Inductor devices – Core forms casing
Reexamination Certificate
1999-11-29
2001-06-26
Mai, Anh (Department: 2832)
Inductor devices
Core forms casing
C336S200000
Reexamination Certificate
active
06252481
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electronic part for use in an electrical circuit; and, more particularly, to a chip-type electronic part and a method for the manufacture thereof, wherein the chip-type electronic part includes a chip inductor, a chip capacitor, a LC coupled chip or a combination thereof.
DESCRIPTION OF THE PRIOR ART
Generally, a chip-type electronic part includes a chip-type main body and a pair of external electrodes respectively formed on two opposing sides of the main body. The main body is essentially a ceramic composite body with sheet-type internal electrodes placed therein. Some of the internal electrodes have one of their ends exposed at the opposing sides of the main body where the external electrodes are formed, allowing an electrical connection to be made therebetween.
When the chip-type electronic part is a chip inductor, the main body is essentially made of a magnetic material with an internal electrode formed therein having a substantially spiral shape. When the chip-type electronic part is a chip capacitor, the main body may essentially be made of a dielectric material with a plurality of internal electrodes regularly placed therein such a way that the internal electrodes are parallel to each other and separated by the dielectric material constituting the ceramic composite body and one end of each of the electrodes is in contact with either one of the external electrodes.
The above described ceramic composite body is usually formed using the following method: stacking a plurality of ceramic green sheets with electrode patterns formed thereon using a conductive paste, e.g., silver, to thereby form a multi-layered structure; stacking on top and bottom of the multi-layered structure with a plurality of ceramic green sheets without electrode patterns and pressing it, the ceramic green sheets without electrode patterns functioning as the protective layers; dicing the pressed multi-layered structure into chip-type multilayered structures; and sintering the chip-type multi-layered structures.
The external electrodes are respectively formed on two opposing sides of the ceramic composite body by coating thereon a conductive paste material and bake-pasting it. Further, surfaces of the external electrodes are then electroplated to prevent the external electrodes from being damaged by soldering. Presence of electrolytes in the pores located on the surfaces of the ceramic composite body and the external electrodes will degrade the chip's resistance to water, which, in turn, will degrade chip's electric properties. To solve this problem, synthetic resins are applied onto the surfaces of the ceramic composite body and the external electrodes prior to the electroplating process. There are certain deficiencies associated with the above method for manufacturing the chip-type electronic part. During the sintering of the chip-type multi-layered structures to form the ceramic composite body, the ceramic green sheets in the chip-type multi-layered structures may shrink non-uniformally, resulting in a delamination at the interfaces between the neighboring ceramic green sheets or between the ceramic green sheet and the internal electrodes, which will, in turn, result in the formation of voids therebetween.
As a result of the delamination, instead of being supported by two ceramic sheets, the internal electrode is supported by only one ceramic sheet, which, in turn, in presence of external impacts, causes the internal electrode to vibrate, resulting in fatigue being accumulated and eventually the internal electrode to be electrically disconnected.
The above described phenomena become more pronounced when the chip-type electronic part is an inductor. For example, when a high frequency current is supplied to the internal electrode, the internal electrode vibrates in the voids as a result of it becoming subjected to rapidly changing electromagnetic field generated by the magnetic material surrounding the internal electrode, resulting in fatigue being accumulated therein and eventually causing it to be electrically disconnected.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the present invention to provide a chip-type electronic part and a method for the manufacture thereof, the chip-type electronic part being capable of preventing an internal electrode therein from vibrating in presence of external impacts or large rapidly changing electromagnetic forces, thereby keeping it electrically connected.
It is another object of the present invention to provide a method for manufacturing said chip-type electronic part.
In accordance with one aspect of the present invention, there is provided with a chip-type electronic part comprising: a chip-type main body and a pair of external electrodes formed on two opposing sides of the chip-type main body, the main body comprising a ceramic composite body with a sheet-type internal electrode formed therein, wherein the external electrodes are made of a porous conductive material, both ends of the internal electrode are electrically connected to the pair of external electrodes, and synthetic resins are impregnated into voids between the ceramic composite body and the internal electrode and also into the external electrodes.
In accordance with another aspect of the present invention, there is provided a method for manufacturing a chip-type electronic part, the method comprising the steps of: forming a main body including a ceramic composite body with a sheet-type internal electrode; forming a pair of external electrodes made of a porous conductive material on two opposing sides of the main body, wherein the pores in the porous conductive material of the external electrodes extend from surfaces of the external electrodes to surfaces of the main body; impregnating synthetic resins into the main body and the external electrodes by immersing the main body and the external electrodes into a synthetic resin solution; and hardening the impregnated synthetic resins.
In accordance with further aspect of the present invention, there is provided a chip-type electronic part comprising: a chip-type main body and a pair of external electrode formed on two opposing sides of the chip-type main body, the main body including a ceramic composite body with a sheet-type internal electrode placed therein, wherein the external electrodes are made of a conductive synthetic resin, both ends of the internal electrodes are electrically connected to the pair of external electrodes, and synthetic resins are impregnated into the ceramic composite body.
In accordance with still aspect of the present invention, there is provided a method for manufacturing a chip-type electronic part, the method comprising the steps of: forming a main body including a ceramic composite body with a sheet-type internal electrode; impregnating synthetic resins into the main body by immersing the main body into a synthetic resin solution; hardening the impregnated synthetic resins; and forming a pair of external electrodes made of a conductive synthetic resin on two opposing sides of the main body.
REFERENCES:
patent: 4658328 (1987-04-01), Sakabe
patent: 5144527 (1992-09-01), Amano et al.
patent: 5426560 (1995-06-01), Amaya et al.
patent: 5781402 (1998-07-01), Fujiyama et al.
patent: 4250607 (1989-01-01), None
patent: 4061106 (1992-02-01), None
patent: 1009607 (1992-09-01), None
Arai Mayumi
Hoshi Kenichi
Iwao Hidemi
Nakazawa Mutsuo
Mai Anh
Rosenman & Colin LLP
Taiyo Yuden Co. Ltd.
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