes  20   a  and  20  is excessively large, the external electrodes  20   a  and  20   b  become thick, thus increasing the equivalent series resistance. 
     Also, when the multilayer ceramic capacitor  10  is mounted on a substrate, tensile stress is applied to the external electrodes  20   a  and  20   b  on both ends of the ceramic element body  12 . However, the external electrodes  20   a  and  20   b  each preferably include a convex central portion, and thus stress is easily relaxed. 
     In the multilayer ceramic capacitor  10 , when the external electrodes  20   a  and  20   b  are completely flat, stress cannot be easily relaxed. 
     In addition, in the multilayer ceramic capacitor  10 , the metal particles contained in the conductive resin layers  24   a  and  24   b  preferably contain Cu or Ag, and thus good conductivity is secured in the conductive resin layers  24   a  and  24   b.    
     Further, in the multilayer ceramic capacitor  10 , the sintered metal layers  22   a  and  22   b  preferably include Cu, and thus good conductivity is secured in the sintered metal layers  22   a  and  22   b.    
     Further, in the multilayer ceramic capacitor  10 , the plating layers  26   a  and  26   b  include the Ni plating layers  28   a  and  28   b , respectively, and thus moisture inside of the plating layers  26   a  and  26   b  is trapped by the Ni plating layers  28   a  and  28   b , respectively. Therefore, during reflow mounting, solder popping in which the moisture contained inside of the plating layers  26   a  and  26   b  is popped together with solder is prevented. 
     In the multilayer ceramic capacitor  10 , in each of the external electrodes  20   a  and  20   b , the thickness T5 of a portion located on the first main surface  12   a  or the second main surface  12   b  of the ceramic element body  12  is larger than the thickness T3 of a portion located on each of the end surfaces  12   e  and  12   f  of the ceramic element body  12 . Therefore, when the multilayer ceramic capacitor  10  is mounted on a mounting substrate, each of the external electrodes  20   a  and  20   b  has a larger thickness on the mounting substrate side, thus easily relaxing the stress applied to the multilayer ceramic capacitor  10 . 
     In the multilayer ceramic capacitor  10 , the plating layers  26   a  and  26   b  include Ni plating layers  28   a  and  28   b , respectively, and the thickness of each of the Ni plating layers  28   a  and  28   b  preferably is about 1 μm to about 5 μm, for example. Therefore, although the external electrodes  20   a  and  20   b  are flat to some extent, moisture contained inside of the plating layers  26   a  and  26   b  is trapped by the Ni plating layers  28   a  and  28   b  because the Ni plating layers  28   a  ad  28   b  are thick. Therefore, for example, during reflow mounting, solder popping in which the moisture contained inside of the plating layers  26   a  and  26   b  is popped together with solder is prevented. 
     Further, in the multilayer ceramic capacitor  10 , the external electrodes  20   a  and  20   b  are provided on the first main surface  12   a  and the second main surface  12   b  of the ceramic element body  12 , thus facilitating mounting using any one of the first main surface  12   a  and the second main surface  12   b  as a mounting surface. 
     In addition, in the multilayer ceramic capacitor  10 , the external electrodes  20   a  and  20   b  are also provided on the first side surface  12   c  and the second side surface  12   d  of the ceramic element body  12 , thus improving moisture-proof reliability. 
     Next, a non-limiting example of a method for manufacturing the multilayer ceramic capacitor  10  is described. 
     First, ceramic green sheets containing a ceramic material and constituting the ceramic element body  12  (ceramic layers  14 ) are prepared. 
     Next, a conductive paste is applied on each of the ceramic green sheets to form a conductive pattern. The conductive paste can be applied by, for example, a printing method such as a screen printing method or the like. The conductive paste may contain a binder and a solvent in addition to the conductive fine particles. 
     Then, a plurality of the ceramic green sheets not having the conductive patterns formed thereon, the ceramic green sheets having the conductive patterns formed thereon in a shape corresponding to the first or second internal electrode, and a plurality of the ceramic green sheets not having the conductive patterns formed thereon are stacked in that order and then pressed in the stacking direction to form a mother stack. 
     Then, the mother stack is cut along virtual cut lines on the mother stack to form a plurality of ceramic green stacks from the mother stack. The mother stack can be cut by dicing or push cutting. The edges and corners of the ceramic green stack may be rounded by barrel grinding. 
     Then, the ceramic green stack is fired. In the firing step, the first and second internal electrodes are fired. The firing temperature can be appropriately determined according to the types of the ceramic material and conductive paste used. The firing temperature may be, for example, about 900° C. to about 1300° C. 
     Then, the conductive paste is applied to both ends of the ceramic stack (ceramic element body) after firing by a method such as dipping. 
     Next, the conductive paste applied to the ceramic stack is dried with hot air at about 60° C. to about 180° C. for approximately 10 minutes. 
