JP2007242995A - Multilayer ceramic electronic component and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to prevent a short circuit between external electrodes at both ends due to a plating flow.
To achieve this object, the present invention provides a ceramic element 3 having an internal electrode layer 1 and an external element provided outside the ceramic element 3 and electrically connected to the internal electrode layer 1. An electrode 4, and at least a portion of the outer surface of the ceramic element 3 other than the portion of the external electrode 4 is covered with a glass layer 5, and at least a part of the glass layer 5 is covered with an oxide layer 6 or an insulating layer. And the external electrode 4 has a plating layer.
[Selection] Figure 1

Description

  The present invention relates to a multilayer ceramic electronic component such as a ceramic capacitor or a multilayer varistor and a method for manufacturing the same.

  For example, a ceramic capacitor has a structure including a ceramic element having an internal electrode layer and an external electrode provided outside the ceramic element and electrically connected to the internal electrode layer. Of these outer surfaces, at least the surface other than the external electrode portion is covered with a glass layer for the purpose of electroplating or protection in a corrosive atmosphere.

In addition, the following patent document 1 exists as a prior art document corresponding to such a conventional technique.
JP 2000-164406 A

  As described above, if at least the surface of the ceramic element other than the external electrode portion is covered with a glass layer, the ceramic element can be protected when electroplating with this glass layer or in a corrosive atmosphere. However, when external electrodes electrically connected to the internal electrode layer by plating are formed at both ends of the ceramic element, a plating layer is also formed on the glass layer between the external electrodes at both ends (so-called plating flow). This may cause a problem that the external electrodes at both ends are short-circuited.

  There are various reasons for this, but the glass layer covering the outer surface of the ceramic element cannot be made too thick due to the coefficient of thermal expansion. As a result, the surface irregularity of the ceramic element on the lower surface is formed on the glass layer. The protrusions formed on the glass layer are substantially transferred, thereby forming the core of the plating, and as described above, a plating layer is also formed on the glass layer between the external electrodes at both ends (so-called plating flow). The problem that a short circuit occurs between the external electrodes is caused.

  Therefore, the present invention aims to prevent a short circuit between external electrodes at both ends due to a so-called plating flow.

  In order to achieve this object, the present invention comprises a ceramic element having an internal electrode layer, and an external electrode provided outside the ceramic element and electrically connected to the internal electrode layer, Of the outer surface of the ceramic element, at least a surface other than the external electrode portion is covered with a glass layer, and at least a part of the glass layer is covered with an oxide layer or an insulating layer, and the external electrode includes a plating layer. It is set as the structure which has.

  As described above, according to the present invention, at least a part of the outer surface of the ceramic element other than the external electrode portion is covered with the glass layer, and at least a part of the glass layer is covered with the oxide layer or the insulating layer. Therefore, the projections and depressions transferred onto the glass layer can be reduced and the protrusions that become the core of the plating can be substantially eliminated, so that a short circuit between the external electrodes at both ends due to the so-called plating flow can be prevented.

(Embodiment 1)
Hereinafter, an embodiment in which an embodiment of the present invention is applied to a multilayer varistor as an example of a multilayer ceramic electronic component will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the laminated varistor of this embodiment includes a ceramic element 3 having an internal electrode layer 1 made of Pd and a varistor layer 2, and is provided outside the ceramic element 3. An external electrode 4 that is electrically connected is provided.

  The outer surface of the ceramic element 3 is covered with a glass layer 5, and the outer surface of the glass layer 5 is covered with an oxide layer 6. In this embodiment, the oxide layer 6 is formed of ZnO as a main component, which will be described in detail later. The varistor layer 2 is mainly composed of ZnO, and a small amount of Co, Cr, or the like is added thereto. This is due to the formation.

  The internal electrode layer 1 penetrates the glass layer 5 and the oxide layer 6 and is electrically connected to the external electrode 4, while the external electrode 4 is composed of an Ag layer 7 and its An Ni layer 8 is formed on the upper surface by plating, and an Sn layer 9 is formed on the upper surface by plating.

  FIG. 2 is an enlarged view of a part of the outer surface of the ceramic element 3. As described above, the outer surface of the ceramic element 3 is covered with the glass layer 5, and the outer surface of the glass layer 5 is covered with the oxide layer 6. ing. The inner glass layer 5 is a silicon oxide-based glass layer, and the glass layer 5 cannot be made too thick due to the coefficient of thermal expansion. As a result, the lower ceramic element is formed on the glass layer 5. The surface unevenness shape 3 is substantially transferred, whereby a protrusion is formed on the glass layer 5.

  However, in this embodiment, an oxide layer 6 is formed on the glass layer 5, and the oxide layer 6 is 0.3 to 0.5 μm thicker than the glass layer 5 (0.1 μm). Therefore, as will be described in detail later in the manufacturing method, it is possible to substantially eliminate protrusions that become the core of plating on the oxide layer 6, and short-circuit between the external electrodes 4 at both ends due to so-called plating flow. Can be prevented.

  FIG. 3 shows a manufacturing method. First, a varistor material containing ZnO as a main component and adding a small amount of Co, Cr or the like to this is prepared (A).

  Next, the varistor material is slurried with an organic binder and a plasticizer mixed therein (B).

  Thereafter, a green sheet is prepared using this slurry (C), and the internal electrode layer 1 of FIG. 1 is printed on the green sheet.

