Coating processes – Electrical product produced – Condenser or capacitor
Reexamination Certificate
2000-01-18
2001-12-04
Talbot, Brian K. (Department: 1762)
Coating processes
Electrical product produced
Condenser or capacitor
C029S025420, C427S455000, C427S531000, C204S192170
Reexamination Certificate
active
06326052
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a ceramic capacitor and particularly relates to plate like ceramic capacitor which is used in a high temperature environment.
Generally, the ceramic capacitor of this type is structured such that electrodes are provided on both surfaces of the plate like ceramic element assembly, and further, a lead terminal is soldered to each of the electrodes. Then, as a conventional electrode, a baked coated electrode or a wet pated electrode made of Ag, Cu or the like, which is a metal easily soldered, is applied or it has been considered to form a baked coated electrode or a wet plated electrode made of Ni, Zn or the like, which is a metal in which the Sn contained in the solder is hardly diffused, is applied.
When the ceramic capacitor having the baked coated electrode or the wet plated electrode made of Ag, Cu or the like is used in a high temperature environment (for example, about 150° C.), the Sn contained in the solder used for bonding the lead terminal diffuses into the electrode so that the bonding strength between the electrode and the ceramic deteriorates. Accordingly, there is a risk of problems such as the dielectric loss of the ceramic capacitor being increased, and corona discharge produced in the gap between the electrode and the ceramic will break the ceramic capacitor.
In the case of the ceramic capacitor having the coated baked electrode or the wet plated electrode made of Ni, Zn and the like, since Sn contained in the solder is hardly discharged, the above troubles do not occur. However, there occurs another problem such that the soldering operation of the electrode is deteriorated. Accordingly, ti becomes necessary to use a chloride flux which has a problem in reliably bonding the lead terminal and to provide another electrode for mounting the lead terminal on the electrode made of Ni, Zn or the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a ceramic capacitor having an improved performance when soldering an electrode, and no diffusion of solder even in the case of being used in a high temperature environment and reduced characteristic deterioration.
In order to achieve the above object, in accordance with the present invention, there is provided a ceramic capacitor comprising:
(a) a ceramic element assembly and a dry plated electrode provided on a surface of the ceramic element assembly; and
(b) the dry plated electrode having a first layer made of any one or more of Cu, Ni-Cu alloy and Zn, a second layer provided on a surface of the first layer and of a material different from the material of the first layer and is any one or more of Cr, Ni-Cr alloy, Fe-Cr alloy, Co-Cr alloy, Ti, Zn, Al, W, V and Mo, and a third layer provided on a surface of the second layer and made of any one or more of Cu, Ni-Cu alloy, Ag and Au. Further, it is preferable that the thickness of the first layer is about 500 angstroms or more, the thickness of the second layer is about 100 angstroms or more and the thickness of the third layer is about 500 angstroms or more.
Due to the above structure, the first layer secures a suitable strong bonding between the ceramic element assembly and the electrode. The second layer prevents diffusion of the solder (particularly, of Sn contained in the solder) from developing at the interface between the ceramic element assembly and the electrode. Further, the third layer improves the operability of the soldering.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 4584629 (1986-04-01), Garcia et al.
patent: 4604676 (1986-08-01), Senda et al.
patent: 4908685 (1990-03-01), Shibasaki et al.
patent: 5021921 (1991-06-01), Sano et al.
patent: 5162973 (1992-11-01), Miyashita et al.
patent: 5251094 (1993-10-01), Amano et al.
patent: 5426560 (1995-06-01), Amaya et al.
Kishi Masanobu
Murata Makoto
Nagashima Mitsuru
Yoshida Kazuhiro
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
Talbot Brian K.
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