     Then, the dried conductive paste is baked to form the sintered metal layers. In this case, the number of recesses formed in the surface of each of the sintered metal layers can be changed by changing the baking temperature for forming the sintered metal layers. In addition, the material of the conductive resin layers which enters the recesses can be adjusted by adjusting a dimension of the inlet and depth of the recesses in the surfaces of the sintered metal layers. Therefore, high adhesion can be achieved between the sintered metal layers and the conductive resin layers. 
     Then, a mixture containing a first metal powder of Cu or Ag which forms metal particles of the conductive resin layers, a second metal powder having a predetermined average particle diameter, and a resin is heat-cured to form the conductive resin layer on each of the sintered metal layers. 
     In this case, the ratio of the number of the spherical particles to the number of the flat particles of the metal particles contained in each of the conductive resin layers preferably is about 3/7 to about 7/3, for example. This can be achieved by, for example, adjusting the ratio between materials that form the flat particles and the spherical particles in the material of the conductive resin layers or adjusting a formation condition of the conductive resin layers, such as the heating temperature of the mixture used as the material of the conductive resin layers. 
     Also, in this case, in a section including each of the additional interfaces between the conductive resin layers and the plating layers, the number of the metal particles exposed from the conductive resin layer preferably is 50 to 250 per a length of about 1 mm at each of the additional interfaces between the conductive resin layers and the plating layers, for example. This can be achieved by, for example, adjusting the ratio between the first metal powder, the second metal powder, and the resin in the material of the conductive resin layers or adjusting a formation condition of the conductive resin layers, such as the heating temperature of the mixture used as the material of the conductive resin layers. 
     Similarly, the recesses can be formed in the surfaces of the conductive resin layers by adjusting the formation conditions of the conductive resin layers. Also, the recesses can be formed in the surfaces of the conductive resin layers by applying physical external force, for example, by performing sand blasting. 
     Then, plating layers (Ni plating layer and Sn plating layer) are formed on each of the conductive resin layers preferably by electrolytic plating, thus completing the multilayer ceramic capacitor  10 . The Ni plating enters the recesses formed in the surfaces of the conductive resin layers, and thus projections projecting from the Ni plating layer to the conductive resin layer are provided. 
     Experimental Examples 
     As an example, 20 multilayer ceramic capacitors  10  according to a preferred embodiment of the present invention described above were formed. 
     As a comparative example, 20 multilayer ceramic capacitors each having 2 or more recesses within a length of 70 μm at an interface between a sintered metal layer and a conductive resin layer were formed. The multilayer ceramic capacitors had the same design structure except the number of recesses. 
     Each of the multilayer ceramic capacitors was mounted on a substrate, and the substrate was deflected. In this case, separation occurred between the sintered metal layer and the conductive resin layer of each of 5 multilayer ceramic capacitors among the 20 multilayer ceramic capacitors of the comparative example. On the other hand, in each of the multilayer ceramic capacitors of the example, deflection occurred at the interface between the sintered metal layer and the conductive resin layer. 
     Although, in the example of the preferred embodiment described above, the external electrodes were formed on the side surfaces of the ceramic element body, the external electrodes may not be formed on the side surfaces of the ceramic element body. The external electrodes may be formed only on the end surfaces and on at least the first main surface or the second main surface of the ceramic element body. When the external electrodes are formed on a multilayer ceramic electronic component in this manner, the multilayer ceramic electronic component can be easily mounted using as a mounting surface the first main surface or the second main surface on which the external electrode is formed. 
     Although, in the example of the preferred embodiments described above, a plating layer preferably includes a Ni plating layer and a Sn plating layer, for example, the plating layer may include one plating layer or three or more plating layers, for example. 
     Although, in the example of the preferred embodiments described above, dielectric ceramic was preferably used as a material of the ceramic element body, in the present invention, magnetic ceramic such as ferrite, semiconductor ceramic such as spinel-type ceramic, piezoelectric ceramic such as PZT-type ceramic, or the like can be used as the material of the ceramic element body according to the types of multilayer ceramic electronic components. 
     When magnetic ceramic is used as the ceramic element body, a multilayer ceramic electronic component defines and functions as a multilayer ceramic inductor; when semiconductor ceramic is used as the ceramic element body, a multilayer ceramic electronic component defines and functions as a multilayer ceramic thermistor; and when piezoelectric ceramic is used as the ceramic element body, a multilayer ceramic electronic component defines and functions as a multilayer ceramic piezoelectric component. However, when a multilayer ceramic electronic component defines and functions as a multilayer ceramic inductor, an internal electrode includes a coil-shaped conductor. 
     Although, in the example of the preferred embodiments described above, a multilayer ceramic capacitor having a specified configuration is described as an example, the configuration of a multilayer ceramic capacitor according to the present invention may be arbitrarily changed within the scope of the configuration defined by the claims. 
     In particular, a multilayer ceramic electronic component according to various preferred embodiments of the present invention can be preferably used as a multilayer ceramic capacitor, a multilayer ceramic inductor, a multilayer ceramic thermistor, a multilayer ceramic piezoelectric component, or the like. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.