  Next, the green sheet with the internal electrode layer 1 is laminated (D), then cut into individual pieces, the molded body is chamfered (E) to expose the internal electrode layer 1 at both ends of the molded body, and then degreased. Baked (F), and then impregnated with resin on the outer surface (G), and then the ceramic element 3 in this state is in a glass coating solution (manufactured by AZ Electric Materias Co., Ltd.) mainly composed of perhydropolysilazane. Then, the ceramic element 3 is pulled up from the glass coating solution and heat treated at 450 degrees.

  As a result, the outer surface of the ceramic element 3 is covered with the glass layer 5 as shown in FIGS. 1 and 2, and the outer surface of the glass layer 5 is covered with the oxide layer 6. Among these, the glass layer 5 is formed with silicon oxide as a main component, and the oxide layer 6 is formed with ZnO as a main component in this embodiment.

  This is because the varistor layer 2 is formed by adding ZnO as a main component to the varistor layer 2 and adding a small amount of Co or Cr to the varistor layer 2. When this is immersed in the glass coating solution, a part of the ZnO component is eluted. In this state, when the glass coating solution is pulled up and heat-treated at 450 ° C., the outer surface of the ceramic element 3 is covered with the glass layer 5 as shown in FIGS. 1 and 2, and the outer surface of the glass layer 5 is covered with the oxide layer 6. It becomes the state covered with.

  In this way, in this embodiment, the oxide layer 6 is formed on the glass layer 5, and this oxide layer 6 has a thickness of 0.3 to 0.3 which is much thicker than the glass layer 5 (0.1 micron). Since the thickness is 0.5 microns, it is possible to substantially eliminate protrusions that are the cores of plating on the oxide layer 6, and prevent short circuit between the external electrodes 4 at both ends due to so-called plating flow. Can do.

  That is, the Ag layer 7 is first formed as the external electrode 4 by coating (I), and then the Ni layer 8 and the Sn layer 9 are plated using the plating apparatus shown in FIG. 4 (J).

  In the plating apparatus shown in FIG. 4, a plating solution 11 and a plating container 12 are placed in a container 10, and a large number of ceramic elements 3 and steel balls 13 (step I) in FIG. 3 are placed in the plating container 12. The Ni layer 8 and the Sn layer 9 are plated in order by applying a plus to the anode 15 from the power source 14 and a minus to the plating container 12 while rotating.

  At the time of plating, in this embodiment, an oxide layer 6 is formed on the glass layer 5, and the oxide layer 6 is 0.3 to 0 which is much thicker than the glass layer 5 (0.1 micron). Since the thickness is .5 microns, it is possible to substantially eliminate the protrusions that become the core of the plating on the oxide layer 6, and as a result, a short circuit between the external electrodes 4 at both ends due to the so-called plating flow is prevented. can do.

  In the present embodiment, the oxide layer 6 formed on the glass layer 5 has been described. However, an insulating layer is provided in place of the oxide layer 6 so that the protrusions serving as the core of plating are substantially formed. Alternatively, a short circuit between the external electrodes 4 at both ends due to a so-called plating flow may be prevented.

  As described above, the present invention is such that at least a part of the outer surface of the ceramic element other than the external electrode portion is covered with a glass layer, and at least a part of the glass layer is covered with an oxide layer or an insulating layer. Since there are so small irregularities transferred onto the glass layer and the protrusions that become the core of plating can be substantially eliminated, it is possible to prevent short-circuiting between external electrodes at both ends due to so-called plating flow. It can be widely applied to multilayer ceramic parts.

Sectional drawing in one embodiment of this invention Partially enlarged sectional view of an embodiment of the present invention The figure which shows the manufacturing process of one embodiment of this invention Sectional drawing which shows the manufacturing process of one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal electrode layer 2 Varistor layer 3 Ceramic element 4 External electrode 5 Glass layer 6 Oxide layer 7 Ag layer 8 Ni layer

Claims (7)

A ceramic element having an internal electrode layer; and an external electrode provided outside the ceramic element and electrically connected to the internal electrode layer, the outer surface of the ceramic element other than at least the external electrode portion A multilayer ceramic electronic component in which at least a part of the glass layer is covered with an oxide layer or an insulating layer, and the external electrode has a plating layer. The multilayer ceramic electronic component according to claim 1, wherein the oxide layer or the insulator layer is thicker than the glass layer. The multilayer ceramic electronic component according to claim 1, wherein the oxide layer or the insulating layer is the same as a main component of the ceramic element. The multilayer ceramic electronic component according to claim 1, wherein the oxide layer or the insulator layer and the ceramic element are formed mainly of zinc oxide. A sintered ceramic element having an internal electrode layer is immersed in a glass coating solution, and then the ceramic element taken out of the glass coating solution is heat-treated to cover the outer surface of the ceramic element with a glass layer. A method for producing a laminated ceramic electronic component, wherein at least a part of a layer is covered with an oxide layer or an insulating layer, and thereafter an external electrode electrically connected to the internal electrode layer is formed by plating. The method for manufacturing a multilayer ceramic electronic component according to claim 5, wherein the external electrode is formed by providing a plating layer on the silver electrode layer. The method for producing a multilayer ceramic electronic component according to claim 5 or 6, wherein the ceramic element is formed mainly of zinc oxide, and the glass coating solution is mainly composed of perhydropolysilazane.

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