Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
2002-03-27
2004-04-06
Dinkins, Anthony (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C361S309000, C361S528000, C361S532000
Reexamination Certificate
active
06717793
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface mount type condenser or capacitor, which is mounted on a substrate and is mainly used as a noise filter.
2. Description of the Related Art
Reduction in the size of an electronic power supply has rapidly been developed accompanied by an advancement of high-performance, a downsizing, and a reduction in the weight of electronic parts in recent years.
The reduction in the size of the electronic power supply can be achieved by increasing the operational frequency of the power supply to a high frequency level. However, requirements for the performance of electronic parts used for an electronic power supply circuit employing such power supply, particularly, the performance of a noise filter surface mounted on a substrate, i.e., a condenser has become more and more strict. As a surface mount type condenser capable of meeting such strict requirements for the performance, an aluminum solid electrolytic condenser employing an electro-conductive functional polymer as a cathode and surface mounted on a substrate has been developed and brought into practical use.
Compared with a conventional aluminum condenser or tantalum condenser, this aluminum solid electrolytic condenser is advantageous in that the equivalent series resistance thereof is 1/20 through 1/50 of that of the above-mentioned conventional aluminum or tantalum condenser.
FIG. 1
is a cross-sectional view of the conventional constitution of a surface mount type condenser.
As shown in
FIG. 1
, conventional surface mount type condenser has such a constitution that two substantially planar-plate shape cathodes
2
sandwich a first metallic plate
7
in the shape of a planar plate. Two cathodes
2
are vertically connected to one another at the sides thereof.
Therefore, respective faces of cathodes
2
, which are not in contact with first metallic plate
7
form surfaces of two cathodes
2
, and one of such surfaces, i.e., a surface
2
a
is connected to cathode terminal
4
, and opposite ends of first metallic plate
7
projecting from between two cathodes
2
forms two anodes. On the respective ends of these anodes are formed two anode terminals
5
, which are connected, respectively, to lands
11
arranged on substrate
6
.
Further, in order to prevent occurrence of short-circuiting of cathodes
2
(cathode terminals
4
) and anodes
3
(anode terminals
5
), either electrical insulation layers are provided on the surfaces of anodes
3
and anode terminals
5
or surface mount type condenser 1 per se is sealed by insulating resin.
Accordingly, when this surface mount type condenser 1 is mounted on substrate
6
, direct current containing noise inputted from one of anode terminals
5
is filtered, and the direct current component only is output to the other of anode terminals
5
.
However, with the conventional surface mount type condenser, in a high frequency region equal to or more than 10 MHz, such a phenomenon conspicuously occurs that a part of noise input in one of the anode terminals is transmitted as an electromagnetic wave in the air so as to arrive at the other of the anode terminals. Namely, when such phenomenon occurs, since signals input in one of the anode terminals is transmitted as an electromagnetic wave (noise) in the air to short-circuit to the other of the anode terminals, it is difficult to thoroughly remove noise in the signals. This fact means that in the high frequency region equal to or more than 10 MHz, sufficient removal of noise could not hitherto achieved.
SUMMARY OF THE INVENTION
Taking into consideration the above-described problems encountered by the prior art, an object of the present invention is to provide a surface mount type condenser capable of preventing transmission of electromagnetic wave between anode terminals and being excellent in its noise removal performance in a high frequency region.
A surface mount type condenser according to a first invention of the present patent application, provided for solving the above-described problems of the prior art, comprises: two anode portions; two anode terminals connected to respective of the two anode portions in a manner of confronting a substrate; two planar plate-shape cathode portions; a first substantially planar plate-shape metallic plate sandwiched by the two cathode portions and including the two anode portions; a cathode terminal connected to one of the cathode portions in a manner of confronting the substrate; and a second substantially planar plate-shape metallic plate electrically connected to a surface of the other of the cathode portions and arranged in a manner of covering predetermined regions of the anode terminals.
According to the above-described constitution, when high-frequency electric current is permitted to flow into the surface mount type condenser, an action of electromagnetic wave discharged particularly from the anode terminals can be suppressed between the anode terminals and the second metallic plate.
At this stage, the second metallic plate is provided not for interrupting the passage of the electromagnetic wave so as to prevent transmission of the electromagnetic wave between the two anode terminals but for electrically suppressing the action of the electromagnetic wave by an arrangement in which the second metallic plate electrically connected to the cathode portions having electrolyte confronts the anode terminals.
Accordingly, an occurrence of short-circuiting of the electromagnetic wave in the air due to transmission of the electromagnetic wave between the two anode terminals can be cancelled, and an appropriate removal of noise by the surface mount type condenser can be effected, so that noise can be more efficiently removed in the case of high frequency range.
Further, the above-mentioned predetermined regions indicate regions of the anode terminals, which should be covered by the second metallic plate when the second metallic plate is arranged for covering portions of the anode terminals to an extent such that the action of the electromagnetic wave can be electrically suppressed.
A surface mount type condenser according to a second invention of the present patent application comprises a substantially planar plate-shape second metallic plate connected to a surface of the other of the cathode portions and having a surface thereof confronting the surfaces of anode terminals.
According to the above-described constitution, a phenomenon of short-circuiting of electromagnetic wave in the air, namely transmission of the electromagnetic wave between the two anode terminals can be decreased.
At this stage, the second metallic plate of this constitution may be arranged to confront the surfaces of the anode terminals in compliance with an arrangement requested by the function of the surface mount type condenser.
Namely, at least a portion of the surface of the second metallic plate may be arrange to confront a portion of the surfaces of the anode terminals. Hereby, a decrease in a space necessary for the installation of the surface mount type condenser, and reduction in the manufacturing cost thereof can be achieved.
A surface mount type condenser according to a third invention of the present patent application comprises a substantially planar plate-shape second metallic plate connected to a surface of the other of the cathode portions and having a surface thereof confronting the whole of surfaces of the anode terminals.
According to this constitution, the electromagnetic wave discharged from the surfaces of at least two anode terminals can be suppressed by the confronting surface of the second metallic plate having an area equal to or greater than those of the surfaces of the anode terminals, so that appropriate removal of noise can be achieved by the surface mount type condenser, and further the removal of noise in the high frequency range can be more efficiently achieved.
A surface mount type condenser according to a fourth invention of the present patent application is characterized in that the second metallic plate has
Arai Satoshi
Masuda Koichiro
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