Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
2000-12-21
2002-06-11
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C361S321200
Reexamination Certificate
active
06404616
ABSTRACT:
BACKGROUND OF THE INVENTION
A conventional multilayer ceramic capacitor comprises a multilayer body made by alternately laminating ceramic dielectric layers and conductor layers, and connecting external electrodes to the conducting layers formed at both ends of the multilayer body. Alternate conductor layers are connected to the external electrodes at both ends such that a first external electrode is connected to every other conductor layer, and a second external electrode is connected to the remaining conductor layers, that is the layers which are not connected to the first external electrode are connected to the second external electrode.
For example, in the case of a multilayer ceramic capacitor with an external size of 2.1 mm×1.25 mm×1.25 mm and an electrostatic capacity of 10 &mgr;F, the number of the laminated conductor layers is 330, the thickness of each ceramic dielectric layer is 1.8 &mgr;m, and the thickness of each conductor layer is 1.5 &mgr;m. That is, the thickness of each ceramic dielectric layer is about 1.2 times the thickness of each conductor layer.
Generally, in a multilayer ceramic capacitor, there are some cases requiring a capacitor with a high resistance to thermal shock. Furthermore, recently, a small-sized multilayer ceramic capacitor with a large capacity has been required. However, in some cases, a conventional multilayer ceramic capacitor has not had sufficient thermal shock resistance. Especially, when attempting to make a small-sized capacitor with a large capacity by increasing the number of laminated layers, in some cases, a sufficient thermal shock resistance has not been obtained.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a multilayer ceramic capacitor with excellent thermal shock resistance.
In order to attain this object, one aspect of the present invention proposes a multilayer ceramic capacitor comprising a multilayer body having alternate laminated conductor layers and ceramic dielectric layers, wherein each of said ceramic dielectric layers has a thickness not more than the thickness of each of said conductor layers.
In a multilayer ceramic capacitor, generally, the conductor layers have a comparatively higher flexibility to thermal shock than ceramic grain making up the ceramic dielectric layers. Therefore, according to the present invention, the ceramic dielectric layers are not thicker than the conductor layers. Consequently, as a whole, the ratio of the occupation of the conductor layer becomes large, and as a result of this, the resistance to thermal shock is improved.
Furthermore, another aspect of the present invention proposes a multilayer ceramic capacitor comprising a multilayer body having alternate laminated conductor layers and ceramic dielectric layers, wherein said ceramic dielectric layers comprise (1) ceramic grains, (2) a secondary phase that is between said ceramic grains, and (3) a part in which said ceramic grains do not exist between said opposite conductor layers and which includes only said secondary phase.
In a multilayer ceramic capacitor, generally, the secondary phase that is between the above described ceramic grains has a comparatively higher flexibility to thermal shock than the ceramic grains making up the ceramic dielectric layer. Therefore, according to the present invention, the part including only the above described secondary phase relieves thermal shock, and therefore, thermal shock resistance is improved.
The objects, constitution, and effects of the present invention other than those in the above description will be clear by the following detailed description.
REFERENCES:
patent: 4471406 (1984-09-01), Sawairi
patent: 4959745 (1990-09-01), Suguro
patent: 10-208969 (1998-08-01), None
Dinkins Anthony
Lowe Hauptman & Gilman & Berner LLP
Taiyo Yuden Co. Ltd.
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