Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-09-04
2004-08-24
Mayes, Melvin C. (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S089160, C156S233000, C156S235000
Reexamination Certificate
active
06780267
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of manufacturing ceramic electronic components such as multilayer ceramic capacitors and the like.
BACKGROUND ART
FIG. 7
is a partially cut-away perspective view of a typical multilayer ceramic capacitor comprising a ceramic dielectric layer
1
, a conductive layer
2
and a pair of external electrodes
3
, in which an end of each respective conductive layer
2
is alternately connected with one of the pair of external electrodes
3
at the two side of the ceramic dielectric layer
1
.
Next, a description is given to a method of manufacturing multilayer ceramic capacitors in a prior art.
First, a ceramic sheet eventually constituting the ceramic dielectric layer
1
is prepared by mixing an organic material to a powder mainly composed of barium titanate ,and a metallic paste is applied thereon in a required pattern by a printing method to form the conductive layer
2
. Then, a plurality of the ceramic sheets, each applied with the conductive layer
2
thereon, are superimposed one over another in such a way that any two adjoining conductive layers
2
are located opposite to each other with the ceramic sheet sandwiched therebetween, thus obtaining a laminate. The laminate is fired thereafter and a pair of the external electrodes
3
are formed on both side where the conductive layer
2
is exposed.
However, when the porosity of a ceramic sheet is large, the foregoing prior art method allows part of the metallic constituent in the metallic paste to penetrate into the ceramic sheet during the printing process to print directly the metallic paste on the ceramic sheet.
In recent years, a ceramic sheet for a multilayer ceramic capacitor is made thinner and thinner in order to gain higher capacitance in said capacitor, thereby causing a problem of short-circuiting between adjoining two electrodes because of the metal constituent that has penetrated into the ceramic sheet.
The object of the present invention is to provide a method of manufacturing ceramic electronic component with less failures due to said short-circuiting.
SUMMARY OF THE INVENTION
In order to solve the aforementioned problems, the method of manufacturing ceramic electronic components according to the present invention is characterized in that the porosity of a ceramic sheet is first reduced and then a conductive layer is formed on the surface thereof, thereby allowing a metallic constituent to be prevented from penetrating into the ceramic sheet with resulting prevention of short-circuiting failure that may otherwise occur between the conductive layers.
A method of manufacturing ceramic electronic components in a first exemplary embodiment of the present invention comprises:
a first step of applying a pressing force to a ceramic sheet containing a ceramic powder and an organic material to have the porosity thereof reduced;
a second step of forming a conductive layer on the ceramic sheet by the use of a metallic paste;
a third step of producing a laminate by stacking a plurality of ceramic sheets, each having the conductive layer formed thereon, in such a way as having the ceramic sheet sandwiched between the adjoining conductive layers located opposite to each other; and
a fourth step of firing the laminate, thus allowing a ceramic electronic component free of short-circuiting failures to be realized.
A method of manufacturing said components in a second exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the porosity of the ceramic sheet before a reduction in porosity after the first step is 50% or more, thereby allowing a ceramic electronic component free of short-circuiting failures to be realized.
A method of manufacturing said components in a third exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the ceramic sheet contains at least a ceramic constituent and polyethylene at the first step, thereby achieving a great effect in reducing short-circuiting failures, because of a high level of porosity in the ceramic sheet containing polyethylene,compared with other organic materials.
A method of manufacturing ceramic electronic components in a fourth exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the porosity of a ceramic sheet at the first step is less than 50%, thereby allowing a metallic constituent to be prevented from penetrating into the ceramic sheet.
A method of manufacturing ceramic electronic components in a fifth exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the pressing force applied to the ceramic sheet at the first step is made less than the pressing force as applied in forming the laminate at the third step, thereby allowing a sufficiently uniform pressing force to be applied to the entire laminate in both areas, with and without a conductive layer at the third step, resulting in a realization of an electronic component that has little structural defect due to failures in adhesion between the ceramic sheets.
A method of manufacturing ceramic electronic components in a sixth exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the ceramic sheet is heated while a pressing force being applied thereto at the first step, thereby allowing the fluidity of an organic material to be enhanced by the application of heat with a resulting quick reduction in porosity of the ceramic sheet.
A method of manufacturing ceramic electronic components in a seventh exemplary embodiment of the present invention is the method of said components according to the sixth exemplary embodiment, in which the ceramic sheet is heated at the temperature between the glass transition point and the melting point of at least one organic material contained in the ceramic sheet, thereby allowing the fluidity of organic materials to be enhanced by the application of heat with a resulting quick reduction in porosity of the ceramic sheet.
A method of manufacturing ceramic electronic components in an eighth exemplary embodiment of the present invention comprises:
a first step of applying a pressing force to reduce the porosity in a ceramic sheet comprising a ceramic powder and an organic material;
a second step of forming a conductive layer by a metallic paste on a base film in advance and superimposing the conductive layer on the ceramic sheet;
a third step of producing a laminate by stacking a plurality of the ceramic sheets, each having the conductive layer superimposed thereon, in such a way as having the ceramic sheet sandwiched between the adjoining conductive layers located opposite to each other; and
a fourth step of firing the laminate, thereby allowing a ceramic electronic component free of short-circuiting failures to be realized.
A method of manufacturing ceramic electronic components in a ninth exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, in which the porosity of the ceramic sheet before the first step is 50% or more, thereby allowing a said component free of short-circuiting failures to be realized.
A method of manufacturing ceramic electronic components in a tenth exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, in which the ceramic sheet is prepared so as to contain at least a ceramic powder and polyethylene at the first step, thereby achieving a great effect in reducing short-circuiting failures. The rate of volumetric shrinkage of the ceramic sheet after the application of a pressing force thereto is made uniform in those composition because of the high level in porosity of the ceramic sheet before applying the pressing force thereto and allowing a further reduction in porosity of the ceramic ceramic sheet t
Kuramitsu Hideki
Nagai Atsuo
Sakaguchi Yoshiya
Matsushita Electric - Industrial Co., Ltd.
Mayes Melvin C.
McDermott & Will & Emery
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